Mechanical Engineering and Materials

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Authors: Balakrishnan Ramesh, Thiyagarajan Senthilvelan
Abstract: During deformation process, it is essential to control the formability parameters viz., stress, strain, temperature, aspect ratio, volume fraction etc., to obtain sound and defect free products. Moreover, in deformation process in general, upsetting in particular, conducting too many trail experiments results in increased experimental time and cost. Hence modeling of process parameter attracts attention of researchers. The objective of modeling the process parameters is to determine which variables are most influential during metal forming operations. In the present investigation, by connecting the influential process parameters during metal forming in general upsetting in particular, a mathematical model have been developed using Design of Experiments (D.O.E) which could be applied to estimate the flow stress. Aluminium MMCs with silicon carbide (SiCp) and aluminium oxide (Al2O3) as reinforcement have been chosen in this current study as it has significant advantage over conventional materials.
Authors: Jing Tao Yang, Lei Wang, Zheng Yuan Huo, Jie Feng, Feng Chen, Ming Qiang Zhong
Abstract: A super-hydrophobic surface on the polypropylene matrix was fabricated via micromolding and photograft polymerization. A micro-convex body structure was molded by etching templates. The water contact angle could be increased to 138°. The fluoro methacrylate monomers were further grafted to the surface through UV-induced photograft polymerization. The morphology characterization and the spectroanalysis indicated that the rough hierarchical structure (confirmed by scanning electron microscope) and the grafted fluoropolymers (measured by fourier transform infrared spectrum and X-ray energy dispersive spectrometer) made a critical difference. A water contact angle of 160° was arrived.
Authors: Hai Long Yi, Yang Xu, Zhen Yu Liu, Guo Dong Wang
Abstract: A Nb-Ti-Mo high strength steel was selected at two different cooling rates through ultra-fast cooling process, and its microstructures and strengthening mechanisms were analyzed. The results show the size of ferrite was decreased and the amount of bainite and micro-hardness were increased with increasing of cooling rate through thermal simulation. The UFC technology can improve the yield and tensile strength 25MPa and 35MPa, respectively, compared with conventional TMCP. The microstructure of this steel is mainly ferrite and good strength and toughness are caused by the refinement of ferrite and fine precipitates. Ultra-fast cooling technology improves the strength and toughness of this steel effectively.
Authors: Wei Jun Xia, Ling Liu, Fu Quan Zhang, Cong Chang Xu
Abstract: AZ31 magnesium alloy sheets were prepared by multi-pass differential speed rolling (DSR) with small mismatch roll speed ratio. Effect of pass thickness reduction on microstructure, texture and formability at room temperature were investigated. The results showed that the low pass thickness reduction DSR is effective to improve the formability by refining the grain size and weakening the basal texture, which is characterized by the increasing of strain hardening exponent (n value) and elongation as soon as decreasing of yielding ratio and normal anisotropy ratio (r value). With the increasing of pass thickness reduction, more effective grain refinement is achieved due to the forming of deformation bands. While the ability of forming the title basal texture is weakened and the formability is reduced.
Authors: Chun Gao
Abstract: Applied in the construction of Wuhan railway station of the Wuhan-Guangzhou high-speed railway, the super-lightweight aggregate pumping concrete has been developed by the independent study on the tackifier, the substitute of lightweight aggregate for sand and tackifier for sand. The concrete has been used for 58000m3. The dry bulk density of the lightweight aggregate concrete is controlled at 1160kg/m³. And the concrete has a good performance in the homogeneity and working condition, and is easy for pumping.
Authors: Yun Ying Wang, Jiang Yan Meng
Abstract: Aviation polysulfide sealants have been subjected to thermo-oxidative ageing. Their morphologies, Shore A hardness, and tensile properties have been tested by means of an optical microscope, a glossiness meter, a Shore A hardness meter, and a universal testing machine. Changes in their microstructures were measured by Fourier-transform infrared spectroscopy and dynamic mechanical analysis (DMA). The results showed that glossiness was gradually reduced, and bubbles appeared on the surface of the samples during the course of ageing. The Shore A hardness of the sealant first decreased and then remained unchanged. Likewise, the tensile strength and tensile elongation percent first decreased and then remained unchanged. The infrared monitoring showed that the sealant underwent a post-cure reaction. The glass transition temperature and the room-temperature storage modulus of the sealant remained unchanged. No new functional groups were formed during ageing of the sealant. The aviation sealants did not undergo chemical degradation, showing that they have good endurance under thermo-oxidative conditions.
Authors: Qing Sheng Guo, Qing Shan Yang
Abstract: Considering the structure type of the steel staggered-truss (SST) system, the effect of infilled walls will be major and need to be studied amply, some scientific design regulations need to be found for referrence. Based on two different 3D models considering or ignoring the stiffness of infilled walls (SIW), a numerical investigation is presented on the structural behaviors of the SST system utilizing the finite element 3D simulation analysis soft ware ETABS. The longitudinal structure is asymmetrical due to the SIW, it causes the torsion forces in the building. Comparing to the different results of response spectrum analysis, including storey drift and equivalent base shear under frequent earth quake and rare earth quake, some conclusions were made, including the capacity of the SST system under seismic load and the effect of the SIW for SST system. The increased base shear force factors due to the effect of the SIW were suggested for SST structure design, it is different from the other steel structure types.
Authors: Li Hong Lu, De Jiu Shen, Jing Wu Zhang, Chang Hong Guo
Abstract: The hybrid method of plasma electrolytic oxidation (PEO) and hot-dipping aluminum (HDA) was employed to deposit composite ceramic coatings on the surface of Q235 steel. The cross-section microstructure and surface morphology of the treated specimens were investigated with scanning electron microscopy (SEM). Especially, the composition of the composite coatings was investigated with transmission electron microscopy (TEM). The corrosion resistance was analyzed by immersing and corrosion polarizing experiments. The results indicate that metallurgical bonding can be observed between the ceramic coatings and the steel substrate. There are many micro-pores which act as discharge channels in the PEO coatings. The phase composition of the ceramic coatings is mainly composed of amorphous phase and crystal Al2O3 oxides. The crystal Al2O3 phase includes κ- Al2O3, θ- Al2O3 and β- Al2O3.The corrosion resistance of the PEO samples is much better than that of the HDA samples whether immersed in the NaCl solution or in the sea water.
Authors: Fang Cai, Jin Sheng Sun, Ting Ting Zhao, Jing Li
Abstract: Although biosorption for reclaiming single precious metal was frequently reported, the actual subsistent adsorptive competition among different metal ions sometimes shows diverging reinforcement or prohibition for different species. This study tries to screen bacteria that are able to absorb certain precious metals with high selectivity under competitive conditions. The activated sludge was cultivated from enrichment by magnetotactic bacteria medium proposed by Blakemore. Then four microbes, microaerobic bacteria(A) acclimated micro-aerobic bacteria (B), anaerobic bacteria(C) and acclimated anaerobic bacteria(D) were obtained for the following adsorption experiments. The four microbes have high removal efficiency of Au3+ both in its unitary and Au3+-Cu2+ binary system. The microaerobic bacteria (B) are good metal catchers and carriers for the uptake of gold in aquatic solution with coexistence of copper. In Pd2+-Cu2+system, there is a collaborative adsorption effect, especially on (B).

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