| Pressure vessels are widely used in nuclear,chemical and other fields,and are developing towards multi-functional,specialized and large-scale.In many areas of scientific research,pressure vessels play a very important role,and their working environment is more complex.Therefore,in order to ensure the safe and reliable operation of the equipment,it is necessary to evaluate the safety and reliability of pressure vessels.In this paper we discuss the degradation of mechanical properties of pressure vessels containing defects based on probabilistic analysis and numerical methods.Firstly,based on the weight function method,the integral expression of the stress intensity factors at the tip of the axial surface crack in the cylinder of the pressure vessel under two different working conditions is derived.The correctness of the method is verified by comparing with previous works.Secondly,the effects of internal pressure,inertia force and temperature difference on the stress intensity factors at crack tip are studied.According to the coupling of internal pressure and inertia force,the probabilistic fracture mechanics analysis of pressure vessel with axial surface crack is carried out,and the failure probability of pressure vessel is calculated by Monte-Carlo method.The results show that the influence of pressure variation on the stress intensity factor is far greater than the inertia force,and it plays a leading role in the failure of the pressure vessel containing the axial surface crack.In addition,the temperature difference inside and outside the cylinder of the pressure vessel has a significant influence on the stress intensity factor of the crack tip.Finally,based on the finite element modeling,the natural frequencies of pressure vessels at different crack depths and the natural frequencies of the pressure vessels at different crack locations are calculated.The results show that the natural frequency of the pressure vessel decreases with the increase of the crack depth,and the stiffness of the cylinder decreases when the axial crack of the inner surface is near the center of the cylinder,that is,the existence of the crack reduces the safety of the cylinder,and the most dangerous crack is in the middle.These studies can provide reference for fracture calculation and reliability analysis of pressure vessels. |
