The Determination Of Texture Coefficients For Metal Materials By Ultrasonic Measurement

Metal meterials are widely used in manufacturing chemical process equipments and pressure vessels. In meso-scale, metal sheets can be regarded as a mounted aggregation of tiny grains. Because of anisotropy of grain elasticity and plasticity properties, the elasticity and plastic properties of metal polycrystalline in macro-scale depend not only on the material properties, but also on the crystal grain orientation distribution, which can be described as orientation distribution function (ODF), and its coefficients were called texture coefficients. Measurement of texture coefficients can be used to test the properties of material in the manufacturing process, and give guidance to the production.Anisotropy of polycrystalline elastic constitutive directly leads to the anisotropy of ultrasonic velocity inside the polycrystalline. If the anisotropic velocity along different directions can be accurately measured, we can calculate the texture coefficients reflecting anisotropy degree of polycrystalline. In this paper, we gave the expressions between the ultrasonic velocity and texture coefficients c204 and c004. The expressions can ignore the effects of thickness and density. With the help of the expressions, we can use one transducer to determine 3 types ultrasonic velocity at the same time, obtaining more accurate results. In addition, the expressions were given between the velocity and the texture coefficients when the ultrasonic travelled along arbitrary direction parallel with the plane of metal sheets. Because the expressions are complicated, we used the method of linearization to simplify the expressions, and with the help of these expressions,we deduced another relationship between ultrasonic velocity and texture coefficients c204, c004 and c404, and then we used an example to demonstrate the linearization does not have any influence on the results. We also give numeric area for c204, c004 and c404.By using the instrument of RETIC-SNAP-5000 and EMAT, we determine c004,c204 of 2mm aluminum sheet, the results have a good agreement on the results obtained by PZT. This experiment showed the reliability of using EMAT to determining texture coefficients. Because EMAT can get 3 velocity in just one experiment, the results are more accurate than PZT.Using Pulse echo method, we determined cco4,c204 and c404 of 10mm steel sheets, and compared them with the results got by tensile test. Both are nearly identical.