Differences in the response to in-phase and out-of-phase multiaxial high-cycle fatigue loading

Abstract

This paper discusses the phase shift effect occurring between two and more load channels of multiaxially loaded specimens. The discussion concludes that there is an extreme shortage of good experimental data that would prove the existence and the trend of the phase shift effect in the highcycle fatigue region. It is no wonder that there are so many fatigue strength estimation criteria that use quite different computational concepts, because the response to the phase shift effect in the experimental base is often hidden in a conglomeration of other interacting effects. The paper presents results of a sensitivity study that compares the fatigue strength estimation results for various such criteria for the same stress amplitudes, but for different phase shifts between the push-pull and torsion load channels. These results show that, with the exception of criteria that assume a zero phase shift effect, the phase shift affects the results of each studied fatigue strength estimation criterion in a different way. A proposal for an experimental setup that would show the real trend unambiguously, and that would enable researchers to check the multiaxial fatigue strength criteria is provided in the paper.

Validating the Methods to Process the Stress Path in Multiaxial High-Cycle Fatigue Criteria

“…A more practical comparison of the output of individual stress path description methods is thus desirable. Papuga et al designed in [ 13 ] a special sensitivity study, which allowed them to assess the response of various multiaxial fatigue strength criteria to the condition of a varying phase shift effect. Three different fictive materials were established to simulate a potentially different material response.…”

“…The same procedure was also processed here. Whereas [ 13 ] focused solely on the MCC approach, here the MCE and MOI approaches were tested additionally. To check the typical response to various concepts of the multiaxial fatigue strength analysis, six different multiaxial criteria were chosen to compute the equivalent stress amplitude .…”

“…Such a claim should be supported by appropriate experimental data, but most of the validations done until now are inconclusive. Papuga et al [ 13 ] explain that the way of treating the shear stress path on a specific plane need not have the expected impact on the critical plane criteria. If the detected maximum damage decides the critical plane there, the planes found critical for either MCE or for MCC concepts need not be the same.…”

Validation of Multiaxial Fatigue Strength Criteria on Specimens from Structural Steel in the High-Cycle Fatigue Region

“…All analyses, results of which are described hereafter, were done with the analysis of the stress path parameters via the minimum circumscribed circle concept, as described by Papadopoulos et al in [ 25 ]. It is important to note that there are alternatives to this solution, as discussed by Meggiolaro et al [ 33 ] or by Papuga et al [ 34 ]—e.g., the minimum circumscribed ellipse method or the maximum prismatic hull. The difference in the method of processing the shear stress path would, however, concern only the two load cases of FF003 and FF004 run with the non-zero phase shift (see Table 4 ).…”

Various parameters of the multiaxial variable amplitude loading and their effect on fatigue life and fatigue life computation

“…It proves statistically how simply the observation can lead to erroneous results if the testing matrix used for the proof is too small or if the number of interacting effects involved is too large. The recent research of Papuga et al 10 has revealed the considerable insufficiency of the existing experimental basis to prove whether the phase shift between tension and torsion load channels affects the fatigue life in high‐cycle fatigue and to what extent. The response to the phase shift effect is very important for a real variable amplitude loading.…”