A Proposal of Strain-Gage Rosette for Measurement Residual Stress Around a Circular Hole in a Plate With Circular Hole

Abstract

Hole-drilling strain-gage rosette method is an experimental technique used to measure residual stresses near the surface of a mechanical component. Various types of rosettes are available with different geometric configurations and dimensions. The strain field high gradients observed near the hole, where the strain-gage rosette is bonded, makes the problem of choosing the optimal rosette position a critical one. In this work a methodology of residual stress measurement for the technique Hole-Drilling was developed to simulate the effect of a through circular hole in a thin plate submitted under nominal uniaxial and biaxial loads up to the yield strength (Se). In the biaxial case was considered relations between the nominal components load of σ_nx/σ _ny = 0,25, 0,50, 0,75 and 1,00. It was simulated by finite elements the measurement residual stress methodology named “Hole- Drilling” in plate submitted nominal biaxial big loading until the yielding stress for the API 5L X60. In this study was projected and a strain gage rosette containing 5 strain gages positioned 0, 90, 150, 225 and 300 degrees. The relative error was evaluated between the numeric solution and the theoretical solution proposed by ASTM E837 (elastic) and by Savin (elastoplastic). It was verified that the relative errors for the main strain ɛ₁ and ɛ₂, obtained by the strain gages redundant to decrease. It is worth to emphasize that the strain gages rosette proposed with five strain-gages didn’t eliminate the problem of the eccentricity, but it quantified with larger precision this effect.