In this study, residual stresses in heat treated specimen were measured by using ESPI (Electronic Speckle-Pattern Interferometry) combined with the hole-drilling method.The specimen, made of SUS 304 austenitic stainle...In this study, residual stresses in heat treated specimen were measured by using ESPI (Electronic Speckle-Pattern Interferometry) combined with the hole-drilling method.The specimen, made of SUS 304 austenitic stainless steel, was quenched and water cooled to room temperature.Numerical simulation using a hybrid FDM/FEM package was also carried out to simulate the heat treatment process.As a result, the thermal stress fields were obtained from both the experiment and the numerical simulation.By comparision of stress fields, results from the experimental method and numerical simulation well agreed to each other, therefore, it is proved that the presented experimental method is applicable and reliable for heat treatment induced residual stress measurement.展开更多
Local postweld heat treatment (PWHT)is usually performed when it is impractical to heat treat the whole vessel in a furnace, Many factors have an influence on PWHT procedures, such as size of the pipe,heated widths, i...Local postweld heat treatment (PWHT)is usually performed when it is impractical to heat treat the whole vessel in a furnace, Many factors have an influence on PWHT procedures, such as size of the pipe,heated widths, insulation conditions, heating rates soak temperatures and hold times, material composition etc,. However up to now the influences these factors have on PWHT are not very clearly understood and different criteria for sizing the parameters can be found in different codes. This study provides a direct method to assess the effectiveness of local PWHT.An axisymmetrical model was used based on the thermal-visco-elastic-plastic Finite Element Method with the consideration of creep phenomena. By using this method both temperature and stress distributions can be simulated during whole local PWHT history. The computation results of temperature distributions and the strain histaries during local PWHT are compared with the experiments, and good agreements are obtained, Investigations show that the thermal stresses induced by local PWHT are much affected by creep behavior and the changes of Young’s Modulus. The study of stress relief history shows that the stresses decrease quickly in the heating stage, then decrease slowly according to creep law in the hold stage and then studdenly increase when the cooling stage starts. The study shows the possibility that through a series of computations the effects of many factors can be assessed and the optimum parnmeters can be found. Compared with the heated widths based apon some applicable codes, it is found that a heated area of 2.5 on either side of the weld seems more reasonable.展开更多
文摘In this study, residual stresses in heat treated specimen were measured by using ESPI (Electronic Speckle-Pattern Interferometry) combined with the hole-drilling method.The specimen, made of SUS 304 austenitic stainless steel, was quenched and water cooled to room temperature.Numerical simulation using a hybrid FDM/FEM package was also carried out to simulate the heat treatment process.As a result, the thermal stress fields were obtained from both the experiment and the numerical simulation.By comparision of stress fields, results from the experimental method and numerical simulation well agreed to each other, therefore, it is proved that the presented experimental method is applicable and reliable for heat treatment induced residual stress measurement.
文摘Local postweld heat treatment (PWHT)is usually performed when it is impractical to heat treat the whole vessel in a furnace, Many factors have an influence on PWHT procedures, such as size of the pipe,heated widths, insulation conditions, heating rates soak temperatures and hold times, material composition etc,. However up to now the influences these factors have on PWHT are not very clearly understood and different criteria for sizing the parameters can be found in different codes. This study provides a direct method to assess the effectiveness of local PWHT.An axisymmetrical model was used based on the thermal-visco-elastic-plastic Finite Element Method with the consideration of creep phenomena. By using this method both temperature and stress distributions can be simulated during whole local PWHT history. The computation results of temperature distributions and the strain histaries during local PWHT are compared with the experiments, and good agreements are obtained, Investigations show that the thermal stresses induced by local PWHT are much affected by creep behavior and the changes of Young’s Modulus. The study of stress relief history shows that the stresses decrease quickly in the heating stage, then decrease slowly according to creep law in the hold stage and then studdenly increase when the cooling stage starts. The study shows the possibility that through a series of computations the effects of many factors can be assessed and the optimum parnmeters can be found. Compared with the heated widths based apon some applicable codes, it is found that a heated area of 2.5 on either side of the weld seems more reasonable.
