Non destructive inspection of plates using frequency measurements

摘要

This paper examines the use of natural frequency measurements and energy formulation of vibration theory to detect damage present in a structure. The extent of change in natural frequencies of the structure due to damage, which is highly dependent on the location and size of damage, is used to detect and characterise damage. An analytical solution to detect and characterise damage in plates from just change in natural frequencies is presented here for the first time. Damage is modelled as a spring with finite stiffness which is less than that of the undamaged structure. Using the strain energies stored in the plate and that of spring, calculated from discrete values of deflection mode shapes, the location and size of the damage is determined. The applicability of this approach is demonstrated through a numerical study, where the location and size of through thickness centre cracks in simply supported plates is deduced with greater than 95 percent accuracy.