Bending Test Rig for Validating the Hole Drilling Method Residual Stress Measurement

This paper shows a large validation activity of the strain gage Hole Drilling Method. The residual stress measurements can not be validated easily, unless with Round Robin activity and/or comparison with other residual stress measurements such as X-ray diffraction. An accurate validation procedure is reported in the present paper, using abending test rig. The bending stress experimentally simulated a residual stress (known with uncertainty lower than 1%) that was considered as the reference stress distribution. The results showed very accurate measurement in terms of relaxed strain distributions, that were compared with the prediction obtained with the Influence Function technique. The differences were in the order of 0.5 microepsilon as standard deviation on a large number of tests. The bending stress prediction was consequently very accurate and the stress differences were as small as 1 MPa showing the accuracy potentiality of the method.