ELASTICITY: The Missing Link

Author:  Dr. David Kirk | Coventry University
Source:  The Shot Peener magazine, Vol 38, Issue 2, Spring 2024
Doc ID:  2024014
Year of Publication:  2024
Abstract:  
INTRODUCTION In spite of its importance, elasticity is rarely even mentioned in peening articles. This rarity justifies it being considered as a “missing link”. This article is divided into two parts. Part A covers the relationship between elasticity and induced indentations. Part B deals with effect of elastic modulus, E, on the deflection of shot-peened Almen strips. PART A INTRODUCTION Elasticity is a very important property for shot peening. It’s magnitude is the link that controls the proportion of a flying shot’s kinetic energy that is used to produce indentations in components. When a flying shot particle strikes a component part of its kinetic energy, ½mv2, is absorbed by the component and part is retained as the kinetic energy of the rebounding particle. This important principle is illustrated in fig.1. Imagine a ball bearing being dropped from a height of 1 m onto a steel plate rebounding to the half-height of 0.5 m. This ratio has been shown, by experiment, to be similar to when steel shot strikes steel components. Two inter-related parameters indicate the degree of elasticity for materials. These are “Coefficient of Restitution” and “Elastic Modulus”. These parameters and their relevance to shot peening form the subject of this article.