Advanced Materials Research Vols. 239-242

Abstract: A thermal-mechanical coupled analysis of superplastic differential temperature deep drawing (SDTDD) with the MARC finite element code is performed in this paper. Initial drawing blank of an AA5083 bracket was calculated and adjusted according to the simulation result. During the SDTDD simulation, the power-law constitutive model of AA5083 was established as function of temperature and implanted in software MARC through new complied subroutine. Under the guide of the numerical simulation, the die was fabricated and the AA5083 bracket was successfully manufactured via superplastic differential temperature deep drawing. In forming practice, the temperature of female die was kept at 525°C, i.e. the optimal superplastic temperature of AA5083, and the punch was cooled by the flowing water throughout the forming process. The drawing velocity of punch was 0.1mm/s. Results revealed that the formed bracket had a sound uniform thickness distribution. Good agreement was obtained between the formed thickness profiles and the predicted ones.

Abstract: The bonded structures in vehicles are usually in different enclosure conditions. A finite element (FE) model, based on fluid-solid coupling method, has been established for analyzing the temperature distribution of adhesive single-lapped joint when curing in a closed enclosure. The heat transferring process of the adhesive joint in an exposed environment has also been executed for comparison purpose. The FE temperature results of both joints are validated by experiments. It has been found that the joint temperature in a closed enclosure rises much more slowly compared with the joint in an exposed environment within the curing process. Due to the thickness variation along the adhesive joint, it can be observed on both joints the lap area always obtains the lowest temperature while the joint ends obtain the highest ones.

Abstract: The method to improving surface corrosion resistance of 6063 aluminum alloy was studied, and the mechanism of surface corrosion resistanc was discussed in theory. The results indicate that the adjustment of chemical composition is of advantage to corrosion resistance of the alloy, its property is better as Mg, Si mass ratio at about 1.55. The necessary homogenizing treatment of cast ingot subserves corrosion resistanc of aluminum extrusion, and the cast ingot should be cooled quickly after heat treatment. Significant effect of extrusion technology on erosive property is observed from aluminum alloy, aluminum extrusion has good corrosion resistance when outlet temperature is at about 510 degree centigrade.

Abstract: To improve brittleness and optimize interface of glass-fiber/PVC composites, reinforcing and toughening technologies for glass-fiber/PVC composites were studied. Influences of glass-fiber and diallyl orthophthalate(DAOP) resin on their mechanical properties were observed. Diallyl orthophthalate(DAOP) resin was blended with PVC in various weight ratios by melt compounding. The compatibility between diallyl orthophthalate(DAOP) resin and PVC resin was analysed by measuring the impact toughness, tensile strength and bending strength. The results clarified that each mechanical properties improved, in addition to,SEM images show that the interface of glass-fiber/PVC composites added with DAOP was much closer , PVC resin surrounds completely the glass-fiber.

Abstract: TiAl/Ti₅Si₃ in situ composites were successfully fabricated by reactive hot-press method from powder mixtures of Ti, Al and Si. The influence of the Si addition on the microstructures and mechanical properties of TiAl/Ti₅Si₃ composites was investigated in detail. The results show that an appropriate amount of addition of Si refined the matrix structure obviously due to the in situ formed Ti₅Si₃, and as a result, the flexural strength and fracture toughness of the composites are modified. When the Si content is 1.82 wt %, the flexural strength and the fracture toughness reach the maximum value of 685.67 MPa and 9.02 MPa·m^1/2, respectively. The enhancing mechanism was also discussed.

Abstract: Dissimilar metal of Steel and Magnesium alloy by friction stir spot welding is studied. Based on using orthogonal test method to optimize the process parameters and get satisfactory joint, SEM is used to observe the features of joint, fracture morphology, and XRD is used to determine the joint phase, and the results show that: the design of rotating tool without pin is reasonable and it can form satisfactory joints without keyhole for spot welding; spot welding nugget zone on the magnesium side shows the phenomenon of melting and solidification in the range of hundreds microns, and its microstructure appears a structure of dendrites; The fracture mode of spot welding joint is a mixed mode of cleavage and dimpled rupture.

Abstract: It is assumed that the material properties of arches vary with the thickness direction as a power function. Based on Kirchhoff’s assumption of straight normal line and the theory of axial extension and geometric nonlinearity, the in-plane buckling behavior of FGM elastic arches subjected to uniformly distributed radial follow loads is studied. In this paper, the governing equations for the nonlinear stability of FGM elastic arches are derived, the effect of composition parameters of FGMs, geometric parameters of arches and ends restraints on critical loads and balance configurations is investigated, and corresponding graphs are plotted.

Abstract: According to the low current efficiency of magnesium sacrificial anode, magnesium sacrificial anode material with gadolinium addition was investigated. The electrochemical properties of the material were measured by constant current method. The microstructure and composition of the anode material were characterized by metallurgical microscope and energy spectrum analysis. The results show that addition of gadolinium in magnesium sacrificial anode can refine grain size, change second-phase distribution, maximize current efficiency, and minimize potential of magnesium sacrificial anode. When the addition of gadolinium reaches 0.1%, the highest current efficiency is reached as much as 65.32%, which increases by 10%, compared with magnesium anode without gadolinium addition.

Abstract: For obtaining higher quality casting, the lost foam casting is used to produce reaper underpan. While the raw materials are selected, the fireproof coating and sand are chosen well, the sand box is designed according to the technology, pouring system is calculated, under the above operation strictly, such as air hole can be avoided.

Abstract: Nano-structured magnesium hydroxide (nano-MH) has been added into LDPE/LLDPE, the technological parameters, flame and mechanical properties, M.F.R. of LDPE/LLDPE/nano-MH samples have been examined. It is indicated two time extruder pelletization is a good technological route, which can make nano-MH disperse evenly in PE. The optimum rotational speed of screws changes from 37 to 42 rad/min, the die pressure changes from 35 to 61.5 bar. Nano-MH has good flame retardant and smoke suppressing properties. The samples added 60% nano-MH can reach UL94 FV-0 flame retardant rating. When nano-MH content is more than 40%, no smoke emits. With nano-MH content increases, the tensile strength, impact strength, elongation and M.F.R decreases, Young’s modulus increases.