Fatigue Strength Analysis Of Tension-Shear Spot Weld Specimen Based On Structure Stress

Resistance spot welding technology is widely used in various industry fields including automobile, aerospace, nuclear energy, electronics, light industry, household appliances, dueing to its operation simplicity, low cost and high efficiency. Spot structure is often under multiaxial stress and complex loading conditions, so its mechanical analysis is very difficult.In many fatigue studies, two level load is often used as the basic form of the complex loading conditions, so the fatigue studies of spot weld structure have very important practical significance.In this paper, a single spot welding specimen which is made of ST12 low carbon steel plate is chosen researched. The spot welding specimens are set on MTS fatigue testing machine with constant amplitude and two-level loading test. And spot welding joints metallographic are tested, comparison and analysis of the performance of six kinds of fatigue feature parameters correlated single, double spot weld fatigue life, a fatigue life prediction mathod for fatigue life of spot weld specimen under two-level loading is given based on GA-BP neural networks. The paper mainly studied the following aspects:1. By combining Dong’s structure stress method with Rupp’s structure stress method, this paper proposes a new fatigue feature parameter be called simplified structural stress. It’s proven by experimental data that this parameter can effectively correlate the fatigue life of single, double spot weld sample, and reduce the scattering of fatigue life data.2. Carrying on linear regression of single, double spot weld fatigue life by Kang’s structure stress, Sheppard’s structural stress, equivalent stress intensity factor etc. respectively, comparison and analysis of the performance of six kinds of fatigue feature parameters correlated the fatigue life of single, double spot weld sample.3. GA-BP neural network is used to simulate fatigue life of spot weld specimen under two-level loading in this paper.The results indict simulated results match experimental data well and small error is achieved.Through the whole process simulation for fatigue life of spot weld specimen under two-level loading it proves that this method can be used to simulate the whole Proeess and reflect the law of fatigue life of spot weld specimen under two-level loading.