How Precise can be the Residual Stress Determined by XRay Diffraction? A summary of the Possibilities and Limits

Author:  Eckehard Mueller, Materials Research Forum LLC
Source:  Residual Stresses 2016: ICRS-10
Doc ID:  2024017
Year of Publication:  2024
Abstract:  
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. Introduction Today the determination of residual stresses for many products is a common procedure, e.g. to prove the efficiency of the shot peening process or other hardening processes. Mostly it is done with the help of the x-ray diffraction method, because it is fast and not so expensive. The demands of the automotive industry concerning the accuracy and the number of measurements are still increasing. The question is whether precise measurements can be even performed. Here, round robin tests are reported designed to calibrate such a x-ray-diffractometer.