This study demonstrates that an artificial flaw that has an arbitrary boundary profile and the response to non-destructive testing similar to a natural crack can be fabricated by bonding surfaces with artificial grooves using diffusion bonding. Artificial flaws with a small openings and widely spread boundary profiles inside can be realized by bonding Type 316L stainless steel blocks with artificial grooves. The artificial flaw is designed so that its surfaces have a 20% physical contact. The conditions for bonding are based on the results of preliminary experiments. Validations are carried out using two electromagnetic non-destructive testing methods: direct current potential drop and eddy current tests, whose results are well reproduced by finite element simulations. Subsequent destructive testing confirms that the actual profile of the artificial flaw agrees well with the designed one.

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The fatigue limit estimation method based on energy dissipation measured by infrared thermography has been introduced in various industries in recent years because of its time and cost effectiveness. In this method, the temperature change due to irreversible energy dissipation during one loading cycle is measured for different levels of applied stress amplitude. The obtained relationship between temperature change and stress amplitude shows a significant inflection at a certain stress level where temperature change due to energy dissipation shows a steep increase. It is known that this stress level coincides with the fatigue limit. In this study, the measurement conditions for appropriate fatigue limit determination based on the energy dissipation are discussed experimentally in conjunction with: (i) the required number of loading cycles in each stress level, (ii) the appropriate number of loading cycles, (iii) the influence of loading history and fatigue damage accumulation, and (iv) the influence of loading frequency.

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