Experimental Validation of the Calibration Function of the Hole Drilling Method and Ring Core Method for Residual Stress Measurement

Residual stresses in mechanical components can result in both detrimental but also beneficial effects on the strength and lifetime of the components. The most detailed knowledge of the residual stress state is of advantage or a pre-requisite for the assessment of the component performance. The mechanical methods for residual stress measurement are divided into the groups of non-destructive and destructive methods. Two commonly used mechanical methods for determination of residual stresses are the hole drilling method (HDM) and the ring core method (RCM) which can be regarded as semi-destructive. This investigation will experimentally determine the calibration functions for residual stress measurements of the HDM and RCM. These functions are used for RS analyses using the differential method. With a four point bending testing machine a defined stress can be triggered between the middle bearings. The strain in this area can be measured with strain gauges, so the stress is well-known. In this defined loading area, the strains in two load cases with HDM configuration and RCM configuration were measured using strain gauge rosettes. With these measured strains and the actually known stresses, the specific calibration functions can be calculated and were presented together with the numerical functions.