Advanced Materials Research Vols. 472-475

Abstract: Whether selection of chip removal air volume is reasonable or not, do affect the performance of blasthole drill and bit’s life. How to calculate air volume always make the designers confused. In this paper, writer use theory of gas-solid two-phase flow and energy principle combined with characteristic of rock ballasts from the mine site to determine particle rising speed, free floating speed and air flow rate of the rock ballasts. And according to the relation between particle and particle group’s floating speed calculate floating speed and the corresponding chip removal air volume among different diameter of particle of the same minerals. It can provide a method of calculation to designer, which is very reference value to for the practical application.

Abstract: The paper presents the results of radial strain distribution measurement throughout the part after multi-pass conventional metal spinning by the circle grid analysis method. The influence of the mandrel speed, workpiece geometry and planar anisotropy of material on the radial strain was studied. For experiment design, an orthogonal array L27 was used and ANOVA (Analysis of Variance) was carried out. Based on the results it is determined that the sequence of factors affecting radial strain corresponds to geometry of spun part, mandrel speed, planar anisotropy of the sheet. In particular, it is found that the workpiece geometry (specific areas of spun part: mandrel/workpiece radius, conical area, cylindrical area) is the most important factor which influences the radial strain of the spun part.

Abstract: Grain refinement is quite important for producing 7050 alloy billet especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ500 mm billets and study the effect of electromagnetic field on the microstructure. The sound Φ500 mm billets of 7050 alloys without any grain refiner can be successfully prepared by the LFEC process. The results show that low frequency electromagnetic field has a significant grain refining effect on 7050 alloy and can effectively eliminate feather grain structure. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed grains and are finer and more uniform than that of conventional direct chill (DC) cast billets. The LFEC process also shows a strong power to eliminate hot tearing during casting large sized billet of high strength aluminium alloy.

Abstract: Several Nb-Ti-Al based alloys have been investigated by X-ray diffraction (XRD) and optical microscope (OM). It was found that the morphology of the B2/β phase was different from the O phase (Ti2AlNb) and δ phase (Nb3Al). The B2 phase can not be separated from the disordered β phase by metallography and XRD easily. And the typical morphology of O phase alloy is large herringbone structure. After that the aberrance of the lattice parameters was discussed in this article. The present result indicates in these alloys the lattice parameters were mainly determined by the ratio of Nb to Ti. As the ratio of Nb to Ti in alloys increased, the lattice parameters increased too.

Abstract: In this paper, finite element analyses of thread rolling process for the micro-sized screw with the diameter of 800 μm and the thread pitch of 200 μm are firstly carried out. For the finite element analysis of the thread rolling process, hardening behavior of SUS has been estimated by the compression and tensile tests. And then, process design has been conducted with the aid of simulations and the prototype of the micro screw finally has been fabricated. In order to verify the CAE based process design for micro-sized screws, the deformed shape and dimensions obtained from the CAE are compared with those from the experiment. The deformed shapes of the pitch part and the top part of threads can be demonstrated the feature of experimental result.

Abstract: This study evaluates the effect of the compression between the punch and the die on spring-back after the punch reaches the dead point. Utilizing the elastic-plastic FEM, the forming and spring-back process of aluminum alloy V-shape sheet is simulated. The investigation is also carried out through experiment. It is shown that spring-back decreases as the ratio of the average pressure and tensile strength increases when the ratio is small; Spring-back increases slightly as the radius of the punch increases from 8mm to 16mm. The results of the 2D plain strain element are in good agreement with the experiment results.

Abstract: The effects of technical parameters on initial silicon melting in cold crucible continuous casting were studied. These parameters include the materials, the shape and the position of the base, the mass of the silicon that set on the top of the base. Through experimental and theoretical analysis, the optimized parameters were finally given: the base graphite with obconical shaped should be put at the level of the second turn of the coil, and the initial silicon with 10g should be put on the base. The mechanism of these parameters affecting on the initial melting are discussed and revealed.

Abstract: Traditional regenerated cellulose fiber (viscose or viscose fiber) had a poor wet breaking strength and wet modulus, which to some extent limited the application of the fiber. Hollow viscose was difficult to get for its instability during the cellulose regenerating process. This paper introduced one kind of new spinning method for hollow viscose through a spinneret of concentric shaft structure using HWM technology. The hollow viscose fiber produced in this experiment had a big crystalline structure and an excellent fibril orientation which gifted the fiber a good mechanical performance even under wet circumstances. The fiber had a bright future in textile application as one component of blending fabrics.

Abstract: The electrical resistivity of metal fiber-filled polymer composite always increases during injection molding process because the conductive fibers were easily broken down to shorter under the action of high shear stress. In order to decrease electrical resistivity of the molding, we investigated the microstructure at different layers within the molding made from stainless steel fiber-filled polypropylene and measured their resistivities. High resistive zone mediate resistive zone and low resistive zone were found within the molding. The results showed that the high resistivity zone located at the skin area of the molding where average length of filled fibers was less than other zones, and the smallest resistive zone located at the core area where most fibers preserved large ratio of length to diameter and oriented along flowing direction of the melt, and the sub-skin zone is mediate resistive zone.

Abstract: The hydro-mechanical differential turning mechanism is the new type of double power flow turning mechanism of tracked vehicle. The hydraulic stepless speed regulation and the high efficiency of mechanical transmission are integrated into the turning mechanism. The stepless turning of tracked vehicle can be achieved. Basing on hydro-mechanical differential turning theory, the scheme design of steering wheel control system of tracked vehicle of hydro-mechanical differential turning is finished. By establishing model of steering wheel control system, its working stability and following characteristic is simulated and analyzed in this paper. The demand of hydro-mechanical differential turning of tracked vehicle can be realized by the steering wheel control system designed through the simulation results.