Almen Strip Consistency Testing

摘要

Shot peening intensity is the measure of the energy of the shot stream and intensity control is one of the essential means of meeting peening specifications. Intensity is measured using Almen strips. When an Almen strip is shot peened, the residual compressive stress causes the Almen strip to bend or arc toward the peened side. The Almen strip arc height is a function of the energy of the shot stream and is very repeatable. Therefore, for Almen strips to provide reliable and repeatable intensity verification, it is critical that they are consistent in thickness, flatness and hardness. Electronics Inc. (El) brand of Almen strips have undergone extensive testing to ensure consistency from lot to lot. Before bringing their Almen strips to market, El developed a custom air blast test cabinet and shot peened approximately 4,000 strips manufactured over a three-year period. The data was put into histograms for accurate analysis. The histograms show nearly identical lot-to-lot arc height results. For example, the means range from 11.99 to 12.14 (0.001-inch units) and standard deviations range from 0.096 to 0.185. (Histogram samples are avail- able on page 16.) El's testing capabilities and test results validate El's ability to produce reliable Almen strips.