Patent ID: 6234020
Filing Date: 2001-05-22
Classification: G01N

Abstract:
Method of measuring residual stress in a metallic specimen wherein, by means of an ultrasound transducer an ultrasound entry wave having a ground frequency f.sub.g is introduced into a surface of the metallic specimen, the amplitude of the ultrasound entry wave is measured by means of an entry wave detector and the amplitude of the succeeding ultrasound exit wave is measured by means of a exit wave detector and the measured values of the amplitude of the ultrasound entry and exit wave are used to determine residual stress, characterized in that, for a selected entry gate time .tau..sub.n the value of ##EQU4##wherein x is a constant, this integral also referred to as the entry convolution integral, of the measured ultrasound entry wave w.sub.n (t) and a periodic wave p.sub.n (t)of the ground frequency f.sub.g is calculated and during a selected exit gate time .tau..sub.x the value of ##EQU5##wherein y is a constant, this integral also referred to as the exit convolution integral, of the measured ultrasound exit wave w.sub.x (t) and a periodic wave q.sub.x (t) of the ground frequency f.sub.g is calculated and the residual stress is determined using the calculated values of the entry convolution integral and the exit convolution integral.