Feasibility evaluation of EDM hole drilling method for residual stress measurement

The feasibility of the electrodischarge machining (EDM) hole drilling method for residual stress measurement was evaluated with the aim of extending application of the hole drilling strain gauge method. For comparison, a series of non-stressed and prestressed workpieces made of AISI 1045 were employed to perform the stress measurement with both high speed (HS) hole drilling and EDM hole drilling methods. Experimental results reveal that the additional stress induced by EDM is dependent upon the pulse on duration rather than the pulse current. Both methods exhibit a linear relationship between measured stress and prestress. These two nearly parallel lines indicate that the additional stress induced by EDM remains constant regardless of the stress state of the sample for a specified EDM condition. Thus the EDM hole drilling method can be used successfully once a positive calibration factor has been applied, and can achieve the measurement accuracy afforded by the HS hole drilling method.