Ultrasonic testing of grain distortion direction in cold formed aluminium profile

Cold deformation process of metals causes distortion of crystalline structure. When a material is formed, the grains are usually distorted and elongated in one or more directions which make the material anisotropic. Anisotropy can be defined as a difference in a material's physical or mechanical properties in different directions of taking of testing samples. In exploitation, it is very important to recognize the direction of grain elongation so that the best orientation of working part can be chosen. For that purpose ultrasonic testing is used. The ultrasonic velocity of the material is determined by using a digital oscilloscope under condition that thickness of the material is known. Testing shows the difference in wave velocity for different orientations of grain structure. In order to determine whether there is a significant difference in the ultrasonic velocity, the measurement results were statistically analyzed and graphically presented. The results are verified by performing the same measurement procedure on annealed homogenous testing samples. The result of this work leads to a non-destructive, simplified way of anisotropy recognition, without more expensive, destructing, testing by cutting out a large number of testing samples.