Abstract: The generally textured techniques used in industry can make the roller surface fall off or damage by burning to form aculeate concave. The textured rollers produced by the method mentioned above have some disadvantage performances that include rapid roughness attenuation, limited use time and more concave. These disadvantages are not suitable for the formation of roughness on the cold roller surface. On account of high hardness and excellent wearable capability, the element chrome, which can be deposited on the cold roller surface, can increase the use life of textured cold roller enormously. In this paper, an experiment of DC superimposed pulse was performed to obtain certain roughness chrome textured and hemisphere-shaped chrome coatings. From the results, it was shown that the roughness and hardness of coating obtained by electroplating was 3.79μm at 850mA/cm2 and 1000 Hv respectively.
Abstract: Microstructure of A357 alloy modified by Sr has been investigated by the Electron Back Scattering Diffraction (EBSD) mapping technique using a Field Emission Gun Scanning Electron Microscopy (FEG-SEM). An appropriate sample preparation technique by ion milling was applied to obtain a sufficiently smooth surface for EBSD mapping. Results show that the eutectic morphology in microstructure of A357 alloy modified by Sr was changed to fine fibrous, and the grain size was refined. By comparing the orientation of the aluminum in the eutectic to that of the primary aluminum dendrites, the nucleation and growth mechanism of the eutectic solidification in A357 cast alloy was determined. The eutectic Si phase of the modified sample nucleates on the heterogeneous nuclei located in the region between primary α-Al dendrites and grows up, while the eutectic Si phase of the sample without modification nucleates on the primary α-Al dendrites and grows up.
Abstract: Ultra high strength steel plays an important role of light weighting in automotive industry. The hot forming simulation of car door bar is processed with 22MnB5 ultra high strength boron steel. FEM is built with the 12 nodes shell elements and MAT 106 is selected in LS-DYNA. The hot forming processes include two heat transfers. One is the process from the oven to the tools after the blank is heated. The other is the process after the blank contacts the tools. The hot forming simulation results are obtained by LS-DYNA. The results show that the thickness distribution, the forming limit and the maximum effective plastic strain and other performances attain to standards. It is proved that the hot forming simulation method is correct.
Abstract: In this study, the decomposition of phosphogypsum at different atmospheres of pure CO, N2 and 10% of CO were investigated to gain knowledge about the thermal decomposition of phosphogypsum. It was found that the starting decomposition temperature is 820°C in pure CO, the temperatures are 1080°C for N2 and 890°C for 10% of CO, respectively. Quantitative XRD method was applied to determine the amounts of CaSO4, CaO and CaS in the residues. The results indicate that CaS was mainly formed during Phosphogypsum decomposition in pure CO. In N2 CaO is the main residue from reactions, accompanying a small amount of CaS, and there are CaO and CaS in the decomposed productions, in 10% of CO. Moreover, The Starink,Kissinger and Flynn-Wall-Ozawa methods were used to calculate the kinetic parameters, respectively. The results have shown that the activation energy is in the range of 290.84-317.34 kJ/mol for in pure CO, 335.98-360.90 kJ/mol for 10% CO, 476.39 kJ/mol for N2.
Abstract: The cold rolling technology of thread was rapidly developed due to its high efficiency, low cost and perfect property of its production. But theoretical researches on the precise forming were very few, especially for the hollow parts. In the rolling process, empirical (trial and error) methods have been a mainly part. This is unfavorable for the development of the new technology. In this paper, numerical simulation of the cold rolling process of hollow thread was studied. The DEFORM soft was used to perform the simulation work. The stress field, strain field and velocity field in the workpiece were obtained. The change curve of the rolling force and the relation curve of tangential force and torque were obtained. The failure process of hollow thread in the rolling process was also simulated. The failure reason of thin wall thread in the rolling process was analyzed according to the change of effective stress in the workpiece. The result is well agreement with theoretical ones. The further research will be done to promote the application of numerical simulation in the cold rolling of hollow thread parts.
Abstract: Sandwich construction consists of two thin composite or metal facesheets separated by a core material. Despite extensive researches on the sandwich constructions, their mechanical properties and failure behaviours are still not fully understand. The objective of the paper is to use a experimental and theoretical predicting failure mode for sandwich beam consisting of GFRP facesheets and Nomex honeycomb core. Two kinds of composite sandwich beams are observed in quasi-static three-point bending and indentation test.
Abstract: The iterative optimization method of using equivalent model is used to design launch vehicle payload bearing structure—composite cross beam. The strategy is based on the idea of the substitution of equivalent models for detailed models. Using the engineering software Patran/Nastran, optimization finds geometry of cross-sectional with a minimum weight and stacking sequences satisfying laminate design rules. Equivalent model method can decrease numbers of design variable as well as ensures reliability of result. The strategy showed weight savings of 38% compared with the initial design with little computational effort. This has demonstrated that the strategy appears efficient, reliable and extendable into the cross beam structure.
Abstract: Fine denier fiber fabric has unique wicking effect and good hydrophobic property, which can keep dry and moisture comfortable when people are in heavy and continued sweat. This paper studied the dynamic moisture comfort property of fine denier fiber fabric compared with conventional fiber fabrics. Firstly, a series of experiments was performed on studying the dynamic moisture transferring procedure and evaluating moisture comfort property of fine denier fiber fabrics in two different environmental conditions, which were the most comfortable condition and an extremely uncomfortable condition for humans. Then, by measuring the real time changes of relative humidity in inner and outer surfaces of test fabrics, fabrics’ dynamic comprehensive index was obtained to characterize fabrics’ dynamic moisture comfort property. Finally, grey system theory was introduced to establish prediction models that could describe the relationship between fabric’s static parameters and dynamic comprehensive index. Results show that fine denier fiber fabric has better moisture comfort property than conventional fiber fabrics.
Abstract: First-principles calculations were performed to study the relative stabilities of MgH2 and Mg7XH16(X=Nb,V,Ti).The calculated results show that MgH2 has the higher stability than Mg7XH16. The density of states of MgH2 and Mg7XH16 were obtained and analysized. It shows that the extinction of the gap at 0~4eV interval , the increment of N(EF) and the weakening of Mg-H bonds impaired the stability of Mg7XH16.
Abstract: We performed first-principles calculations to the electronic structure and bonding characteristic of LaMgNi4H4. The calculation results show that the H—Ni units are formed by the covalent H—Ni bonds, the surrounding Mg and La atoms provide electrons to the H—Ni units, and the Ni-Ni bonds between the different H—Ni units are covalent, making the H—Ni units not isolated. These bonding characteristics show that LaMgNi4H4 is similar with interstitial metal hydride in some aspects, and similar with complex metal hydrides in other aspects, indicating LaMgNi4H4 is the intermediate between interstitial metal hydrides and complex metal hydrides.