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Influence of surface morphology on fatigue behavior of metastable austenitic stainless steel AISI 347 at ambient temperature and 300°C
Smaga, M. ; Skorupski, R. ; Mayer, P. ; Kirsch, B. ; Aurich, J. C. ; Raid, I. ; Seewig, J. ; Man, Jiří ; Eifler, D. ; Beck, T.
The effect of surface modification by cryogenic turning on fatigue behavior of metastable austenitic stainless steel AISI 347 was investigated in stress-controlled fatigue tests at ambient temperature (AT) and 300 °C in air. Five different surface morphologies were manufactured by the variation of turning parameters. Surface and near surface morphology were comprehensively characterized by various experimental techniques. The experimental data on the cyclic deformation behavior, stress-strain response and fatigue life for all surface morphologies are reported.
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Fatigue damage prediction of short edge crack under various load: Direct Optimized Probabilistic Calculation
Krejsa, M. ; Seitl, Stanislav ; Brožovský, J. ; Lehnert, P.
Fatigue crack propagation depends on a number and value of stress range cycles. This is a time factor in the course of reliability for the entire designed service life. Three sizes are important for the characteristics of the propagation of fatigue cracks - initial size, detectable size and acceptable size. The theoretical model of a fatigue crack progression can be based on a linear elastic fracture mechanics (uses Paris-Erdogan law). Depending on location of an initial crack, the crack may propagate in structural element (e.g. from the edge or from the surface under various load) that could be described by calibration functions. When determining the required degree of reliability, it is possible to specify the time of the first inspection of the construction which will focus on the fatigue damage. Using a conditional probability and Bayesian approach, times for subsequent inspections can be determined based on the results of the previous inspection. For probabilistic modelling of a fatigue crack progression was used the original and a new probabilistic method - the Direct Optimized Probabilistic Calculation ('DOProC'), which uses a purely numerical approach without any simulation techniques or approximation approach based on optimized numerical integration. Compared to conventional simulation techniques is characterized by greater accuracy and efficiency of the computation.
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Effect of rivet holes on calibration curves for edge cracks under various loading types in steel bridge structure
Seitl, Stanislav ; Miarka, Petr ; Kala, Z. ; Klusák, Jan
Attention has been paid to fatigue cracks in steel structures and bridges for a long time. In spite of efforts to eliminate the creation and propagation of fatigue cracks throughout the designed service life, cracks are still revealed during inspections. There is some limitation of crack sizes which are detectable on structure (from 2 up to 10 mm). Note that depending on the location of the initial crack, the crack may dominantly propagate from the edge or from the surface. The theoretical model of fatigue crack progress is based on linear elastic fracture mechanics. Steel specimens are subjected to various load types (tension, three- and four-point bending, pure bending etc.). The calibration functions for short edge cracks that are near the hole for a rivet or bolt are compared for various loads and the discrepancies are discussed.
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