Research On Fatigue Life Prediction Method Of Welded Structure Based On Master S-N Curve Method And 3D Visualization Technology

Up to now,most of the fatigue life assessment methods of welds in welded structures have some limitations,it often encounters welded joint type is difficult to classify,weld stress concentration is difficult to determine and other issues in predicting the fatigue life of welds in complex welded structures,which result in inaccurate predictions of weld fatigue life.The master S-N curve method predicts the weld fatigue life by using a master S-N curve and computing the grids-insensitive structural stress,based on massive fatigue test and fracture mechanics theory.It greatly improves the accuracy of fatigue life prediction by us.The fatigue life evaluation of welds in complex welding structures always produces massive discrete data,which is difficult to be arranged or handled,because of a large number of welds and weld nodes.Therefore,it is difficult to efficiently obtain effective information from the evaluation.However,the interactive processing and analysis of calculation result data can be realized by using visualization technology to present the result data in geometric figures or images.The expression of the calculation results will be intuitive and the comprehensive information will be also reflected.This paper combines the weld fatigue life assessment theory of master S-N curve method with the visualization method to form a weld fatigue life computing and visualization system base on master S-N curve method for realizing the fatigue life calculation of the weld in the welded structure and the color nephogram display of the fatigue life calculation results through the intensive study of them.The specific contents of research are as follows.(1)Firstly,it studies the fundamental theory of master S-N curve method.The calculation program of the weld fatigue life is established using the C++ language programming,according to the weld fatigue life computational method of master S-N curve method.Secondly,it extracts the nodal force and the nodal moment of the weld by fetching the ANSYS results data.Meanwhile,it calculates the weld fatigue life with master S-N curve method.Finally,it calculates the weld fatigue life of finite element model with program and outputs calculation results.Besides,the results are compared with results calculated by professional computing software of the weld fatigue life for verifying the accuracy of the results calculated by program.(2)It studies C++ and OSG for writing the visualization program of calculation results,and realizes the display and establishment of the welded structure finite element model and the color nephogram of the weld fatigue life calculation results.(3)It studies and establishes the computing and visualization system of master S-N curve method of weld fatigue life which integrates the calculation program of weld fatigue life and the visualization program of calculation results.Meanwhile,it takes the C70 E wagon car body as the application example to calculate the weld fatigue life,to make the color nephogram of calculation results and to show the practical application effect of the system.The weld fatigue life computing and visualization system base on master S-N curve method in this paper has the function of 3D visualization which is not contained in other traditional weld fatigue life calculation software base on master S-N curve method,such as FE-WELD.The software becomes more convenient and smooth due to the visualization interaction of 3D model.The calculation results,examined by traditional weld fatigue life calculation software,show that the calculation results of weld fatigue life are accurate with small relative error.Meanwhile,the color nephogram of calculation software,made through visualization,has the smooth color transition and can correctly reflect the distribution of the calculated results in the weld of the finite element model.