Finite Element Analysis On Bending Fretting Of Axle Material

Fretting is defined as a small displacement oscillatory motion between two surfaces in contact. The displacement oscillatory is usually in micron scale. The fretting is usually divided into three categories:fretting wear, fretting corrosion and fretting fatigue. Fretting fatigue is the most common and serious case of fretting damage, and widely occurs in various mechanical components. Fretting fatigue is often accompanied by a cyclic external stress. The fretting, a tiny slippage caused in the contact area will lead to the wear and damage of contact surfaces, which thereby reduces the fatigue strength of components and accelerate the initiation and propagation of fatigue crack. Finally, the fretting can greatly reduce the fatigue life of components, and even cause a catastrophic fracture of the component. However, most of researches for fretting damage are done under the tension and compression conditions. The fretting behavior of materials has not been extensively observed under the bending conditions. In this case, the stress-strain distribution in the tested materials is more complex. Previous studies showed that the bending fretting fatigue is the main failure mode for high-speed railway axle. Therefore, it is extremely necessary to carry out the research of bending fretting damage, and the obtained results will be significant for the development of high-speed and heavy rail transportation, as well as other areas of engineering.This paper focuses on the bending fretting damage, and mainly contains the following topics:1. Experimental study on uniaxial ratcheting of LZ50 steel under stress-controlled cyclic loading.2. Predict the ratcheting behavior of LZ50 steel by employing a cyclic elastic-plastic constitutive model originally proposed by Abdel-Karim and Ohno (2000), simplified as the Ohno-Karim model.3.Based on the finite element software ABAQUS and the UMAT subroutine of the Ohno-Karim model, simulate the distribution and evolution rules of stress-strain field in the stick zone and slip region, and discuss the effect of normal loads, cyclic loading and friction coefficient on the bending fretting damage and the characteristics of fretting fatigue. The evolution of ratcheting and its effect on the bending fretting is also considered in this work. Finally, predict the fatigue crack initiation location under bending fretting by using the G and Ruiz criterion.