Applied Mechanics and Materials Vols. 184-185

Abstract: Using weight-loss method combined with metallographic to analysis the effect of annealing temperature (600°C, 640°C, 680°C) on the corrosion resistance of cold rolled strip of complex brass HAl72-2.5Al-1.0Ni alloy. Corrosive solutions for testing the corrosion velocity were 3.5% of the neutral sodium chloride solution, artificial acid rain (3.5% NaCl+H₂SO₄ solution) and artificial sweat solution. The research results show that the corrosion of cold rolled strip occurs easily because grains stretched along the direction of deformation and the existence of residual stress. The maximum corrosion depth of cold-rolled strip is 94.8μm. Annealing treatment can effectively reduce the corrosion depth of alloy. Corrosion resistance of alloy rises with the increase of annealing temperature, because the recrystallization degree of alloy goes on more sufficient. The corrosion depth of samples annealed at 600°C and 680°C drops from 64.45μm to 56.32μm respectively. Aluminum content in the alloy also affects the corrosion resistance of the alloy, because oxygen oxidizes aluminum to density Al₂O₃ film which prevents the further corrosion of the alloy. The corrosion velocity of samples in the solution of artificial acid rain is fastest and lowest in artificial perspiration solution.

Abstract: Polylactic acid (PLA) fiber, as a biodegradable synthetic aliphatic polyester fiber, has properties of biocompatibility, biodegradability and processing. Therefore, this study used PLA multifilament to prepare numerous plied yarns, respectively 75D, 75D×2, 75D×3, 75D×4 and 75D×5. Afterwards, these yarns were twisted with 3, 5, 7 twist/inch and then heat-treated respectively. The resulting yarns were tested for their tensile property tensile tenacity and tensile elongation. Moreover, the heat-treated effect was discussed on influencing tensile property.

Abstract: On the basis of finishing research of flame resistance level-2 asphalt, further experiment is carried out to research high and low-temperature pavement performance of flame retarding asphalt of the phosphorous-phosphorous, halogen-phosphorous and other collaboration system and analyze influences on the asphalt pavement performance by flame retardant of different systems.

Abstract: High volume fraction silicon carbide particulate reinforced aluminum matrix (SiCp/Al) composite are new class of difficult-to-machine materials due to their high strength. This paper presents an experimental investigation on the machinability of 60 vol% SiCp/Al composites by comparing the rotary ultrasonic milling method with the conventional machining method. The test scheme is designed, and the measurement method of the cutting force, surface roughness and morphology are illustrated. Based on the constructed experimental platform, the influences of machining parameters, such as cutting speed, feed rate and cut depth, on the cutting force and surface roughness are discussed. The experimental results show that ultrasonic machining is an effective method for machining high volume fraction SiCp/Al.

Abstract: A series of experiments are conducted to polish glass-ceramic by a circular-type integrated electrode tool in the electrorheological(ER) fluid-assisted polishing process. In this study, the microstructure of fibrous columns formed by particles perpendicular to the electrodes is observed when the electrical field is applied. The mass of ER polishing fluid gathered on the tip of tool electrode and the normal pressure in polishing area are measured by the dynamometer. The influential regularities of the concentrations of abrasive particles, the applied voltage, the spindle rotational speed, mixing ratio for abrasives and the gap between tool electrode and workpiece on the surface roughness are obtained by experiments.

Abstract: In the present work, an experimental study has been made to optimize the drilling process parameters. Response surface methodology based on central composite design (CCD) has been used to study and analyze the experiments. Twist drill diameter, cutting speed and feed of drilling were chosen as variables to study the process performance for the responses of the hole surface quality (Ra) and the roundness error on aluminum 7075. Experiments were performed on a newly designed experimental setup developed in the laboratory. The results identified the most important parameters to maximize the hole surface quality and minimize roundness error. Finally, regression equations were obtained to predict the responses for different values of variables.

Abstract: Use of hollow material in slab can reduce self-weight and deflection than solid slab with CFRP reinforcement. This study was intended to evaluate the bending performance of void flexural members with CFRP reinforcements by bending tests. Test results showed that specimens with void and solid section had the similar failure mode by concrete crushing at the compression zone, and that there was a big flexural capacity difference between the two section. Flexural capacity of solid section with CFRP bars was increased by 55% for void section. Thus, for the design of flexural members with CFRP bars by concrete crushing failure, it is important to calculate the exact distribution of strains and stresses, and to consider the reduction of flexural strength of void section.

Abstract: Aqueous gel-casting of beryllia using polyelectrolyte NH₄PAA as a dispersant has been investigated. The effects of the dispersant amount, pH values on the surface properties of BeO powders in aqueous solvent were studied and high solids loading BeO suspension (45 vol.%) was developed. A premix solution containing 15-20 wt.% of AM monomer can provide enough mechanical strength for the green body obtained from 45 vol.% BeO suspension. SEM photography indicates that BeO ceramics with homogeneous microstructure can be fabricated. The thermal conductivity of sintered green body is 182.1±10 W/(m.K). Gelcasting is a suitable process to form BeO ceramic parts.

Abstract: The growth details of strained GaAsSb layers on GaAs(001) substrates were studied by reflection high energy electron diffraction (RHEED) beam intensity oscillations as a function of both substrate temperature and Sb/As flux ratio. Both the RHEED intensity and RHEED oscillation cycles are reduced with decreasing substrate temperature and Sb/As flux ratio. InAs QDs with high dot density, small dot size and narrow size distribution have been achieved on strained GaAs / GaAsSb buffer layer. The average lateral size of dots shows a trend toward to smaller size and dots’ density shows a trend toward to higher density as the surface Sb composition increasing. The QDs with higher density and smaller size distributions at high Sb composition, indicates that the Sb plays an important role in the dot formation under this growth condition. The lattice mismatch of InAs layer with the GaAsSb buffer layer is reduced with increasing of Sb composition in the GaAsSb interlayer. This result indicates that the density, size and size distribution of self-assembled quantum dots (QDs) can be controlled through the manipulation of the Sb-mediated strain field in the lattice mismatched system.

Abstract: In the present study, amorphous coatings on plain steel substrate were prepared by electric arc spraying technique. The high-speed dry sliding tribological properties of the coating were investigated on a pin-on-disc tribo-meter. The results show that amorphous phase generates in the sprayed coating. When the sliding speeds are less than 40m/s, the friction coefficient increases. The friction coefficients decrease with the sliding speed exceeding 60m/s. The wear rates increase with increasing the sliding. Phase transition occurs in the friction process.