Inference of stress and texture from the velocities of ultrasonic plate modes
An ultrasonic approach is proposed to independently charac- terize stress and texture in rolled metal plate. The approach is based on the theory for the angular dependence of the ultrasonic wave velocity in a symmetry plane of an orthorhombic, stressed material. The theory for the angular dependence of the velocities reveals terms with two-fold, four-fold, and six-fold symmetry, which are utilized in the separation of the stress and texture contributions. The experimental implementation has utilized measurements of the velocities of SH(,o) and S(,o) guided wave modes in thin plates. These modes are generated and detected by electromagnetic acoustic transducers. The ability to determine the directions and differences in magnitudes of principal stresses from the SH(,o) data is described. From a combination of the SH(,o) and S(,o) data, a procedure is proposed for determining the coefficients W(,400), W(,420), and W(,440) in terms of an expansion to fourth order of the crystallite orientation distribution function in terms of generalized Legendre functions. Experimental results are presented for the cases of aluminum, 304 stainless steel, and copper. The results fully confirm the proposed stress measure- ment technique. Predictions of W(,440) are also in good agreement;with independent measurements based on X-ray pole figures. Refine- ments in the X-ray techniques are required before the accuracies of the predictions of W(,400) and W(,420) can be fully assessed; *DOE Report IS-T-1269. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.