Abstract: Fatigue limits and damage are investigated experimentally on the grade B cast steel for Chinese railway freight car bogie frame. Small sample up-and-down test method is employed for the study. Results reveal that fatigue cracks are initiated mostly from the cast flaws and shrinkage cavities. The fatigue cracks grow with river like flowers and many sub-cracks. Distinct tough eddies are distributed on the fracture surface. Maximum likelihood method is applied for the probabilistic measurement of the fatigue limits, in which the limits are defined as the fatigue strengths following normal distribution at an expected fatigue life. The statistical parameters are estimated by the likelihood function meeting the definition. A comparison analysis is carried out to the existing conventional, DIXON-MOOD and ZHANG-KECECIOGLU methods. The maximum likelihood method is verified to be only approach meeting the definition. Others, especially the Zhang-Kececioglu approach, have bigger deviational predictions.

Key words: Bogie, Cast steel, Fatigue limit, Probabilistic analysis, Railway