## A INVERSE PROBLEM IN ULTRASONIC TESTING AND MECHANICAL PROPERTIES OF POLYCRYSTALLINE MATERIALS

Mathematical Modeling, Vol. 2 (2018), Issue 1, pg(s) 26-27

The direct problem in ultrasonic testing (UT) is: “Evaluation of attenuation coefficient by means velocity of ultrasonic wave propagation, frequency and grain size in polycrystalline materials”. The inverse problem in UT is formulate as “Non-destructive evaluation of grain size by measurement of acoustical characteristics”. The values of acoustical characteristics (V V f ) L T L ; ;α ; are measured, according ASTM E 494:2015. In this article a equation for grain size (D) is derived.

## KINETIC DIAGRAMS OF FATIGUE DAMAGE IN FRACTURE MESOMECHANICS

The fatigue of metals is a relatively new part of mechanics of destruction. In modern theories to explain the destruction of a material of fatigue is considered that the process begins and flow the basis of generation and accumulation of micro-cracking in the material. To describe this process is by using kinetic diagrams of fatigue. The interest to the theory is a discussion of the process of fatigue of middle level. This article examined the kinetic diagrams of fatigue of middle level and evaluate their parameters by ultrasound measurements.

• ## EVALUATION OF FATIGUE LIMIT FOR ALUMINIUM ALLOYS BY ULTRASONIC MEASURING

The evaluation of fatigue limit-σ−1 for AlSi7Mg, AlCu6Mn aluminum alloys is frequently encounter in material testing. In this method there is necessity of manufacture of test-tube from tested material or detail and made tension test.. There is destructive method. For many details there is not acceptable. Calculated in the usual ways fatigue limit appear only their statistical averaging between a number of structural factors indicating the influence. In material testing there is interest to non-destructive evaluation of fatigue limit σ−1 for the specimens and details. In this paper is lock at possibility for non-destructive evaluation of fatigue limit σ−1 by means measure velocities of propagation of longitudinal and transversal ultrasonic waves – VL and VT in tested materials and details.