Estimating Peening Intensity

Author:  Dr. David Kirk | Coventry University
Source:  The Shot Peener magazine, Vol 38, Issue 4, Fall 2024
Doc ID:  2024033
Year of Publication:  2024
Abstract:  
INTRODUCTION The estimation of peening intensity is an essential tool for shot peeners. Its magnitude is normally estimated using an Almen strip data set. This data set comprises the arc heights of several Almen strips that have been shot peened for different periods of time using the same shot stream. Plotted as arc height versus peening time then yields a curve. The curve, commonly known as a “Saturation Curve”, is used to estimate the peening intensity. Specifications generally require the determination of a point on the curve such that “A doubling of the peening time corresponds to a 10% increase in the arc height.” Computer-based techniques enable this determination to be obtained objectively. Fig.1 illustrates one such technique in action, deriving 14.24 as being the peening intensity. Computer-based curve fitting requires prior knowledge of an appropriate equation. Initial studies indicated that exponential equations were appropriate, with either 2, 3 or 4 parameters, giving increasingly close fits to data. This led to the “Solver Suite” of programs. A later equation has been introduced via a French specification. It is very important to note that the peening intensity of a shot stream varies within the stream. This feature is illustrated by fig.2 showing variation within a cross-section.