Testing Shot Peening Stresses in the Field

Author:  K. Tiitto, P. Francino, American Stress Technologi
Source:  The Shot Peener magazine, Vol 04/Issue 4, Winter 1991
Doc ID:  1991103
Year of Publication:  1991
Abstract:  
The benefits of shot peening are work hardening of the surface and subsequent generation of beneficial compressive stresses at and below the surface. The conventional way of measuring these stresses is x-ray diffraction, which is a well-established method and provides accurate stress values. The beneficial compressive stresses are subsurface; consequently, to quantify shot peening quality, evaluation below the surface is necessary. The penetration depth of x-rays in many cases is limited to several microns. To measure the subsurface stress with x-ray diffraction requires succesive removal of material and repeated x-ray measurements. Such a procedure is acceptable for laboratroy evaluations on selected samples but is impossible for 100% non-destructive evaluations in shot peened components in the field. Difficult-to-reach areas such as holes, fillets or roots of gears cannot be directly tested with this method. Additional techniques which overcome these problems and have sufficient accuracy are desirable.