Structural properties of materials change under stress, temperature and work environment. These changes are generally unfavorable. They cause a reduction in strength of materials. This has an impact on the safety and service life of machines and constructions.
In the chemical and petrochemical industry the destruction of a structure can be activated by chemical substances. In the energy industry, a key element in assisting the destruction is temperature. In aviation, the typical cause of damage is the process of fatigue. Regardless of the differences regarding/concerning the mechanisms of degradation, typical of the sectors of industry, the end result is the emergence of microvoids and microcracks in the material. In the final phase of the process, dominant cracks are formed.
The term of measure of material damage, introduced by Kachanov and Rabotnow, can be effectively used also when considering the impact of microdamages on measurable macroscopic acoustic quantities. A damage parameter proposed by Johnson allows to correlate changes in acoustic birefringence of the material with the parameter describing the degree of damage.
In this article the authors presented the nondestructive tests results concerning Inconel 718 alloy subjected to damage caused by plastic deformation. This paper focuses on the evaluation of acoustic properties in relation to the degradation of the materials tested.
 Socha G., Madejski B., Krysztofik J., Czarnewicz S. (2014). Sposób badania uszkodzenia struktury materiału wywołanego deformacją trwałą próbki poddanej rozciąganiu i próbka do badania uszkodzenia struktury materiału, UPRP nr P-409294
 Szelążek J., Kowalewski Z. L., Mackiewicz S., Deputat J. Zmiany parametrów mechanicznych i ultradźwiękowych stali w wyniku pełzania, 33 KKBN Licheń 2004