Papers by Keyword: Fatigue Property

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Authors: Hua Ping Xu, Hui Hu, Gao Feng Song, Chong He Li, Xie Min Mao
Abstract: In this paper, single crystal of CuAlNiBe shape memory alloy (SMA) was prepared in a high temperature gradient directional solidification furnace with a selective growing crystallizer. And its performance characters were systematically studied. The results show that the mechanical and shape memory properties of the single crystal of CuAlNiBe SMA alloy has much better than that of the polycrystalline material. This may be explained that the stress concentration at grain boundary caused by the difference of bilateral strains is the dominant reason of deterioration of fatigue properties; therefore single crystal alloy possesses the excellent properties duo to its elimination of grain boundary.
Authors: Siti Zuliana Salleh, Hanafi Ismail, Zulkifli Ahmad
Abstract: In this research, natural rubber (NR) with halloysite nanotubes(HNTs)/carbon black (CB) hybrid filler at various filler loading was investigated where the total filler loading used in each compound were 40 phr. The curing characteristics, fatigue life and morphological properties of HNTs/CB/NR nanocomposites were studied. Laboratory two-roll mill was used for mixing process. The results revealed that vulcanizates containing more HNTs in hybrid filler exhibit longer scorch time (ts2) and cure time (t90) for curing characteristics and higher in fatigue life compared to vulcanizates with 40 phr of CB. The images from scanning electron microscope (SEM) confirmed that replacement of carbon black with halloysite nanotubes improved the fatigue life by showing more tearing surface on vulcanizates.
Authors: Shu E Hu, Wei Hua Sun, Xiao Dong Liu, Dong Hua Hou, Rui Zhou, Feng Qiang Xia, Yu Zhen Liu, Guo Dong Wang
Abstract: To save energy, the heavy machinery industries are encountering the challenge of reducing the equipment weight. The paper introduced a 550 MPa grade steel plate to replace the traditional 345 MPa grade steel for heavy machinery manufacturing. The niobium and vanadium micro-alloyed steel plate is characterized as bainite microstructure with high toughness, improved welding performance, and good fatigue resistance. A comparison between the present 550 MPa grade steel plate and a Ni, Mo, Cu bainite steel was studied. The developed steel plate shows competitiveness for a high performance and low cost. The 15% of weight reduction is achieved in a 50 ton digger at a typical engineering machinery plant.
Authors: Dock Young Lee, Suk Won Kang, Ki Bae Kim
Abstract: The mechanical properties of electromagnetically stirred billet of Al alloy during continuous casting such as a tensile, impact, and fatigue property was examined with respect to a size and roundness of primary α phase to examine the influence of the globularization and refining of primary α phase on the dynamic mechanical property. The billet was continuously cast in a casting speed of 100 to 600 mm/min during the electromagnetic stirring with a magnetic flux density of 700 Gauss and then was heat-treated. All tensile properties were enhanced with decreasing the size of primary α crystal and the ultimate tensile strength (UTS), yield strength, and elongation was obtained 320MPa, 235MPa, and 17.8%, respectively, at a size of primary α phase of 77 um. The fatigue life at fracture was largely improved by 37% from 1.25×105 to 1.7×105 cycles and the fracture toughness was obtained approximately 7.25 joules as a maximum value at a minimum size of primary α phase on the present experiment condition. Therefore, it indicates that all mechanical properties can be improved at the higher casting speed owing to the fine microstructure of a primary α phase and also eutectic phase due to the higher cooling rate.
Authors: Wen Xian Sun, S. Nishida, Nobusuke Hattori, X.L. Yue
Abstract: In the present study, fatigue tests have been performed to study the effect of pre-strain on fatigue properties of NHH (New Head-Hardened) rail. The objectives of this study were: (1) to observe the microscopic behavior of specimens during pre-strain process, (2) to research the influence of pre-strain on fatigue strength of NHH rail and (3) to investigate initiation and propagation behavior of the fatigue crack. The results showed that plastic pre-strain decreased the fatigue strength of NHH rail; fatigue limits had no obvious variation among the different pre-strain ratios. Fatigue cracks initiated in the microscopic cracking or slip lines that were originated in the pre-strain process and propagated from these sites in the later fatigue test.
Authors: Dong Liang Kuang, Zhen Gang Feng, Heng Long Zhang, Jian Ying Yu
Abstract: Effects of different viscosity rejuvenators on performance of recycled hot mix asphalt (RHMA) mixture were investigated by testing of water stability, fatigue property and rutting resistance. The results indicate that rejuvenator with low viscosity shows more significant influence on the enhancement of fatigue property at high stress ratio and water stability of RHMA mixture than rejuvenator with high viscosity due to its better diffusion ability into aged bitumen. The water stability and fatigue property of RHMA mixture with 15 wt% low viscosity rejuvenator can be close to virgin hot mix asphalt mixture. Compared with rejuvenators of medium and high viscosity, the rutting resistance of RHMA mixture is reduced more obviously by rejuvenator with low viscosity, but still meets the application requirements of RHMA mixture.
Authors: Xin Hong Shi, Mei Juan Shan
Abstract: A series of fatigue tests is performed for polymethyl methacrylate (PMMA) specimens without scratches and with scratches. The scratch depth is set to be 0.2mm, 0.3mm and 0.4mm, respectively. Based on the experimental results, it can be deduced that contained fatigue limit of specimens with scratches significantly decreases compared to specimens without scratches. Besides, contained fatigue limit decreases gradually with scratch depth increasing from 0.0mm to 0.4mm. Consequently, it can be concluded that fatigue properties of PMMA will decrease when there exists scratch and for scratch depth from 0.0mm to 0.4mm, fatigue property decreases remarkably with deeper scratch.
Authors: Jian Ke Sun, Zhen Li, Qing Fen Li
Abstract: Ti-alloy is widely used in engineering because it possesses excellent specific strength and corrosion resistance. The effect of welding process on J-integral value and fatigue crack growth (FCG) rate in a Ti-alloy is experimentally investigated in this paper. A series of test is performed with SENB specimens for J-integral test and CT specimens for the FCG rate test respectively. Base metal, welded joint and HAZ materials were used to make different test specimens. Results show that the J-integral values of welded joint and HAZ are obviously smaller than those of the base metal. And that the FCG rate value of welded joint is much higher than those of base metal and HAZ material. It means that welding process may lead to a great reduction in fracture toughness and the fatigue property for titanium alloy. Therefore, the inhomogeneity of the welded joint must be considered when assess welded structures.
Authors: Mian Zhang, Nobusuke Hattori, Shinichi Nishida
Abstract: Diamond-like carbon (DLC) is an amorphous hard carbon, which has very high hardness, high resistivity, and dielectric optical properties. Economically and technologically attractive properties have drawn almost unparalleled interest towards the coatings. Eutectoid steel is a kind of material that has been widely used in shafts and various kinds of industrial components. Three kinds of fatigue specimens with different DLC conditions were used in this study. Fatigue test had been performed to investigate the effects of DLC on fatigue properties of eutectoid steel. The fractography was analyzed by a scanning electron microscope (SEM), and surface hardness was also evaluated. The fatigue limits of the DLC coated specimens did notincrease after DLC process, though the compressive residual stress which produced by DLC process can prevent fatigue fracture. According to the results of fatigue test, the optimal DLC method for improving the fatigue properties of eutectoid steel is determined and the relationship between fatigue limits and coating bias are obtained.
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