Application of Distributed Dislocation Technique in Heat Conduction and Multiphysical Problems of Cracked Structures

Abstract

The use of smart materials, particularly piezoelectric materials, has seen significant growth due to their unique capabilities in sensing, actuation, and energy harvesting. However, these materials are frequently subjected to various thermal loads, necessitating robust fracture criteria for ensuring their structural integrity. The primary objective of this research is to develop an analytical framework to analyze the fracture behavior of smart materials, particularly piezoelectric materials, and to provide insights for the design of smart devices subjected to different thermal loading conditions. Using the Distributed Dislocation Technique (DDT), this work aims to provide a deeper understanding of the fracture behavior of structures with multiple cracks of different spatial distribution patterns, investigating how thermal, mechanical, and electrical fields affect crack propagation. The research begins by examining a single curved crack in a piezoelectric plane under general steady state temperature loading. The effects of heat source location, loading parameters, and crack geometry on stress intensity factors (SIFs) are thoroughly analyzed. Building on these insights, multiple cracks in a finite-sized, piezoelectric half-plane are studied, focusing on crack interaction, boundary effects, and crack angles on the multiphysical response of cracks under thermal loading conditions. In the subsequent phase, the research extends to study the transient thermal response of multiple cracks in a half-plane or along the interface between a thermal coating and a substrate by considering non-Fourier heat conduction. The comprehensive analysis reveals significant deviations from traditional Fourier models, highlighting the importance of thermal relaxation time, loading parameters, crack dimensions, and spacing in predicting the thermal response of cracked structures. Key findings demonstrate that the presence of thermal relaxation time results in dynamic overshooting, emphasizing the necessity for accurate modeling of transient thermal responses. This thesis provides a robust framework for analyzing the thermal and multiphysical behavior of cracked structures under various loading conditions. Inclusion of multiphysical effects under dynamic transient loading presents a more complex and challenging scenario for future studies. The insights gained are crucial for the design and optimization of thermal protection systems, particularly in extreme thermal environments, in order to enhance their reliability and performance. The integration of smart materials and advanced heat conduction models offers new perspectives for developing innovative solutions in material science and engineering