Applied Mechanics and Materials Vols. 190-191

Abstract: Hybrid composites are increasingly concerned by the investigators and widely used in many areas, especially aerospace industry, for its multi-functional properties. In the present study, the mechanical properties and thermal properties of a structural component manufactured by a new hybrid composite consisting of quartz fiber, carbon fiber and cyanate ester resin has been investigated by finite element numerical simulation. The results show that the mechanical properties of the structural component are very good. And the temperature of inside face is 43.8 °C. The thermal strain is lower than 0.15%.

Abstract: To extend the service life of the equipment, a novel, efficient and cost-effective method is used to recover the damaged component of the equipment. The mechanical properties of unidirectional M40J/epoxy composites, prepared by molding process, were studied. Then the centre-cracked thick LC52CS aluminum plates were single and double side repaired with the composites patches by vacuum bagging technology in which three cure cycles were applied. Results show that a low cure temperature induce a small thermal residual stress. Choosing the cure cycle with the highest tensile strength of single-side repaired specimens, the tensile strength of single-side and double-side repaired specimens enhance 31.50% and 47.29% of that of the unrepaired specimens, respectively. And fatigue life of the double-side repaired specimens extends that of the cracked aluminum plate over 76 times, which is also significantly better than that of the single-side repaired specimen.

Abstract: Compression tests of the hydrogenated Ti6Al4V0.2H alloy were carried out using an Instron 5569 machine at room temperature. True stress-strain curves of the hydrogenated Ti6Al4V0.2H alloy under different compressive strains were obtained. Microstructure evolution of the hydrogenated Ti6Al4V0.2H alloy during the process of compression was investigated by optical microscopy and transmission electron microscopy. Results show that true stress-true strain curves of Ti6Al4V0.2H alloy have good repeatability. The deformation of grains, the dislocation density and slipping evolution during the process of compression are discussed.

Abstract: Using fractal theory simulation of dendrite crystal DLA growth model of pure substance, the undercooling during solidification process of crystal nucleation is simulated; and then in the crystal nuclei are formed on the basis of a pure substance, the phase field model and combined with the finite difference method further differentiation simulation of dendrite crystal growth. According to MATLAB programming, the simulation results obtained by field and temperature field can be seen in the DLA growth, growth model with random premise, for the same kind of material simulated dendrite crystal have both similarities and differences exist. Then, we can get the conclusion, through fractal growth of DLA model with phase field model of dendrite nucleation, growth process is carried out the simulation results, a simple by phase field model is more accord with the dendrite crystal in the experiment.

Abstract: Poly-2, 5-dimethoxyaniline (PDMA) coating was successfully prepared by electrochemical method on the surface of active carbon (AC) electrodes in oxalic acid aqueous solution. The resulted coating was hydrolyzed to produce poly-2,5-dihydroxyaniline (PDHA) to enhance the capacitance of the composite electrode. Scanning electron microscope (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge test, and electrochemical impedance spectroscopy (EIS) were used to investigate the properties of these electrodes. A comparative analysis on the electrochemical properties of bare-carbon electrode was also conducted under similar conditions. The specific capacitance of the PDHA/AC composite electrode was 947.04 F•g-1 between 0.0 and 1.0 V at a current density of 3.0 mA•cm-2 in 0.5 M H2SO4 electrolyte. The capacitance retention of composite electrode was about 89.2% during 700 charge-discharge cycles.

Abstract: In order to obtain TiO2-pillared materials, montmorillonite (MMT) from Xinghe Co. of Neimeng as matrix, was used. The tetrabutyl titanate was used as precursor for the preparation of the TiO2-pillared montmorillonite, which was applied to introduce TiO2 into its interlayer space (15 mmol Ti/g clay). The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR). The XRD patterns and the SEM photograph illustrated that the layers of MMT were delaminated and all samples were of the anatase phase. The TiO2-pillared montmorillonite was shown high photoactivity for the photodegradation of methyl orange dyestuff in aqueous solution under UV irradiation. The results showed that TiO2-pillared montmorillonite containing the anatase phase of TiO2 by calcination at 773 K and it was with the highest photocatalytic activity. Comparative photodegradation experiments were also conducted under different conditions. The experimental results demonstrated the feasibility of utilizing TiO2-pillared clays as a catalyst for removing methyl orange from water.

Abstract: A steel plate with thickness（3~12）mm named 30CrMo（%：0.29~0.34C、0.17~0.37Si、0.40~0.70Mn、≤0.015P、≤0.010S、≤0.30Mo、0.80~1.10Cr）was developed by converter melting and hot continuous rolling. Good metallurgical quality, mechanical properties and strip shape are ensured by accurately control of smelting, rolling, coiling and decoiling process. The results show that 30CrMo steel has high purity, uniform structure and stable properties, perfect plate shape, and meets requirements of consumer.

Abstract: The interfacial cracking behaviors of a chromium (Cr) coating/laser pre-quenched steel substrate system and a Cr coating/original steel substrate system under thermal fatigue loading were investigated in this work. The experiment results show that the Cr coating on the pre-quenched substrate surface exhibited a higher resistance of interfacial cracking than that of the Cr coating on the original substrate surface under the same loading condition. This indicates the technology of laser pre-quenching of steel substrate surface prior to plating the Cr coating can improve the interfacial adhesion properties between the coating and substrate.

Abstract: Detailed studies on the ablation threshold of Mo with picosecond laser pulses are reported in this paper. The laser pulses used for the research were 1064 nm in wave length and 15 ps in pulse duration. Scanning electronic microscope (SEM) and optical surface analyzer were used to analyze the ablation sample, and by analyzing the linear relationship between the squared diameter of ablation crater and pulses energy we obtained the ablation threshold of Mo with single- and multi-pulses. Influence factors of ablation threshold were observed while analyzing machining process. Finally, the shape and topography of holes drilled by percussion with ablation regularity in Mo were studied, which provided an important guidance for the following applications on picosecond micro-machining.

Abstract: Abstract. Oil rig derrick is a large and complex metal frame with lots of bars and complex force. Moreover, the use of working condition is complex and harsh, so it is quite necessary to analyze strength and calculate oil rig derrick. In this paper, with the basic structure and force characteristic of JJ225/42-KC type oil derrick, the ANSYS finite element software is used to establish JJ225/42-KC type oil derrick structure finite element model. The strength and stability analysis of the maximum hook load working condition, the working wind load working condition and the maximum wind load working condition of three combined working conditions indicates that the overall structural design of JJ225/42-KC type oil derrick is reasonable with good both dynamic and static characteristics and the derrick meets the requirements of the strength. What is more, the derrick has a excellent overall stability. In the end, the strength of the lifting devices and the derrick leg pin of JJ225/42-KC type oil derrick are calculated and checked, showing that all meet the requirements of the strength.