Welding residual stress is one of the main concems for fabrication and operation of steel structures due to its potential effect on structural integrity.This paper focuses on the effect of welding residual stress on t...Welding residual stress is one of the main concems for fabrication and operation of steel structures due to its potential effect on structural integrity.This paper focuses on the effect of welding residual stress on the ductile crack growth resistance of circumferentially cracked steel pipes.Two-dimensional axi-symmetry model has been used to simulate the pipe.Residual stresses were introduced into the model by using so-called eigenstrain method.The complete Gurson model has been employed to calculate the ductile crack growth resistance.Results show that residual stresses reduce the ductile crack growth resistance.However,the effect of residual stresses on ductile crack growth resistance decreases with the increase of crack growth.The effect of residual stress has also been investigated for cases with different initial void volume fraction,material hardening and crack sizes.展开更多
The accuracy of fluctuating pressure test in wind tunnel is affected by the tube system. By employing contradistinctive experimental method, systematic study was conducted to investigate the effects of the tube system...The accuracy of fluctuating pressure test in wind tunnel is affected by the tube system. By employing contradistinctive experimental method, systematic study was conducted to investigate the effects of the tube system on fluctuating pressure. The analyzed tube system parameters include tube length, inside diameter, curvature, deflection angle, thickness, material, restrictor length,restrictor inside diameter, and restrictor place. It is found that all the tube system parameters mentioned above except tube curvature have non-negligible effects on fluctuating pressure. Based on the research results, test methods were presented for the fluctuating pressure measurement in low-speed wind tunnel, which can obviously improve the data accuracy but not lose test efficiency. The effectiveness of the method is verified by the wind tunnel test.展开更多
Deposition patterns can significantly affect residual stress distribution in additive manufacturing processes.In this paper,a novel pattern,the S-pattern,is proposed for the metal additive manufacturing process.The fi...Deposition patterns can significantly affect residual stress distribution in additive manufacturing processes.In this paper,a novel pattern,the S-pattern,is proposed for the metal additive manufacturing process.The finite element method is used to study the temperature field and the stress field of a cuboid structure under the S-pattern and five other representative patterns:zig-zag,raster,alternate-line,in-out spiral,and out-in spiral.The results show that the S-pattern achieves the lowest values of both equivalent residual stress and maximum principal residual stress,and the warpage of the S-pattern is close to that of counterparts.By analyzing the temperature and stress fields under all patterns,it is found that the residual stress distribution is determined by the uniformity of temperature distribution which is correlated with the peak temperatures of corners.The equivalent residual stress and the maximum principal residual stress are inversely correlated with the average peak temperature and the minimum peak temperature of corners,respectively.These correlations between temperature and residual stress provide an effective approach to evaluate the residual stress of different patterns and guide the deposition process in practice.展开更多
基金The financial support from the Research Council of Norway(PETROMAKS Contract No.192967/S60),Statoil,Gassco,Technip and EFD Induction through DEEPIT project is gratefully acknowledged.
文摘Welding residual stress is one of the main concems for fabrication and operation of steel structures due to its potential effect on structural integrity.This paper focuses on the effect of welding residual stress on the ductile crack growth resistance of circumferentially cracked steel pipes.Two-dimensional axi-symmetry model has been used to simulate the pipe.Residual stresses were introduced into the model by using so-called eigenstrain method.The complete Gurson model has been employed to calculate the ductile crack growth resistance.Results show that residual stresses reduce the ductile crack growth resistance.However,the effect of residual stresses on ductile crack growth resistance decreases with the increase of crack growth.The effect of residual stress has also been investigated for cases with different initial void volume fraction,material hardening and crack sizes.
基金supported by the Pre-research Fund of Vibration and Noise Control Technology (No. 51334060101)
文摘The accuracy of fluctuating pressure test in wind tunnel is affected by the tube system. By employing contradistinctive experimental method, systematic study was conducted to investigate the effects of the tube system on fluctuating pressure. The analyzed tube system parameters include tube length, inside diameter, curvature, deflection angle, thickness, material, restrictor length,restrictor inside diameter, and restrictor place. It is found that all the tube system parameters mentioned above except tube curvature have non-negligible effects on fluctuating pressure. Based on the research results, test methods were presented for the fluctuating pressure measurement in low-speed wind tunnel, which can obviously improve the data accuracy but not lose test efficiency. The effectiveness of the method is verified by the wind tunnel test.
基金funded by the Chinese Scholarship Council and the Research Council of Norway through the Petromaks2 program(Project No.281927)the BIA Program(Project No.269558)。
文摘Deposition patterns can significantly affect residual stress distribution in additive manufacturing processes.In this paper,a novel pattern,the S-pattern,is proposed for the metal additive manufacturing process.The finite element method is used to study the temperature field and the stress field of a cuboid structure under the S-pattern and five other representative patterns:zig-zag,raster,alternate-line,in-out spiral,and out-in spiral.The results show that the S-pattern achieves the lowest values of both equivalent residual stress and maximum principal residual stress,and the warpage of the S-pattern is close to that of counterparts.By analyzing the temperature and stress fields under all patterns,it is found that the residual stress distribution is determined by the uniformity of temperature distribution which is correlated with the peak temperatures of corners.The equivalent residual stress and the maximum principal residual stress are inversely correlated with the average peak temperature and the minimum peak temperature of corners,respectively.These correlations between temperature and residual stress provide an effective approach to evaluate the residual stress of different patterns and guide the deposition process in practice.
