PSI - Issue 22

S.M. Xie et al. / Procedia Structural Integrity 22 (2019) 353–360

356

4

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

(4)

max      

min

5) The stress factor of the welded joint is evaluated by calculating the ratio of the stress variation amplitude to the allowable stress variation amplitude corresponding to the FAT grade of the welded joint, and then the stress state level of the welded joint can be determined. 3.2 Proceduralization of evaluation methods The fatigue evaluation program based on IIW-2008 standard nominal stress is written in parameter design APDL language. The analysis program is mainly composed of four sub-modules, and the steps of implementation process are as follows: 1) Weld classification module: according to the geometry, load-bearing mode and type of welded joints, the welds are divided into different FAT grades; 2) Node parameter extraction module: use the *GET statement to access the ANSYS database, the principal stresses and six stress components of weld joints in fatigue calculation conditions are extracted from ANSYS calculation results *.rst files; 3) The stress parameter calculation module: calculate the maximum principal stress of the weld joint and determine the direction cosine by the direction cosine function DIRCOS of the vector operation function *VFUN, the formulas (3) and (4) are used to calculate the minimum principal stress and principal stress variation range of the weld joint, and the stress factor of the weld joint is determined; 4) Calculation result output module: the fatigue analysis result such as the principal stress variation range and the stress factor of the weld joint is evaluated and stored in the form of a *.txt file by creating a macro file statement *CFWRITE. 4. Evaluation of welded joints stress state level of aluminum alloy EMU body The finite element analysis model of the vehicle body is the basic guarantee for the simulation analysis. Only on the reliable analysis model, the stress level of welded joint of vehicle body can be effectively studied[7]. Using IIW 2008 and DVS1608-2011 standards, the stress state level of welded joint of aluminum alloy EMU body of was considered, the process is shown in Figure .1.

Fig.1. The assessment flow chart of weld stress state level of aluminum alloy EMU body