How Precise Can Be the Residual Stress Determined by X-ray Diffraction? A summary of the Possibilities and Limits

Author:  Eckehard Mueller | University of Applied Sciences Bochum
Source:  The Shot Peener magazine, Vol 38, Issue 3, Summer 2024
Doc ID:  2024026
Year of Publication:  2024
Abstract:  
Many springs are shot peened and the quality of shot peening is essential for the fatigue life. Today the determination is often done via x-ray diffraction. The lattice distance is measured and out of this information the residual stress is determined (and not directly measured). For this kind of measurement an absolute measurement is not available. The only way is to calibrate it in some way. It is shown how precise measurements today are in relation to different x-ray diffractometers and a specimen must be designed to get something like a usable calibration sample. The difference between statistical and systematic errors is shown and the consequences of these errors are discussed.