2008 Volume 49 Issue 8 Pages 1905-1910
Recent studies revealed that EDM hole-drilling strain gage method is applicable for the measurement of residual stress in materials with higher hardness and toughness. However, the metallurgical transformation layer formed on the wall of the hole induces an additional stress and therefore generates a measurement error. Usually this error can be calibrated by estimating and reducing the hole-drilling induced extra stress, σIS. However, the value of σIS is highly sensitive to the EDM parameters. Accordingly, the current study aimed at lowering σIS by optimizing the working parameters of pulse current, pulse-on duration and pulse-off duration with experiments. An inverse power law relationship was constructed to predict the magnitude of the hole-drilling induced stress where was referred. A convenient calibration method was proposed where calibration factor can be easily determined. The calibrated results revealed good accuracy where deviation is no more than 10 MPa. The accuracy of the proposed calibration scheme was confirmed in study.
