Reliability Analysis And Bayesian Updating Of Edge-crack Structures Based On XFEM

Due to the defects in manufacture and the cyclic loads,the mechanical structures generate cracks easily.The presence of cracks may lead to decreasing of structural intensity and reliability.Under the cyclic loads,the initial cracks will grow until the structure break to failure.Therefore,it is very important to study the reliability and reliability based sensitivity of edge-crack structures in engineering.Furthermore,products' initial performance tests and monitor process can obtain some datum,Bayesian theory can combine those few datum to update the products' evaluations effectively,making the results more accurate.Thus,Bayesian updating has a significant value to study.The thesis mainly studied on an 18Cr2Ni4WA plate that has an initial edge-crack.Established a XFEM model by the Extend Finite Element Method(XFEM),studied the reliability and reliability based sensitivity of edge-crack plate.Besides,obtained few inspected datum and updated the analysis results of edge-crack plate using the Bayesian method and Markrov Monte Carlo Method(MCMC).Details are as follows:Firstly,based on the XFEM theory,programed with MATLAB,established the XFEM model of edge-crack plate.Assuming that the initial crack do not grow,studied the influence of random parameters to the stress intensity factor(SIF)of edge-crack plate.Combined with the reliability theory,used the Kriging model to approximate the XFEM results,analysed the reliability and reliability based sensitivity of the static edge-crack plate.Obtained the important parameters as well as the sensitivity to the reliability of edge-crack plate.Then,conducted the simulation of crack grow based on the XFEM model.Analysed the factors that influence the crack grow and its law.Also,studied the gradual dynamic reliability and reliability based sensitivity,obtained the time-varying results.Finally,combined the prior distribution of random parameters with observations of void's radius as well as initial crack length,updated the static reliability and reliability based sensitivity of edge-crack plate.Furthermore,combined the datum of crack length with the prior information,updated the gradual dynamic reliability and reliability based sensitivity.Results lead to a more accurate confidence level,and better in line with engineering practice.