Effects of thermal processing of blended and roll compacted Ti6Al4V strips on microstructure and properties
- Authors: Muchavi, Noluntu Skhumbuzo
- Date: 2019
- Subjects: Titanium - Processing , Titanium - Metallurgy , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/297356 , uj:32415
- Description: Abstract: Titanium and titanium alloys are considered to be one of the most significant advanced materials used in the aerospace, structural, chemical, marine, oil and gas, petrochemical, medical and other industries today. This can be attributed to its comprehensive properties such as excellent corrosion resistance, high heat resistance, specific strength and fracture toughness, good low temperature toughness and low density. Due to the high cost of producing titanium metal through the conventional way of using Ingot Metallurgy (IM), alternative cost effective methods of such as Powder Metallurgy (PM) have been developed. There are several forms of powder metallurgy processes but the process that was used for the research work is that of Direct Powder Rolling (DPR). This process uses powder as a feedstock for a roll compaction mill. The rolling mill consolidates the feedstock into a green strip that has some form of ductility. DPR of Ti and titanium alloy powder has been successfully demonstrated by CSIRO as well ADMA Incorporated using different processing techniques which contain multiple fabrication stages. The proposed research work was aimed at evaluating an alternative DPR processing route containing far less fabrication stages which leads to a further reduction in cost whilst achieving mechanical properties equivalent to those of wrought materials. The aim of this work was to produce roll compacted Ti6Al4V strips though roll compaction and sintering as well as to study the effect of thermal processing of the strips on density, microstructure and mechanical properties. The objectives of this work were therefore to define roll compaction parameters that will achieve green strips of 85 ±2% theoretical density of Ti6Al4V, define sintering parameters that will produce a perfectly homogeneous strip with a high final sintered density of ≥99% theoretical density and to achieve mechanical properties equivalent to those of Ti6Al4V sheets as per ASTM B265-15 standard specification for Ti and Ti alloy strip, sheet and plate. The roll compacted strips were sectioned and characterised for density using the volumetric density determination method. The strips were sintered at temperatures of 1200, 1300 and 1400°C with holding times of 2, 3 and 4 hours in a Carbolite tube... , M.Tech. (Engineering Metallurgy)
- Full Text:
- Authors: Muchavi, Noluntu Skhumbuzo
- Date: 2019
- Subjects: Titanium - Processing , Titanium - Metallurgy , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/297356 , uj:32415
- Description: Abstract: Titanium and titanium alloys are considered to be one of the most significant advanced materials used in the aerospace, structural, chemical, marine, oil and gas, petrochemical, medical and other industries today. This can be attributed to its comprehensive properties such as excellent corrosion resistance, high heat resistance, specific strength and fracture toughness, good low temperature toughness and low density. Due to the high cost of producing titanium metal through the conventional way of using Ingot Metallurgy (IM), alternative cost effective methods of such as Powder Metallurgy (PM) have been developed. There are several forms of powder metallurgy processes but the process that was used for the research work is that of Direct Powder Rolling (DPR). This process uses powder as a feedstock for a roll compaction mill. The rolling mill consolidates the feedstock into a green strip that has some form of ductility. DPR of Ti and titanium alloy powder has been successfully demonstrated by CSIRO as well ADMA Incorporated using different processing techniques which contain multiple fabrication stages. The proposed research work was aimed at evaluating an alternative DPR processing route containing far less fabrication stages which leads to a further reduction in cost whilst achieving mechanical properties equivalent to those of wrought materials. The aim of this work was to produce roll compacted Ti6Al4V strips though roll compaction and sintering as well as to study the effect of thermal processing of the strips on density, microstructure and mechanical properties. The objectives of this work were therefore to define roll compaction parameters that will achieve green strips of 85 ±2% theoretical density of Ti6Al4V, define sintering parameters that will produce a perfectly homogeneous strip with a high final sintered density of ≥99% theoretical density and to achieve mechanical properties equivalent to those of Ti6Al4V sheets as per ASTM B265-15 standard specification for Ti and Ti alloy strip, sheet and plate. The roll compacted strips were sectioned and characterised for density using the volumetric density determination method. The strips were sintered at temperatures of 1200, 1300 and 1400°C with holding times of 2, 3 and 4 hours in a Carbolite tube... , M.Tech. (Engineering Metallurgy)
- Full Text:
Laser metal deposition of functionally graded Ti6Al4V/TiC
- Mahamood, R. M., Akinlabi, Esther Titilayo
- Authors: Mahamood, R. M. , Akinlabi, Esther Titilayo
- Date: 2015-06-20
- Subjects: Functionally graded materials , Laser metal deposition , Titanium alloys
- Type: Article
- Identifier: uj:5119 , ISSN 02641275 , http://hdl.handle.net/10210/14077
- Description: Functionally graded materials (FGMs) are advanced materials with improved properties that enable them to withstand severe working environment which the traditional composite materials cannot withstand. FGM found their applications in several areas which include: military,medicine and aerospace. Various manufacturing processes are used to produce functionally graded materials that include: powder metallurgy, physical vapour deposition, chemical vapour deposition process and laser metal deposition process. Laser metal deposition (LMD) process is an additive manufacturing process that can be used to produce functionally graded material directly from the three dimensional (3D) computer aided design (CAD) model of the part in one single process. LMD process is a fairly new manufacturing process and a highly non-linear process. The process parameters are of great importance in LMD process and they need to be optimized for the required application. In this study, functionally graded titanium alloy composite was produced using optimized process parameters for each material combination as obtained through a model that was developed in an initial study and the FGM was characterized throughmetallurgical, mechanical and tribological studies. The results showthat the produced FGM has improved properties when compared to those produced at constant processing parameters for all material combinations.
- Full Text: false
- Authors: Mahamood, R. M. , Akinlabi, Esther Titilayo
- Date: 2015-06-20
- Subjects: Functionally graded materials , Laser metal deposition , Titanium alloys
- Type: Article
- Identifier: uj:5119 , ISSN 02641275 , http://hdl.handle.net/10210/14077
- Description: Functionally graded materials (FGMs) are advanced materials with improved properties that enable them to withstand severe working environment which the traditional composite materials cannot withstand. FGM found their applications in several areas which include: military,medicine and aerospace. Various manufacturing processes are used to produce functionally graded materials that include: powder metallurgy, physical vapour deposition, chemical vapour deposition process and laser metal deposition process. Laser metal deposition (LMD) process is an additive manufacturing process that can be used to produce functionally graded material directly from the three dimensional (3D) computer aided design (CAD) model of the part in one single process. LMD process is a fairly new manufacturing process and a highly non-linear process. The process parameters are of great importance in LMD process and they need to be optimized for the required application. In this study, functionally graded titanium alloy composite was produced using optimized process parameters for each material combination as obtained through a model that was developed in an initial study and the FGM was characterized throughmetallurgical, mechanical and tribological studies. The results showthat the produced FGM has improved properties when compared to those produced at constant processing parameters for all material combinations.
- Full Text: false
Towards energy management during the machining of titanium alloys
- Oosthuizen, G., Laubscher, R.F., Tayisepi, N., Mulumba, J.
- Authors: Oosthuizen, G. , Laubscher, R.F. , Tayisepi, N. , Mulumba, J.
- Date: 2013
- Subjects: Manufacturing industry - South Africa , Machining - South Africa , Titanium alloys , Energy management
- Type: Article
- Identifier: uj:4955 , http://hdl.handle.net/10210/13055
- Description: The manufacturing industry needs to address challenges as regards to the machining process in the multifaceted context of sustainability. The current cost of energy and the reduction in material reserves highlights the need for machining systems to be more energy-efficient. This paper aims to provide a systematic overview of advanced approaches to manage energy and resource efficiency in cutting operations. The research experimentation focuses on the machining of a selected titanium alloy, Ti6Al4V, using carbide cutting tools. Tool wear, chip formation, cutting force and energy use were measured and analysed for selected cutting parameters. The experimental results illustrate the importance of selecting optimum cutting parameters and machining strategy. The results further help to define the boundary conditions for the various input parameters. Future research is also discussed.
- Full Text:
- Authors: Oosthuizen, G. , Laubscher, R.F. , Tayisepi, N. , Mulumba, J.
- Date: 2013
- Subjects: Manufacturing industry - South Africa , Machining - South Africa , Titanium alloys , Energy management
- Type: Article
- Identifier: uj:4955 , http://hdl.handle.net/10210/13055
- Description: The manufacturing industry needs to address challenges as regards to the machining process in the multifaceted context of sustainability. The current cost of energy and the reduction in material reserves highlights the need for machining systems to be more energy-efficient. This paper aims to provide a systematic overview of advanced approaches to manage energy and resource efficiency in cutting operations. The research experimentation focuses on the machining of a selected titanium alloy, Ti6Al4V, using carbide cutting tools. Tool wear, chip formation, cutting force and energy use were measured and analysed for selected cutting parameters. The experimental results illustrate the importance of selecting optimum cutting parameters and machining strategy. The results further help to define the boundary conditions for the various input parameters. Future research is also discussed.
- Full Text:
Laser additive manufacturing technology for crack repairs in titanium alloy components
- Authors: Marazani, Tawanda
- Date: 2016
- Subjects: Laser welding , Welded joints - Cracking , Manufacturing processes , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366385 , http://hdl.handle.net/10210/213019 , uj:21067
- Description: Abstract: Laser additive technology (LAT) uses a laser beam which locally melts the target material surface. The technology has been widely used for high value and critical components mainly in the aerospace and the biomedical industries. Due to its favourable properties, titanium has become a workhorse metal, particularly the grade 5 titanium alloy (Ti-6Al-4V). Recent years have seen increased research and development studies on the application of the laser additive technology in the production of Ti-6Al-4V components. These ranged from free form fabrication, materials processing, manufacturing, maintenance and repairs. Attempts to use the laser additive technology for the repair of cracks in Ti alloy components have been recently reported where V-grooves have been recommended. Further attempts to use narrow U-grooves for crack repairs were not successful and hence not widely adopted. There is limited published work on the use of narrow rectangular grooves for crack repairs in Ti-6Al-4V.There is therefore a need to further investigate the potential repairing of U-cracks using LAT. This research work established through experimental design, mechanical and metallographic characterization, a process that was used for the laser additive repair of cracks in Ti-6Al-4V components. The preliminary repairs were made without laser re-melting. They were analysed for defects using the optical microscopy (OM) and their macrographs revealed lack of sidewall fusion, lack of interlayer fusion, lack of intralayer fusion, unmelted powder and porosity. The matrix used for the preliminary repairs was then optimised using the observations made during the preliminary phase. It was from this preliminary phase optimization that the final experimental matrix of the research was developed. Controlled laser re-melting, reduction of the spot size diameter and lowering of the scanning speed were introduced as main process parameters of the optimized matrix. The optimized repairs were further characterized using the optical microscopy (OM) and the scanning electron microscopy (SEM). The optimized repairs were observed to have very limited defects. The energy dispersive spectroscopy (EDS) analyses revealed that the deposits were dominated by Ti, Al and V which were the main compositions of the material. The Vickers microhardness tests, microhardness-tensile strength correlations and the Charpy impact tests obtained results confirmed mechanically sound repairs with good evolving microstructural properties... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Marazani, Tawanda
- Date: 2016
- Subjects: Laser welding , Welded joints - Cracking , Manufacturing processes , Titanium alloys
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366385 , http://hdl.handle.net/10210/213019 , uj:21067
- Description: Abstract: Laser additive technology (LAT) uses a laser beam which locally melts the target material surface. The technology has been widely used for high value and critical components mainly in the aerospace and the biomedical industries. Due to its favourable properties, titanium has become a workhorse metal, particularly the grade 5 titanium alloy (Ti-6Al-4V). Recent years have seen increased research and development studies on the application of the laser additive technology in the production of Ti-6Al-4V components. These ranged from free form fabrication, materials processing, manufacturing, maintenance and repairs. Attempts to use the laser additive technology for the repair of cracks in Ti alloy components have been recently reported where V-grooves have been recommended. Further attempts to use narrow U-grooves for crack repairs were not successful and hence not widely adopted. There is limited published work on the use of narrow rectangular grooves for crack repairs in Ti-6Al-4V.There is therefore a need to further investigate the potential repairing of U-cracks using LAT. This research work established through experimental design, mechanical and metallographic characterization, a process that was used for the laser additive repair of cracks in Ti-6Al-4V components. The preliminary repairs were made without laser re-melting. They were analysed for defects using the optical microscopy (OM) and their macrographs revealed lack of sidewall fusion, lack of interlayer fusion, lack of intralayer fusion, unmelted powder and porosity. The matrix used for the preliminary repairs was then optimised using the observations made during the preliminary phase. It was from this preliminary phase optimization that the final experimental matrix of the research was developed. Controlled laser re-melting, reduction of the spot size diameter and lowering of the scanning speed were introduced as main process parameters of the optimized matrix. The optimized repairs were further characterized using the optical microscopy (OM) and the scanning electron microscopy (SEM). The optimized repairs were observed to have very limited defects. The energy dispersive spectroscopy (EDS) analyses revealed that the deposits were dominated by Ti, Al and V which were the main compositions of the material. The Vickers microhardness tests, microhardness-tensile strength correlations and the Charpy impact tests obtained results confirmed mechanically sound repairs with good evolving microstructural properties... , M.Ing. (Mechanical Engineering)
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Laser metal deposition of Ti6Al4V/Cu composite : a study of the effect of laser power on the evolving properties
- Erinosho, Mutiu F., Akinlabi, Esther Titilayo, Pityana, Sisa
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2014
- Subjects: Porosity , Laser metal deposition , Titanium alloys
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/375937 , uj:4740 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11726
- Description: A study of the effect of laser power was investigated over the volume of deposited composite, microstructure and microhardness. The laser power was varied between 600 and 1800 W while keeping all other parameters constant. An indication shows that the area and the volume of the deposited composites are directly proportional to the laser power employed. The volume of the deposit obtained falls between 358.6 mm3 and 1009 mm3. The microstructures were analyzed and found that the formation of the Widmanstatten structures improved the hardness of Ti6Al4V/Cu composites. The hardness values of the deposits varied between HV335 and HV490. The percentages of porosities of the samples were also presented and found to have an inverse relationship with the laser power. The results are presented and discussed.
- Full Text:
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2014
- Subjects: Porosity , Laser metal deposition , Titanium alloys
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/375937 , uj:4740 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11726
- Description: A study of the effect of laser power was investigated over the volume of deposited composite, microstructure and microhardness. The laser power was varied between 600 and 1800 W while keeping all other parameters constant. An indication shows that the area and the volume of the deposited composites are directly proportional to the laser power employed. The volume of the deposit obtained falls between 358.6 mm3 and 1009 mm3. The microstructures were analyzed and found that the formation of the Widmanstatten structures improved the hardness of Ti6Al4V/Cu composites. The hardness values of the deposits varied between HV335 and HV490. The percentages of porosities of the samples were also presented and found to have an inverse relationship with the laser power. The results are presented and discussed.
- Full Text:
Effect of powder density variation on premixed Ti-6Al-4V and Cu composites during laser metal deposition
- Erinosho, Mutiu F., Akinlabi, Esther Titilayo, Pityana, Sisa
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2016
- Subjects: Powder density , Laser metal deposition , Titanium alloys , Copper
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/123406 , uj:20787 , Citation: Erinosho, M.F., Akinlabi, E.T & Pityana, S. 2016. Effect of powder density variation on premixed Ti-6Al-4V and Cu composites during laser metal deposition.
- Description: Abstract: This paper reports the effect of powder density variation on the premixed Ti-6Al-4V/Cu and Ti-6Al-4V/2Cu Composites. Two sets of experiment were conducted in this study. Five deposits each were made for the two premixed composites. Laser powers were varied between 600 W and 1700 W while a scanning speed of 0.3 m/min is kept constant throughout the experiment. Investigations were conducted on the microstructures and microhardness of the laser deposited premixed Ti-6Al-4V/Cu and Ti-6Al-4V/2Cu composites. It was found that the evolving microstructures of the composites were characterised with the formation of macroscopic banding and Widmanstatten; and disappears as it grows towards the fusion zone (FZ) and this could be attributed to the changes in the distribution of heat input. Sample A2 of premixed Ti-6Al-4V/Cu composite gives the highest hardness of 393 ± 6.36VHN0.5 while sample B4 of premixed Ti-6Al-4V/2Cu composites depicts the highest hardness value of 373 ± 9.18VHN0.5.
- Full Text:
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2016
- Subjects: Powder density , Laser metal deposition , Titanium alloys , Copper
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/123406 , uj:20787 , Citation: Erinosho, M.F., Akinlabi, E.T & Pityana, S. 2016. Effect of powder density variation on premixed Ti-6Al-4V and Cu composites during laser metal deposition.
- Description: Abstract: This paper reports the effect of powder density variation on the premixed Ti-6Al-4V/Cu and Ti-6Al-4V/2Cu Composites. Two sets of experiment were conducted in this study. Five deposits each were made for the two premixed composites. Laser powers were varied between 600 W and 1700 W while a scanning speed of 0.3 m/min is kept constant throughout the experiment. Investigations were conducted on the microstructures and microhardness of the laser deposited premixed Ti-6Al-4V/Cu and Ti-6Al-4V/2Cu composites. It was found that the evolving microstructures of the composites were characterised with the formation of macroscopic banding and Widmanstatten; and disappears as it grows towards the fusion zone (FZ) and this could be attributed to the changes in the distribution of heat input. Sample A2 of premixed Ti-6Al-4V/Cu composite gives the highest hardness of 393 ± 6.36VHN0.5 while sample B4 of premixed Ti-6Al-4V/2Cu composites depicts the highest hardness value of 373 ± 9.18VHN0.5.
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Characterising the effect of laser metal deposited Ti6Al4V/Cu composites in simulated body fluid for biomedical application
- Erinosho, M. F., Akinlabi, Esther Titilayo, Pityana, S.
- Authors: Erinosho, M. F. , Akinlabi, Esther Titilayo , Pityana, S.
- Date: 2015-01-15
- Subjects: Hank’s solution , Laser metal deposition , Surface morphologies , Titanium alloys
- Type: Article
- Identifier: uj:5120 , ISBN 9789384935108 , http://hdl.handle.net/10210/14078
- Description: Ti6Al4V alloy has been known to have very excellent corrosion resistance due to the oxide layer formed on its surface. Due to this property, the alloy is found applicable for biomedical implants. Copper shows an excellent antimicrobial property and has been found to stabilize the immune system. In this study, laser metal deposition of Ti6Al4V powder and Cu powder on Ti6Al4V substrates were conducted by varying the laser power between 600 W and 1800 W while the scanning speed, the powder flow rate and the gas flow rate were kept constant. The surface behaviour and the morphologies of the composites were evaluated under the microscope and the SEM after soaking for 4 hours, 5 days and 2 weeks respectively. The simulated body fluid (hank’s solution) was maintained at normal body temperature of about 37±1oC. The surfaces showed fracture topography with porous bone-like structures and some trivial pitting were observed.
- Full Text:
- Authors: Erinosho, M. F. , Akinlabi, Esther Titilayo , Pityana, S.
- Date: 2015-01-15
- Subjects: Hank’s solution , Laser metal deposition , Surface morphologies , Titanium alloys
- Type: Article
- Identifier: uj:5120 , ISBN 9789384935108 , http://hdl.handle.net/10210/14078
- Description: Ti6Al4V alloy has been known to have very excellent corrosion resistance due to the oxide layer formed on its surface. Due to this property, the alloy is found applicable for biomedical implants. Copper shows an excellent antimicrobial property and has been found to stabilize the immune system. In this study, laser metal deposition of Ti6Al4V powder and Cu powder on Ti6Al4V substrates were conducted by varying the laser power between 600 W and 1800 W while the scanning speed, the powder flow rate and the gas flow rate were kept constant. The surface behaviour and the morphologies of the composites were evaluated under the microscope and the SEM after soaking for 4 hours, 5 days and 2 weeks respectively. The simulated body fluid (hank’s solution) was maintained at normal body temperature of about 37±1oC. The surfaces showed fracture topography with porous bone-like structures and some trivial pitting were observed.
- Full Text:
An investigation on the effects of high speed machining on the surface integrity of grade 4 titanium alloy
- Authors: Mawanga, Philip
- Date: 2012-08-01
- Subjects: Titanium alloys , High-speed machining , Titanium alloys - Testing
- Type: Thesis
- Identifier: uj:8924 , http://hdl.handle.net/10210/5394
- Description: M.Ing. , Grade 4 titanium is a commercially pure grade titanium alloy extensively used in various industries including the chemical industry and more recently in the biomedical industry. Grade 4 has found a niche as a biomedical material for production of components such as orthopaedic and dental implants. Its physical properties such as high corrosion resistance, low thermal conductivity and high strength make it suitable for these applications. These properties also make it hard-to-machine similar to the other grades of titanium alloys and other metals such as nickel based alloys. During machining of titanium, elevated temperatures are generated at the tool-workpiece interface due to its low thermal conductivity. Its high strength is also maintained at these high temperatures. These tend to impair the cutting tool affecting its machinability. Various investigations on other grades of titanium and other hard-to-machine materials have shown that machining at high cutting speeds may improve certain aspects of their machinability. High speed machining (HSM) is used to improve productivity in the machining process and to therefore lower manufacturing costs. HSM may, however, change the surface integrity of the machined material. Surface integrity refers to the properties of the surface and sub-surface of a machined component which may be quite different from the substrate. The properties of the surface and sub-surface of a component may have a marked effect on the functional behaviour of a machined component. Fatigue life and wear are examples of properties that may be significantly influenced by a change in the surface integrity. Surface integrity may include the topography, the metallurgy and various other mechanical properties. It is evaluated by examination of surface integrity indicators. In this investigation the three main surface integrity indicators are examined. These are surface roughness, sub-surface hardness and residual stress. White layer thickness and chip morphology were also observed as results of the machining process used. The effect of HSM on the surface integrity of grade 4 is largely unknown. This investigation therefore aims to address this limitation by conducting an experimental investigation on the effect of HSM on selected surface integrity indicators for grade 4. Two forged bars of grade 4 alloy were machined using a CNC lathe at two depths of cut, 0.2mm and 1mm. Each bar was machined at varying cutting speeds ranging from 70m/min to 290m/min at intervals of approximately 20m/min. Machined samples were prepared from these cutting speeds and depths of cut. The three surface integrity indicators were then evaluated with respect to the cutting speed and depth of cut (DoC). iv Results show that a combination of intermediate cutting speeds and low DoC may have desirable effects on the surface integrity of grade 4. Highest compressive stresses were obtained when machining with these conditions. High compressive stresses are favourable in cases where the fatigue life of a material is an important factor in the functionality of a component. Subsurface hardening was noticed at 0.2mm DoC, with no subsurface softening at all cutting speeds. Surface hardness higher than the bulk hardness tends to improve the wear resistance of the machined material. Though surface roughness values for all depths of cut were below the standard fine finish of 1.6μm, roughness values of samples machined at 0.2mm DoC continued to decrease with increase in cutting speed. Low surface roughness values may also influence the improvement of fatigue life of the machined components. These machining conditions, (intermediate cutting speeds and low DoC), seem to have promoted mechanically dominated deformation during machining rather than thermal dominated deformation. Thermal dominated deformation was prominent on titanium machined at DoC of 1mm.
- Full Text:
- Authors: Mawanga, Philip
- Date: 2012-08-01
- Subjects: Titanium alloys , High-speed machining , Titanium alloys - Testing
- Type: Thesis
- Identifier: uj:8924 , http://hdl.handle.net/10210/5394
- Description: M.Ing. , Grade 4 titanium is a commercially pure grade titanium alloy extensively used in various industries including the chemical industry and more recently in the biomedical industry. Grade 4 has found a niche as a biomedical material for production of components such as orthopaedic and dental implants. Its physical properties such as high corrosion resistance, low thermal conductivity and high strength make it suitable for these applications. These properties also make it hard-to-machine similar to the other grades of titanium alloys and other metals such as nickel based alloys. During machining of titanium, elevated temperatures are generated at the tool-workpiece interface due to its low thermal conductivity. Its high strength is also maintained at these high temperatures. These tend to impair the cutting tool affecting its machinability. Various investigations on other grades of titanium and other hard-to-machine materials have shown that machining at high cutting speeds may improve certain aspects of their machinability. High speed machining (HSM) is used to improve productivity in the machining process and to therefore lower manufacturing costs. HSM may, however, change the surface integrity of the machined material. Surface integrity refers to the properties of the surface and sub-surface of a machined component which may be quite different from the substrate. The properties of the surface and sub-surface of a component may have a marked effect on the functional behaviour of a machined component. Fatigue life and wear are examples of properties that may be significantly influenced by a change in the surface integrity. Surface integrity may include the topography, the metallurgy and various other mechanical properties. It is evaluated by examination of surface integrity indicators. In this investigation the three main surface integrity indicators are examined. These are surface roughness, sub-surface hardness and residual stress. White layer thickness and chip morphology were also observed as results of the machining process used. The effect of HSM on the surface integrity of grade 4 is largely unknown. This investigation therefore aims to address this limitation by conducting an experimental investigation on the effect of HSM on selected surface integrity indicators for grade 4. Two forged bars of grade 4 alloy were machined using a CNC lathe at two depths of cut, 0.2mm and 1mm. Each bar was machined at varying cutting speeds ranging from 70m/min to 290m/min at intervals of approximately 20m/min. Machined samples were prepared from these cutting speeds and depths of cut. The three surface integrity indicators were then evaluated with respect to the cutting speed and depth of cut (DoC). iv Results show that a combination of intermediate cutting speeds and low DoC may have desirable effects on the surface integrity of grade 4. Highest compressive stresses were obtained when machining with these conditions. High compressive stresses are favourable in cases where the fatigue life of a material is an important factor in the functionality of a component. Subsurface hardening was noticed at 0.2mm DoC, with no subsurface softening at all cutting speeds. Surface hardness higher than the bulk hardness tends to improve the wear resistance of the machined material. Though surface roughness values for all depths of cut were below the standard fine finish of 1.6μm, roughness values of samples machined at 0.2mm DoC continued to decrease with increase in cutting speed. Low surface roughness values may also influence the improvement of fatigue life of the machined components. These machining conditions, (intermediate cutting speeds and low DoC), seem to have promoted mechanically dominated deformation during machining rather than thermal dominated deformation. Thermal dominated deformation was prominent on titanium machined at DoC of 1mm.
- Full Text:
Effect of constitutive modeling during finite element analysis of machining-induced residual stresses in Ti6Al4V
- Oosthuizen, Gert A., Laubscher, Rudolph F., Styger, Gary
- Authors: Oosthuizen, Gert A. , Laubscher, Rudolph F. , Styger, Gary
- Date: 2014
- Subjects: Residual stresses , Titanium alloys , Finite element method , Machining
- Type: Article
- Identifier: uj:5028 , http://hdl.handle.net/10210/13547
- Description: Residual stress is an important surface integrity descriptor that may have a marked effect on the functional performance of machined alloy parts. This paper describes a finite element evaluation of the effect of different constitutive models on machining induced residual stresses for Ti6Al4V titanium alloy. A two dimensional orthogonal turning process is modelled and the results compared to experimental data. Residual stress is evaluated with respect to different elastic-viscoplastic constitutive models at certain cutting speeds and feeds. The general-purpose finite element code MSC Marc@ was used with comparisons with experimental data made relative to residual stress, cutting force and temperature. The magnitude and extent (depth) of the residual stress field is evaluated with regards to the different material models and compared with experimental data.
- Full Text:
- Authors: Oosthuizen, Gert A. , Laubscher, Rudolph F. , Styger, Gary
- Date: 2014
- Subjects: Residual stresses , Titanium alloys , Finite element method , Machining
- Type: Article
- Identifier: uj:5028 , http://hdl.handle.net/10210/13547
- Description: Residual stress is an important surface integrity descriptor that may have a marked effect on the functional performance of machined alloy parts. This paper describes a finite element evaluation of the effect of different constitutive models on machining induced residual stresses for Ti6Al4V titanium alloy. A two dimensional orthogonal turning process is modelled and the results compared to experimental data. Residual stress is evaluated with respect to different elastic-viscoplastic constitutive models at certain cutting speeds and feeds. The general-purpose finite element code MSC Marc@ was used with comparisons with experimental data made relative to residual stress, cutting force and temperature. The magnitude and extent (depth) of the residual stress field is evaluated with regards to the different material models and compared with experimental data.
- Full Text:
Effect of number of laser scans on the corrosion behavior of laser formed titanium alloy
- Akinlabi, Esther Titilayo, Akinlabi, Stephen A.
- Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
- Date: 2014
- Subjects: Titanium alloys , Laser beam formation
- Type: Article
- Identifier: uj:4749 , http://hdl.handle.net/10210/11735
- Full Text:
- Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
- Date: 2014
- Subjects: Titanium alloys , Laser beam formation
- Type: Article
- Identifier: uj:4749 , http://hdl.handle.net/10210/11735
- Full Text:
Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy
- Franklin, Ochonogor O., Akinlabi, Esther Titilayo, Nyembwe, Kasongo D., Pityana, Sisa, Shongwe, Mxolisi Brendon
- Authors: Franklin, Ochonogor O. , Akinlabi, Esther Titilayo , Nyembwe, Kasongo D. , Pityana, Sisa , Shongwe, Mxolisi Brendon
- Date: 2016
- Subjects: Heat treatment , Titanium alloys
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/214859 , uj:21334 , Citation: Franklin, O.O. et al. 2016. Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy.
- Description: Abstract: A hybrid Ti-6Al-4V based metal matrix composites characterized of martensitic structure was formed using three hoper system. Different volume percentages used were as follows: 3.0 vol. % of Ti-6Al-4V, 3.2 vol. % of Ti-6Al-4V and 3.4 vol. % of Ti-6Al-4V respectively while an equal amount of BN and B4C mixed with the Ti-6Al-4V powder particle was fed through the hoper systems at a constant laser power 2000 W and scanning speed of 1.0 m/s. The influence of rapid cooling and varied powder particle at constant coating temperature on the surface morphology and hardness property of Ti-6Al- 4V/B4C/BN alloy systems was however investigated. The hardness result of experimental showed a general improvement. Further result showed that the Ti-6Al- 4V/B4C/BN system fabricated at 3.0 Ti Vol. percent had a hardness improvement as high as 986.9 HVO.5 compared to the as receive Ti-6Al-4V substrate Hardness value of about 357.3 HVO.5. 3.2 Ti Vol. percent systems recorded a hardness value of 723.4 HVO.5 and 3.2 Ti Vol. percent system recorded a hardness value of 609.6 HVO.5. Optical microscope (OM) Scanning electron microscope (SEM) was also carried out for microstructural evaluation and Energy Dispersive Spectroscopy (EDS) to confirm the elemental composition of coating when necessary.
- Full Text:
- Authors: Franklin, Ochonogor O. , Akinlabi, Esther Titilayo , Nyembwe, Kasongo D. , Pityana, Sisa , Shongwe, Mxolisi Brendon
- Date: 2016
- Subjects: Heat treatment , Titanium alloys
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/214859 , uj:21334 , Citation: Franklin, O.O. et al. 2016. Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy.
- Description: Abstract: A hybrid Ti-6Al-4V based metal matrix composites characterized of martensitic structure was formed using three hoper system. Different volume percentages used were as follows: 3.0 vol. % of Ti-6Al-4V, 3.2 vol. % of Ti-6Al-4V and 3.4 vol. % of Ti-6Al-4V respectively while an equal amount of BN and B4C mixed with the Ti-6Al-4V powder particle was fed through the hoper systems at a constant laser power 2000 W and scanning speed of 1.0 m/s. The influence of rapid cooling and varied powder particle at constant coating temperature on the surface morphology and hardness property of Ti-6Al- 4V/B4C/BN alloy systems was however investigated. The hardness result of experimental showed a general improvement. Further result showed that the Ti-6Al- 4V/B4C/BN system fabricated at 3.0 Ti Vol. percent had a hardness improvement as high as 986.9 HVO.5 compared to the as receive Ti-6Al-4V substrate Hardness value of about 357.3 HVO.5. 3.2 Ti Vol. percent systems recorded a hardness value of 723.4 HVO.5 and 3.2 Ti Vol. percent system recorded a hardness value of 609.6 HVO.5. Optical microscope (OM) Scanning electron microscope (SEM) was also carried out for microstructural evaluation and Energy Dispersive Spectroscopy (EDS) to confirm the elemental composition of coating when necessary.
- Full Text:
The effect of high speed machining on the fatigue performance of Ti6Al4V
- Authors: Madyira, Daniel M.
- Date: 2016
- Subjects: High-speed machining , Titanium alloys - Mechanical properties , Metal-cutting , Titanium alloys
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/225157 , uj:22734
- Description: Abstract: Grade 5 titanium alloy (Ti6Al4V) is the workhorse titanium alloy used in many industrial applications including aerospace, automotive, chemical and biomedical. Its attractive mechanical properties such as high strength-to-weight ratio, low density and corrosion resistance make it eminently suitable for such applications. However, its use is limited to these specialized applications due to its high cost. This high cost is mainly due to the primary processing of the material using the Kroll process. Little can be done, currently, to reduce the primary processing cost due to the high reactivity of titanium with oxygen. However, cost reduction measures can be implemented during secondary processing to make this alloy more affordable for general engineering applications. Such measures may include powder metallurgy, laser additive manufacturing, high performance machining and high speed machining. High speed machining (HSM) has been used to improve productivity and reduce component manufacturing costs in aerospace applications such as wing sections. HSM involves machining at high cutting speeds. Such high speed cutting can be implemented under milling or turning conditions. In this investigation, high speed cutting using turning was investigated. However, high speed machining has an effect on the surface and sub-surface condition of a machined component. This may affect the service performance of a component, especially fatigue life. Surface integrity descriptors that may be influenced by machining, and which may affect component fatigue life include surface roughness, micro hardness, microstructure and residual stresses. The cumulative effect of HSM on the fatigue behavior and life of components is largely unknown. This work aims to redress this by conducting experimental investigations supported by numerical analysis, on the effect of HSM on the fatigue performance of turned components for finish cutting conditions of Ti6Al4V. Literature study showed that residual stresses induced during HSM have a significant influence on fatigue performance. The effect of HSM on residual stresses was therefore investigated on specimens machined on 75 mm diameter forged bar of Ti6Al4V. The specimens were... , D.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Madyira, Daniel M.
- Date: 2016
- Subjects: High-speed machining , Titanium alloys - Mechanical properties , Metal-cutting , Titanium alloys
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/225157 , uj:22734
- Description: Abstract: Grade 5 titanium alloy (Ti6Al4V) is the workhorse titanium alloy used in many industrial applications including aerospace, automotive, chemical and biomedical. Its attractive mechanical properties such as high strength-to-weight ratio, low density and corrosion resistance make it eminently suitable for such applications. However, its use is limited to these specialized applications due to its high cost. This high cost is mainly due to the primary processing of the material using the Kroll process. Little can be done, currently, to reduce the primary processing cost due to the high reactivity of titanium with oxygen. However, cost reduction measures can be implemented during secondary processing to make this alloy more affordable for general engineering applications. Such measures may include powder metallurgy, laser additive manufacturing, high performance machining and high speed machining. High speed machining (HSM) has been used to improve productivity and reduce component manufacturing costs in aerospace applications such as wing sections. HSM involves machining at high cutting speeds. Such high speed cutting can be implemented under milling or turning conditions. In this investigation, high speed cutting using turning was investigated. However, high speed machining has an effect on the surface and sub-surface condition of a machined component. This may affect the service performance of a component, especially fatigue life. Surface integrity descriptors that may be influenced by machining, and which may affect component fatigue life include surface roughness, micro hardness, microstructure and residual stresses. The cumulative effect of HSM on the fatigue behavior and life of components is largely unknown. This work aims to redress this by conducting experimental investigations supported by numerical analysis, on the effect of HSM on the fatigue performance of turned components for finish cutting conditions of Ti6Al4V. Literature study showed that residual stresses induced during HSM have a significant influence on fatigue performance. The effect of HSM on residual stresses was therefore investigated on specimens machined on 75 mm diameter forged bar of Ti6Al4V. The specimens were... , D.Ing. (Mechanical Engineering)
- Full Text:
Experimental investigation and CFD modelling of laser metal deposited hybrid coating on grade five titanium alloy
- Authors: Gharehbaghi, Rezvan
- Date: 2018
- Subjects: Titanium alloys , Metal coating , Pulsed laser deposition , Computational fluid dynamics
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284286 , uj:30697
- Description: M.Ing. (Mechanical Engineering) , Abstract: The aim of this research project is to investigate the effect of laser deposited hybrid coatings (Al-Cu-Fe) on the physical, mechanical and metallurgical properties of titanium alloy (Ti-6Al-4V) by experimental techniques and numerical analysis. Laser Additive Manufacturing is relatively new in the manufacturing industry. Laser metal deposition (LMD) can be used to manufacture freeform shapes, to produce parts from graded porous to fully dense solid structures as well as to directly create various surface coatings on a part. This investigation also enhances the mechanical and corrosion properties of hybrid coatings of Al-Cu-Fe on Ti-6Al-4V alloy applicable in the aerospace industry through LMD technique. Icosahedral Al-Cu-Fe as quasicrystals are a relatively new class of materials which exhibit unusual atomic structure with useful physical and chemical properties. Ti6Al4V/Al-Cu-Fe composites were analysed using optical microscopy, scanning electron microscopy (SEM) with energy dispersive microscopy (EDS), indentation testing, x-ray diffraction (XRD) analysis. The hardness and wear resistance performances of the laser coatings were examined by high diamond dura scan microhardness tester and CERT UMT-2 reciprocating sliding machine. The anti-corrosion performances were evaluated by linear polarization technique in 3.5 M NaCl. It was found that the geometrical properties (deposit width and height, heat affected zone (HAZ) height), dilution rate, aspect ratio and powder efficiency of each sample remarkably increased with increasing laser power due to the laser-material interaction. However, the geometrical properties decrease with increasing scanning speed. Solidification began with formation of some large particles such as Al and Fe. The atomic migration of Cu into Ti lattice resulted in the formation of β-Ti phase during cooling and travels a longer distance in the Ti lattice than other elements which opens more crystallographic structure of the β matrix. It was observed that there was higher number of titanium and aluminium presented in the composite as per the theoretical expectation. The indentation testing reveals that Ti6Al4V/Al-Cu-5Fe composite has the highest mean hardness value and it decreases with increasing laser power at scanning speed of 0.8 m/min and 1 m/min. The corrosion and wear resistance of titanium alloy was improved by depositing Al-Cu-Fe quasicrystalline coating. The results obtained from numerical simulation using CFD analysis demonstrated that Ti6Al4V/Al-Cu-10Fe has the highest dilution rate, aspect ratio and HAZ height, and this corresponded with the experimental results. Finally, it was found that Ti6Al4V/Al-Cu-Fe composite have useful mechanical, physical and...
- Full Text:
- Authors: Gharehbaghi, Rezvan
- Date: 2018
- Subjects: Titanium alloys , Metal coating , Pulsed laser deposition , Computational fluid dynamics
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284286 , uj:30697
- Description: M.Ing. (Mechanical Engineering) , Abstract: The aim of this research project is to investigate the effect of laser deposited hybrid coatings (Al-Cu-Fe) on the physical, mechanical and metallurgical properties of titanium alloy (Ti-6Al-4V) by experimental techniques and numerical analysis. Laser Additive Manufacturing is relatively new in the manufacturing industry. Laser metal deposition (LMD) can be used to manufacture freeform shapes, to produce parts from graded porous to fully dense solid structures as well as to directly create various surface coatings on a part. This investigation also enhances the mechanical and corrosion properties of hybrid coatings of Al-Cu-Fe on Ti-6Al-4V alloy applicable in the aerospace industry through LMD technique. Icosahedral Al-Cu-Fe as quasicrystals are a relatively new class of materials which exhibit unusual atomic structure with useful physical and chemical properties. Ti6Al4V/Al-Cu-Fe composites were analysed using optical microscopy, scanning electron microscopy (SEM) with energy dispersive microscopy (EDS), indentation testing, x-ray diffraction (XRD) analysis. The hardness and wear resistance performances of the laser coatings were examined by high diamond dura scan microhardness tester and CERT UMT-2 reciprocating sliding machine. The anti-corrosion performances were evaluated by linear polarization technique in 3.5 M NaCl. It was found that the geometrical properties (deposit width and height, heat affected zone (HAZ) height), dilution rate, aspect ratio and powder efficiency of each sample remarkably increased with increasing laser power due to the laser-material interaction. However, the geometrical properties decrease with increasing scanning speed. Solidification began with formation of some large particles such as Al and Fe. The atomic migration of Cu into Ti lattice resulted in the formation of β-Ti phase during cooling and travels a longer distance in the Ti lattice than other elements which opens more crystallographic structure of the β matrix. It was observed that there was higher number of titanium and aluminium presented in the composite as per the theoretical expectation. The indentation testing reveals that Ti6Al4V/Al-Cu-5Fe composite has the highest mean hardness value and it decreases with increasing laser power at scanning speed of 0.8 m/min and 1 m/min. The corrosion and wear resistance of titanium alloy was improved by depositing Al-Cu-Fe quasicrystalline coating. The results obtained from numerical simulation using CFD analysis demonstrated that Ti6Al4V/Al-Cu-10Fe has the highest dilution rate, aspect ratio and HAZ height, and this corresponded with the experimental results. Finally, it was found that Ti6Al4V/Al-Cu-Fe composite have useful mechanical, physical and...
- Full Text:
On high speed machining of titanium alloys : analysis and validation
- Authors: Sonnekus, Reino
- Date: 2010-08-30T06:55:07Z
- Subjects: Titanium alloys , High-speed machining
- Type: Thesis
- Identifier: uj:6906 , http://hdl.handle.net/10210/3418
- Description: M.Ing. , This report documents the steps taken to gain insight into the phenomena of high speed machining (HSM) of titanium alloys. This was done by firstly studying titanium alloys and the problems associated with machining titanium alloys. An experimental set-up and procedure was developed for measuring and recording both the machining temperature and component forces. A sufficient set of experimental data was collected through extensive experimentation. The cutting temperatures and component forces in HSM of Ti-6Al-4V were examined simultaneously. The cutting speed was found to be the most influential and limiting parameter on the machining temperature and component forces. A new approach for modeling the temperatures in HSM of titanium alloys was developed. Analytical predictions of the cutting temperatures were performed and used to evaluate the influence of a variation in the process parameters on the cutting temperature. The research provides insight for future work into the phenomena of HSM of titanium alloys . The results of the analytical model were found to be representative and comparable to the experimental data. It is however expected that the deviation between the predicted and measured result may be significantly reduced by changing the experimental approach. It is recommended that a complete set of experiments be done, using a new tool insert for every cut, thus removing the effect of possible tool wear on the experimental data obtained. In addition it is recommended that the iterative solution be improved through more in depth programming, considering the change in both the thermal and mechanical materials properties with a change in temperature. Ultimately the assumptions made in order to simplify the problem addressed in this report needs to be improved upon, in order to analyze data trends and even magnitudes to a greater degree of certainty.
- Full Text:
- Authors: Sonnekus, Reino
- Date: 2010-08-30T06:55:07Z
- Subjects: Titanium alloys , High-speed machining
- Type: Thesis
- Identifier: uj:6906 , http://hdl.handle.net/10210/3418
- Description: M.Ing. , This report documents the steps taken to gain insight into the phenomena of high speed machining (HSM) of titanium alloys. This was done by firstly studying titanium alloys and the problems associated with machining titanium alloys. An experimental set-up and procedure was developed for measuring and recording both the machining temperature and component forces. A sufficient set of experimental data was collected through extensive experimentation. The cutting temperatures and component forces in HSM of Ti-6Al-4V were examined simultaneously. The cutting speed was found to be the most influential and limiting parameter on the machining temperature and component forces. A new approach for modeling the temperatures in HSM of titanium alloys was developed. Analytical predictions of the cutting temperatures were performed and used to evaluate the influence of a variation in the process parameters on the cutting temperature. The research provides insight for future work into the phenomena of HSM of titanium alloys . The results of the analytical model were found to be representative and comparable to the experimental data. It is however expected that the deviation between the predicted and measured result may be significantly reduced by changing the experimental approach. It is recommended that a complete set of experiments be done, using a new tool insert for every cut, thus removing the effect of possible tool wear on the experimental data obtained. In addition it is recommended that the iterative solution be improved through more in depth programming, considering the change in both the thermal and mechanical materials properties with a change in temperature. Ultimately the assumptions made in order to simplify the problem addressed in this report needs to be improved upon, in order to analyze data trends and even magnitudes to a greater degree of certainty.
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Outside turning of commercially pure titanium alloys by minimum quantity lubrication
- Authors: Mathonsi, Thabo Nelson
- Date: 2019
- Subjects: Titanium alloys , Machining , Lubrication systems , Titanium alloys - Mechanical properties
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280269 , uj:30113
- Description: M.Ing. (Mechanical Engineering) , Abstract: Machining is a widely used class of industrial manufacturing operation, wherein cutting fluids play a vital role in terms of machining accurate dimensional quality objects due to their cooling, lubricant and chip removal abilities. Although certain advanced cutting fluids have changed the manufacturing industry for the better, there are some environmental concerns associated with some of these fluids. The use and disposal of cutting fluids may be costly and subjected to stringent government laws. Hence, the ever-growing research conducted on environmentally friendly cutting fluids that may lead to enhanced sustainable manufacturing. The aim of this investigation is therefore to investigate the viability of Minimum Quantity Lubrication (MQL) during machining of titanium alloys with specific focus on the commercially pure grades (Grade 2 & 4). This implies minimizing the consumption of harmful cutting fluids by exploring the use of environmentally friendly lubricants and sustainable lubrication techniques. In addition, minimizing the overall manufacturing cost by increasing the tool life, enhancing the work surface integrity, eliminating the need of post finishing operations and minimizing the energy consumption and cutting forces. An extensive literature review was conducted with the focus of machining titanium, effect of machining parameters on tool wear, surface roughness, cutting forces, cutting temperatures and power consumption. A related review was also conducted on the effect of MQL during the turning of titanium alloys. This was followed by the development of an experimental program, which comprised of the design of experiment, experimental setup, measurement and compilation of data. The experimental work was subdivided into; pilot experiments, main experiments and a comparative study. The aim of the pilot experiment was to determine the experimental protocol that was ultimately used in the main experiments. This included: exploring and solving all practical issues or challenges that may occur during the experimentation and optimizing the settings of MQL parameters in order to fix them during the main experiments. During the pilot experiment, the machining tests were conducted according to a 3-level and 3-factor 𝐿9 orthogonal array, at 3 different levels of MQL flow rate, nozzle distance and air pressure. The machining parameters; cutting speed, feed rate and depth of cut were kept constant at 125m/min, 0.2mm/rev and 1mm respectively. The Taguchi method and Grey relational optimisation was used to obtain the optimized parameters settings for Grade 4. The optimization showed that flow rate was the most significant parameter, followed by nozzle distance. Air pressure was the least significant. The analysis showed that the optimum MQL parameters for Grade 4 were: flow rate of 70ml/hr, nozzle distance of 30 mm and air pressure of 4 bar. A similar scheme was used to optimize the MQL parameters for Grade 2. The relative significance of the MQL parameters were similar to Grade 4. The analysis showed that the optimum MQL parameters for Grade 2 were: flow rate of 50ml/hr, nozzle distance of 30 mm and air pressure of 5 bar...
- Full Text:
- Authors: Mathonsi, Thabo Nelson
- Date: 2019
- Subjects: Titanium alloys , Machining , Lubrication systems , Titanium alloys - Mechanical properties
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280269 , uj:30113
- Description: M.Ing. (Mechanical Engineering) , Abstract: Machining is a widely used class of industrial manufacturing operation, wherein cutting fluids play a vital role in terms of machining accurate dimensional quality objects due to their cooling, lubricant and chip removal abilities. Although certain advanced cutting fluids have changed the manufacturing industry for the better, there are some environmental concerns associated with some of these fluids. The use and disposal of cutting fluids may be costly and subjected to stringent government laws. Hence, the ever-growing research conducted on environmentally friendly cutting fluids that may lead to enhanced sustainable manufacturing. The aim of this investigation is therefore to investigate the viability of Minimum Quantity Lubrication (MQL) during machining of titanium alloys with specific focus on the commercially pure grades (Grade 2 & 4). This implies minimizing the consumption of harmful cutting fluids by exploring the use of environmentally friendly lubricants and sustainable lubrication techniques. In addition, minimizing the overall manufacturing cost by increasing the tool life, enhancing the work surface integrity, eliminating the need of post finishing operations and minimizing the energy consumption and cutting forces. An extensive literature review was conducted with the focus of machining titanium, effect of machining parameters on tool wear, surface roughness, cutting forces, cutting temperatures and power consumption. A related review was also conducted on the effect of MQL during the turning of titanium alloys. This was followed by the development of an experimental program, which comprised of the design of experiment, experimental setup, measurement and compilation of data. The experimental work was subdivided into; pilot experiments, main experiments and a comparative study. The aim of the pilot experiment was to determine the experimental protocol that was ultimately used in the main experiments. This included: exploring and solving all practical issues or challenges that may occur during the experimentation and optimizing the settings of MQL parameters in order to fix them during the main experiments. During the pilot experiment, the machining tests were conducted according to a 3-level and 3-factor 𝐿9 orthogonal array, at 3 different levels of MQL flow rate, nozzle distance and air pressure. The machining parameters; cutting speed, feed rate and depth of cut were kept constant at 125m/min, 0.2mm/rev and 1mm respectively. The Taguchi method and Grey relational optimisation was used to obtain the optimized parameters settings for Grade 4. The optimization showed that flow rate was the most significant parameter, followed by nozzle distance. Air pressure was the least significant. The analysis showed that the optimum MQL parameters for Grade 4 were: flow rate of 70ml/hr, nozzle distance of 30 mm and air pressure of 4 bar. A similar scheme was used to optimize the MQL parameters for Grade 2. The relative significance of the MQL parameters were similar to Grade 4. The analysis showed that the optimum MQL parameters for Grade 2 were: flow rate of 50ml/hr, nozzle distance of 30 mm and air pressure of 5 bar...
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A numerical analysis of machining induced residual stresses of Grade 5 titanium alloy
- Laubscher, R.F., Styger, G., Oosthuizen, G.A.
- Authors: Laubscher, R.F. , Styger, G. , Oosthuizen, G.A.
- Date: 2014-06
- Subjects: Numerical analysis , Machining , Residual stresses , Titanium alloys
- Type: Article
- Identifier: uj:5055 , http://hdl.handle.net/10210/13603
- Description: Machining induced residual stresses may have a significant effect on the mechanical performance of machined parts. AdvantEdge is an advanced finite element code dedicated to the modelling of the machining process. This paper describes a comparative evaluation of modelling results obtained with AdvantEdge with experimental results obtained during turning of Grade 5 (Ti6Al4V) titanium alloy. A two dimensional orthogonal turning process is modelled and compared with experimental data. Comparisons are made relative to residual stress, cutting force and cutting temperature for various different cutting parameters including cutting speed, feed rate and cut depth.
- Full Text:
- Authors: Laubscher, R.F. , Styger, G. , Oosthuizen, G.A.
- Date: 2014-06
- Subjects: Numerical analysis , Machining , Residual stresses , Titanium alloys
- Type: Article
- Identifier: uj:5055 , http://hdl.handle.net/10210/13603
- Description: Machining induced residual stresses may have a significant effect on the mechanical performance of machined parts. AdvantEdge is an advanced finite element code dedicated to the modelling of the machining process. This paper describes a comparative evaluation of modelling results obtained with AdvantEdge with experimental results obtained during turning of Grade 5 (Ti6Al4V) titanium alloy. A two dimensional orthogonal turning process is modelled and compared with experimental data. Comparisons are made relative to residual stress, cutting force and cutting temperature for various different cutting parameters including cutting speed, feed rate and cut depth.
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Effects of wire electrical discharge machining on fracture toughness of grade 5 titanium alloy
- Madyira, Daniel M., Akinlabi, Esther Titilayo
- Authors: Madyira, Daniel M. , Akinlabi, Esther Titilayo
- Date: 2014
- Subjects: Titanium alloys , Electrical discharge machining , Fracture toughness , Compact tension
- Type: Article
- Identifier: uj:4752 , ISSN 2078-0958 , http://hdl.handle.net/10210/11738
- Description: Grade 5 titanium (Ti6Al4V) is considered as the workhorse material when it comes to automotive and aerospace applications. It is widely referred to as an aerospace alloy and is relatively a new engineering material. The main attraction of this material is its high strength to weight ratio when compared to such common engineering materials such as steel and aluminum alloys. One of the major challenges in the use of this aerospace material is its machinability. Its high strength which is maintained at elevated temperatures, low thermal conductivity, low elastic modulus and high reactivity with oxygen is a perfect recipe for machining challenges. This leads to high tool wear and long production times. Such challenges are sometimes overcome by electrical discharge machining (EDM). Given that titanium is usually applied to mission critical components (gears, shafts, wing sections), it is important to understand the possible effect of wire EDM on their structural performance. One of the structural integrity indicators in such applications is fracture toughness. Fracture toughness is widely used for damage tolerance analysis of aerospace components in which critical crack sizes are computed for given loading conditions to arrive at safe inspection and maintenance intervals. It is therefore the purpose of this paper to conduct a study on the effect of wire EDM on the fracture toughness of this aerospace material. Standard test procedure using compact tension (CT) specimen is used to measure the fracture toughness. Four specimens are produced using wire EDM. This includes the pre-crack which is usually produced by fatigue cycling. Obtained results indicate a slight decrease in fracture toughness compared to that reported in literature. In addition, it can also be concluded that wire EDM can be used as an alternative to fatigue pre-cracking in fracture toughness testing of titanium alloys.
- Full Text:
- Authors: Madyira, Daniel M. , Akinlabi, Esther Titilayo
- Date: 2014
- Subjects: Titanium alloys , Electrical discharge machining , Fracture toughness , Compact tension
- Type: Article
- Identifier: uj:4752 , ISSN 2078-0958 , http://hdl.handle.net/10210/11738
- Description: Grade 5 titanium (Ti6Al4V) is considered as the workhorse material when it comes to automotive and aerospace applications. It is widely referred to as an aerospace alloy and is relatively a new engineering material. The main attraction of this material is its high strength to weight ratio when compared to such common engineering materials such as steel and aluminum alloys. One of the major challenges in the use of this aerospace material is its machinability. Its high strength which is maintained at elevated temperatures, low thermal conductivity, low elastic modulus and high reactivity with oxygen is a perfect recipe for machining challenges. This leads to high tool wear and long production times. Such challenges are sometimes overcome by electrical discharge machining (EDM). Given that titanium is usually applied to mission critical components (gears, shafts, wing sections), it is important to understand the possible effect of wire EDM on their structural performance. One of the structural integrity indicators in such applications is fracture toughness. Fracture toughness is widely used for damage tolerance analysis of aerospace components in which critical crack sizes are computed for given loading conditions to arrive at safe inspection and maintenance intervals. It is therefore the purpose of this paper to conduct a study on the effect of wire EDM on the fracture toughness of this aerospace material. Standard test procedure using compact tension (CT) specimen is used to measure the fracture toughness. Four specimens are produced using wire EDM. This includes the pre-crack which is usually produced by fatigue cycling. Obtained results indicate a slight decrease in fracture toughness compared to that reported in literature. In addition, it can also be concluded that wire EDM can be used as an alternative to fatigue pre-cracking in fracture toughness testing of titanium alloys.
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Experimental investigation of laser beam forming of titanium and statistical analysis of the effects of parameters on curvature
- Akinlabi, Stephen A., Akinlabi, Esther Titilayo
- Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
- Date: 2013
- Subjects: Laser beam forming , Titanium alloys
- Type: Article
- Identifier: uj:4746 , ISSN 2078-0966 , http://hdl.handle.net/10210/11732
- Description: Laser beam forming, a non-contact manufacturing process has become a viable manufacturing process for shaping metallic components. The capability of laser beam forming and bending demands more experimental studies to identify an optimized parameter setting and the likely parameters influencing the formed curvature. This paper investigates experimental laser beam forming of Ti6Al4V titanium alloy using a 4.4 kW Nd: YAG laser and studied the effects of the process parameters on the formed curvature. It was established that an increase in both the laser beam power and the number of scan tracks reduces the radius of curvature in the formed sheets having a more dome shape. The scan speed on the other hand, achieved the same good curvature at a slower or reduced scan speed to allow enough laser – material interaction. Furthermore, both the ANOVA and the regression analysis confirmed the repeatability of the experimental data. A simple regression model was developed based on the known active parameters to determine approximate curvatures instead of running a series of experiments.
- Full Text:
- Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
- Date: 2013
- Subjects: Laser beam forming , Titanium alloys
- Type: Article
- Identifier: uj:4746 , ISSN 2078-0966 , http://hdl.handle.net/10210/11732
- Description: Laser beam forming, a non-contact manufacturing process has become a viable manufacturing process for shaping metallic components. The capability of laser beam forming and bending demands more experimental studies to identify an optimized parameter setting and the likely parameters influencing the formed curvature. This paper investigates experimental laser beam forming of Ti6Al4V titanium alloy using a 4.4 kW Nd: YAG laser and studied the effects of the process parameters on the formed curvature. It was established that an increase in both the laser beam power and the number of scan tracks reduces the radius of curvature in the formed sheets having a more dome shape. The scan speed on the other hand, achieved the same good curvature at a slower or reduced scan speed to allow enough laser – material interaction. Furthermore, both the ANOVA and the regression analysis confirmed the repeatability of the experimental data. A simple regression model was developed based on the known active parameters to determine approximate curvatures instead of running a series of experiments.
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An investigation on the effect of high speed machining on the osseointegration performance of grade 4 titanium alloy
- Authors: Reddy, Andrish
- Date: 2015-02-12
- Subjects: Titanium alloys , Titanium alloys - Testing , High-speed machining
- Type: Thesis
- Identifier: uj:13323 , http://hdl.handle.net/10210/13339
- Description: M.Eng. (Mechanical Engineering) , High speed machining (HSM) has the potential to greatly increase productivity and to lower manufacturing costs if workpiece surface integrity can be controlled. The surface fmish of a biomaterial is vitally important for proper implant functioning, and is the focus of this study. Grade 4 titanium was turned on a lathe with cutting speeds increasing from the conventional to the high speed range. The surface finish was assessed using profilometry, atomic force microscopy, and contact angle measurement. The ability of the material to bond directly with bone was predicted by cell adhesion studies. Results indicate that there is a general relationship between cutting speed, surface roughness, contact angle, and cell adhesion. Turning grade 4 titanium at cutting speeds between 150m/min and 200m/min may provide an optimal surface for osseointegration.
- Full Text:
- Authors: Reddy, Andrish
- Date: 2015-02-12
- Subjects: Titanium alloys , Titanium alloys - Testing , High-speed machining
- Type: Thesis
- Identifier: uj:13323 , http://hdl.handle.net/10210/13339
- Description: M.Eng. (Mechanical Engineering) , High speed machining (HSM) has the potential to greatly increase productivity and to lower manufacturing costs if workpiece surface integrity can be controlled. The surface fmish of a biomaterial is vitally important for proper implant functioning, and is the focus of this study. Grade 4 titanium was turned on a lathe with cutting speeds increasing from the conventional to the high speed range. The surface finish was assessed using profilometry, atomic force microscopy, and contact angle measurement. The ability of the material to bond directly with bone was predicted by cell adhesion studies. Results indicate that there is a general relationship between cutting speed, surface roughness, contact angle, and cell adhesion. Turning grade 4 titanium at cutting speeds between 150m/min and 200m/min may provide an optimal surface for osseointegration.
- Full Text:
Characterizing the effect of laser power on laser beam formed titanium sheets
- Authors: Akinlabi, Esther Titilayo
- Date: 2014
- Subjects: Laser beam formation , Titanium alloys
- Type: Article
- Identifier: uj:4751 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11737
- Description: Laser forming is a new advanced technology in manufacturing for the bending of sheet metals and the joining of metallic components in automobile, microelectronics and the aerospace industries. In the laser forming process, various factors such as the laser parameters and the material properties need to be considered in order to achieve optimum properties after laser forming. This paper reports the effects of the laser power on the resulting curvatures of the laser beam formed Titanium sheets. The laser formed samples were characterized through the microstructure and the mechanical properties. The results obtained during the microscopic evaluation of the specimen showed that the grain sizes of the formed samples increases and is proportional to the laser power employed to form the samples. It was also found that the Vickers microhardness is directly proportional to the laser power and the radius of curvature increases with a decrease in the Laser power. Hence, the grain size is also directly proportional to the Vickers microhardness of the sample
- Full Text:
- Authors: Akinlabi, Esther Titilayo
- Date: 2014
- Subjects: Laser beam formation , Titanium alloys
- Type: Article
- Identifier: uj:4751 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11737
- Description: Laser forming is a new advanced technology in manufacturing for the bending of sheet metals and the joining of metallic components in automobile, microelectronics and the aerospace industries. In the laser forming process, various factors such as the laser parameters and the material properties need to be considered in order to achieve optimum properties after laser forming. This paper reports the effects of the laser power on the resulting curvatures of the laser beam formed Titanium sheets. The laser formed samples were characterized through the microstructure and the mechanical properties. The results obtained during the microscopic evaluation of the specimen showed that the grain sizes of the formed samples increases and is proportional to the laser power employed to form the samples. It was also found that the Vickers microhardness is directly proportional to the laser power and the radius of curvature increases with a decrease in the Laser power. Hence, the grain size is also directly proportional to the Vickers microhardness of the sample
- Full Text: