Papers by Keyword: Metallic Material

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Authors: Stefano Marini, Giulio di Francesco
Abstract: Through a series of standard tests conducted on homogeneous metallic materials (carbon steel, stainless steel and non ferrous metal alloys) we have obtained the corresponding values of the elastic module. Non-destructive local penetration tests in the elastic field are carried out on materials identical to each of those indicated above. For each of the aforementioned materials the results obtained by the two tests described above are correlated. Lastly, we have calibrated the measuring chain created especially for the micropenetration tests, and then validated the measurement procedure.
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Authors: Y.C. Lin, Dong Xu Wen
Abstract: In hot forming processes, metallic materials often undergo a series of plastic deformation and heat treatments. Hot working parameters, including deformation temperature, strain rate, and strain, exert great impacts on hot deformation behavior of alloys. Work hardening (WH), dynamic recovery (DRV), dynamic recrystallization (DRX), phase transformation, and metadynamic recrystallization (MDRX) often take place, and affect hot deformation behavior of metallic materials. Therefore, a comprehensive investigation on the intrinsic interactions between microstructural evolution and hot deformation behavior is necessary. In this study, a novel unified dislocation-density based model is presented to characterize the hot deformation behavior of a nickel-based superalloy In the Kocks-Mecking model, a new softening item is proposed to represent the impacts of dynamic recrystallization behavior on dislocation density evolution. The grain size evolution and dynamic recrystallization kinetics are incorporated into the developed model. Material parameters of the developed model are calibrated by a derivative-free method in MATLAB toolbox. Comparisons for the experimental and predicted results confirm that the developed unified model can accurately reproduce the hot deformation behavior, DRX kinetics, and grain size evolution in wide scope of initial grain size, deformation temperature, and strain rate.
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Authors: Lucrezia Cascini, Raffaele Landolfo, F. Portioli
Abstract: To develop a durability design procedure based on lifetime safety factor method, different dose-response functions based on both ISO standards and the literature are presented for the prediction of the thickness loss due to atmospheric corrosion in metal structures. Finally, serviceability and ultimate limit states are defined for the durability design against corrosion.
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Authors: Tie Xin Yang, He Ming Cheng, Jian Yun Li, Si Qing Zhou, Ji Feng Dai
Abstract: In order to study thecharacteristics of this new type of quenching process that is atomized waterspray quenching, this article analyzes the influence factors of atomized waterspray quenching based on the newly developed aerosol spray quenching experimentdevice. Based on 2 method, the two factors of water flow and nitrogen pressureare controllable, we analyzed the influences of the two factors of nitrogenpressure and water flow to the quenching cooling time. This paper induces andanalyses the experiment results and numerical calculation results[1]. The conclusions are: water flow is the main factor ofaffecting the quenching rate, the interaction of the nitrogen pressure andwater flow is significant: when the nitrogen pressure is low ,the water flow ishigh, the quenching cooling rate is guaranteed.
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Authors: Chuan Hui Chen, Yang Bai, Wei Chen, Xu Chu Ye
Abstract: Nickel-base alloys with different boron contents were prepared by vacuum arc furnace. The effect of the boron contents to metallography was characterized simultaneously by XRD and SEM with EDS part. The thermal behavior was analyzed by DSC curves which mainly represents the eutectic temperature of alloys. The Vickers hardness and ball-on-flat wear test were carried out to reveal the relationship between metallographic phase formation and wear resistance. The results indicated that main composites are eutectic Ni-Cr as matrix and CrB, Ni3B as precipitated phase. A considerable amount of dislocation and stacking faults exist in the specific orientation (200) of Ni3B. 2.0~4.0%B alloys melt at 1060oC, while the boride-poor alloy melts at 1085oC. 3.0~4.0%B alloys performed the best on wear resistance. Wear volume reduces along with increasing hardness at the beginning, and then keeps invariant. Borides are main reinforcing phases, which affects hardness and wear resistance greatly.
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Authors: Xiang Hai Ye, Hong Gang Shi, Min Ming Zou, Kai Wen Tian, Jin Bo Liu, Li Jun Zhu, Zhong Ya Zhang, Qun Wang
Abstract: Because of excellent mechanical, physical and chemical property Wf/Zr-based amorphous matrix composite attracts people’s interest and becomes the hot spot of science study and engineering application. In this paper, change regulation of hardness of target around crater by Wf/Zr-based amorphous matrix composite projectile and its mechanism are studied after firing test, and it is found that the section can be divided into 3 layers: the Martensite layer, the deformed fine grain layer and the normal matrix from the crater surface to the interior of the steel target and that the thickness of Martensite layer increases first and then decreases in the penetration direction when the velocity of projectile is 1200m/s.
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Authors: Giulio di Francesco, Stefano Marini
Abstract: In the structural analysis of mechanical elements, both in the design and testing phase, the Young’s modulus value influences the precision of the results and must be taken into consideration during the calculation. The E value is usually shown in tables that do not report precise values, but ranges of values that are characterized by a certain amplitude. In the structural calculation analytically or numerically developed, an approximate reference E value that is hypothesized constant in the material is usually used. Moreover, this value does not take into consideration possible thermal-chemical-mechanical treatments used on the material. A mechanical designer needs to know the precise E value of the material in the final operation state in order to develop a structural analysis. According to what has been specified above, it is necessary to know the value of the elastic characteristics for every point of material in order to associate a value in the development of a correct and deepened numerical analysis for every zone in examination. We have developed a finely tuned experimental system having the following main steps: - measurement of the penetration of a metallic microsphere, as a function of the applied load, in a single point of the analyzed material; - determination of Young's modulus. This procedure allows for E to be measured, if necessary, at points very close to each other in such a way as to be able to take into consideration, when performing structural analysis requiring a high degree of accuracy, the influence of the gradient of the longitudinal elastic modulus. The precision of the punctual values obtained for E is comparable with that of traditional experimental methodologies (e.g. tensile test), since the proposed procedure expects the use of the experimental calibration curve, which is precisely constructed based upon the data obtained through the above methodologies.
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Authors: Yuriy S. Nechaev, Andreas Öchsner
Abstract: An annotated analytical essay of possible nanofabrication and nanotechnology applications is presented with respect to: (1) some techniques and original results [1-4] concerning the regularities and micromechanisms (physics) of the hydrogen fluoride gas activator influence on the diffusion-controlled oxidation processes of titanium, zirconium and zirconium-based alloys with niobium, and also – on nitriding, boriding and carbiding a series of refractory metals (Ti, Zr, Nb, Mo, W, Ta); (2) some techniques, original results and physics of the diffusion-controlled formation processes of the compound-like nanosegregation [5-13] and the results [13-23] on the liquid-like phase at grain boundary regions in metals and alloys. In the scope of this review, a constructive analysis, the Arrhenius-type treatment, and the original data interpretation [16-21] has been carried out for the first time; (3) some techniques, original analytical results, and physics [24, 25] of the diffusion-controlled processes of the hydrogen multilayer intercalation (physisorption of a condensation or clustering type) with carbonaceous nanostructures. The main objective of the given analytical essay is to attract the researchers’ attention to the expediency of such a non-conventional data analysis and interpretation.
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Authors: S.I. Kwun, Jai Won Byeon
Abstract: Microstructural parameters (kinds of phases, inter-lamellar spacing of pearlite, precipitate size, number of precipitates), mechanical properties(UTS, Vickers hardness) and non-destructive parameters(ultrasonic velocity, ultrasonic attenuation coefficient, electrical resistivity, magnetic coercivity, magnetic remanence, Barkhausen noise) in various metallic materials were measured in order to investigate the mutual relationship among these parameters. The optimum non-destructive parameters were selected for particular purposes in order to evaluate the level of damage to the metallic structures, to differentiate the microstructures and to predict the mechanical properties of superalloy, low and eutectoid steel and Cu alloys non-destructively.
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