A Portable Optical DSPI System for Residual Stresses Measurement by Hole Drilling Using the Integral Method in Terms of Displacement

Abstract

Abstract.A portable optical device for residual stresses measurement is presented here. It combines an achromatic digital speckle pattern interferometer (DSPI) with radial sensitivity with a high speed pneumatic drilling unit. The system automatically acquires a 1280 x 960 pixel image for each step of incremental hole drilling. The number of drilling steps, as well the drilling increments, is fully programmable. The data is processed and fitted to a set of displacement curves obtained by the Finite Element Method according to the integral formulation. This paper describes the device as well as the data reduction procedure. The system has been applied to measure residual stress profiles in four to eight points of cross-sections of pipes and, from that, to compute the amount of bending moment induced in pipelines used for oil transportation. The paper presents results of a calibration test in a 12 m long test bench with a 200 mm steel diameter pipe.