Drilling strains in measuring residual stress with hole-drilling strain-gage method

A new calibration method in measuring residual stress with hole-drilling strain-gage method was used to study the relationship between drilling strain and external stress. The results indicate that the value of strains induced by drilling hole (as called drilling strain) is not only related to stress level but also with the stress sing (position or negative).The relationship between the drilling strain and the stress is simple,as shown as follows:ε_pm=a△ε+b,in which,a and b are the measuring coefficients concerned with drilling hole method metal material measured and so on,ε_pm is the drilling strain, △ε is whole relaxed strains during drilling hole. Theequation makes the measuring accuracy of residual stresses with hole-drilling method with cut-ting tools improved greatly.