MONITORING SURFACE STATE OF AA7075-T6 DURING DYNAMIC LOADING WITH FBG SENSOR.

The AA7075-T6 material is widely used in aerospace applications due to its favourable strength-to-weight ratio and cost-effectiveness. The material undergoes a process of cold rolling and subsequent stretching to form metal sheets. This process generates residual compressive stresses on the surface of the material. Surface changes in the material are observed at low stress levels, resulting in variations in residual stresses and surface roughness. This article presents an approach to monitor the surface state changes of AA7075-T6 material during dynamic loading using Fiber Bragg Grating (FBG) sensor. Numerical Finite Element Method (FEM) simulations analyse the transfer of deformations from the damaged surface through the adhesive layer to FBG with different cladding thicknesses. Loading induces microcrack-related intensity changes in the FBG optical spectrum and deformation response. The magnitude of the response is greater, when the cladding thickness of the optical fibre is thinner. Experimental results show that the FBG optical spectrum response varies with cumulative number of dynamic cycles. [ABSTRACT FROM AUTHOR]