Efficient modelling of guided wave interaction with contact acoustic nonlinearity in thin-walled structures for advanced structural health monitoring applications

Project description

Guided wave techniques are promising candidates for structural health monitoring (SHM) of thin-walled structures such as pipelines, aircraft fuselages, pressure vessels, and ship hulls. Along with in-built sensors and actuators, they can detect and characterise small flaws very efficiently and effectively. Generally, guided wave-based methods require baseline data to be acquired for the pristine structure with which service data is compared to detect defects. However, a major issue in all baseline-based SHM methods is that the baseline signals acquired in the healthy structure may alter due to changes in environmental or operational conditions, which may lead to false alarms. Moreover, in many cases, baseline data may not be available at all.

These issues have triggered the current surge of research in baseline-free SHM techniques. Recently, nonlinear ultrasonics has emerged as a new concept to alleviate the need for baseline data by exploiting unique features generated when guided waves interact with structural nonlinearities such as clapping and/or friction between the contacting faces of closed cracks or delaminations. These nonlinear features, known as contact acoustic nonlinearities (CANs), include the generation of new frequency components such as higher harmonics, sub-harmonics, and zero frequency response. In addition, nonlinear mixing of non-collinear guided waves at a contact interface generates additional features such as frequency selectivity, modal selectivity, and directional selectivity.

This project aims to develop computationally efficient finite element analysis tools for simulating the interaction and mixing of guide waves in thin-walled structures with CANs. Time-domain spectral finite elements and wave packet enriched finite elements will be investigated using higher-order 1-D beam and 2-D laminate theories. A comprehensive numerical study will be performed to examine the efficacy of the use of nonlinear interaction and mixing of guided waves for the detection of fatigue cracks in metallic structures and delaminations in laminated composite structures.

Outcomes

The successful project is expected to deliver the following outcomes which make a number of fundamentally new contributions in the area of SHM of thin-walled structures:

• to demonstrate the application of nonlinear guided wave ultrasonics as promising methods and techniques to develop baseline free structural health management systems for thin-walled structures.
• to identify the potential of using time-domain spectral finite elements and wave packet enriched finite elements to simulate the nonlinear interaction of guided waves with closed cracks and delaminations.
• to develop a finite element simulation framework to efficiently simulate the interaction of guided waves with CAN damage.

Essential capabilities

Proven record of high quality, independent research.

Desireable capabilities

Advanced knowledge in finite element simulation and Lamb wave propagation in thin-walled structures.

Expected qualifications (Course/Degrees etc.)

Bachelor of Engineering or Master of Engineering in Mechanical Engineering with first class honours with distinction or high-distinction in capstone thesis project.