On the Influence of Ultimate Number of Cycles on Lifetime Prediction for Compression Springs Manufactured from VDSiCr Class Spring Wire

Abstract

For the generation of fatigue curves by means of fatigue tests, an ultimate number of cycles must be chosen. This ultimate number of cycles also limits the permissible range of the fatigue curve for the design of components. This introduces extremely high costs for testing components that are to be used in the Very High Cycle Fatigue regime. In this paper, we examine the influence of the ultimate number of cycles of fatigue tests on lifetime prediction for compression springs manufactured from VDSiCr class spring wire. For this purpose, we propose a new kind of experiment, the Artificial Censoring Experiment (ACE). We show that ACEs may be used to permissibly extrapolate the results of fatigue tests on compression springs by ensuring that a batch-specific minimum ultimate number of cycles has been exceeded in testing. If the minimum ultimate number of cycles has not been exceeded, extrapolation is inadmissible. Extrapolated results may be highly non-conservative, especially for models assuming a pronounced fatigue limit.

On the Influence of Control Type and Strain Rate on the Lifetime of 50CrMo4

“…This does not mean that the homoscedastic log-normal distribution is a good model overall. Actually, problems about model consistency and accordance to reality have been brought up in literature [81,[125][126][127][128][129][130][131]. At a significance level of 5%, the Shapiro-Wilk test rejects normality for three out of twelve data sets.…”

Generalization of the Weibull probabilistic compatible model to assess fatigue data into three domains: LCF, HCF and VHCF

“…An alternative assessment of the staircase method replacing the normal distribution proposed in the original version by a three-parameter Weibull distribution is presented by Castillo et al [53], in which a comparison is performed between the results provided by the staircase method and those from the Castillo-Canteli model, see [3]. Besides some light comments about the unsuitability of the staircase method, as devoted in Schijve [10], Pascual [54] and Snyder et al [55], detailed analyses of the main limitations of the staircase model, as a nonrecommendable procedure to estimate fatigue limits even for finite lifetimes, is provided in [53,56].…”

“…For instance, if constant scatter along the S-N curve, i.e. homoscedasticity, or linear heteroscedasticity is assumed [6][7][8][9][10], the factual non-linear evolution of the scatter along the S-N field, evidenced in the experimental fatigue campaigns, cannot be replicated, see [11][12][13].…”

“…In this paper the stochastic fatigue model of Castillo-Canteli [3][4][5][6][7][8][9][10][11][12][13][14] is modified to extend its application validity to the three regions, i.e. LCF, HCF and VHCF, while keeping their compatibility and other important properties.…”

Special Issue: Probabilistic Mechanical Fatigue and Fracture of Materials

“…Another pending goal in the design of fatigue experimental campaigns is the assessment of the limit number of cycles in the very high cycle region where the runouts are usually assumed to be established at 10 6 -10 7 cycles, which is an important topic addressed by Geilen et al [11]. In this work, the authors propose a new method denoted artificial censoring experiment (ACE), where an original fatigue model fitted with real data, such as the well-known bi-linear model, is compared with the resulting model if artificial censored data are simulated beyond the original ultimate number of cycles.…”