Quantification of subsurface cracks in a thin aluminium beam by the use of nonlinear guided wave theory ? a numerical and model-based approach
Sprache des Vortragstitels:
9th European Workshop on Structural Health Monitoring
Sprache des Tagungstitel:
In lightweight design it is common to use thin-walled structures made from lightweight materials, e.g. aluminium alloys or polymeric composites. The approach of guided waves as a Structural Health Monitoring method is a simple possibility to localize and detect damages in such structures. Especially damages within the material, like subsurface cracks or delaminations which are not visible from outside, may decimate the structural load capability and result in a safety issue. Therefore further requirements on an advanced structural health monitoring systems are the qualification and quantification of damages. Only then it is possible to decide if a damage is acceptable or if the damaged part has to be repaired or should be replaced. This contribution deals with the quantification of subsurface cracks in a thin aluminium beam using nonlinear guided wave theory. Due to the effect that a crack interacts with the passing elastic wave higher harmonics are observable in the sensor signal, which is known as the contact acoustic nonlinearity. Depending on different parameters and relations like wavelength to cracklength or position of the crack within the structure, the irregularities in the sensor signal are more or less noticeable. Therefore this contribution presents a numerical approach of the effect of delaminations, modelled as subsurface cracks, on guided wave modes. Combined with varying excitation signal frequencies it is thereby possible to quantify a subsurface crack.