The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Wing Kong Chiu - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical investigations alleviating tensile residual stresses in flash Butt welds by localised rapid post weld heat treatment
Journal of Materials Processing Technology, 2008Co-Authors: David Tawfik, Peter Mutton, Wing Kong ChiuAbstract:Abstract Flash-Butt Welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during Welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after Welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-Butt Welding procedure that should result in improved weld performance under high axle load conditions.
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experimental and numerical investigations alleviating tensile residual stresses in flash Butt welds by localised rapid post weld heat treatment
Journal of Materials Processing Technology, 2008Co-Authors: David Tawfik, Peter Mutton, Wing Kong ChiuAbstract:Abstract Flash-Butt Welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during Welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after Welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-Butt Welding procedure that should result in improved weld performance under high axle load conditions.
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verification of residual stresses in flash Butt weld rails using neutron diffraction
Physica B-condensed Matter, 2006Co-Authors: David Tawfik, O Kirstein, Peter Mutton, Wing Kong ChiuAbstract:Abstract Residual stresses developed during flash-Butt Welding may play a crucial role in prolonging the fatigue life of the welded tracks under service loading conditions. The finished welds typically exhibit high levels of tensile residual stresses in the web region of the weld. Moreover, the surface condition of the web may contain shear drag or other defects resulting from the shearing process which may lead to the initiation and propagation of fatigue cracks in a horizontal split web failure mode under high axle loads. However, a comprehensive understanding into the residual stress behaviour throughout the complex weld geometry remains unclear and is considered necessary to establish the correct localised post-weld heat treatment modifications intended to lower tensile residual stresses. This investigation used the neutron diffraction technique to analyse residual stresses in an AS60 flash-Butt-welded rail cooled under normal operating conditions. The findings will ultimately contribute to developing modifications to the flash-Butt-Welding procedure to lower tensile residual stresses which may then improve rail performance under high axle load.
David Tawfik - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical investigations alleviating tensile residual stresses in flash Butt welds by localised rapid post weld heat treatment
Journal of Materials Processing Technology, 2008Co-Authors: David Tawfik, Peter Mutton, Wing Kong ChiuAbstract:Abstract Flash-Butt Welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during Welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after Welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-Butt Welding procedure that should result in improved weld performance under high axle load conditions.
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experimental and numerical investigations alleviating tensile residual stresses in flash Butt welds by localised rapid post weld heat treatment
Journal of Materials Processing Technology, 2008Co-Authors: David Tawfik, Peter Mutton, Wing Kong ChiuAbstract:Abstract Flash-Butt Welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during Welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after Welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-Butt Welding procedure that should result in improved weld performance under high axle load conditions.
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verification of residual stresses in flash Butt weld rails using neutron diffraction
Physica B-condensed Matter, 2006Co-Authors: David Tawfik, O Kirstein, Peter Mutton, Wing Kong ChiuAbstract:Abstract Residual stresses developed during flash-Butt Welding may play a crucial role in prolonging the fatigue life of the welded tracks under service loading conditions. The finished welds typically exhibit high levels of tensile residual stresses in the web region of the weld. Moreover, the surface condition of the web may contain shear drag or other defects resulting from the shearing process which may lead to the initiation and propagation of fatigue cracks in a horizontal split web failure mode under high axle loads. However, a comprehensive understanding into the residual stress behaviour throughout the complex weld geometry remains unclear and is considered necessary to establish the correct localised post-weld heat treatment modifications intended to lower tensile residual stresses. This investigation used the neutron diffraction technique to analyse residual stresses in an AS60 flash-Butt-welded rail cooled under normal operating conditions. The findings will ultimately contribute to developing modifications to the flash-Butt-Welding procedure to lower tensile residual stresses which may then improve rail performance under high axle load.
Peter Mutton - One of the best experts on this subject based on the ideXlab platform.
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experimental and numerical investigations alleviating tensile residual stresses in flash Butt welds by localised rapid post weld heat treatment
Journal of Materials Processing Technology, 2008Co-Authors: David Tawfik, Peter Mutton, Wing Kong ChiuAbstract:Abstract Flash-Butt Welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during Welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after Welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-Butt Welding procedure that should result in improved weld performance under high axle load conditions.
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experimental and numerical investigations alleviating tensile residual stresses in flash Butt welds by localised rapid post weld heat treatment
Journal of Materials Processing Technology, 2008Co-Authors: David Tawfik, Peter Mutton, Wing Kong ChiuAbstract:Abstract Flash-Butt Welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during Welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after Welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-Butt Welding procedure that should result in improved weld performance under high axle load conditions.
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verification of residual stresses in flash Butt weld rails using neutron diffraction
Physica B-condensed Matter, 2006Co-Authors: David Tawfik, O Kirstein, Peter Mutton, Wing Kong ChiuAbstract:Abstract Residual stresses developed during flash-Butt Welding may play a crucial role in prolonging the fatigue life of the welded tracks under service loading conditions. The finished welds typically exhibit high levels of tensile residual stresses in the web region of the weld. Moreover, the surface condition of the web may contain shear drag or other defects resulting from the shearing process which may lead to the initiation and propagation of fatigue cracks in a horizontal split web failure mode under high axle loads. However, a comprehensive understanding into the residual stress behaviour throughout the complex weld geometry remains unclear and is considered necessary to establish the correct localised post-weld heat treatment modifications intended to lower tensile residual stresses. This investigation used the neutron diffraction technique to analyse residual stresses in an AS60 flash-Butt-welded rail cooled under normal operating conditions. The findings will ultimately contribute to developing modifications to the flash-Butt-Welding procedure to lower tensile residual stresses which may then improve rail performance under high axle load.
Yanguo Li - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of flash Butt Welding of high manganese steel crossing with carbon steel rail
Advanced Materials Research, 2010Co-Authors: Yanguo LiAbstract:A flash Butt Welding model of a high manganese steel crossing was established using the thermal coupled finite element method (FEM). The model considers comprehensively the physical parameters of materials, which change with temperature, as well as the burning material caused by the splutter during Welding process. The temperature field of the flash Butt Welding joint and the cooling curves of the high manganese steel crossing at various locations near the Welding seam were simulated. Comparisons with actual Welding specimens of high manganese steel crossing indicated that flash Butt Welding model of the high manganese steel crossing is reasonable, and the temperature field distribution near the Welding seam after flash Butt Welding can thus be appropriately evaluated by the simulation results.
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flash Butt Welding of high manganese steel crossing and carbon steel rail
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Fucheng Zhang, Bo Lv, Baitao Hu, Yanguo LiAbstract:Abstract This study sets out to introduce the flash Butt Welding of high manganese steel crossing and carbon steel rail by employing an austenite–ferrite two-phase stainless steel insert. There are two flash Butt welded joints for the connection of the high manganese steel and the carbon steel rail, one is the welded joint of the carbon steel and the stainless steel, and the other is that of the high manganese steel and the stainless steel. The mechanical properties and the microstructures of the welded joint are studied by means of static bending, three bend-fatigue and metallographic for the practical rail. There is no carbide precipitation on the austenitic grain boundary in the HAZ of the high manganese steel crossing subjected to jetting water cooling after the flash Butt Welding, and there is no martensitic transformation in the HAZ of the carbon steel rail subjected to annealing treatment by a special induction heat treatment device, which will avoid the brittleness of the welded joint effectively. The welded joint of the carbon steel rail and the stainless steel insert is annealed at 900 °C for 10 min, which will release the residual stress of the welded joint and thus enhance the strength of the welded joint. It is indicated that the flash Butt Welding of the high manganese steel crossing and the carbon steel rail via the austenite–ferrite two-phase stainless steel insert is feasible.
Fucheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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flash Butt Welding of high manganese steel crossing and carbon steel rail
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Fucheng Zhang, Bo Lv, Baitao Hu, Yanguo LiAbstract:Abstract This study sets out to introduce the flash Butt Welding of high manganese steel crossing and carbon steel rail by employing an austenite–ferrite two-phase stainless steel insert. There are two flash Butt welded joints for the connection of the high manganese steel and the carbon steel rail, one is the welded joint of the carbon steel and the stainless steel, and the other is that of the high manganese steel and the stainless steel. The mechanical properties and the microstructures of the welded joint are studied by means of static bending, three bend-fatigue and metallographic for the practical rail. There is no carbide precipitation on the austenitic grain boundary in the HAZ of the high manganese steel crossing subjected to jetting water cooling after the flash Butt Welding, and there is no martensitic transformation in the HAZ of the carbon steel rail subjected to annealing treatment by a special induction heat treatment device, which will avoid the brittleness of the welded joint effectively. The welded joint of the carbon steel rail and the stainless steel insert is annealed at 900 °C for 10 min, which will release the residual stress of the welded joint and thus enhance the strength of the welded joint. It is indicated that the flash Butt Welding of the high manganese steel crossing and the carbon steel rail via the austenite–ferrite two-phase stainless steel insert is feasible.
