Virtual Fatigue Test Method for the Fatigue Life Prediction of Welded Structure in Railway Vehicle Based on the Virtual Strain Gauge Technology

摘要

Under the long-term dynamic external load, no matter of subway, or high-speed EMU, or welded bogie frame, or welded aluminum body, its fatigue failure in such structures will always happen in the weld line unless the base metal itself has some fatigue defect. There are two types of the fatigue failure on weld line, the first failure mode is happened in weld toe, the second one is happened in weld root. Once the fatigue failure happens in weld line, which could cause serious accident. Therefore, it is particularly important to predict the fatigue life for each weld line in the design stage. However, it is extremely difficult to predict the fatigue life for each weld line at the design stage by traditional nominal stress method while structure is very complex. Based on the famous Master S-N Curve Theory invented by Professor Dong Pingsha, which has been accepted by ASME standard in 2007. A new virtual strain gauge technology is proposed in this paper. Based on this new technology, structural stress located at each weld line, could be conveniently obtained, which is very important for the fatigue life prediction of each weld line according to the ASME standard. In order to do it, virtual strain gauge sensors will be set nearby each weld line according to certain rules in a FEA model, then taking the stress results at the positions of virtual strain gauge sensors and calculating the structural stresses in each weld line based on some interpolation extrapolation formula. Finally, the fatigue life of each weld line can be calculated using the formula from Master S-N Curve Theory, and its engineering application is economical and convenient.