When measuring the residual stress within a component using the electrical discharge machining (EDM) strain-gage method, a metallurgical transformation layer is formed on the wall of the measurement hole. This transformation layer induces an additional residual stress and therefore introduces a measurement error. In this study, it is shown that given an appropriate set of machining conditions, this measurement error can be compensated directly using a calibration stress factor computed in accordance with the properties of the workpiece material. It is shown that for EDM machining conditions of 120 V/12 A/ (discharge voltage/pulse current/pulse-on duration/pulse-off duration), the hole-drilling induced stress reduces with an increasing thermal conductivity in accordance with the relation and increases linearly with an increasing carbon equivalent (CE) in accordance with . Therefore, a given knowledge of the thermal conductivity coefficient or carbon equivalent of the workpiece material, an accurate value of the true residual stress within a component can be obtained simply by subtracting the computed value of the calibration stress from the stress value obtained in accordance with the EDM hole-drilling strain-gage method prescribed in ASTM E837.
Effect of Material Physical Properties on Residual Stress Measurement by EDM Hole-Drilling Method
Lee, H. T., Tai, T. Y., Liu, C., Hsu, F. C., and Hsu, J. M. (March 21, 2011). "Effect of Material Physical Properties on Residual Stress Measurement by EDM Hole-Drilling Method." ASME. J. Eng. Mater. Technol. April 2011; 133(2): 021014. https://doi.org/10.1115/1.4000219
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