SAE J443_201006

This SAE Recommended Practice provides uniform procedures for using the standard shot peening Almen strips reported in SAE J442. Standard Almen strips are used to establish saturation, determine intensity, monitor repeatability of the shot peening machine operations, and can be used to predict a desired result on a part. It is recommended that the standard Almen strip A be used for intensities that produce arc heights of 0.10 mm A (0.004 in A) to 0.60 mm A (0.024 in A). For intensities below 0.10 mm A (0.004 in A), the standard N strip is recommended, and for intensities above 0.60 mm A (0.024 in A), the standard C strip is recommended. Use of SAE 2597 Computer Generated Shot Peening Saturation Curves is voluntary, existing shot peening processes that do not take advantage of computer generated saturation curves need not be changed to meet the requirements listed herein. The process of shot peening, in common with many other processes, cannot at present be adequately controlled by nondestructive inspection of the peened parts, therefore, it is necessary to control the process itself to achieve consistent, reliable results. Substantial revisions have been made to this document and the (R) symbol to the left of the document title indicates a complete revision. Figure 1 - Eliminate “or less” from the arc height increase criteria so one and only one numeric answer can be derived from a given saturation curve. Use of “or less” may allow extremely long exposure times with corresponding increases in arc heights to erroneously qualify as intensity. Figure 2 - Demonstrates that special cases exist where some peening techniques are accomplished with incremental number of passes through a machine, rotations of a turntable, strokes of a reciprocating nozzle or other methods and due to configuration and machine control constraints the Almen strip is saturated at the first exposure (least amount of exposure available) to the shot stream and additional passes do not significantly increase the arc height further. Section 7.3 - It is common to use a fixture with multiple Almen holders for intensity tests. The peening intensity at each holder position must meet the requested values. The “saturation times” for each holder will be unique. When performing intensity verifications (one strip at saturation time) each holder must be exposed individually to its own saturation time and its arc height must be within the requested tolerance band. An alternative method is allowed by establishing “target arc heights” for use in intensity verification whereby the fixture can be used with all holders simultaneously and the obtained arc heights (within tolerance band) at each location must repeat the arc heights obtained in their respective saturation curve.