Comparison of results of stress cycle counting by the direct spectral method and the Fu-Cebon method for bi-modal type stress processes

Abstract

Abstractis article compares the results of a high cycle fatigue analysis obtained through the application of the two methods dedicated to analysis of response of the structure of the bi-modal type -the direct spectral method and the Fu-Cebon one. the compared parameter is the lifetime for an assumed material S-N curve and stress spectrum de ned in an article by Fu & Cebon.Keywords: fatigue analysis, stress cycle counting, spectral method, bi-modal process Streszczenie W artykule dokonano porównania rezultatów wysokocyklowych analiz zmęczeniowych wykonanych przy zastosowaniu dwu metod dedykowanych dla przypadków odpowiedzi struktury o charakterze dwumodalnym: metody spektralnej bezpośredniej i metody Fu-Cebona. Porównywaną wielkością był czas życia konstrukcji przy założonej postaci krzywej S-N materiału i zmienności naprężeń o charakterystyce wykorzystywanej w artykule Fu i Cebona.Słowa kluczowe: analiza zmęczeniowa, zliczanie cykli naprężeń, metoda spektralna, przebiegi dwumodalne

Using the Effect of Compression Stress in Fatigue Analysis of the Roller Bearing for Bimodal Stress Histories

“…Moreover, the value of T B was easy to determine, due to the fact that T 1 / T 2 = 40. When the known characteristics of stress are in the form of power spectral density, the proposed method can be applied [ 32 ] by a much more natural way than a random attempt.…”

“…On the other hand, if the available data are defined in the frequency domain, e.g., as a power spectral density function, the natural approach will be to use one of the other spectral methods. In such a case, the direct method requires an additional process of identifying the amplitudes for the two deterministic frequencies, which was carried out by the authors in a previous study [ 32 ].…”

“…Originally, the direct spectral method was formulated for completely reversed stress histories of harmonic types, in both primary and secondary cycles [ 31 , 32 , 33 , 34 , 35 ]. For the analyzed case of rolling bearing fatigue, the method’s algorithm was slightly modified due to the fact that the primary cycle was not generally harmonic (i.e., the shape did not have the sine type), and three of the four non-zero stress components had a pulsating type.…”

“…The authors formulated the original method for cycle counting of bimodal stress histories of a completely reversed type, based on their spectral characteristics in the case of superposition of the completely reversed stress cycles (the direct spectral method). This original method was formulated for the simple case of uniaxial stress [ 31 , 32 ], and for multiaxial stress [ 33 , 34 ].…”

“…The next step in fatigue analysis is using the information of identified cycles, including their mean and amplitude values for the estimation of fatigue lifetime, which is realized by the application of the suitable rule of cumulative damage. The most popular rule in engineering applications is the Palmgren-Miner linear cumulative damage rule [ 35 , 36 , 37 ]. The advantages and limitations of its application have been known for many years.…”