A numerical analysis of machining induced residual stresses of Grade 5 titanium alloy
- 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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An investigation of machining induced residual stresses on Grade 4 and 5 titanium alloys
- Authors: Edkins, Kyle Douglas
- Date: 2013-07-18
- Subjects: Residual stresses , Titanium alloys - Mechanical properties , High-speed machining
- Type: Thesis
- Identifier: uj:7645 , http://hdl.handle.net/10210/8515
- Description: M.Ing. (Mechanical Engineering) , Titanium and its alloys have the potential to serve as a strategic economic driver of the South African economy. The manufacture and use of high strength, lightweight materials such as titanium alloys have become of great importance in the aerospace and biomedical industries over the past few decades. The manufacturing costs of titanium alloy components however, are considered high due to the poor machinability of the material. Furthermore, as with all metals during machining, surface residual stresses are induced into the material. These are of particular interest in the aerospace industry as they can be either detrimental or beneficial to the performance and fatigue life of materials. The aim of this investigation is therefore to examine the effect that machining parameters have on the magnitude, sign and distribution of residual stresses induced in Grade 4 and 5 titanium alloys during high performance machining (turning). The effect of these machining parameters is investigated by residual stress measurements conducted with X-ray diffraction and grain structure analysis of the machined surfaces by optical microscopy. Results show that cutting speed and depth of cut have a significant effect on the residual stresses. At low cutting speeds, the surface residual stresses are largely compressive, becoming more tensile with an increase in cutting speed. An increase in depth of cut also introduces more compressive residual stresses into the material. The microstructural analysis of the alloys shows that grain deformation decreases with an increase in cutting speed and cutting depth.
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Effect of constitutive modeling during finite element analysis of machining-induced residual stresses in Ti6Al4V
- 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.
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Effect of post-weld heat treatment on the evolving properties of P355NL1
- Authors: Mamabolo, Masemenya
- Date: 2017
- Subjects: Welding , Shielded metal arc welding , Stainless steel - Welding , Gas tungsten arc welding , Residual stresses
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269810 , uj:28667
- Description: M.Ing. (Mechanical Engineering) , Abstract: Post Weld Heat Treatment (PWHT) in the form of stress relieving consists of heating the steel to a temperature below the critical range to relieve the stresses resulting from welding. The mechanical and microscopic properties may also be affected during this process. The study of the effects of Post-Weld Heat Treatment on the evolving properties of the fine-grain carbon alloy steel P355NL1 was conducted, and presented in this report. The study focused on the mechanical and metallurgical properties of the material. The plates used were 6 mm thick with a length of 350 mm and a width of 150 mm; and they were welded using the Gas Metal Arc Welding (GMAW) method. After the welding; PWHT was performed on the plates, using a furnace with the specified temperature and time. A total of four plates were studied; where three plates underwent the same PWHT method, apart from the cooling methods. There was a control sample wherein the plate did not undergo any PWHT; the second plate was furnace-cooled; the third was air-cooled; while the fourth plate was water-cooled. A comparative study was done on the P355NL1 plates, using three testing methods, namely: the tensile test; the microstructure examination; and the microhardness test to investigate how the different cooling methods had affected the properties of the steel, compared to the control as the basis point of comparison. The hardness properties of air and furnace cooled P355NL1 steel decreased compared to the without sample. The tensile strength properties of the sample had shown some improvement for the water-cooled plate; the furnace and air-cooled samples had, however, decreased in terms of their tensile strength. The yield strength properties of the samples revealed similar findings. Although the metallurgical structures revealed different concentrations of darker (pearlite) and lighter (ferrite) grains in the base metal, the overall study showed that there were no significant changes in the microstructure, however, the cooling media employed can be recommended as required for tailored applications.
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