1 PhD Research position in Simulation of Local Defect Resonance (LDR) – Thermosonics in Belgium | KU Leuven

KU Leuven Kulak – Wave Propagation & Signal Processing Research Group

The research group for ‘Wave Propagation & Signal Processing’ at KU Leuven Kulak is performing experimental and numerical research on the behavior and wave propagation of acoustical and mechanical (ultrasonic) waves. A thorough analysis of the information contained in the waves is of interest in numerous fields of application. One of the most important applications is non-destructive testing (NDT) of materials, where specific techniques and methods are developed in order to detect defects in metals and composites, without destroying the material or changing its properties. The wide field of materials and applications however puts high demands on quality control techniques and therefore pushes research towards the development of more advanced NDT techniques with the goal to combine as many requirements as possible (e.g. high sensitivity, non-contact, fast) in a single technique.

The successful candidate will be developing nurmerical support for innovative non-destructive techniques, based on a combination of ultrasonics and thermography, to improve the sensitivity and resolution of defect detection. Experimental validation through laboratory measurements will complement the study.

Project

Thermosonics is an NDT technique that has recently gained an increasing acceptance as a fast and large area inspection technique. The technique uses infrared thermography to detect thermal energy produced by the mechanical vibrations induced by ultrasonic waves. Under mechanical vibration, heat is released by friction at positions where discontinuities, such as cracks and delaminations, are located. As a result, the local temperature rises and this temperature increase can be measured by a high sensitivity and high resolution infrared imaging camera whose field of view covers a large area. In the context of optimization of the current methodology, a new version of thermosonics, called Local Defect Resonance (LDR) – Thermosonics, was recently introduced. This technique combines conventional thermosonics with the concept of local defect resonance spectroscopy, a novel and efficient NDT technique that takes advantage of characteristic frequencies of a defect (defect resonances) to provide maximum acoustic wave-defect interaction and therefore also a significant enhancement of the thermal defect response. The benefit of LDR-thermosonics is that it requires much lower acoustic power to activate defects and to visualize their thermal response, making it possible to even use thermosonics by way of non-contact ultrasonic excitation, which was not possible until now.

Goal of the project

Despite numerous simulations on conventional thermosonics, so far no numerical studies have been performed to quantify the reliability and capability of the new concept of LDR-thermosonics. The specific objective of this project is therefore to conduct fundamental “multi-physics” research to obtain a better understanding of defect detection using LDR-thermosonics, and to assist in further development of its applications through a parametric optimization study. This will be done by first studying the concept of nonlinear LDR-spectroscopy and extending an existing 3D simulation code for wave propagation in materials containing cracks or delaminations. In a second phase, the objective is to incorporate one or more mechanisms of vibration induced heat generation (friction, plastic deformation, etc.) into the code, and to couple the resulting wave propagation model to thermal physics laws. In a third phase, the coupled thermo-acoustic-mechanic model will be tested extensively by comparison with recent experimental observations found in literature and new dedicated measurements carried out in the lab. Finally, a parametric study will be conducted to identify the optimal operational conditions for successful LDR-thermosonics inspection of materials. Parameters to be investigated include excitation method, frequency range, sample geometry and properties, defect type, defect size, defect position, defect orientation, number of defects, etc.

Profile

• Master Degree in Physics or Mathematics or Engineering
• Background in acoustics and/or thermal physics is a plus
• Interest in modelling and numerical simulations of real physical phenomena
• Determined to go for a Doctorate Degree
• Team player
• Fluent English, Dutch is a plus
• Resident in the environment of Kortrijk