Abstract
The present work aims at developing a new approach towards the analysis of the crack path through the access to the information from the infrared (IR) video imaging of the steady fatigue crack growth. We first test some commonly available infrared image filtering techniques, and then we introduce a new robust algorithm to identify the position of the dynamic crack. The proposed procedure performs the local analysis of the temperature distribution around the fatigue crack tip in the 316L stainless steel. The developed MATLAB framework simplifies the routine processing and permits analyzing multiple experiments reasonably easily. Two filtering procedures - Gaussian and wavelet shrinkage - were implemented and applied successively to denoise the IR images. Both filters produce comparable and good quality results. The new algorithm capable of automatic locating the crack tip position from consecutive filtered IR images is proposed. Remarkably successful results are demonstrated with only small errors caused by materials distortion.
Highlights
I n recent years, numerous energy-based approaches have gained considerable interest in attempts to characterize the fatigue crack growth
Multiple energy criteria for fatigue life estimation based on the hysteresis energy loss [1,2,3,4] or stored energy [4,5] have been proposed in the literature
It was clearly demonstrated that shortly before fracture, stored elastic energy reduced while the heat dissipation energy increased and reached the value of the plastic work as the material at fracture was no longer able to store the mechanical energy in nice agreement with the Orowan energy criterion of ductile fracture [9]
Summary
I n recent years, numerous energy-based approaches have gained considerable interest in attempts to characterize the fatigue crack growth. In 1950, Freudenthal concluded that: “The study of mechanical behavior and properties at different levels of aggregation is possible only in terms of a concept which on all levels has the same meaning It was assumed by the Authors that the damage accumulation mechanism changed as a harbinger of the imminent fracture where the role of macroscopic displacements was essential, and where the energy dissipation increased significantly. They proposed the value of the stored energy in the material to be a failure criterion based on the thermodynamic principles. The exponential relation between these two parameters remained even beyond the applicability of LEFM in the final crack growth stage
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