Effect of corrosion on the fatigue life of aged EMU under fatigue loading

It is very useful to know in advance the remaining life of long life span structure for the reasons of safety assurance or setting up cost effective overhaul strategy. A railroad car is designed to have a very long life span over 40 years, and therefore corrosion and fatigue damage on the major components of the structure are known to big problems. The fatigue damage is accelerated with the growth of corrosion due to the falling-off in strength. For this reason, the railroad industry performs diagnosis of the remaining life of aged railroad cars considering fatigue and corrosion effects on the structure. In this study, the remaining fatigue life of aged railroad cars was calculated by considering the effectivity of corrosion on the static and dynamic strength of the car-body. For this purpose, a series of finite element analyses was performed to quantify the effectivity of corrosion. And the results were implemented for the fatigue life prediction of aged car bodies. The fatigue life was reduced by about 20% at the corrosion thickness of 0.3 mm, the measured thickness on the 23 years aged car, and about 40% at the corrosion thickness of 0.72 mm, the predicted thickness on the 40 years aged car, compared to the base thickness of the car-body. Therefore it can be concluded that consideration of the corrosion effect is very important in prediction of the remaining fatigue life.