Almen Gage Calibration

Author:  Champaigne
Source:  Conf Proc: ICSP-8 Sept. 16-20, 2002 Garmisch-Partenkirchen, Germany
Doc ID:  2002016
Year of Publication:  2002
Author Jack M. Champaigne, Electronics Inc., Mishawaka, IN, USA Introduction The Almen gage is used to measure the curvature or arc height of the Almen test strip that has been subjected to particle impacts on one side. The resulting impingement on the test strip causes it to stretch and arch. The resulting measurement is used to determine the blast stream energy or peening intensity. The Almen gage was invented by J.O. Almen of General Motors Corporation in 1942 and a U.S. Patent was issued in June of 1944 (see Appendix A. for drawing). The original gage used two knife-edge supports for the test strip. However, in November of 1943 Engineers at General Motors revised the original design by replacing the knife-edges with four-ball support and designated the new gage as #2 Almen gage. This same basic design is in use today around the world with only minor modifications. The Society of Automotive Engineers, SAE, has developed a standard practice for the construction of the gage in document J-442 [1]. The present application of the gage includes the use of a digital indicator replaciing the original dial indicator and the addition of end-stops to help assure proper positioning of the strip for measurement. The SAE specification gives dimensional data necessary to construct the gage but does not mandate a calibration procedure. This article will address calibration procedures and recommended practices. Three areas are explored. - Calibration of the indicator - Measurement of ball positions(s) - Matching gages with special gage block

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