Evaluation Of Multiaxial Low-Cycle Fatigue Life Prediction Model

The structural members which are adopted in Modern industrial construction, railway bridge and mechanical engineering field mostly are under complex stress-strain state in the course of their work. Currently, people have achieved a lot success in the research uniaxial low cycle fatigue theory and experiment.However, for the research of low cycle multi-axial fatigue theory and life prediction model is still not perfect, A lot of life prediction model still lacks the broad support of experimental data. Therefore,more deeply experimental study for forecasting model can provide more data to support or consult for the actual structural fatigue design.In this paper, HRB335 steel tube specimens are loaded under different strain amplitude control of low cycle fatigue tests of several single- path at room temperature conditions. And we further carried out the experiments by a series of specimen of two-stage in variant strain amplitude and two-stage variant path to investigate the influence of cumulative damage to fatigue life.The low cycle fatigue test data of this paper is used to evaluate the methods such as equivalent strain method and several critical surface methods to the life prediction models in engineering fields, The results exhibit that when the non-proportional and multi-axial load path are taken, the experimental fatigue lives are differ remarkable from the prediction by effective strain method. The predictions by the methods respectively suggested by KBM, Socie and Zhang Xiaoyuan are found reasonable comparing with experimental results.And the result by Zhang Xiaoyuan’s stretch factor model is the best.The fatigue experiments of amplitude change and path change are performed.Through these experiments,the linear and nonlinear fatigue life prediction cumulative damage model are validated.The results show that the cumulative damage model,Miner linear model,which is widely used in engineering, the tests in two-stage variable amplitude can give reasonable results for residual fatigue life prediction under the condition of uniaxial loading, but for the two-stage non-proportional loading path,the prediction bias dangerous.And the Bilinear’s model,Manson’s nonlinear model and Zhang Xiaoyuan’s nonlinear model,they can applied to life prediction for two-stage proportional loading path fatigue experimental and results are found significantly better than Miner linear model.And the Zhang Xiaoyuan’s model is closest to experiment value.