Applied Mechanics and Materials Vols. 117-119

Abstract: The tensile strength and elongation at break of epoxidized natural rubber (ENR) was investigated by adding different concentration of calcium stearate. Two grades of epoxidized natural rubber (ENR), namely, ENR 25 and ENR 40 were used as model materials. Semi-efficient vulcanization (semi-EV) was used throughout the study. The tensile property of unaged and aged ENR vulcanizates was determined by using U-CAN electron tensile testing machine. Results indicate that tensile strength and elongation at break of unaged ENR 25 and ENR40 vulcanizates increase gradually with increasing concentration of calcium stearate up to about 1phr of calcium stearate and after which, the tensile strength and elongation at break drop with a further increase in calcium stearate loading. For a similar alcium stearate concentration, the tensile strength and elongation at break of ENR 40 vulcanizates exhibits a consistently higher value than that of ENR 25 vulcanizates, which is due to the higher crosslink density of ENR40 which contains more epoxide groups than ENR 25. For aged samples, the addition of calcium stearate could enhance the tensile strength and elongation at break of aged samples. Percentage retention of tensile strength and elongation at break also gradually increases with calcium stearate loading. That means that the incorporation of calcium stearate is found to improve the aging resistance of ENR vulcanizates. This is because calcium stearate neutralizes sulfur acids which can catalyze ring-opening of expoxide groups via ether crosslinks.

Abstract: Mechanical properties and microstructures of Ti811 alloys under different heat treatment conditions were studied. The results show that the microstructures of Ti811 alloy consist of α, massive β and grain-boundary β after normal annealing. The intensity and hardness decreased, while the ductility increased. After double annealing, the primary phase α reduced and needle-like secondary α〞 was formed. The massive β and grain-boundary β changed into intergranular β gradually. The microstructure was relatively uniform. Then the intensity and hardness increased, the ductility decreased when compared to general annealing. The needle-like secondary α〞and metastable β would break down into dispersed α and β after solution hardening and aging. The combination properties of alloys would be improved. According to fractography of titanium alloy, the fracture mechanism of the Ti811 alloy was dissociation - brittle intergranular fracture, which was a type of fracture between the intergranular fracture of brittle and cleavage fracture.

Abstract: In order to improve the electrochemical properties of Al-Zn-In alloys, Al-5Zn-0.02In-1Mg-0.05Ti-xMn (x=0, 0.3, 0.5, 0.7, 1.2) (wt %) alloys were develpoed. Electrochemical properties and corrosion behaviour of the alloys were investigated. The results show that the electrochemical properties are obtained in Al-5Zn-0.02In-1Mg-0.05Ti-0.5Mn alloy. The excellent electrochemical properties of the alloy is mainly attributed to uniform corrosion. Corrosion behaviourof the alloys were analysed by corrosion characteristic parameters such as E_c, E_pit, E_prot and E_ptp. This analysis result has a good agreement with the alloy corrosion morphology.

Abstract: Abstract. Hot dip galvanizing is being widely used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and for some other fields etc.. Recently, the cost of zinc is getting higher and higher, thus, a proper manufacturing process should be developed possibly to reduce the cost of production. In this study, one of hot dip galvanizing process, that is, omission of water washing treatment which is performed after acid cleaning was investigated with some types of flux solution which is added with additives such as acid cleaning solution, NH₄OH, Al(OH)₃ and H₂O₂. The decrement of pH by omission of water washing treatment could be recovered to its original value due to neutralization reaction with addition of NH4OH. The flux solution added with both NH₄OH and Al(OH)₃ exhibited nearly the same color and pH value as those of original flux solution with no added, and the galvanized sample by using this flux solution tended to show a relatively good corrosion resistance compared to other samples treated with different types of flux solution. Furthermore, the flux solution added with NH₄OH, Al(OH)₃ and H₂O₂ exhibited a different color as that of original flux solution, and sediments were observed, in addition, its sample exhibited a lower corrosion resistance. Consequently, it is suggested that simplification of process, so-called, omission of water washing treatment may be able to achieve with development of an optimum type of flux solution added with additives.

Abstract: In this paper, based on ctual large-scale ball mill liners working conditions, effects of different quenching temperature and tempering temperature on the Cr-Mo steel performance, optimize the best heat treatment process.The use of sophisticated electronic universal tensile testing machine, and Rockwell hardness testing machine for testing mechanical properties of steel materials were tested; Using the MMS-1G-type high-temperature high-speed Friction and wear tester, the wear properties of steel samples were studied using JSM-5610LV scanning electron microscope study of the tensile test fracture surfaces of steel and the friction and wear morphology. The results show that: For the high carbon alloy steel, of which 870 °C 620 °C tempered quenched specimen extension rate of 7.0% area reduction rate of 9.5%.

Abstract: The corrosion behaviors of Al-Zn-Sn and Al-Zn-Sn-Ga alloys were investigated according to the results of immersion tests and corrosion morphology observation，and the Fermi energy of the precipitates was calculated by Materials Studio software for discussing the corrosion kinetics of precipitates . The results show that the Al-Zn phase with high Fermi energy (low corrosion potential) dissolved firstly, than caused the forming of Al-Ga amalgam which deposited between passive film and Al matrix. Meanwhile, the Al-Ga phase with higher Fermi energy dissolved too, which made the Al-Zn-Sn-Ga alloy continue to active, Finally, the Al-Zn-Sn-Ga alloy formed uniform corrosion morphology due to the effect of Al-Ga amalgam, while Al-Zn-Sn alloy formed the surface feature with the deep corrosion pits due to the "self-catalysis" mechanism.

Abstract: Based on the high-tin wear-resisting Cu-Sn-Pb-Ni Alloy which the tin content is 9~11%, the inverse extrusion plastic forming experiments in the temperature range of 800°C~ 950°C were completed. The density and hardness of alloy castings were tested and the casting mircostructure was analyzed after plastic forming, which compared with the properties and microstructures of alloy casting prepared by traditional melt casting. The results show that the density and hardness of Cu-Sn-Pb-Ni alloy casting prepared by traditional melt casting are 8.8893g/cm³ and 116HB separately, the density and hardness has increased after inverse extrusion plastic forming in different tempretures, especially at 900°C the density and hardness reached the maximum values, 9.0409g/cm³ and 139HB respectively. Compared with the as-cast microstructure is mainly obvious dendrite structure which are α solid solution and eutectoid（α+δ）, The as-extruded of alloy exhibit better propertief and its grain are obviously refined and densed. Within the range of experiments, the best inverse extrusion plastic forming tempreture is at 900°C.

Abstract: In this paper, we have studied on the absorbing properties of three different types of SiC absorbers such as ultra-fine SiC, SiC whisker and nanometer SiC. Electromagnetic parameters of the three types of SiC were tested in the frequency range of 2~18GHz. Both the real and imaginary parts of complex permittivity of nanometer SiC are higher than that of others. The attenuation constant of nanometer SiC is higher than that of ultra-fine SiC and SiC whisker, increasing from 93.7 to 766.5 with increasing frequency. The minimum reflection loss of -5.53 dB was obtained at 9.72 GHz for the nanometer SiC. The nanometer SiC suggests a better capacity of dielectric loss in microwave range than that of ultra-fine SiC and SiC whisker.

Abstract: In this paper, the influence of nano-silica on adsorption behavior of solvent in polypropylene packaging is reported. A principle of reducing solvent residue in polypropylene packaging was explored through analyses of changes of crystallization behavior, polarity, and solubility parameters of nano-silica /polypropylene composites. The results showed that the value of solvent residue in modified polypropylene films was reduced about 50%. Therefore nano-silica modified polypropylene films with lower solvent adsorption are in accordance with food safety.

Abstract: Vacuum insulation panels are distinguished by their outstandingly low thermal conductivity, which is approximately 0.004 W/ (m • K) to 0.01 W/ (m • K), only 33% to 10% of that of the traditional heat preservation materials. The heat preservation mechanism of vacuum insulation panels is elaborated in the study. The thermal conductivity of the vacuum insulation panel made in our lab were below 0.01 W/ (m • K). By analysis and calculation, with this kind of VIPs applied to refrigerated containers, its exciting properties can save energy consumption by more than 20% compared with traditional heat preservation materials.