Thermoelasticity-based modal damage identification

Frequency response function identification using fused filament fabrication-3D-printed embedded ArUco markers

“…In this research, a Y-shaped specimen, shown in Figure 2, was used [4], [12]. In particular, this geometry was chosen due to its structural dynamic properties.…”

“…In the last years, many image-based analysis have been introduced for the displacement measurements [10], [11] and consequently for the structural dynamics due to several operating advantages, e.g. high spatial density, full-field information, no sensors to be placed on the structure [12]. Javh et al [13] proved the hybrid modal-parameter identification of full-field mode shapes using a DSLR camera for responses far above the camera's frame rate, employing the Lucas-Kanade Optical Flow algorithm [14].…”

Thermoelasticity and ArUco marker-based model validation of polymer structure: application to the San Giorgio’s bridge inspection robot

“…Thermoelasticity is a full-field stress-distribution measurement technique based on the thermoelastic effect [11], [12]. According to this effect, in case of adiabatic process and linear, homogeneous, and isotropic material behaviour, a dynamically excited structure presents surface temperaturechanges proportional to the changes in the stress and strain tensor traces, caused by the external load [19], [49]. Moreover, if the excitation is harmonic, the thermal fluctuation is expected to be at the same frequency of the input load, and its normalized amplitude variation is given by:…”

“…Thus, thermal acquisitions are necessarily post processed in order to obtain readable results [51]. Although general frequency-domain approaches are well established nowadays [19], [52], in this research a classical lock-in analysis was performed in order to single out the thermoelastic signal at a particular frequency (i.e., the load frequency) from the noisy signal acquired through the thermal camera [53], [54]. Being 𝜔 𝐿 the input load frequency, the digital lock-in amplifier gives the temperature fluctuation at 𝜔 𝐿 as magnitude 𝛥𝑇 𝜔 𝐿 and phase 𝛩 𝜔 𝐿 [55]:…”

“…Thermoelastic Stress Analysis was involved in multiple researches, regarding non-destructive testing [13], defect identification [14], and material properties characterization [15], [16]. Thermoelasticity has also been used to determine fatigue limit parameters and crack propagation [17], [18], for modaldamage identification in frequency domain [19], and for stress intensity factor evaluation in complex structures [20]. However, due to the demands of high-speed operation and the use of light structures in modern machinery, static measurements of stress and strain distributions are no longer sufficient [21], [22].…”