Study On Ultimate Load Of Plates With Sharp Notches

Notches resulted by factors such as openings,processing defects,corrosion,and other factors exsit in various types of mechanical equipments(such as pressure vessels,pipelines).The notches may increase the risk and weaken the strength of the equipments by causing local stress concentration.That is,the notches will harm the safety of the equipments.Therefore,numerical simulation,theoretical analysis and experimental testing methods are used to study the stress concentration and ultimate load of the the notched structures,and the researches in this paper are of obvious significance for ensuring the safety of equipments.Stress distributions at the notches on plates notched at the two sides and plates notched at the center were calculated by using finite element method.The results show that the stress distributions at the notched on the two types of plates were approximately the same,and both were in three-dimensional stress states.According to the analysis of stress distributions,the stress concentration coefficients at the notched tips were calculated by the numerical integration method,and the equivalent stress intensity factors at the notch tips were calculated by the multi-node stress extrapolation method.The results obtained by the finite element method were compared with the theoretical solutions.It was shown that the errors of the finite element results are less than 10%.That is,the finite element method was of high reliability.The finite element method was used to analyze the stress distributions at the notch tip of the central notched plates and the plates notched at the two sides,and the relations between the stress concentration factor and equivalent stress intensity factor with the notch geometric parameters were obtained.Based on the failure assessment diagram used in structures containing crack defects,a method for predicting the ultimate load of a plate with a notch was proposed.This method was used to predict the ultimate loads of plates notched at the two sides and plates nothed at the center.The ultimate loads by this method were compared with the experimental results.It was found that the maximum error of the ultimate loads between the two methods was 16.87%,which indicated that the method proposed in this paper was of higher reliability.The influences of the notch radius and the notch angle on the limit loads of plates notched at the two sides,and the influence of the notch width and the notch angle on the limit loads of the plates nothed at the center,are analyzed and summarized,by using the method proposed in this paper.