Influence determination of damage to mechanical structure based on modal analysis and modal assurance criterion

Abstract

Mechanical damages in structures changes its geometry in various ways. However, if damage size comparing to structure size is small, thus observation of this damage could be hard or even impossible in some cases. For this reason, changes in structure’s vibration responses are investigated nowadays. The objective of this research is to investigate the influence of damage size to the vibration response of the mechanical structure – aluminum alloy plate. To achieve this aim, modal analysis of a reference, i.e. health, and multiple damaged structures using ANSYS Workbench, and calculation of modal assurance criterion (MAC) using Matlab were carried out in this research. During this research 6 different damage sizes were modelled and its vibration response was compared to the health one. Obtained results revealed that the bending modes rarely shows any trend towards damages scenario. But, when observing the MAC values matrices, the values related to torsional modes even on the diagonal of the matrices decrease as the damage size increases, which indicates that the damage has more influence on the torsional modes.

Defect identification in electro-mechanical assembly using finite element method and modal assurance criterion

“…H. Chang et al (2003) studied damage identification of ship under different damage conditions through numerical simulation and experimental verification done by COMAC based on orthogonality of modes before and after damage [5]. Influence of damage size onto vibration response of structure is studied with respect to undamaged unit through numerical simulation by Mehran K. et al (2002) [4]. Cornwell P. et al (1999) developed a method based on changes in strain energy of plate like structure with mode shapes of the structure before and after damage [6].…”