Abstract: In this paper a rigid plastic mesh free method for slightly compressible materials is presented for the simulation of bulk metal forming processes. In this model MLS shape functions are used for the approximation of velocity field. These shape functions are defined in initial coordinates of particles. By using this method the support of shape functions covers the same set of particles during material deformation. Transformation method is used for imposition of essential boundary conditions. Transformation matrix is formed only once at the initial stage, because shape functions are defined in initial coordinates system. For evaluation of the presented model, disk upsetting and ring upsetting processes are simulated. Results obtained from this model are compared with experimental data and FEM results and good agreement is observed between them.
Abstract: A method is presented based on geometric-curvature characteristics in which a scanning path planning for laser bending of a straight tube into a curve tube in a two- and three-dimensional space. In a two-dimensional (plane) bending, the steel tube is divided into several segments according to the extreme point and inflection point of the desired shape of the tube, taking the extreme point as the initial place of the path planning, using different scanning space for every segment in order to identify the scanning paths. For a tube bending in a three-dimensional space, a projection decomposition method is used, where the three-dimensional is decomposed into two two-dimensions, and respective scanning path planning and process parameters are thus acquired. By combining the data in the two-dimensional planes, the three-dimensional scanning path plan was obtained. Finally, an experimental verification is carried out to bend straight tubes into a two-dimensional sinusoidal and a three-dimensional helical coil-shaped tube. The results show that the proposed method of scanning path planning is effective and feasible.
Abstract: Deep drawn parts usually have different wall heights because of earing behavior. This behavior is due to the planar anisotropy (Δr) of sheet metals. A measure of the variation of normal anisotropy with the angel to the rolling direction in sheet plane is known as planar anisotropy. If the magnitude of the planar anisotropy is relatively large as absolute value, the earing behavior becomes more effective so larger ears occur. Furthermore, the orientation of the sheet with respect to the die or the part to be formed will be important. In addition, cutting of scraps in the parts which have ears leads to material waste. The scope of this study is to determine the planar anisotropy of AA 5754-O and AA 2024-T4 aluminum alloys and to investigate the earing behavior by the way of deep drawing of cylindrical cups.
Abstract: Flexible forming of metal sheet using plasma arc is a new technique which forms parts by thermal stress without moulds and external force. To improve the surface quality of formed parts, a magnetic-driving plasma arc (MDPA) was applied in monitoring the distribution of heat flux. A mathematical model was developed to study the variations of temperature fields and deformation fields with MDPA and merely with plasma arc, which was validated by the forming experiments. The results indicated that the swing amplitude of MDPA increased linearly when the exciting current Ie < 1.2 A, and the distribution of heat flux with MDPA was more uniform than that merely with plasma arc in the heating zone, which avoided the possible partial melting and ablation of metal sheet. Moreover, the “U-shape” occurred with MDPA, and the material accumulation with MDPA was smaller than that merely with plasma arc on the surface of metal sheet.
Abstract: Flow forming is one of the cold forming process which is used for hollow symmetrical shapes. In this paper, the forward flow forming process is simulated using the finite element method and its results are compared with the experimental process. The variation of thickness of the sample is examined by the ultrasonic tests for the five locations of the tubes. To simulate the process, the ABAQUS explicit is used. The effects of flow forming variables such as the angle of rollers and rate of feeding of rollers, on the external variables such as internal diameter, thickness of tube and roller forces are considered. The study showed that the roller force and surface defects were reduced with low feeding rate and low rollers attack angles. Moreover, the sample internal diameter increased at low feeding rate and low rollers attack angles. The optimum variables for flow forming process were also obtained.
Abstract: There are many different types of manufacturing methods for heat sink fins in the current market. The aim of this study is to design an extrusion die for a radial-finned heat sink using a commercial finite element package, DEFORMTM 3D. We then conduct a series of simulation analyses with different variables such as friction factor, ram velocity, and fin gate stage of the die to evaluate the methods of decreasing the warping in the extrusion process. The die is assumed as a rigid body in the analyses. The results confirm the suitability of DEFORMTM 3D to design an extrusion die achieving a lower warping behavior of the radial-finned heat sink.
Abstract: Die casting process has been used widely for complex automotive products such as the knuckle, arm and etc. Generally, a part fabricated by casting has limited strength due to manufacturing defects by origin such as the dendrite structure and segregation. As an attempt to offer a solution to these problems, forging has been used as an alternative process. However, the forging process provides limited formability for complex shape products. Rheo-forging of metal offers not only superior mechanical strength but also requires significantly lower machine loads than solid forming processes. In order to produce semi-solid materials of the desired microstructure, a stirring process is applied during solidification of molten state. This paper presents the results of an A356 aluminum alloy sample, which were obtained by experiment and by simulation using DEFORM 3D. Samples of metal parts were subsequently fabricated by using hydraulic press machinery. In order to compare the influence of loading method, two types of samples were fabricated: (1) samples fabricated under direct loading die sets (2) those fabricated under indirect loading die sets. The formability and defects, which were predicted by FEM simulation, were similar to those of samples used in practice.
Abstract: In this study, A380 aluminum alloy feedstock produced with cooling slope casting was exposed to isothermal treatment to obtain a globular microstructure which is a key feature for semisolid forming. The dendritic primary phase in the conventionally cast A380 alloy has readily transformed into a non-dendritic one in ingots cast over a cooling plate from pouring temperatures between 615, 630 and 650 °C. After the casting process, isothermal treatment was carried out at 565 °C in induction unit. Isothermal treatment yields a globular microstructure. To determine the tribological properties of this alloy, a pin-on-disc tribometer was used to carry out tribological tests under dry sliding conditions. The results showed that both cooling slope casting and isothermal treatment has an effect on tribological properties.
Abstract: When cooling a boron sheet that has been heated to over 900 °C by hot press forming (HPF) process, the microstructure obtains a martensitic structure by controlling the cooling rate. HPF has advantages such as improvement in formability and material properties, and minimal springback of the formed material. The facts influenced by the cooling rate are determined by the heat transfer characteristics between the heated materials and the dies. In this study, controlling of the cooling rate is addressed by controlling the heat transfer coefficient of the material during the pressing process. This study demonstrates the material properties and microstructures of the formed material during the HPF process wherein cold dies are used to form the heated steel plate. This is achieved by varying the major forming conditions: the cooling rates, which is regarded as the most important process parameter.