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A Theoretical Approach towards the Modeling of Vibrothermography Using Finite Element Methods
Bhargava, Vibhor
Bhargava, Vibhor
Description
A Master of Science thesis in Mechanical Engineering by Vibhor Bhargava entitled, “A Theoretical Approach towards the Modeling of Vibrothermography Using Finite Element Methods”, submitted in April 2019. Thesis advisor is Dr. Bassam Abu-Nabah and thesis co-advisor Dr. Maen Alkhader. Soft and hard copy available.
Abstract
The demand for preventive maintenance in the aerospace industry has been growing as part of life extension programs. Due to its reduced inspection time, part preparation requirements, floor space, and environmental concerns, vibrothermography has become an attractive solution to these programs as a potential replacement to conventional surface inspection methods. It offers the capability to detect surface cracks mainly through capturing vibration-induced frictional heat generation of contacting crack surfaces. The multidisciplinary nature of this inspection technology makes it rather difficult to theoretically capture the system response without the proper application of finite element (FE) methods. It requires relating the material mechanical and thermal properties in a coupled finite element model to properly address wave propagation, contact mechanics, fracture mechanics, friction heat generation and heat diffusion in simulated inspections. In this study, a theoretical model is developed to estimate the dynamic strain response at any location in commonly used cantilever beams oscillating at a given frequency. This model is utilized to assess the convergence of FE-based dynamic system response while determining the element size requirements to realistically model elastic wave propagation throughout the sample. Three different meshing criteria are assessed to properly capture the singularity at the crack tip. It is demonstrated that the use of solid element circular meshing criteria converges to singular quarter-node solid element solution and allows coupling it with heat generation and diffusion around the vicinity of a crack to deliver the most effective approach for modelling vibrothermography. Any deviation from the optimized meshing criteria and element size requirements will adversely affect the relative motion of crack surfaces and frictional heat generation. This effort brings FE modeling of vibrothermography a step closer towards realistic inspection simulation in the future.