Measuring Intensity in Small Areas with Complex Geometry using Mini Almen Strips

Author:  K. McClurg and R. Buckner
Source:  Conf Proc 2014: ICSP-12 Goslar, Germany (pgs.404-409)
Doc ID:  2014111
Year of Publication:  2014
Abstract:  
Mini Almen Strips provide a direct intensity correlation, rather than simply an arc-height correlation, in small, hard to reach areas on a peening surface. Currently, there is no direct way to measure the intensity of areas smaller than 31.75 mm by 19.05 mm since this is the measuring distance for a standard Almen Strip on a standard Almen Gauge. Current practices utilize shaded Almen strips to correlate an arc-height from a standard, unshaded Almen strip saturation curve to a Shaded Almen Strip arc-height. This correlation compares a single point on a curve, and thus creates some ambiguity in the collected data. When a Shot Peening parameter changes, a complete saturation curve must be developed to determine the new intensity. By comparing two points, one from a saturation curve with set parameters and one from a Shaded Strip in a new orientation, it is not a guarantee that the points both occur at the T1 validation point on the intensity curve. Mini Almen Strips provide a solution to this uncertainty. Measuring 25.4 mm by 3.175 mm, Mini Almen Strips can fit on most small peening locations. Since Mini Almen Strips are composed of 1070 Steel, just as standard Almen strips, and maintain the Standard Almen Strip thickness for both "N" and "A" types, they should follow the same material properties and plastic deformation as the Standard Almen Strips. Therefore, Mini strips should follow the 10% Rule to create a full saturation curve and allow for an intensity correlation to Standard Almen Strips, rather than just arc-height correlation. Using this logic, Avion Solutions conducted a Mini Almen Strip study for a Critical Safety Item for the U.S. Army using Ultrasonic Shot Peening (USP). These Mini Almen Strips will allow for an intensity confirmation when the designed USP chamber has an opening smaller than the measuring distance for a Full Almen Strip.