PSI - Issue 52

Alessandro De Luca et al. / Procedia Structural Integrity 52 (2024) 424–429 Alessandro De Luca / Structural Integrity Procedia 00 (2019) 000 – 000

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process permitting the in-service health assessment of a structure through an automated monitoring system [4,5]. Among the different technologies, SHM based on guided waves (GW) has proven to be an advantageous technique: GWs can propagate over large distances with low attenuation and energy loss [6]. Despite their enormous potential, GWs appear to be also sensitive to the environmental operating conditions [7,8] as well as geometric variation [9], altering their damage detection capability. Michaels et al. [10] performed an experimental study on the effects of an applied uniaxial load on guided wave signals, evidencing how signals differently change with respect to both loading direction and GW propagation direction. Palanisamy et al. [11], investigated the effects of the load on GW propagation mechanisms in glass fibre reinforced polymer (GFRP) and aluminium panels. The results showed a change in the GW phase velocities in both materials, with higher evidence for the aluminium panel. Yan et al. [12] analysed the influence of the static load of different magnitudes on the propagation characteristics of guided waves in an aluminium plate. It has been proven that the amplitude of the signals varies linearly with the load, increasing or decreasing depending on the considered direction. Lee et al. [13] presented an experimental study on the effect of applied loads on an aluminium structure analysing GW propagation for different directions. The angular load-dependence of phase velocity follows a sinusoidal pattern. This study investigates on the guided waves propagation mechanisms on an aluminium panel subjected to different levels of tensile load, considering different excitation signals in the frequency range from 100 to 300 kHz. 2. Methodology The aim of this work is to analyse the propagation mechanisms of guided waves (GW) in a damaged aluminium plate subjected to various tensile load levels. The plate is 380 mm x 360 mm x 2 mm sized. Five Lead zirconate Titanate (PZT) sensors were used and located as shown in Figure 1.

Figure 1. Sensor network

The diameter and thickness of the sensors are d = 10 mm and s pzt = 0.25 mm, respectively. Two fixtures were designed and used to uniformly load the plate through a ZwickRoell Z250 testing machine, and three different load levels were applied to the plate: 20, 30 and 40 kN, (Figure 2).