•A Gaussian process-based fatigue life prediction model is proposed.•The shear and normal stress components on the critical plane are the input data.•The fatigue data of S355N steel and 2124 T851 ...alloy are analyzed.•The square exponential kernel predicts the fatigue lives of datasets accurately.•Square mapped input data results in the best life prediction for both datasets.
Fatigue life prediction with failure probability estimation for materials subjected to multiaxial loading is an important task in engineering design because it reduces the financial cost by eliminating expensive experimental tests. Owing to the complex deterioration mechanisms of fatigue failure, existing fatigue life prediction models are of the empirical or semi-empirical type, and their applicability is limited to validating the loading condition and material. Improper selection of the fatigue model could result in non-conservative life prediction with high financial and catastrophic consequences. To solve this problem, an innovative approach based on the Gaussian process for fatigue life prediction under multiaxial loading is presented. The inherent features of the Gaussian process predispose its application to fatigue life prediction under multiaxial loading as an efficient and practical approach to avoid the problem in selecting adequate semi-empirical parametric fatigue models. The model was validated on two sets of experimental data obtained by fatigue testing of S355N steel and 2124 T851 aluminum alloy under uniaxial and multiaxial loadings. In the model training process, only data obtained under uniaxial and pure torsion cyclic loadings were applied. Owing to the implemented physics-based input data, which are related to the stress components acting on the critical plane of crack initiation, the model accurately predicted the fatigue lives of the two tested materials by implementing the squared exponential covariance function. In addition, the fatigue lives were also computed using four parametric fatigue strength criteria (Crossland, Matake, Carpinteri et al., and Papuga–Růžička models). The best results obtained by the parametric models exhibited a lower fatigue prediction performance than the results using the Gaussian process-based model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High cycle and very high cycle fatigue (HCF/VHCF) in a bainite/martensite (B/M) multiphase steel with varying inclusion size and microstructural features was studied using ultrasonic axial cycling ...test. The fatigue crack initiation was predominantly induced by inclusions in specimens with large inclusion size, whereas fatigue crack initiated from the sub-surface microstructure in specimens with coarse microstructure. The fatigue life from granular bright facet (GBF) to fish-eye and from fish-eye to the critical crack size was calculated to obtain an estimate of the contribution to fatigue life by GBF, for the two modes of crack initiation within the HCF/VHCF regime. The results demonstrated that the majority of fatigue life was consumed by the crack initiation process along with the formation of GBF irrespective of whether the crack initiated from inclusions or from sub-surface microstructure. In the case of crack initiation from sub-surface microstructure, the ratio of fatigue crack initiation life to total fatigue life (Ni/Nf) had a wide scatter, which is attributed to varying B/M hierarchical structure in individual prior austenite grains.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•T4 treatment improves the corrosion fatigue strength.•Localized corrosion and cracked TBs compete for the fatigue crack initiation.•T4 treatment alleviates the corrosion attack and weakens the ...HE.•Cracking at TBs reduces the corrosion fatigue lifetimes of T4 samples.
In this work, the corrosion fatigue behaviors of an as-forged Mg-6.7%Zn-1.3%Y-0.6%Zr alloy before and after solid solution treatment (T4) in 3.5 wt% NaCl solution have been investigated and compared. S-N curves showed that the fatigue strength of as-forged samples corresponding to 5 × 106 cycles was 30 MPa, whereas the fatigue strength of T4 samples was 50 MPa. Fracture observations showed that for the as-forged samples, fatigue cracks mainly initiated at localized corrosion sites on sample surfaces. However, for the T4 samples, the crack initiation was respectively related to the localized corrosion and TB cracking at low and high stress amplitudes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Fine shot peening has superior effects on fatigue performance.•FLPF is prolonged more than 25 times.•FSIP is more than 76%.•Fatigue cracks locate beneath the surface enhanced layer induced by shot ...peening.
The effect of shot peening on Ti2AlNb fatigue performance was investigated. Glass fine shot peening was used and residual stresses were measured by XRD technology and electropolishing method. Rotating bending fatigue test was performed. The results show compressive residual stress is introduced and the maximum is 322 MPa, and fatigue property is significantly improved. The high cycle fatigue life is prolonged more than 25 times and fatigue endurance limit is increased from 170 MPa to 360 MPa. Moreover, fatigue cracks initiate beneath surface enhanced layer for SP specimens, while for referenced specimens they are located at surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Material removal operations play a pivotal role in the manufacture of key components, required for engineering systems to operate safely and efficiently under ever more advanced functional ...requirements and over extended life cycles. To further step up the loading capability of machined parts, fundamental understanding of how of machining-induced features can influence the performance of advanced materials under complex service conditions is necessary over finer temporal and spatial scales. As discussed in Part I of this review, when engineering surfaces are generated by material removal processes, a wide range of physical mechanisms (e.g. mechanical, thermal, chemical and their combinations) drive the characteristics of workpiece surface integrity. In Part II of this review, the interplay between the metallurgical and micro-mechanical condition induced by material removal processes and their in-service response will be thoroughly explored, by a critical analysis of the state-of-the-art in the field. Specifically, attention is focused on recent advances made towards the understanding of the mechanisms determining the resistance of machined surface to fatigue crack nucleation (Section 2), corrosion and stress-corrosion cracking (Section 3), and wear (Section 4). Furthermore, the impact of relevant post-machining treatments on the in-service behaviour of machined surfaces is analysed, and the possible strategies for the enhancement of the functional performance of machined surfaces are presented (Section 5). Finally, the current research gaps and the prospective challenges in understanding the in-service behaviour of machined surfaces are critically discussed, providing an interpretation of the possible directions of future scientific development of this field.
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•The physical mechanisms employed to perform material removal influence the surface integrity induced to the machined part.•Machining-induced surface layers can play a primary role in determining the in-service behaviour of machined components.•The review analyses the influence of machining-induced anomalies on fatigue, corrosion, stress-corrosion and wear resistance.•Post-machining strategies to enhance the in-service performance of machined surfaces are discussed.•Future challenges within the understanding of the possible failure mechanisms of machined surfaces are in-depth analysed.
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•Solid solution strengthening is a prime contributor for resisting surface and subsurface initiated damage.•RCF caused strain hardening may not be a significant contributor to extend ...the fatigue life.•Owing its chemical composition and microstructural characteristics, the 3310 steel showed better fatigue performance than 52100.
In this study, different microstructures were generated in steels by varying the heat treat parameters and were tested under rolling contact fatigue (RCF) and under specific test conditions known to cause white etching cracks (WECs). Case carburized AISI 3310 steel showed significantly longer fatigue life than martensitically through-hardened 52100 steel. In addition, this study examined carburized steel that had been heat treated differently and RCF tested. The 3310 steel was carburized at a lower carbon potential and subsequently, the carburized steel was austenitized at a lower temperature so that lesser solute quantities had dissolved into the austenite phase prior to the quench step. The carburized steel samples with less solute dissolution showed higher hardness and more compressive stresses than the original carburized steel; however, they showed 75% shorter RCF life than the original carburized steel. These results suggest that solid solution strengthening is a significant contributor to fatigue resistance under WEC damage conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The model is expanded to include equations for estimating the model parameters in terms of common properties of metals.•The model is able to simulate the hysteresis behavior of materials.•The ...Constant Fatigue Life Diagram for A36 is presented.•Dramatic increase in energy loss before dropping to zero and failure due to fatigue is observed.
This paper presents further development of a spring mechanical system, proposed by Guranlick et al, in (1) deriving equations for the determination of the mechanical system parameters in terms of material properties; (2) developing applications for deriving fatigue life relations with consideration for the ratio of the minimum to maximum stress; and (3) extending the model to incorporate the hysteresis behavior of steel under cycling loading. These applications are demonstrated in this paper with numerical illustrations.
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48.
Combating mental fatigue in soldiers Martin, Kristy
Journal of science and medicine in sport,
November 2017, 2017-11-00, 20171101, Volume:
20
Journal Article
Peer reviewed
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Fatigue is common in individuals with a variety of chronic health conditions and can have significant negative effects on quality of life. Although limited in scope, recent work suggests persons with ...hearing loss may be at increased risk for fatigue, in part due to effortful listening that is exacerbated by their hearing impairment. However, the mechanisms responsible for hearing loss-related fatigue, and the efficacy of audiologic interventions for reducing fatigue, remain unclear. To improve our understanding of hearing loss-related fatigue, as a field it is important to develop a common conceptual understanding of this construct. In this article, the broader fatigue literature is reviewed to identify and describe core constructs, consequences, and methods for assessing fatigue and related constructs. Finally, the current knowledge linking hearing loss and fatigue is described and may be summarized as followsHearing impairment may increase the risk of subjective fatigue and vigor deficits; adults with hearing loss require more time to recover from fatigue after work and have more work absences; sustained, effortful, listening can be fatiguing; optimal methods for eliciting and measuring fatigue in persons with hearing loss remain unclear and may vary with listening condition; and amplification may minimize decrements in cognitive processing speed during sustained effortful listening. Future research is needed to develop reliable measurement methods to quantify hearing loss-related fatigue, explore factors responsible for modulating fatigue in people with hearing loss, and identify and evaluate potential interventions for reducing hearing loss-related fatigue.
•Anisotropic fatigue properties were observed in SLM AlSi10Mg in different build directions.•X-CT was adopted to characterize the size, shape, and location of 3D defects.•The anisotropic fatigue ...resistance is largely controlled by the spatial anisotropy of defects.•Fatigue strength assessment considering defect distribution was proposed via K-T diagram.
Metallurgical defects have a critical influence on the anisotropic fatigue resistance of additively manufactured parts under cyclic loading. Here X-ray computed tomography (CT) has been used to characterise the defect population for laser powder bed fusion processed AlSi10Mg alloy and correlated with the tensile and high cycle fatigue (HCF) properties of specimens loaded both parallel and perpendicular to build direction. Despite similar tensile strengths, those tested perpendicular to the build direction exhibit a higher elongation and a higher fatigue strength (114 MPa) than those tested parallel to it (45 MPa). The near surface defects preferentially act as the fatigue crack initiation site for almost all the tested HCF specimens. The large oblate (pancake-shaped) defects were found to orient primarily within the build plane giving a larger projected area within this plane leading to a highly anisotropic fatigue strength. Extreme value statistics were used to predict the likely defect population in the critical near surface region of fatigue samples based on X-ray CT measurements. Finally, a fatigue performance assessment diagram considering these extreme value defects was established using the Kitagawa-Takahashi diagram.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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