The design and development of a side wall wind tunnel balance using fibre optic Bragg grating sensors
- Authors: Vaz, Nuno Figueira
- Date: 2018
- Subjects: Wind tunnel balances , Bragg gratings , Optical fiber detectors , Strain gages
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284102 , uj:30671
- Description: M.Ing. (Mechanical Engineering) , Abstract: The requirements that a wind tunnel balance needs to satisfy have become increasingly stringent. These requirements, as set out by the wind tunnel testing community at large, include: improved static force accuracy, improved resolution, increased stiffness, temperature compensation and immunity to electromagnetic interference (EMI). In order to satisfy these requirements, wind tunnel balance design philosophy needs to be expanded to include employing alternative strain sensing technologies and alternative manufacturing techniques. This study sets to investigate the design and development of a six component side wall balance using optical fibre Bragg grating sensors (OFBGs). This is done in an attempt to address these stringent requirements by expand on traditional balance design philosophy by determine the viability of using OFBGs in wind tunnel balances. Traditional strain gauge side wall balances (SWB) fundamentally rely on measuring strain, being induced by an applied load, on a balance. For this reasons, the regions of the balance which are intended to be gauged are intentionally made thin. This is done to achieve a high strain gauge output. This however compromises balance stiffness and induces a high level of stress in the balance material at the gauged regions. In order to employ OFBGs on a SWB, the two groove strain sensing method must be employed. The basic working principles of this method is that an optical fibre is spanned between two points across a groove. As a load is applied, the groove deforms. This deformation (displacement) of the groove induces a strain into the optical fibre spanning the groove and a shift in the Bragg grating wavelength. Therefore the design of this SWB is fundamentally based on measuring the displacement between points. Based on these fundamentals, several design iterations were generated and analysed using FEM. The selected design underwent an iterative refinement process, aimed at optimising the design. This balance was manufactured and gauged with OFBGs. The manufactured balance was calibrated at the Counsel for Scientific and Industrial Research (CSIR) wind tunnel testing division in Pretoria, South Africa. The balance was evaluated based on uncertainty, hysteresis and interactions and repeatability...
- Full Text:
- Authors: Vaz, Nuno Figueira
- Date: 2018
- Subjects: Wind tunnel balances , Bragg gratings , Optical fiber detectors , Strain gages
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/284102 , uj:30671
- Description: M.Ing. (Mechanical Engineering) , Abstract: The requirements that a wind tunnel balance needs to satisfy have become increasingly stringent. These requirements, as set out by the wind tunnel testing community at large, include: improved static force accuracy, improved resolution, increased stiffness, temperature compensation and immunity to electromagnetic interference (EMI). In order to satisfy these requirements, wind tunnel balance design philosophy needs to be expanded to include employing alternative strain sensing technologies and alternative manufacturing techniques. This study sets to investigate the design and development of a six component side wall balance using optical fibre Bragg grating sensors (OFBGs). This is done in an attempt to address these stringent requirements by expand on traditional balance design philosophy by determine the viability of using OFBGs in wind tunnel balances. Traditional strain gauge side wall balances (SWB) fundamentally rely on measuring strain, being induced by an applied load, on a balance. For this reasons, the regions of the balance which are intended to be gauged are intentionally made thin. This is done to achieve a high strain gauge output. This however compromises balance stiffness and induces a high level of stress in the balance material at the gauged regions. In order to employ OFBGs on a SWB, the two groove strain sensing method must be employed. The basic working principles of this method is that an optical fibre is spanned between two points across a groove. As a load is applied, the groove deforms. This deformation (displacement) of the groove induces a strain into the optical fibre spanning the groove and a shift in the Bragg grating wavelength. Therefore the design of this SWB is fundamentally based on measuring the displacement between points. Based on these fundamentals, several design iterations were generated and analysed using FEM. The selected design underwent an iterative refinement process, aimed at optimising the design. This balance was manufactured and gauged with OFBGs. The manufactured balance was calibrated at the Counsel for Scientific and Industrial Research (CSIR) wind tunnel testing division in Pretoria, South Africa. The balance was evaluated based on uncertainty, hysteresis and interactions and repeatability...
- Full Text:
The design and development of a platform type wind tunnel balance with optical fibre bragg grating sensors
- Authors: De Ponte, Jules David
- Date: 2015
- Subjects: Wind-pressure , Wind tunnel balances , Wind tunnels - Design and construction , Strain gages
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/56142 , uj:16335
- Description: Abstract: The requirements which a wind tunnel balance must meet are becoming increasingly stringent. The wind tunnel testing community is calling for balances which; offer higher resolution, are stiffer, are immune to electro-magnetic interference (EMI) and provide compensation for thermal effects. It is proposed that in order to meet these requirements, balance design philosophy needs to be further expanded to include different manufacturing methods, materials and sensor technology. This study investigates the design and development of a six component wind tunnel platform balance incorporating Optical fibre Bragg grating (OFBG) sensors. Under an applied load, conventional balances measure strain at the surface of a material, by means of a foil strain gauge. For this reason, sections of material in the balance are purposely made thin, in order for the strain in that section to be sufficiently high to offer adequate resolution. This may compromise the stiffness of the balance. A platform balance is designed which incorporates OFBG sensors using the two-groove method of strain measurement. The optical fibres are spanned between two probes. One probe protrudes from the metric end of the balance, the other protrudes from the fixed end. Under an applied load, the gap between the two protrusions will change, which will induce a strain in the fibre Bragg grating spanning it. This strain in the fibre Bragg grating will cause the Bragg wavelength to shift proportionally to the magnitude of the strain in the fibre. Therefore, the balance is designed around the idea of measuring displacements within the structure of the balance. This displacement is comparatively larger than the deformation at the surface of a material. Therefore, strain induced in the fibre spanning the gap would be larger than the strain at the surface of the material. The balance to which these fibres are bonded can be made stiffer, while still offering a comparable relative resolution. The two-groove method uses two fibres to measure one load component. Each fibre is part of a pair for strain measurement. Each fibre Bragg grating has a different reference Bragg wavelength. These are spanned across two separate gaps. The balance has been designed such that, under an applied load, one fibre of a strain measurement pair experiences a tensile strain, and the other experiences a compressive strain. The final output is determined by calculating the change in difference between the two fibres’ respective Bragg wavelengths. This method compensates for unwanted force and thermal interactions... , M.Ing. (Mechanical Engineering Science)
- Full Text:
- Authors: De Ponte, Jules David
- Date: 2015
- Subjects: Wind-pressure , Wind tunnel balances , Wind tunnels - Design and construction , Strain gages
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/56142 , uj:16335
- Description: Abstract: The requirements which a wind tunnel balance must meet are becoming increasingly stringent. The wind tunnel testing community is calling for balances which; offer higher resolution, are stiffer, are immune to electro-magnetic interference (EMI) and provide compensation for thermal effects. It is proposed that in order to meet these requirements, balance design philosophy needs to be further expanded to include different manufacturing methods, materials and sensor technology. This study investigates the design and development of a six component wind tunnel platform balance incorporating Optical fibre Bragg grating (OFBG) sensors. Under an applied load, conventional balances measure strain at the surface of a material, by means of a foil strain gauge. For this reason, sections of material in the balance are purposely made thin, in order for the strain in that section to be sufficiently high to offer adequate resolution. This may compromise the stiffness of the balance. A platform balance is designed which incorporates OFBG sensors using the two-groove method of strain measurement. The optical fibres are spanned between two probes. One probe protrudes from the metric end of the balance, the other protrudes from the fixed end. Under an applied load, the gap between the two protrusions will change, which will induce a strain in the fibre Bragg grating spanning it. This strain in the fibre Bragg grating will cause the Bragg wavelength to shift proportionally to the magnitude of the strain in the fibre. Therefore, the balance is designed around the idea of measuring displacements within the structure of the balance. This displacement is comparatively larger than the deformation at the surface of a material. Therefore, strain induced in the fibre spanning the gap would be larger than the strain at the surface of the material. The balance to which these fibres are bonded can be made stiffer, while still offering a comparable relative resolution. The two-groove method uses two fibres to measure one load component. Each fibre is part of a pair for strain measurement. Each fibre Bragg grating has a different reference Bragg wavelength. These are spanned across two separate gaps. The balance has been designed such that, under an applied load, one fibre of a strain measurement pair experiences a tensile strain, and the other experiences a compressive strain. The final output is determined by calculating the change in difference between the two fibres’ respective Bragg wavelengths. This method compensates for unwanted force and thermal interactions... , M.Ing. (Mechanical Engineering Science)
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