Shot peening is a basic surface treatment process for metal parts. Shot peening is a process in which a stream of high-energy projectiles performs work on the surface of the part. The result of the work done by the projectile is to leave pits on the surface. As the shot blasting time increases, there are more and more pits and the coverage rate is getting bigger and bigger. Figure 1 illustrates the process of increasing coverage. With the extension of the shot peening time, the growth rate of the coverage rate decreased, following the "law of diminishing marginal utility." In engineering applications, an important practical requirement is to use a relatively economical time to meet the coverage requirements. As the coverage increases, a layer of residual compressive stress will be generated on the surface of the part. This residual compressive stress layer is the "magic skin" that can increase the service life of parts.

Figure 1 Typical coverage/shot peening time curve

    The shot peening beam itself must have a specified intensity level, such as N254 (at a special shot peening time T, that is, saturated Time, the N-type Almen test piece is bent 0.254mm after shot peening), which is a parameter to quantify the strength of shot peening. However, there is currently no parameter that quantifies the ability of the shot peening beam to reach the target coverage.

   This article focuses on the following content:

    (1)The ability of pellets to do work;

    (2) The formation process of the pit;

    (3) The coverage evolution process;

    (4) Comparison of coverage rate and shot peening intensity.

    About measuring shot peening beam to reach target coverage The parameters of the capabilities will be described in some details.