Abstract
The article presents the results of research on low cycle fatigue strength of laser welded joints vs. non-welded material of high-strength steel DOMEX 700 MC. The tests were performed under load controlled using the total strain amplitude ɛac. The operating principle of the special electro-mechanic fatigue testing equipment with a suitable clamping system was working on 35 Hz frequency. Fatigue life analysis was conducted based on the Manson-Coffin-Basquin equation, which made it possible to determine fatigue parameters. Studies have shown differences in the fatigue life of original specimens and laser welded joints analysed, where laser welded joints showed lower fatigue resistance. In this article a numerical analysis of stresses generated in bending fatigue specimens has been performed employing the commercially available FEM-program ADINA.
Highlights
Static or quasistatic loading is rarely observed in modern engineering practice, making it essential to the engineer to implications of repeated loads, fluctuating loads and rapidly applied loads
The majority of engineering design projects involves machine parts subjected to fluctuating of cyclic loads
The most difficult aspect of fatigue is to detect the progressive changes in material properties that occur during cyclic stressing and the failure may occur with no apparent warning
Summary
Static or quasistatic loading is rarely observed in modern engineering practice, making it essential to the engineer to implications of repeated loads, fluctuating loads and rapidly applied loads. In performing smooth specimen tests of this type, it must be recognized that the phenomena of cyclic hardening, cyclic softening and cycle-dependent stress relaxation, as well as sequential loading effects and residual stress effects that may be experienced by the specimen as it accumulates fatigue damage are presumed to be the same as at the critical point of the structure member being simulated. Since, including all these factors in a test is inconvenient, inaccurate and expensive, the use of finite element method has become a powerful tool to calculate the cyclic stress-strain response of any structure or mechanical component. The relatively short fatigue life of welded detail is explained, in the main, by three factors: severe notch effect due to the attachment and the weld filler metal, presence of non-metallic intrusions or micro-flaws along the fusion line, presence of large tensile residual stresses
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