Fatigue Life Prediction Of A Number Of Ways

Fatigue life prediction is important for fatigue design. Increasing prediction precision and developing prediction methods are very significative.In this paper, the concept of fatigue process zone is used for calculating average strain substituting general strain in Manson-Coffin equation. Fatigue life of LY12CZ plate with a central hole was predicted using average method. The results were accurate more than Neuber method.According the viewpoints of energy dissipation and accumulation in fatigue process, dissipated energy density and critical dissipated energy density were defined to describe material fatigue characteristic. Experiments were made to determine the dissipated energy density and critical dissipated energy density of A3 steel, LY12CZ and GH4169. The method for fatigue crack initiation life was established using critical dissipated energy density criterion and was used to predict the fatigue crack initiation life of A3 steel, LY12CZ and GH4169. The results indicated this method would come to good effect.From the results of experiments on A3 steal, residual strains increased with cycles at a linear ratio in fatigue process. The critical value is exists. Prediction for fatigue life of A3 steel plate with a central hole using critical residual strains criterion, the results were acceptable. Residual strains criterion has a good application foreground in practicality because residual strains can been determined by experiment method expediently than general strain range. But for LY12CZ, the residual strains criterion is not practicable from the results of similar experiments.Damage on tip of crack is the result of energy dissipation in materials. The researches of fatigue crack propagation based on dissipated energy density are more significative. For GH4169, respectively at room temperature and 450℃, experiments and calculation methods determined the fatigue crack propagation equation. The trends of results are coherent with equation.