Papers by Keyword: Medium Carbon Steel

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Authors: Hong Yan Duan, You Tang Li, Shuai Tan
Abstract: The fracture problems of medium carbon steel under extra-low cycle axial fatigue loading were studied using artificial neural network in this paper. The training data were used in the formation of training set of artificial neural network. The artificial neural network model exhibited excellent comparison with the experimental results. It was concluded that predicted fracture design parameters by the trained neural network model seem more reasonable compared to approximate methods. Training artificial neural network model was introduced at first. And then the Training data for the development of the neural network model was obtained from the experiments. The input parameters, notch depth and tip radius of the notch, and the output, the cycle times of fracture were used during the network training. The neural network architecture is designed. The artificial neural network model was developed using back propagation architecture with three layers jump connections, where every layer was connected or linked to every previous layer. The number of hidden neurons was determined according to special formula. The performance of system is summarized at last. The result show that the training model has good performance, and the experimental data and predicted data from artificial neural network are in good coherence.
Authors: Ming Kuen Chang, Hua Sui Sun, Jyun Cang Ciou
Abstract: During materials manufacturing process will cause defects occasionally, if the defects located at near surface of material where the testing is not easy to implement. When the defects was stress by outside loading, it will grow up even become fracture, if the material apply ultrasonic testing then can increase material security to ensure structural safety. Practice material defect shape is variable and need complex product procedure. In this study, using wire cutting method to make practice defects specimen instead of the real flaws material, the specimen was made of medium carbon steel and aluminum alloy, defects away from the surface is 2-4 mm, defect shape including round shape hole and square shape hole, bore diameter was 1-3 mm. Using ultrasonic straight beam probe and delay line probe, straight beam probe have 5 MHz and 10 MHz frequency, and delay line probe have 5 MHz, 10 MHz frequency too, finally, compared the relationship between the accuracy and depth of flaws, pore size, flaw shape, material of specimen. Research results demonstrate that accuracy didn’t relate to the flaw shape, flaw size, depth of flaws and material of specimen. The accurately of 10 MHz delayed probe shown the depth of flaw smaller, the measurement than other probes.
Authors: Mohammed Anayet Ullah Patwari, A.K.M. Nurul Amin
Abstract: Surface roughness is important for evaluating the machined surface quality. In this work, an Artificial Neural Network (ANN) surface roughness prediction model was developed by coupling it with Response Surface Methodology (RSM). For this interpretation, advantages of statistical experimental design techniques, experimental measurements, and artificial neural network were exploited in an integrated manner. Cutting experiments were designed based on small centre composite design technique to develop a RSM model. The input cutting parameters were: cutting speed, feed, and axial depth of cut, and the output parameter was surface roughness. The predictive model was created using a feed-forward back-propagation neural network exploiting the experimental data. The network was trained with pairs of inputs/outputs datasets generated by end milling medium carbon steel with TiN coated carbide inserts. The model can be used for the analysis and prediction of the complex relationships between cutting conditions and surface roughness, in metal-cutting operations, with the ultimate goal of efficient production. The ANN model was verified with the optimized parameters predicted by a coupled genetic algorithm (GA) and RSM technique also developed by the authors.
Authors: T. Hanamura, S. Torizuka
Abstract: Medium carbon steels have low yield ratio (YR). In order to obtain high yield strength (YS) for them, different microstructures including ferrite(F)/cementite(C) and ferrite(F)/pearlite(P) are prepared and the microstructure for high YR as well as its mechanism is clarified. The purpose of this study is, therefore, to elucidate the effect of ferrite grain size on YS in the relationship between F/P and F/C structures having the same tensile strength (TS) level. In case of F/C, YS can be significantly improved through grain refinement with a slight decrease in ductile properties. This is particularly clear by comparison of F/C with a ferrite grain size of 0.6m and F/P, where both structures show the same TS level while the YS level is significantly different; F/P representing much smaller YS than that of F/C. It is also to be noted that F/P microstructure shows low YS compared to its high TS with a generation of dislocations at the interface between ferrite and cementite in its pearlite phase. In conclusion it is necessary to consider the difference in the YS-TS relationship between F/C and F/P in order to make the most of its forging processing.
Authors: B.H. Cao, John J. Jonas, P.R. Hastings, Nicholas Nickoletopoulos
Authors: Peng Tian, Zhi Yong Zhong, Wei Jun Hui, Rui Guo Bai, Xing Li Zhang
Abstract: Uniaxial hot compression simulation experiment at 700°C with different true strain was carried out to study the microstructure evolution of medium carbon steel, the predominant mechanism on the cementite softening has been explored, the experimental results show that the volume fraction of deformation induced ferrite (DIF) increased with increasing true strain and even exceeds the equilibrium content. With the increase of DIF, more and more carbon atoms congregated in the boundaries such as the interface of DIF and the interphase of DIF/deformation austenite. Carbon congregation provides the right carbon content and the optimized microstructure for divorced decomposition during the process of controlled cooling. Therefore spherical or rod-like cementite and degenerated pearlite can be obtained.
Authors: Ping Ma, You Tang Li
Abstract: A special clamp for fatigue of shaft under bending-torsion that used on the fatigue machine is designed and manufactured. For the medium carbon steel, the low-cycle fatigue experiments of shaft with annular notch under bending-torsion have been made on Shimadzu EHF-EM100kN high-frequency electro-hydraulic fatigue testing machine. Through experiments and analysis, the effects of tip radius, depth and open angle of notch on low cycle fatigue life of shaft with annular notch under bending-torsion are obtained. The method and results will play an important role on the fatigue life prediction and anti-fatigue design.
Authors: Makoto Egashira, Shigefumi Nishitani, M. Yuya, N. Sano
Abstract: Gaseous ferritic nitrocarburization is one of the major surface hardening methods to improve the fatigue strength of machinery parts made of medium carbon steels. The fatigue strength of nitrocarburized steel parts depends on the hardness profile below the surface; however, the mechanism of its evolution during nitrocarburization has not been fully understood. Recently, as-forged steels, in which thermal refining process like normalizing is omitted from the viewpoints of environmental considerations, energy savings and manufacturing cost reductions, have been widely used in the machinery parts industry. Therefore, it is important to understand the mechanism of hardness increase below the surface of the nitrocarburized steels with respect to the effect of prior refining heat treatment. In the present study, the hardness increase at the subsurface region of nitrocarburized steels containing 0.4mass%C was characterized, and the influence of prior normalizing treatment was investigated. Microstructure of both the as-forged and the normalized specimens was the ferrite/perlite mixture, while the ferrite volume fraction in the as-forged steel was smaller than the latter. These as-forged and normalized steels were gaseous nitrocarburized at 853K for 2 hours under the atmosphere of RX gas and NH3 gas mixture, and then they were oil-quenched to 373K. Overall hardness below the surface after nitrocarburization was higher for the specimen without prior normalizing treatment, although both specimens had the similar nitrogen concentration profiles and precipitation behaviors of the nitrides. However, it was found that the individual ferrite grains in the as-forged steel were more hardened than those in the normalized steel. These indicate that the most likely cause of the hardness increase near the surface after nitrocarburization is the solid solution hardening by dissolved nitrogen and that the ferrite grains of the as-forged steel were likely to soak up more nitrogen and were hardened to the higher degree since the similar amount of nitrogen were incorporated mainly within ferrite grains. Thus, the prior heat treatment strongly affects the amount of hardening through the ferrite fraction.
Authors: Félix Peñalba, Manuel Carsí, Carlos García de Andrés, F. Zapiráin, M.P. de Andrés
Authors: Wei Wei Tang, Hong Wang, Jin Gan Dai
Abstract: The S-N curves of medium carbon steel(MCS) are determined by the ultrasonic symmetric bending fatigue system (20 KHz). The results show that two S-N curves of MCS display the characteristic of “continually decreasing type” up to 109 cycles and exhibit no traditional horizontal plateau beyond 106 cycles. When the fatigue cycles are over 109, fatigue failure do occurs. By comparison of the two curves of 2mm thick and 5mm thick MCS, the results show that in the high-cycle stage(107cycles), size effect has no significant impact on fatigue Properties. This can also be explained by the theory of crack initiation, in high cycle stage, fatigue crack initiation exists in the sample surface, and in ultra-high-cycle stage, fatigue crack initiation exists in internal initiation.
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