Rotating Bending Fatigue Research Articles

Prediction of rotational bending fatigue life of bearing steel based on damage mechanics

Based on the theory of continuous damage mechanics, this paper proposes a fatigue damage evolution model and numerical calculation method considering the influence of vacuum chemical heat treatment process, and studies the rotational bending fatigue damage analysis and life prediction method of M50NiL bearing steel. Firstly, the constitutive model, fatigue damage evolution equation and material parameter calibration method in the theoretical model are given. Secondly, based on the ABAQUS platform, the damage mechanics-finite element numerical calculation method of fatigue damage analysis considering the influence of hardened layer is realized by writing the UMAT subroutine; then, the rotational bending fatigue test of M50NiL bearing steel treated by vacuum chemical heat treatment of quenching and tempering, carburizing and carbonitriding is carried out, and the influence of heat treatment process on fatigue performance is analyzed; finally, based on the proposed fatigue damage model and numerical calculation method, the rotational bending fatigue life of M50NiL bearing steel is predicted, and the results are compared with the experimental results to verify the correctness of the proposed method.

Application of impact-based and laser-based surface severe plastic deformation methods on additively manufactured 316L: Microstructure, tensile and fatigue behaviors

Applying post-processing methods can play a crucial role in addressing defects inherent in the as-built state of additively manufactured materials. This study comprehensively examined the effects of various post-processing techniques, including surface severe plastic deformation (SSPD) methods such as severe shot peening (SSP), ultrasonic shot peening (USP), ultrasonic nanocrystal surface modification (UNSM), and laser shock peening (LSP), combined with stress relieving (SR) on the tensile properties and fatigue behavior of laser powder bed fusion (LB-PBF) stainless steel AISI 316L specimens. Experimental characterization was carried out, focusing on microstructure, porosity, surface texture, hardness, residual stresses, monotonic tensile properties, and rotating bending fatigue behavior. The results demonstrated an excellent combination of enhanced strength and ductility after applying SR and SSPD treatments. Additionally, the post-processing methods significantly improved fatigue behavior by increasing strength, closing subsurface pores, surface layer nanocrystallization and hardening, inducing compressive residual stresses, and modifying the surface texture. Notably, in the high-cycle fatigue regime at the lowest stress amplitude, the SR + UNSM treated specimens exhibited the greatest improvement in fatigue life, followed by SR + USP, SR + SSP, SR + LSP, and SR, when compared to the as-built state.

Prediction of rotational bending fatigue life of bearing steel based on damage mechanics

Based on the theory of continuous damage mechanics, this paper proposes a fatigue damage evolution model and numerical calculation method considering the influence of vacuum chemical heat treatment process, and studies the rotational bending fatigue damage analysis and life prediction method of M50NiL bearing steel. Firstly, the constitutive model, fatigue damage evolution equation and material parameter calibration method in the theoretical model are given. Secondly, based on the ABAQUS platform, the damage mechanics-finite element numerical calculation method of fatigue damage analysis considering the influence of hardened layer is realized by writing the UMAT subroutine; then, the rotational bending fatigue test of M50NiL bearing steel treated by vacuum chemical heat treatment of quenching and tempering, carburizing and carbonitriding is carried out, and the influence of heat treatment process on fatigue performance is analyzed; finally, based on the proposed fatigue damage model and numerical calculation method, the rotational bending fatigue life of M50NiL bearing steel is predicted, and the results are compared with the experimental results to verify the correctness of the proposed method.

Impact of biological environment on bending fatigue lifetime in additive-manufactured polylactic acid fabricated by 3D-printing

Polylactic acid (PLA) has become desirable for biomedical applications, particularly implantable devices. However, the degradation of PLA in biological environments under mechanical stress remains incompletely understood and requires further investigation. This study compared the plain fatigue (PF) and the biodegraded fatigue (BDF) behavior of 3D-printed PLA. For this purpose, two sets of standard fatigue specimens were additively manufactured by the fused filament fabrication (FFF) method. One set was used for plain fatigue testing, and the other was immersed for 330 days in simulated body fluid (SBF). After immersion, the samples were dried and weighed before fatigue testing. The fully reversed rotary bending fatigue tests were conducted on both sets of specimens, and the stress-lifetime (S-N) curves were obtained. Additionally, the fatigue properties of PF and BDF specimens were evaluated. Moreover, the fracture behaviors of the materials were studied using field emission scanning electron microscopy (FESEM). The outcomes implied that the weight of the samples extended during the immersion period, primarily due to water absorption by the PLA. However, after drying, the final weights did not change compared to the weights before immersion. The SBF immersion significantly reduced the fatigue performance of the biodegraded samples comparing the PF result.

Study of the fatigue fractography of dual phase low carbon steel used in automotive industry

Fatigue properties play a crucial role as they are vital to ensuring the durability and integrity of components subjected to repeated loading conditions over long periods. The main objective of this work is to investigate the fatigue behavior of dual-phase low-carbon steels used in automotive applications using a rotating bending fatigue machine. Heat treatments were carried out to analyze the microstructure's effect on the fatigue properties, including quenching low-carbon steel samples at 800 °C and 900 °C. Hardness and tensile tests were performed, and the microstructure was inspected to examine the constitute phases. With the assistance of a scanning electron microscope, fractographic analyses were carried out to reveal the fracture features of the samples at different lifetime ranges. The results show that various failure mechanisms occur depending on the stress levels. Additionally, the specimens quenched at 900 °C exhibited higher fatigue strength.

Enhancing Fatigue Resistance of Polylactic Acid through Natural Reinforcement in Material Extrusion.

This research paper aims to enhance the fatigue resistance of polylactic acid (PLA) in Material Extrusion (ME) by incorporating natural reinforcement, focusing on rotational bending fatigue. The study investigates the fatigue behavior of PLA in ME, using various natural fibers such as cellulose, coffee, and flax as potential reinforcements. It explores the optimization of printing parameters to address challenges like warping and shrinkage, which can affect dimensional accuracy and fatigue performance, particularly under the rotational bending conditions analyzed. Cellulose emerges as the most promising natural fiber reinforcement for PLA in ME, exhibiting superior resistance to warping and shrinkage. It also demonstrates minimal geometrical deviations, enabling the production of components with tighter dimensional tolerances. Additionally, the study highlights the significant influence of natural fiber reinforcement on the dimensional deviations and rotational fatigue behavior of printed components. The fatigue resistance of PLA was significantly improved with natural fiber reinforcements. Specifically, PLA reinforced with cellulose showed an increase in fatigue life, achieving up to 13.7 MPa stress at 70,000 cycles compared to unreinforced PLA. PLA with coffee and flax fibers also demonstrated enhanced performance, with stress values reaching 13.6 MPa and 13.5 MPa, respectively, at similar cycle counts. These results suggest that natural fiber reinforcements can effectively improve the fatigue resistance and dimensional stability of PLA components produced by ME. This paper contributes to the advancement of additive manufacturing by introducing natural fiber reinforcement as a sustainable solution to enhance PLA performance under rotational bending fatigue conditions. It offers insights into the comparative effectiveness of natural fibers and synthetic counterparts, particularly emphasizing the superior performance of cellulose.

Rotating bending fatigue behavior of high-pressure diecast AlSi10MgMn alloy based on T5 heat treatment parameters

Abstract The study investigates fatigue failure, a common phenomenon in machine elements subjected to cyclic stresses. The analysis emphasizes that the actual stress experienced by materials often falls below their tensile and yield strengths due to repetitive variable stresses, leading to fatigue damage. Fatigue life is measured by the number of cycles endured before failure. This paper focuses on the aluminum alloy of AlSi10MgMn, extensively used in manufacturing due to its strength, low density, and corrosion resistance. Experimental procedures encompassed tensile testing, microstructural examination, SEM analysis, and fatigue testing. Tensile tests provided initial stress values for fatigue testing. Microstructure analyses verified that heat-treated samples exhibited precipitates. SEM analysis disclosed microstructural characteristics, while fracture surface examinations demonstrated higher fatigue resistance in heat-treated specimens. Hardness measurements were conducted, with heat-treated samples showing higher values. Theoretical calculations based on stress and cycle numbers were compared to experimental fatigue results. The derived equations aligned well with the tests. Ultimately, the study underlines the importance of heat treatment on material behavior and fatigue resistance, shedding light on alloy performance and durability enhancement.

Influence of Non-Metallic Inclusions on Very High-Cycle Fatigue Performance of High-Strength Steels and Interpretation via Crystal Plasticity Finite Element Method

The fatigue behaviors of high-strength bearing steel were investigated with rotating bending fatigue loading with a frequency of 52.5 Hz. It was revealed that the high-strength steel tended to initiate at interior non-metallic inclusions in a very high-cycle fatigue regime. During fractography observation, it was also seen that the inclusion acting as a failure-originating site was seldom smaller than 10 μm. Moreover, prior austenite grains could also act as the originating source of failure when inclusion was absent. The crystal plasticity finite element method (CPFEM) was adopted to simulate the residual stress distribution around non-metallic inclusions of different sizes under different loading amplitudes. The accumulated plastic strain around the inclusion suggested that the existence of inclusion may reduce material strength and lead to more fatigue damage. The value of accumulated plastic strain around different inclusion sizes also resembled the crack nucleation or propagation of the materials. The simulation results also indicated that inclusions smaller than 5 μm had little influence on fatigue lifetimes, while inclusions larger than 10 μm had a significant influence on fatigue lifetimes.

Evaluation of fatigue characteristics of 3D printed/composites reinforced with carbon fiber using design of experiments

AbstractThis study investigates the fatigue characteristics of 3D‐printed composites made from polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), reinforced with carbon fiber. It involves designing and building a rotating bending fatigue machine, creating standard specimens via FDM, and applying DOE using Taguchi method. Standard specimens are subjected to cyclic loading with a print orientation of 0°, 45°/−45°, and 90°, motor speed and load. Materials such as PLA, ABS, PLA‐CF, and ABS‐CF are tested by maintaining a consistent layer thickness of 0.16 mm and 99.99% infill density while varying stress levels. PLA‐CF outperforms PLA, ABS, and ABS‐CF in fatigue life, with 0° print orientation exhibiting superior fatigue strength. Statistical analysis underscores the significance of print direction, material composition, and stress level. Additionally, the study aims to construct S‐N curves for 3D‐printed PLA/ABS composites with carbon fiber reinforcement, advancing our understanding of mechanical properties and print parameter optimization for enhanced fatigue performance in 3D‐printed composites.Highlights Fatigue characteristics of 3D printed composites made from PLA and ABS, reinforced with carbon fiber investigated. Four polymer composites were used: PLA, ABS, PLA‐CF (short carbon fiber), and ABS‐CF (short carbon fiber). The research focused on the impact of 3D print orientation on fatigue properties, considering print angles of 0°, 45°/−45°, and 90°, alongside adjustable factor like motor speed and load. With a consistent layer thickness of 0.16 mm and 99.99% infill density, the fatigue tests were conducted under stress‐controlled conditions at varying stress levels. Results demonstrate that PLA‐CF specimens exhibit superior fatigue lifetimes compared to PLA, ABS, and ABS‐CF samples.

Development of new AlSi-alloys reinforced with titanium-based particles for laser powder bed fusion: tension and rotary bending fatigue tests

Development of new AlSi-alloys reinforced with titanium-based particles for laser powder bed fusion: tension and rotary bending fatigue tests

Effect of peening with fine iron-sulfide particles on the rotating bending fatigue properties of low alloy steel and formation of iron-sulfide layer

Low alloy steels were subjected to peening with fine iron sulfide particles (FeS-peening) under ambient conditions to transfer a layer of such particles, which can improve seizure resistance and sliding properties, and thus enhance the fatigue characteristics of the steel. This process was performed without the use of aqueous Na2S2O3 and the specimens were assessed using electron probe microanalysis and rotating bending fatigue tests. Treated specimens exhibited higher fatigue limits as a result of high degree of compressive residual stress generated on the steel surface. The effects of residual stress on the fatigue limit were quantitatively investigated using a modified Goodman diagram. Sample cross-sections were observed using electron backscattered diffraction, which confirmed that FeS-peening formed fine surface grains. Grain refinement was determined to be at least partly responsible for the improved fatigue properties of the steel following FeS-peening.

Influence of Inclusion Parameter and Depth on the Rotating Bending Fatigue Behavior of Bearing Steel

Inclusions are an important parameter affecting the fatigue life of materials. In this paper, the type, size, and quantity of inclusions in bearing steel were quantitatively analyzed using scanning electron microscopy and automatic scanning electron microscopy with an X-ray energy dispersive spectroscopy function. The effects of the inclusion parameters and positions on the rotating bending fatigue properties were analyzed using the rotating bending fatigue test. The results proved that for samples 1 and 2, the inclusions were mainly sulfides, Ti-containing inclusions, and their composite inclusions. For samples 3 and 4, the inclusions were mainly oxides or sulfide–oxide complexes. The number and maximum size of inclusions in sample 2 were relatively small. This was mainly due to the difference in the content of Al, S, and Ca elements in the different samples. The inclusion distance to the surface and the maximum inclusion size had a larger influence on the rotating bending fatigue life in comparison to the inclusion type. Moreover, nitride–oxides had a more detrimental effect on the rotating bending fatigue life as compared to the sulfide–oxide complex inclusions. A model was established on the basis of the inclusion size, depth, and stress by using the Python software. The simulation demonstrated that using five parameters fit well with the experiment results.

Pre-stress effect of metal bars in low-stress separation technology

This paper proposes a low-stress separation technology based on pre-stress effect. It connects notching and loading to take advantage of the rotating bending fatigue to achieve the cropping of metal bars. The real-time positions of the notching tool and loading hammer are calculated based on energy equivalence theory. Compared to the conventional notching method, it achieves 25.1 % reduction of cutting force in the case of AISI1045 steel bars. A testing platform is set up and the loading curve is designed to meet the requirements of deflection law and fatigue cyclic loading law. The bending stress for the minimum cutting force, crack angle and deviation under different notch parameters, and the reasonable pre-loading of different materials are determined through cropping tests and finite element simulation. Cropping results indicate that the optimized notch angle and depth are 60° and 1.5 mm, respectively.

Fatigue crack extension mechanism and mode-type analyses of martensitic steels for proposing fatigue strength evaluation method: Example of 18% Ni BCC martensitic steel

The fatigue properties of martensitic steels tend to differ significantly from those of low- and medium-strength steels. Even if the hardness is the same, the fatigue strength varies substantially depending on the microstructure. Thus, for using martensitic steel rationally and developing materials with high fatigue strength, it is desirable to establish a fatigue strength evaluation method that can consider the microstructural effects on fatigue properties. For this purpose, 18% Ni bcc martensitic steel was used as a model metal to conduct rotating-bending fatigue tests in this study. The fatigue crack behavior on the smooth specimen surface was examined, and the fracture surface morphology on both sides of the broken specimen and the microplastic strain distribution near the fatigue crack tip were analyzed. The results clarified the mechanism underlying fatigue crack extension (FCE). The analytical results revealed three types of FCE mechanisms dependent on the stress amplitude, stress state (i.e., plane stress or plane strain), and martensitic microstructure. Considering these mechanisms, a unique stress–life curve was predicted, and a particular fatigue crack shape and fractography were confirmed. The material indices were speculated to be the representative properties of martensitic steels.

Gradient residual stress evolution and its influence on fatigue life under combined carburising heat treatment and ultrasonic surface rolling process

This study combined carburising heat treatment (CHT) with the ultrasonic surface rolling process (USRP) to improve the rotary bending fatigue properties of 18CrNiMo7-6 alloy steel. Based on the experimentally obtained fatigue limit (σ-1), the evolution of gradient compressive residual stress (CRS) of CHT- and CHT + USRP-treated specimens was analysed below the fatigue limit stress level. Subsequently, the evolution mechanism of gradient CRS of the two reinforced specimens was discussed and analysed from the opposing effects of austenite transformation and dislocation density change on the evolution of CRS. The results demonstrated that the selective bending fatigue performance of the alloy was evidently improved after the introduction of CRS; however, the change in fatigue limit was not evident. The durability under other loads (such as cyclic tension/compression and torsion loads) needs further study. The gradient CRS evolution of CHT specimens was mainly caused by the large residual austenite transformation and small dislocation density change. Therefore, the volume expansion caused by residual austenite transformation gradually increased the gradient compression residual stress of CHT specimens with an increased number of cycles. Contrarily, the degree residual stress evolution of CHT + USRP specimens was more affected by the dislocation density, and the gradient compression residual stress gradually decreased with an increased number of cycles. Finally, the residual stress evolution rate of the two reinforced specimens was divided into two stages: fast and slow.

Synergistic impact of corrosion pitting on the rotating bending fatigue of additively manufactured 316L stainless steel: Integrated experimental and modeling analyses

In this study, the ex-situ rotating bending corrosion fatigue behavior of laser powder bed fused stainless steel (SS) 316L has been studied incorporating experimental analyses and modeling. The findings revealed significant variations (almost 20 %) in fatigue lifetime in pre-corroded specimens relative to non-corroded (virgin) specimens because of corrosion-derived pitting phenomena on the surface. To this end, the fatigue strength of virgin (non-corroded) and pre-corroded SS 316L were recorded at 242 MPa and 203 MPa, respectively. Upon conducting the fatigue tests and extracting stress-life trends, advanced microstructural characterization and postmortem analyses were used to quantify fatigue crack behavior and fracture surface. An empirical model is also developed employing depth-sensing indentation testing, linear elastic fracture mechanics, and computer tomography scans to propose an optimum predictive trend. The analysis comparing existing models with our proposed model demonstrates reasonable agreement between experimental findings and the predicted life for the studied laser powder bed fused SS 316L material exposed to corrosion rotating bending fatigue test. The findings of this research carry important contributions to the structural integrity and longevity of marine engineering, ship construction, naval operations, and naval aviation where materials and components are exposed to cyclic loading and corrosion.

Study on rotary bending fatigue performance of TC4 lattice structure fabricated by selective laser melting

Prediction of the fatigue performance of lattice structures in additive manufacturing still lacks widely applicable methods. To address this issue, we investigated the effect of a BCC lattice structure combined with thin walls and ribs on the fatigue performance of TC4 alloy samples. The lattice-structured samples were fabricated by selective laser melting. In addition, we proposed a prediction model of fatigue performance that combined ABAQUS finite element analysis with FE-safe fatigue analysis. The simulation and experimental results verified the reliability of the model. Based on this method, the effects of lattice and ribbed plate structures on the bending fatigue performance were investigated. The experimental results showed that the stress concentration generated by lattice structures weakened the fatigue performance. On the contrary, ribbed plates can enhance fatigue performance, which also depends on the orientation of the rib structure. The simulation results showed that increasing the volume fraction of unit cells can mitigate the stress concentration, leading to improved fatigue performance. The lattice structure combined with the rib structure exhibited superior fatigue performance. In addition, the proposed models can also be applied to other metallic materials. The findings in this study can provide a theoretical basis for the design of lattice structures with better fatigue performance.

Enhancing high cycle fatigue performance of plasma nitrided AISI 4140 steel by post-aging treatment and direct current magnetic field

Machine elements become unable to perform their duties as a result of fatigue damage. In addition, machine elements that are subjected to fatigue under cyclic loads are exposed to electric and magnetic fields when they are close to electrical and magnetic field sources such as electric motors. Moreover, plasma nitriding is often used to increase the fatigue strength of materials. Although the fatigue properties of surface-treated materials are frequently studied, the fatigue behavior of these materials under a magnetic field is not fully known. Therefore, this study focuses on examining the effects of magnetic field on the fatigue properties of surface-treated materials. For this purpose, AISI 4140 steel samples were plasma nitrided and subsequently post-aged, and then they were tested using a rotating bending fatigue testing system by exposing them to a magnetic field for 30 % and 100 % of their fatigue life. ε-Fe2–3N and γ’-Fe4N phases were seen in surface-treated samples, in addition to these phases, peaks belonging to the α”-Fe16N2 phase were observed in post-aged samples. Plasma nitriding raised the hardness of the material because of nitride phases and α”-Fe16N2 caused an extra increase. The highest diffusion depth was seen in the post-aged samples because post-aging facilitated the diffusion of nitrogen. Surface treatments increased the fatigue strength of the material. All samples tested under a magnetic field exhibited higher fatigue strength than samples tested without a magnetic field because fatigue crack initiation was prolonged by the magnetic field. Compared to non-magnetic and 30 % magnetic samples, the fatigue strengths of the samples in a 100 % magnetic field were lower. Furthermore, it was observed that applying a magnetic field had no effect on the samples' fractographic structure.

Abnormal fatigue behavior of a CoCrW-based wear-resistant alloy

The fatigue characteristics of a CoCrW-based wear-resistant alloy, which underwent hot forging and a solution treatment resulting in ultimate tensile strength (UTS) and yield strength (YS) levels of 911 and 540 MPa respectively, were analyzed through rotary bending fatigue tests at 600 °C. An exceptionally elevated threshold at 107 cycles, measuring 700 MPa, marks a 1.29-fold increase over the YS and a 0.77-fold increase over the UTS. Notably, the observation of strain-induced martensitic transformation in the superficial layer underscored the alloy’s superior fatigue resistance, primarily attributed to its significant work-hardening capacity.

Fatigue performance testing and life prediction of welded fuel pipes

The external piping system which connects power devices, valve control devices, actuators, etc. is an essential system on the aero engine. Under the combined effects of high fluid pressure and external vibration, multiaxial fatigue failure is the main factor that seriously affects the safety of the piping system. The objective of this paper is to establish the multiaxial fatigue life model for the typical welded fuel pipe of the piping system by combining fatigue testing, simulation and theoretical analysis which is of great guiding significance for the engineering application of the piping system. Firstly, the fatigue limits of welded fuel pipes under no and 13.5 MPa internal pressure are obtained by rotational bending fatigue tests using the up-and-down method. Three additional stress levels of rotational bending fatigue tests under no internal pressure are supplemented and then the S-N curve is further obtained by the group method. Since the corresponding fracture surface of the specimens locates at the weld toe near the fixed end, peak stress method is adopted to evaluate the fatigue performance of the weld toe on the pipe specimens. In addition, by comparing the fatigue limit with no and 13.5 MPa internal pressured pipes, it is obvious that the equivalent uniaxial stress corrected by Gerber formula is not applicable for the multiaxial fatigue condition which is caused by the combined effect of fluid pressure and displacement load. The local stress concentration factor caused by the weld toe is determined and based on Findley critical plane model, the multiaxial fatigue life model is established which simultaneously takes the local stress concentration effect, mean stress effect and multiaxial stress effect into consideration. The results of rotational bending fatigue tests under 13.5 MPa internal pressure are within the triple error dispersion band and the accuracy of the proposed life model are verified.