Advanced Materials Research Vols. 189-193

Abstract: One of the most sensitive features of sheet metal forming processes is the elastic recovery during unloading, called spring-back, which leads to some geometric changes in the product. This phenomenon will affect bend angle and bend curvature, and can be influenced by various factors. In this research, the effects of sheet thickness and die radiuses on spring-back in L-die bending of CK67 and St 14 steel sheet were studied by experiments and numerical simulations.

Abstract: Based on precision forging method, a single stage hot forging process of alternator poles is put forword, which the heated blank can be forging by only one press in a special closed die. In the last this process is verified by the software of Deform-3D which is employed rigid-plastic FEM method.

Abstract: Hydroforming processes of a Y-shaped stainless steel tube with d/t (ratio of diameter to thickness) of 183 is presented. FEM simulations were carried out for analyzing the stress states and thickness distribution in the workpieces during hydroforming of the Y-shaped tube. A two-step process with preform procedure is presented to improve the stress states in the protrusion and to avoid the severe thinning at the top of the protrusion. Through the two-step hydroforming, the wrinkling and cracking defects were all avoided and sound components were produced.

Abstract: Water quality monitoring plays an important role in contamination control and environment protection. This paper describes an on-line multiparametric water quality monitoring system based on visible spectrophotometry, which combines embedded technology with GPRS telecommunication technology. This system can realize online wireless monitoring to concentrations of chromium (Cr), plumbum (Pb), A surfactant (AS), chemical oxygen demand (COD), ammonia nitrogen (AN), total phosphorus (TP) and total phenol (TPh) in real time. The mechanical structure, hardware circuit and software design of the system are completed. The absorption spectrums of pure water and MB-SDS complex have been measured. Preliminary experiments using a model machine show that each mechanism of the system runs well. Moreover, the monitor possesses many advantages, such as high degree of automation, high reliability, high efficiency, compact structure, small size, and so on.

Abstract: Peripherally clamped thin shallow hyperbolic metal shells under internal pressure are widely used as rupture discs, quick opening devices and the structures in metal plastic processing. In the bulging process of shells, if the corner radius of the up-holder is too large, negative-curvature zone close to boundary will be enlarged. Contrarily, if the radius is too small, shear rupture will happen in the clamped rim. The contact between the shell and the up-holder corner in deformation is explored by elasto-plastic finite element analysis, and the results are verified with experiments. Influence of the up-holder corner on the mechanical behavior of bulging shells is closely related to the non-dimensional parameter ru/s0 (ratio of the corner radius ru to the original thickness s0). The influence can be partitioned into four regions by three demarcation points, ru/s0 = 0.52, 1.50, and 2.00. The four regions are respectively full effect region, unstable region, near-stable region, and no effect region.

Abstract: Continuous semisolid extruding extending forming process was adopted to produce LY11 alloy flat bar. The forming process, metal flow behavior in die cavity and microstructure and mechanical property of flat bar were investigated. It is shown that the LY11 alloy flat bar with transverse section of 10×50 mm and with good surface and fine equiaxed grains can be obtained by the continuous semisolid extruding extending forming process with melt pouring temperature of 770～780°C. The metal streamlines show that the semisolid slurry fills the die cavity in radiation manner and moves forward layer by layer and the velocity of slurry flow in the central area of die cavity is the maximum, and then decreases gradually from the center to side of die cavity. The tensile strength and elongation of flat bar with T6 heat treatment are 420.5 MPa and 14.2%, respectively.

Abstract: The uneven elongation between flange and web can make long tongue in the head of H-beam, which can lead to too long crop end length. In order to control the tongue length of H-beam head, different elongation ratio between flange and web is put forward to control the head displacement of H-beam. If the flange and web elongation is uniform, the loss of crop end length will be reduced. At the same time, different cooling speed of flange and web is set to keep the section uniform temperature. Experimental investigations of H-beam rolling are carried out on the universal mill in the Rolling Lab of Hebei polytechnic University. Comparisons between experimental value and simulation results prove the correctness of elongation ratio of flange and web.

Abstract: The purpose of this experiment is to find the effects on structures and cementite of rapid induced heating and tempering. The author designed a travelling magnetic field device, using a frequency conversion power supplier, the well prepared SS400 plates were heated, and some parameters are investigated through changing their values (frequency, current, gap from the pole surface to the steel plate and heating time). The temperatures during the heating process are recorded continuously. Meanwhile, the structures and hardness are investigated. The results show that the heating temperature affected the structure and the low temperature impact energy of the steel, at a suitable process parameters combining, the size and morphology of the separation and precipitation particles are very fine and distributed uniformity inside grains.

Abstract: Constrained groove pressing is a simple and effective method of grain refinement. Using the experimental data obtained by regression analysis, this paper analyzes the simulation of the four pass constrained groove pressing deformation of 7050 aluminum alloy. The simulation results show that the grain size of the billet is refined significantly after four pass constrained groove pressing deformation and decreases from the original 90 μm to a minimum of 14.0 μm. With the increase of the number of deformation passes, refinement effect becomes weakened gradually, the grain size tends to stabilize and the organization is more uniform.

Abstract: The influences of low frequency magnetic field and static magnetic field on the air film casting process are studied in this paper. 6063 aluminum alloy ingot of 174-mm diameter were produced by electromagnetic air film casting process; intensity of the coil current is from 50 to 200A, and frequency is from 15 to 30Hz. The results showed that low-frequency magnetic fields can speed up the flow of liquid metal in sump and the air film stability was undermined, leading to folds and segregations appeared on the ingot surface. Static magnetic field could inhibit the melt to erosion the solidified shell effectively, it’s help to improve the speed and pull good surface quality.