Errors Research On The Calibration Coefficients For Using The Hole-Drilling Method

Since1930, the residual stress testing technology has been engaged inresearch. Up to the present time the hole-drilling method has been the mostextensive application in the engineering. In the residual stress measurement by thehole-drilling method, the strain calibration coefficients are determined by theuniform tension in the laboratory and apply to calculating the non-known residualstress fields. Yet residual stress fields in practical components are complicated andoffen under non-uniform stress state.The numerical calculating method of calibration coefficients in thedrilling-hole method is mainly researched in this thesis. Comparing the simulatedmeasurement results with the pre-stressed load, it has been shown that the error isgreatly influenced by the gradient of the load. Through simulating residual stressfields warying as linear, quadratic and cubic functions,correspectively the errorscaused by the calibration coefficients are analysed. Otherwise, the effects of thehole diameter and the strain rosette’s deviation angle on the measurement accuracyare also studied. The results show that the measurement errors caused by thecalibration coefficients are mainly due to the first order and third order terms ofthe stress distribution function in the non-uniform residual stress field. Andmeasurement errors increases with the increment of the hole diameter or therosette’s deviation angle.Based on the above analysis, a correction method-five-rosette drilling methodis proposed to improved the traditional drilling method. As shown in the examples,the method can reduce the measurement errors effectively in the non-uniformresidual stress and improve the measurment accuracy.