Influence Of Welding Residual Stress On Ultimate Strength Of Pressure Structure

Pressure structure is the key parts of deep sea equipment because it affects the safety and credibility of the equipment.Welding process is the important factor that influences structure manufacturing quality and production cycle and cost.Owing to welding,residual stress is inevitable and affects the bearing capacity of pressure structure.Therefore,the research on the effects of residual stress on bearing capacity of has important theoretical significance and practical value.Residual stress of welding plank is measured by X-ray in this paper to acquire the law of surface treatment for residual stress.Residual stress of welding plank is measured by X-ray to acquire the residual stress distribution law which is coincident with the numerical simulation results.The numerical simulation results of multi-pass welding show that maximal welding stress appears at the boundary between the HAZ and parent metal within the material.As a typical pressure structure,the spherical hull with a radius of 1000 millimeter is designed and manufactured by welding,and actual initial defection、thickness and residual stress of spherical hull are measured.The analysis results of different methods show that the calculation result based on initial imperfection of test model is in better agreement with the experiment result than other methods.In this paper,a program of loading welding residual stresses is done with APDL of ANSYS and the effect of residual stress on ultimate strength of pressure spherical hull and the control standard of residual stress are investigated.By contrasting relative stress and absolute stress,this study on evolvement rule of residual stress in the process of loading shows that residual stress always exists and raises the level of the structure stress with superposition of working stress which lead to structure damage in advance.On this basis,the ultimate strength of a number of spherical hulls with different thickness-radius ratio and residual stress is studied,the results indicate that,when the residual is lower than 0.3s?,residual stress has no effect on ultimate strength;however,the ultimate strength decreases by 10% to 20% with residual stress reaching material yield strength.The effect of residual stress on ultimate strength increases at first and then decreases with the increase of thickness-radius ratio.