Bending Fatigue Characteristics Research Articles

Greatly Improved the Tunable Amplitude of Ferromagnetism Based on Interface Effect of Flexible Pt/YIG Heterojunctions.

Flexible quantum spin electronic devices based on ferromagnetic insulators have attracted wide attention due to their outstanding advantages of low-power dissipation and noncontact sensing. However, ferromagnetic insulators, such as monocrystalline yttrium iron garnet (Y3Fe5O12, YIG), hve weak stress effects with a small magnetostrictive coefficient (λ110, 10 ppm), making it difficult to achieve a large magnetic tunable amplitude. In this paper, large-scale (with a diameter of 40 mm), flexible Pt/YIG heterojunctions were obtained by double-cavity magnetron sputtering technology, indicating typical soft magnetism and good bending fatigue characteristics. Here, the 3 nm thickness of the Pt layer triggers an obvious magnetic proximity effect, in which the in-plane ferromagnetic resonance field is decreased by 70 Oe compared to flexible Cu/YIG heterojunctions. Meanwhile, it shows a wide tunable amplitude of 110 Oe under the flexible bending stresses, which is induced by the sensitive interface effect of Pt (3 nm)/YIG heterojunctions. The saturation magnetization of Pt/YIG heterojunctions is negatively correlated with Pt thickness rather than the relative stability of Cu/YIG heterojunctions, depending on the magnetic proximity effect. It brings greater application possibilities for flexible stress-sensitive magnetic oxides in spin logic electronic devices.

A Novel Ultrasonic Fatigue Test and Application in Bending Fatigue of TC4 Titanium Alloy

The very high cycle fatigue (VHCF) problems of thin-plate structures are usually caused by high-frequency vibrations. This paper proposes an accelerated fatigue test method based on ultrasonic loading technology in order to develop a feasible bending testing method and explore the bending fatigue characteristics of thin-plate structures in the VHCF regime. A new bending fatigue specimen with an intrinsic frequency of 20 kHz was designed based on cantilever bending through finite element simulation. It was verified by the axial load test with R = -1. The results showed that the method could effectively transfer the dangerous cross-section at the first-order cantilever bending restraint to the internal part of the specimen, thereby making the fracture location independent of the complex stresses. The linear relationship between the vibration amplitude and the maximum stress was also verified using strain measurements. Furthermore, the S-N curves and fracture morphology for different loading types were consistent with conventional studies to a certain extent, which indicated that the design of the bending test model was reasonable.

Experimental and Numerical Studies on Fatigue Characteristics of CFRP Shaft Tube

Carbon Fiber Reinforced Plastic (CFRP) shaft tube structure is widely applied in different fields, including aerospace, automotive, and wind power. Since CFRP shaft tube is often subjected to bending fatigue loads, it is of great significance to research its bending fatigue characteristics. Because of its unique advantages, such as a smaller size, lighter weight, and the outstanding ability to form a sensor network, the Fiber Bragg Grating (FBG) sensor is very applicable for health monitoring research of composite material structures. Taking the CFRP shaft tube under bending load as the research object, based on the theory of composite material mechanics and applying the research idea of combining simulation analysis and experiment, the fatigue life, residual stiffness, and fatigue damage evolution of CFRP tubes under three-point bending fatigue loading were studied. Moreover, the fatigue characteristics of CFRP tubes under different fatigue loading were analyzed. At the same time, the ultrasonic phased array was used to obtain the fatigue damage evolution rule by scanning and analyzing the damage to the CFRP shaft tube after different fatigue loading times. Through the application of the FBG sensors, the whole process of fatigue evolution of the CFRP shaft tube was fully monitored.

Evaluations of microstructure and fatigue properties of Ti-Ta alloys

In recent years, the demand for implants has increased in the orthopedic field due to the aging of the population. Among them, Ti-6Al-4V alloy is very often used. However, its high Young's modulus and cytotoxicity are regarded as problems. Therefore, we are focusing on titanium and tantalum, which are highly corrosion-resistant elements, and are developing Ti-Ta alloy, which is a β-type titanium alloy that exhibits low Young's modulus and low cytotoxicity. Furthermore, from the viewpoint of safety and durability, both high strength and low elasticity and excellent fatigue characteristics are required. In this study, we identified the microstructure and crystal structure of 4-types of heat-treated Ti-Ta alloys. In addition, torsional fatigue and plane bending fatigue tests were performed. By comparing these results, we investigated the relationship between structure and fatigue characteristics. From SEM and TEM observation, EBSD and EDS results, it was found that Tantaulum was dissolved in the β-Ti matrix in any heat treatment conditions. Furthermore, α-Ti was deposited at the grain boundaries by 500℃ aging. It was also found that the average crystal grain size increased due to the increase in the solution temperature and the aging treatment. Then, the torsional fatigue characteristics improved as the crystal grain size became smaller. The plane bending fatigue characteristics were improved by strengthening precipitation with α-Ti.

Effect of metal and polymer mating gears on the bending fatigue performance of asymmetric polymer gears

The material of the mating gear influences the fatigue life of polymer gears. The bending fatigue characteristics of polyamide 66 asymmetric gears (34°/20° and 20°/34°) corresponding to steel–polymer and polymer–polymer material combinations were investigated. The performance of symmetric gear pairs (20°/20°) was determined to serve as a comparison. Quasi-static numerical simulations were performed in a finite element analysis tool to predict root bending stress, load sharing ratio, and tooth deflection. The bending fatigue strength of steel–polymer and polymer–polymer pairs of each test configuration was determined using bending fatigue tests. The load sharing ratio and root bending stress of polymer–polymer pairs decreased substantially compared to steel–polymer pairs. The extent of deflection-induced load sharing was greater in polymer–polymer pairs. The bending fatigue life of polymer–polymer pairs was lower than that of steel–polymer pairs owing to the higher operating temperature. In polymer–polymer pairs, polymer driving and driven gears increased the heat generated and diminished the heat dissipation to the environment. In steel–polymer and polymer–polymer pairs, the configuration with the highest bending fatigue strength was 34°/20° and 20°/34°, respectively. This divergence was caused by the increase in temperature difference between the two configurations for polymer–polymer pairs. Analysis of hysteresis loops indicated that the loop area was higher for polymer–polymer pairs, signifying the increased amount of dissipated energy. No noticeable variation was observed between the failure modes of steel–polymer and polymer–polymer pairs despite the significant difference in the operating temperatures. The bending stress and operating temperature were the dominant factors affecting the performance of steel–polymer and polymer–polymer gear pairs, respectively.

Ultra-high three-point bending fatigue performance of nano-silica-reinforced CFRP

The effect of silica nano-particles on the three-point bending fatigue characteristics of plain weave carbon fiber composites (CFRP) was analyzed in the VHCF regime. The addition of silica had a significant effect on the fatigue life of CFRP, which extended the life by multiples. Rigid nano-particles enhanced the connection strength between polymer and carbon fiber, and had a passivating and even blocking effect on the growth of fatigue cracks. The fatigue damage morphologies of nano-particles modified CFRP were closely related to the stress magnitude. The stiffness degradation changed with the evolution of damage morphologies, showing a staged change characteristics.

Formation of a hydroxyapatite layer on Ti–29Nb–13Ta–4.6Zr and enhancement of four-point bending fatigue characteristics by fine particle peening

A hydroxyapatite (HAp) surface layer was generated at room temperature on a beta-titanium alloy (Ti-29Nb-13Ta-4.6Zr, TNTZ) using fine particle peening (FPP), as a means of enhancing fatigue resistance. This material is commonly employed in bio-implants, but has a suboptimal Young's modulus. Treated specimens were assessed using scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and electron backscatter diffraction, as well as by measuring the Vickers hardness. Performing FPP using shot particles made of HAp was found to transfer the particles to the TNTZ surface to rapidly produce a HAp layer that became thicker as the FPP process progressed. Room-temperature four-point bending fatigue tests in air showed that the HAp layer resulting from the FPP process increased the endurance limit of test specimens. This improved performance is ascribed to the appearance of a hardened surface layer having a significant degree of compressive residual stress.

Effect of broken wire on bending fatigue characteristics of wire ropes

The life of damaged wire rope is difficult to judge and the damaged wire rope is prematurely replaced resulting in an enormous economic waste. This paper studies the effect of different distributions of pre-broken wires on bending fatigue behavior of wire ropes using a self-made bending fatigue test facility. The fatigue lives of wire ropes with different distributions of pre-broken wires were studied using both visual inspection and commercial non-destructive inspection technology, combined with electron microscopy. It is found that broken wires on the surface reduce the bending fatigue life of wire ropes. The broken wires increase the stress in the inner wire strands as well as the contact force between the wires. This leads to a concentration of severe wear, which accelerates the density of broken wires locally, leading to short fatigue lives especially in the case with the most concentrated number of pre-broken wires (1×4). After numerous wires fail by wear and fatigue, others fail by tensile overload, as evidenced microscopically by necking and ductile failure. The damage in the rope at failure defined by counting broken wires is nearly 50% smaller than the damage value given by the commercial non-destructive damage value, based on magnetic measurements.

Rotary Bending Fatigue Characteristics According to Optimal Friction Welding of SF45 to SM45C Steel Bars

Rotary Bending Fatigue Characteristics According to Optimal Friction Welding of SF45 to SM45C Steel Bars

Effect of equal channel angular extrusion on Al-6063 bending fatigue characteristics

The purpose of this investigation was to refine the grains of annealed 6063 aluminum alloy and to improve its yield stress and ultimate strength. This was accomplished via the equal channel angular extrusion (ECAE) process at a temperature of 200°C using route A, with a constant ram speed of 30 mm/min through a die angle of 90° between the die channels for as many as 6 passes. The experiments were conducted on an Avery universal testing machine. The results showed that the grain diameter decreased from 45 μm to 2.8 μm after 6 extrusion passes. The results also indicated that the major improvement in fatigue resistance occurred after the first pass. The subsequent passes improved the fatigue life but at a considerably lower rate. A maximum increase of 1100% in the case of low applied stresses and an approximately 2200% increase in fatigue resistance in the case of high applied stresses were observed after 5 passes. The improvement of fatigue resistance is presumed to be due to (1) a reduction in the size and the number of Si crystals with increasing number of ECAE passes, (2) the aggregation of Cu during the ECAE process, (3) the formation and growth of CuAl2 grains, and (4) grain refinement of the Al-6063 alloy during the ECAE process.

Fatigue life estimation of cold drawn contact wire

To evaluate the bending fatigue characteristics of contact wire, a stroke-based bending fatigue tester on contact wire has been developed by Kang et al. But this tester is too cumbersome and complicated. This paper is investigated with a new fatigue life estimation method based on Juvinall’s method for estimation of S-N curve, which is widely used in steel structure, in order to estimate the bending S-N curve of cold drawn contact wire. First, the ultimate tensile strength and the axial tension fatigue test was performed with standard specimens, and the bending fatigue life for the cold drawn contact wire structure was predicted by using an improved S-N curve prediction method. Finally, the tested bending fatigue life of the structure was compared with the fatigue life estimated by the new method. As the result, the predicted bending S-N curve of the contact wire agreed fairly well with the experimental bending fatigue lives using the S-N curve and ultimate tensile strength of cold drawn material.

Bending fatigue characteristics of corroded wire ropes

The corrosion of a wire rope reduces its life expectancy. In this study, repeated bending tests were conducted using a bending fatigue tester by changing the tensile load and corrosion time of wire ropes, which were the same type as those used in elevators. The number of broken wires was studied, and a tensile test was conducted for cases in which the fracture was severe. The effect of corrosion fatigue on life expectancy was considered by comparing fracture strength values and observing fracture surfaces. The results indicate that an increase in accumulated corrosion fatigue, a greater tensile load, and repeated bending cycles may yield a rapid decrease in fracture strength and an increase in the number of broken wires. Therefore, it is concluded that corrosion fatigue is an important factor that decreases the life expectancy of wire rope.

A study on the evaluation of bending fatigue strength for 20CrMoH gear

A test apparatus for determining the bending fatigue characteristics of gear teeth was used in this paper. Experiments were performed in the test apparatus using a standard spur gear test specimens made from 20CrMoH gear steel. Test apparatus, specimen fixture, spur gear test specimens, the properties of gear material were also introduced as well as the method to determine the stress levels. The test data was analyzed and processed by statistical methods, and the equation parameters of gear bending fatigue and the bending fatigue limit were obtained. The analysis results showed that the three-parameter Weibull distribution was to fit the given stress for the bending fatigue life of 20CrMoH carburized gear with better precision and adaptability. And the P-S-N (Probability-Stress-Life) curves for the bending fatigue strength had been obtained by the reliability theory. It would provide a reliable basis for the reliability design for 20CrMoH carburized gear fatigue life.

J044062 Cu-A1-Mn形状記憶合金ワイヤ材の曲げ疲労特性

The purpose of present study is to investigate bending fatigue characteristics of Cu-Al-Mn-based shape memory alloys. The Cu-17mol%Al-l lmol%Mn wires with a 1.8mm in diameter arc used. The heat treatment condition is 900°C for 5 minute and then aged 100°C for 15 minute. The transformation temperatures were measured by differential scanning calorimetly (DSC). The mechanical properties were measured by tensile machine. The property of bending fatigue life is measured by bending fatigue tester. The results in present study arc as follows: (1) Fatigue life specimens were broken around grain boundary. (2) The distribution of the fatigue life grows accompanying an increase of the strain by the cause whose grain size is about 30mm. (3) The fatigue life average about 10000 times at 1% strain, about 3000 times at 2% and between about 1000 times at 3%, respectively.

Size effects on the fatigue behavior of bulk metallic glasses

Size effects on bending fatigue characteristics are investigated on Zr-based bulk-metallic glasses (BMGs). The fatigue lifetimes and endurance limits of the large-size samples are greater than those of the small-size samples. The results suggest that although a BMG exhibits good ductility due to the formation of multiple shear bands when its size decreases, the fatigue resistance of BMGs might degrade when the specimen size becomes smaller. The current study finds that small-size BMG samples under bending fatigue could fail in the flexural or fracture mode.

920 Cu-Al-Mn系形状記憶合金の曲げ疲労特性(OS9-5 形状記憶材料の特性と応用)

The purpose of this study is to investigate fatigue characteristics of Cu-Al-Mn superelastic alloy for lumbago prevent apron and assistance tools for grape faming. The specimen was made from five Cu-Al-Mn superelastic wires of 1.7mm in diameter and 400mm in length. Specimens were made by Furukawa Techno Material Co., Ltd. The apparatus generated the power to use superelastic component. The transformation temperatures were measured by differential scanning calorimetry (DSC). The bending fatigue characteristics of superelastic components were investigated by fatigue tester. The maximum strain ration of bending fatigue test was about 3.4%. Fatigue lives of the superelastic components were about 1,300 times.

334 脳ベラ用鋳造形状記憶合金の疲労特性(知的材料・構造システムおよび複合機能化材料・デバイス(3),ものづくりにおける基礎研究と先端技術の融合)

In order to develop a brain spatula or a brain retractor made of a shape memory alloy (SMA), the bending fatigue characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed. The results obtained can be summarized as follows. (1) At the room temperature, the fatigue life in pulsating-plane bending is longer than that in alternating-plane bending. (2) The relationship between the dissipated work and the number of cycles to failure can be expressed by the unified power function for alternating- and pulsating-plane bendings. (3) The above mentioned characteristics of the SMA-brain spatula obtained in this study can be substantially applied to the development not only for the brain spatula but also for other retractors and instruments used in other surgery operations.

654 Bending Fatigue Properties of TiNi Shape Memory Alloy

The bending fatigue characteristics of the precision-tasted TiNi shape memory alloy for brain spatula were studied. The characteristics of fatigue life in alternating-plane bending between bending at RT under constant frequency and bending with heating and cooling were investigated. Also, the progress of fatigue crack was investigated from the fracture surface by microscopic observation.

Bending Fatigue Characteristics of WC-βt-Co Alloys

WC-βt-Co alloys have been widely applied to cutting tools because they are superior to WC-Co alloys in oxidation, plastic deformation and adhesion resistances. In this study, the effects of HIP treatment, WC grain size and content of βt phase on bending fatigue characteristics were investigated for fine and coarse-grained WC-6.7mass%βt-10.4mass%Co alloys （6.7βt(F) and 6.7βt(C) alloys） and fine-grained WC-20mass%βt-11.3mass%Co alloy (20βt(F) alloy) by comparing with the case of fine-grained WC-10mass%Co alloy（10Co(F) alloy） without βt phase. The results obtained were as follows: 1) The bending fatigue life of HIP-ed 6.7βt(F) alloy was longer than that of normally sintered 6.7βt(F) alloy. The S-N curve of HIP-ed alloy showed a small gradient in a high stress range and a large gradient in a low stress range. 2) The fatigue life of HIP-ed 6.7βt(F) alloy remarkably decreased in the high stress range, but slightly decreased in the low stress range, compared with that of 10Co(F) alloy. 3) The fatigue life of HIP-ed 6.7βt(C) alloy was superior in all the stress range, compared with that of HIP-ed 6.7βt(F) alloy. 4) The fatigue life of HIP-ed 20βt(F) alloy was shorter than that of 6.7βt(F) alloy in all the stress range．The above-mentioned results were mainly discussed relating to the fatigue fracture origins such as pore, Co pool, agglomerate of βt grains, etc.

Bending Fatigue Characteristics of WC-βt-Co Alloys

WC-βt-Co alloys have been widely applied to cutting tools because they are superior to WC-Co alloys in oxidation, plastic deformation and adhesion resistances. In this study, the effects of HIP treatment, WC grain size and content of βt phase on bending fatigue characteristics were investigated for fine and coarse-grained WC-6.7mass%βt-10.4mass%Co alloys （6.7βt(F) and 6.7βt(C) alloys） and fine-grained WC-20mass%βt-11.3mass%Co alloy (20βt(F) alloy) by comparing with the case of fine-grained WC-10mass%Co alloy（10Co(F) alloy） without βt phase. The results obtained were as follows: 1) The bending fatigue life of HIP-ed 6.7βt(F) alloy was longer than that of normally sintered 6.7βt(F) alloy. The S-N curve of HIP-ed alloy showed a small gradient in a high stress range and a large gradient in a low stress range. 2) The fatigue life of HIP-ed 6.7βt(F) alloy remarkably decreased in the high stress range, but slightly decreased in the low stress range, compared with that of 10Co(F) alloy. 3) The fatigue life of HIP-ed 6.7βt(C) alloy was superior in all the stress range, compared with that of HIP-ed 6.7βt(F) alloy. 4) The fatigue life of HIP-ed 20βt(F) alloy was shorter than that of 6.7βt(F) alloy in all the stress range．The above-mentioned results were mainly discussed relating to the fatigue fracture origins such as pore, Co pool, agglomerate of βt grains, etc.