Nondestructive assessment of tensile properties of cold worked AISI type 304 stainless steel using nonlinear ultrasonic technique

A new approach based on nonlinear ultrasonic (NLU) technique is presented for nondestructive evaluation of yield strength and tensile strength of cold worked AISI type 304 stainless steel (SS). In this approach, the ultrasonic harmonics generated in cold worked stainless steel, as a result of interaction of ultrasonic wave with dislocations and substructural changes, are measured precisely and the nonlinear ultrasonic parameter, β is determined. A quadratic relationship, with a correlation coefficient better than 0.99, is found between the yield strength and the β parameter as well as between the tensile strength and β parameter of the cold worked specimens. The observed behavior is explained based on microscopy, variations in martensite volume fraction and dislocation density determined from X-ray diffraction profile analysis. The proposed approach can be effectively used for nondestructively ensuring the uniformity of tensile properties of steel components on shop-floor during various stages of manufacturing and also as feedback module in intelligent processing of materials concept.