Experimental investigation of effect of shot peening on various curvature and thickness

• Main Author: Muhammad Azrul Shukri Azmi
• Other Authors: Seah Leong Keey
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150667
• Institution: Nanyang Technological University

Shot peening process induces compressive stresses in a material to enhance the fatigue life. The output of Intensity from the process can be correlated to the amount of residual stress induced and together with coverage, they affirm the consistency of the shot peening process. Actual peened components are exposed to peening from all sides. In addition, these components that are peened can be of very thin thicknesses, and the thicknesses will vary throughout the component. In the current applications, there are limitations in accurately determining the residual stress and its effects on various thickness. Understanding this prove to be critical, especially in the Aerospace industry, where adhering strictly to the specifications are needed for safety purposes. This motivated this research on determining the effects of peening on various thicknesses, where peening of single sided and double sided IN718 coupons were compared in terms of its residual stresses, hardness and microstructure. Coupons of various thickness were shot peened at an Intensity of 0.142mmA and full coverage. The Precision Real-time Instrument for Surface Measurement (PRISM) was used to quantify the compressive residual stress and its effective depth across the various thickness. Subsequently, samples were grinded, polished and etched and hardness testing was conducted on both the peened surface as well as cross sections. Optical Microscope (OM) was then used for microscopic analysis. The research established a correlation between the maximum effective residual stress depth together with the Hardness value (HV) along the cross-section of the samples. There were no significant changes of HV across the surface as well as cross-sections for all thicknesses, and the HV obtained were generally similar. Minor microscopic changes were also seen near to the peening surface with the OM. However, other than the minor dislocations of microstructure grains near the surface, significant changes of microstructures of various sample thicknesses could not be seen due to the limitations OM. Disclaimer: Due to the Covid-19 restrictions and the reduced usage of laboratory and equipment in ARTC, the scope of this project was reduced to studying the effects of shot peening on various thickness of IN718 material.