Technical condition assessment of metallic structures based on computer modelling

Objective – determination of the causes of structural failure using computer modelling based on stress-strain state analysis. The initial data for the computer modelling included photographic material from the site of the accident, design documentation and technical specifications of the vehicle (loaded with timber) and the hydraulic shears. The software packages used were APM WinMachine, NX and Autodesk Inventor. The Finite Element Method in displacements was selected as the primary research method. Various crack initiation scenarios were considered, computer models were developed and an engineering analysis of the vehicle frame structure was performed. Computer modelling also identified the most likely cause of failure of the upper part of the hydraulic shear – exceeding the critical stress level (345 MPa, the yield strength of the 09G2S steel) for the material. The studied structures were characterised by complex geometries and a variety of loads acting on them. Welded seams were considered in their modelling. Geometric models of the structures, including the welded seams, were created in the software packages using the finite element method. On this basis finite element models of the structures were developed and analysed. As a result of the stress state calculations for the hydraulic shear, the maximum stress value (391 MPa), which is significantly higher than the yield strength, and the stress localisation for different loading cases were determined. Analysis of the results of the strength and stiffness calculations for all the models developed were used to test the hypotheses considered in the software packages. This made allowed identification of the most probable causes of failure. The developed methodology, along with the computer models and the results obtained, can be applied in the engineering and technical analysis of a variety of technical objects.