Fatigue Life Estimation of Welds on Truck Frames for Rolling Stock Based on Stress Frequency Caused by Service Loads

Abstract

The fatigue strength of weld surfaces on truck frames has been estimated according to the fatigue limit diagram in JIS E 4207, General Rules for Design of Truck Frames for Railway Rolling Stock. However, it is not possible to predict actual fatigue life using this diagram. This study demonstrates the possibility of fatigue life estimation for welds on truck frames based on a modified Miner's rule. In order to estimate fatigue life, three factors are needed: the S-N diagram assumed from the allowable stress in JIS E 4207 or the JSSC fatigue design curve, the relationship between crack occurrence and running distance, and the stress frequency distribution caused by service loads.

Effects of Vehicle Running Conditions on Stress Frequency Distribution of Welds on Truck Frames for Railway Rolling Stock

“…In the case of calculating equivalent stress according to the modified Miner's rule and evaluating fatigue life, as shown in a former report (1) , m can be assumed as 5.5. This numerical value comes from evaluation of rolling stock truck frames using the results of discussion on the distribution situation of stress frequency and the evaluation of fatigue life using previous examples of damage in actual situations (1) (5) .…”