Applied Mechanics and Materials Vol. 470

Abstract: This paper has designed electrochemical corrosion experiment of T2 copper in 3.5% NaCl solution to investigate influence of thermal effect on electrochemical corrosion behavior of copper in simulated seawater. Solution temperature was 20°C, 30°C, 40°C and 50°C. The water quality parameters and polarization curve have been measured and analyzed. Corrosion morphology and composition of corrosion products have been observed and analyzed. Thermal effect would lead to water quality variation which influenced the corrosion behavior of copper samples and corrosion potentials would fluctuate with temperature rising. Sample surface of 30°C was neatly covered with fine, uniform and granular corrosion products. There're Cu₂O and CuCl on both samples of 20°Cand 30°Cand trace corrosion product of CuC₂O₄0.5H₂O and CuCl₂ of only 30°C.

Abstract: The internal defects of bonding structure of 2A50 block wrought aluminum were researched by a sequence thermal images which were obtained in the cooling process by thermal infrared imager with thermal excitation. Each image in the sequence could visually reveal internal defects of the specimen, which shapes projected on the surface. And sequence diagrams could reflect the differences between the temperature gradient of the defects and that of the uniform in the cooling process. Moreover, the more continuous and smooth edges of defects were obtained by rotating track the maximum gradient edge detection method in order to further quantify the size of the defects. The test results showed that infrared thermal imaging technology should be the rapid and effective method to detect internal defects of composite materials.

Abstract: The carbon fiber cement has compression sensibility. In this paper, the compression sensitivity of carbon fiber concrete is analyzed by Scanning Electron Microscopy with single fiber pull-out testing. Results show that the resistance of carbon fiber cement increases during the tensile test, the fractional change in resistance per unit strain of The carbon fiber cement is 38.38±0.05. In the meantime, the variation of resistance of single fiber pull-out under cyclic loading was studied. The resistance change caused by the elastic deformation is reversibility.

Abstract: A UV curable hybrid system with a dual mechanism of radical and cationic photo-polymerization, was investigated. A kind of free radical oligomer with low viscosity named hexahydrophthalic acid diglycidyl acrylate was first synthesized. The structure of the oligomer was characterization by FTIR. The UV curing processing of hybrid system was traced by real-time FTIR, and compared with free radical, cationic system. Thermal decomposition temperature and glass transition temperature of UV curing film for various system were determined by thermogravimetric analysis (TGA) and differental scanning calorimetry (DSC), respectively. And physical and mechanical properties of those curing films were analyzed and compared. The results show that the radical polymerization of double bond and cationic polymerization of epoxy group could occur simultaneously in hybrid system. The conversion rate of epoxy group for hybrid system was higher than that of epoxy group for cationic system, which demonstrated that the cationic photo-initiator (DPI·PF6) can be sensitized by the free radical photo-initiator (Irgacure 184). Compared with free radical and cationic system, the hardness and mechanical properties of hybrid system curing film were better than those of the cationic system curing film, while closed to those of free radical system.

Abstract: The facture behavior of a chromium (Cr) coating/ original steel substrate material was investigated in this work. The results presented in this work show the crack density of the Cr coating on the substrate increases with the increase of the thermal fatigue times, and the failure process and modes of the Cr coating /original steel substrate system can be described as follows: Firstly, the micro-cracks of the coating grew and interconnected as the thermal fatigue time increased. Secondly, the pocket cracking at the coating and the substrate interface occurred, and the main cracks of the coating formed. Finally, the spallation or (and) collapse of the coating occurred.

Abstract: Oxidation desulfurization, particularly to the deep oxidation desulfurization, is one of the most effective routs to meet the environmental requirements prior to the application of diesel. In this article, the author developed an improved way of oxidation desulfurization for diesel by the aid of ultrasound, which opens up a new technology. As the experiment results show that in comparison with traditional oxidation desulfurization, ultrasound-aided oxidation desulfurization for diesel achieves better desulfurization result, along with the reduction of oxidant-oil ratio, reaction temperature and time. In sum, it has proved ultrasound-aided oxidation desulfurization being a facile and significant way with a bright prospect for upgrading diesel.

Abstract: To investigate the effects of grinding media size on the grinding kinetics of cassiterite-polymetallic sulfide ores, the ball grinding media with diameters of 25mm, 30mm, 35mm and 40mm were studied in a laboratory ball mill. The results showed that the coarse and fine particles obeyed the first-order grinding kinetics laws in the process of grinding and the ball grinding media with 35mm diameter had a significant advantage on grinding up the coarse particles and controlling the generation of fine particles, which could provide theoretical guidance for practical production so that the grinding effects would be improved effectively and the problem of cassiterite over-grinding would also be settled very well.

Abstract: Recent attention is focused on issues of utilization of industrial wastes. The paper deals with the Tribological characteristics of Al356 alloy reinforced with red mud of different volume fractions. Red mud is a gangue produced during the extraction of alumina, disposal of which has become a major issue. In recent years, the utilization of red mud as a filler material has increased due to its chemical composition, which includes metals like Fe2O3, Al2O3, Na2O and TiO2, etc. These metals exhibit good wear characteristics. The red mud collected from Malco, TamilNadu, India, is preheated in the furnace up to 500^o C and 53 micron sized particles are mixed with Al356 alloy. Al MMC disc is manufactured by stir casting technique using Al356 alloy reinforced with different volume percentage (5%, 10%, 15% and 20%) of red mud. Pins of 10 mm diameter are machined from the brake shoe liner of commercial passenger car. The wear tests are then carried out on a pin-on-disc machine.. Wear rate is calculated for different percentage of reinforcement under different test conditions. The wear grooves formed on the Al MMC disc for all percentage of red mud are analyzed using optical micrograph. The results show that applied load and sliding velocity have significant influence on wear rate of composite. The co-efficient of friction decreases when the load increases. Experimental analysis is carried using Taguchis Design of Experiment method with various parameters like sliding velocities, applied load and composite volume fraction to identify the key factors that influence the wear rate. The Taguchi experiments results confirm the actual results obtained from the numerical calculation.

Abstract: Establish the ultrasonic single-point extrusion experiment platform to carry out the experiment of conventional extrusion and ultrasonic extrusion for different materials. Compared with experimental results, explore volume effect of ultrasonic vibration plastic forming and analyze the impact of different amplitude of ultrasonic resonance on material's plastic deformation volume. It can be found that ultrasonic vibration has an influence on stress-strain of material to a certain extent. Take advantage of the MSC.Marc finite element simulation software to continually modify the stress-strain curves of the material, finally the simulation result coincides with experimental conclusion. The results show that ultrasonic vibration has a significant impact on metal forming, improving the flowing property of metallic material processing, and softening materials, which further proves that ultrasonic vibration has great effects and provides the theoretical basis for it in material of plastic processing application.

Abstract: A modeling methodology is presented for printed circuit board(PCB) assembly optimization based on polychromatic sets(PS) theory. A computable model framework with hierarchical structure includes three layers, which are set layer(SL), logic layer(LL) and numerical layer(NL). Based on the hierarchical model and the mapping relationship among each layer, a computable model is formulated to describe the PCB assembly optimization problem in multiple PCB assembly tasks and multiple machines. The computable model not only involves various computation parameters, complicate constraint relationships such as process constraints, resource constraints and so on in PCB assembly optimization, but also describes the shortage of component, machine failure, order change and other uncertain factors. The optimization problems of PCB assembly in low-volume environment and multiple tasks can be solved efficiently.