Influence of the Elastoplastic Strain on Fatigue Durability Determined with the Use of the Spectral Method

Abstract

The paper presents experimental static and fatigue tests results under random loading conditions for the bending of 0H18N9 steel. The experimental results were used in performing calculations, according to the theoretical assumptions of the spectral method of fatigue life assessment, including elastoplastic deformations. The presented solution extends the use of the spectral method for material fatigue life assessment, in terms of loading conditions, above Hooke’s law theorem. The work includes computational verification of the proposal to extend the applicability of the spectral method of determining fatigue life for the range of elastoplastic deformations. One of the aims of the proposed modification was to supplement the stress amplitudes used to calculate the probability density function of the power spectral density of the signal with correction, due to the plastic deformation and its use for notched elements. The authors have tested the method using four of the most popular probability density functions used in commercial software. The obtained results of comparisons between the experimental and calculation results show that the proposed algorithm, tested using the Dirlik, Benasciutti–Tovo, Lalanne, and Zhao–Baker models, does not overestimate fatigue life, which means that the calculations are on the safe side. The obtained results prove that the elastoplastic deformations can be applied within the frequency domain for fatigue life calculations.

Effect of Micro-Shot Peening on the Fatigue Performance of AISI 304 Stainless Steel

“…It is reported that a plastic deformation zone on the shot-peened AISI 4140 surface, which consists of a refined grain structure, increases the corrosion resistance of the material in 3.5 wt.% NaCl solution [13]. Moreover, elastoplastic strain is taken account to assess fatigue life of 304 SS with the use of spectra method [14].…”

Spectral Fatigue Prediction with Strain-Based Reformulation to Handle Overloads and Localized Elastic-Plastic Deformation

“…Spectra that Exceed Elastic Response. Several papers in the literature ( [33,32,7]) have aimed to address the focus of this current research work, spectra that produce localized elastic-plastic response.…”

Special Issue: Probabilistic Mechanical Fatigue and Fracture of Materials

“…Nevertheless, these methods are rarely applied in notched conditions, or when the amplitude is above the yield's stress and the fatigue lifetime prediction is limited to elastic deformations. For this reason, Böhm et al [12] proposes a novel algorithm to extend the spectral methods for considering elastoplastic deformations and notched conditions. The proposed algorithm is successfully exemplified with an experimental campaign on 0H18N9 steel in uniaxial bending loading.…”