Endurance limit determination in porous materials

The theory describing the fatigue mechanism in elasto-plastic material containing pores or inclusions has been developed. An attempt at quantitative determination of the effect of endurance limit reduction by analysis of sizes of plastic zones formed near the inclusions, and their cracking has been -done. The geometrical configuration, consisting of round, horizontal, vertical and angular elliptical inclusions from which a nucleating crack emerged, was considered, and the stress intensity factory of such configurations was analysed. Based on threshold value of 6K below which crack propagation ceases, the critical value of loading stress was determined. Finite element technique was used to obtain theoretical results. A source code developed by Owen and Hinton for solving elastoplastic applications using finite element concept was used for solving the problem. Experimental analysis was done using photoelasticity method. Theoretical results were compared with results from experiments, showing quite good agreement.