Contact fatigue life testing and analysis of remanufactured components

• Main Author: Teo, Shaun Han Wei
• Other Authors: Zhou Kun
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/64014
• Institution: Nanyang Technological University

This report covers a project on contact life fatigue testing and analysis of the remanufactured components. The main objective of this report is to identify the behaviour of the contact fatigue life of the remanufactured components when subjected to a series of different loading conditions. In this project, contact life fatigue experiments were performed on the 4340 alloy steel specimens using a range of different stress loadings. Results were gathered to identify the lifespan of the specimens and also to plot the S-N curves. Further observations were performed on the fracture surfaces of the specimens to identify the effects of contact fatigue. The features of the fracture surfaces indicated that the location of the crack initiation is at the corner surface of each specimen and the type of fracture is mixed mode; i.e. brittle fracture and ductile fracture, represented by a flat fracture surface and a sheared fracture surface respectively. The main difference between the contact and no contact fatigue fracture surfaces is the number of shear lips; i.e. the fracture surface of the contact specimen has two shear lips while the one with no contact has only one. The maximum contact pressure and maximum shear stress generated by the contact loading were calculated using Hertz theory. Further calculations were performed to find the values of the principal stresses and principal shear stresses. The values of these stresses were found to be higher in the contact fatigue experiments. This increase in the magnitude of the stresses experienced in the contact fatigue experiments can be used to account for the decrease in the fatigue life of the contact specimens.