Papers by Keyword: Finite Element (FE) Simulation

Abstract: Hollow parts with variable cross-section are widely used in the area of automotive and aerospace industries due to their excellent properties. Wrinkling is one of the most common forms of instability in the process of manufacturing the parts. The minimum curvature of the cross-section profile of bugled workpieces is proposed in this paper to as a wrinkling indicator to characterize the form and extent of the wrinkle. The wrinkle distribution of 1Cr13Mn9Ni1N stainless steel tube in hydroforming with radial crushing under linear and constant hydraulic pressures is analyzed and the influence of the bulging methods on the wrinkling is investigated via finite element simulation. The results indicate that wrinkling under constant hydraulic pressure is more obvious than that under linear one, wrinkling in hydroforming with radial crushing is more serious than that in free hydro-bugling, wrinkling on the cross-section away from the middle cross-section is more distinct and the wrinkling on the side edge is obvious than that on the bottom of the bugled workpiece.

Abstract: The orthotropic mechanical behaviors of weft-knitted flax fiber fabric reinforced polypropylene (PP) composites, which were produced by hot pressing of knit layers composed of a commingled yarn with a flax fiber content of 50vol.%, are investigated in both meso- and macro-scales. In meso-scale, the repeating unit cell (RUC) finite element (FE) model is developed, in which impregnated yarns are assumed to be isotropic elastic while the matrix is modeled as an elastoplastic, isotropic solid. Then, stress-strain curves of the RUC are simulated for its elastoplastic orthotropic parameters. Finally, in macro-scale of its specimen, the tensile behavior of the composite laminates with six parallel plies is simulated by means of 3D elastoplastic FE method. The applicability and limitation of this model have been discussed.

Abstract: Conical parts forming is one of the complex and difficult fields in sheet metal forming processes; because of the low contact area of the sheet with the punch in the initial stages of forming, too much tension is applied to the sheet causing bursting occurrence. Furthermore, since the major part of the sheet surface between the blank holder and punch tip is free, wrinkles appear on the wall of the drawn parts. Therefore, these parts are normally formed in the industry by spinning, explosive forming or multi-stage deep drawing processes. In this paper, the effect of punch tip radius and conical- cylindrical radius on formability and thickness distribution of the conical parts for three different punch angles were studied.

Abstract: Forming conical parts is one of the complex and difficult fields in sheet metal forming processes. Because of low contact area of the sheet with the punch in the initial stages of forming, too much tension is applied to the sheet causing burst occurrence. Furthermore, since the major part of the sheet surface between the blank holder and punch tip is free, wrinkles appear on the wall of the drawn parts. Therefore, these parts are normally formed in industry by spinning, explosive forming or multi-stage deep drawing processes. In this paper, the effect of punch conical angle in hydroforming of conical-cylindrical parts has been studied. It is shown that by increasing the angle the thickness reduction will be reduced.

Abstract: The relevant introduction development of the micro electromechanical systems (MEMS) is carried out in this paper. The pressure sensor is an important component of micro electromechanical systems (MEMS). Many aspects of the pressure sensor are studied，simulated and analyzed by us. The principle of work of the pressure sensor is elaborated in details and the material selection is studied also. The correlative performance indexes, such as precision and the repeatability of pressure sensor, are explored. In the following part of this paper, through the finite element simulation software, the analytic study of some performance parameters of the sensor chip is carried out in detail. Through the analysis, we find that the sensor designed here has many advantages.

Abstract: In order to predict the size and shape of the laser ablative hole, a 3D finite element model was developed to simulate the Nd:YAG laser ablation of carbon fiber epoxy composite. For given irradiation conditions, good agreement with experimental data relating to hole dimensions. The numerical results and experimental observations indicate that with the irradiation time increasing, the domain under investigation temperature raises rapidly and the further to the spot center, the smaller the temperature raises. After 0.093s the target surface temperature is higher than the critical temperature of composite, so the removal of the material on first composite layer occurs. It also can be observed that heat energy of the laser spread within the material and the isotherm ribbon, as well as crater border, is step-like.

Abstract: The cylindrical cup drawing of 5A90 Aluminum-Lithium alloy sheets at various forming conditions was studied by both the experimental approach and the finite element analysis. The uniaxial tensile tests and forming limit tests of 5A90 Al-Li alloy sheets at various temperatures were first carried out. The tests results were then employed in the finite element simulations to investigate the effects of process parameters, such as forming temperature, holder force, and die corner radius, on the formability of cylindrical cup drawing with 5A90 sheets. In order to validate the finite element analysis, the corresponding deep drawing tests were also carried out. It is shown that the simulation results are in qualitative agreement with the experimental observations. The optimal forming temperature, diameter of blank, holder force, punch radius and die corner radius were then determined for the cylindrical cup drawing of 5A90 sheets, and the limit drawing ratio (LDR) reached 2.4 in the optimal parameter conditions.

Abstract: Determination of the flow stress curve is an important step for precisely describing material behavior in Finite Element simulations. The flow stress curve is generally determined by taking a uniaxial tensile test as a standard. In the case of very thin sheet, since the fracture is generated at a low strain, there is not enough uniaxial data obtained to be applied in the FE simulation. The reason for this is that charactering plastic deformation at a large strain values by extrapolating a flow stress curve which is based on insufficient measurement data is highly susceptible to error. Bulge test is useful method for determining the equivalent biaxial flow stress curve up to a large strain. In this paper, the biaxial flow stresses curve for very thin copper sheet with thickness 35 and 50 μm were determined using the aero-bulge test. A new empirical model was derived for the estimation of the sheet thickness at the pole. After the compatibility between uniaxial and biaxial flow stresses was verified, the uniaxial flow stress curve was determined from the aero-bulge test using reverse engineering. The methodology of extrapolation of the flow stress curve at a large strain was finally proposed for application in FE simulations.

Abstract: One potential application of aluminium foam sandwich panels in civil engineering is the cladding system which is employed to protect other structures again impact and blast loadings. Finite element (FE) simulation of these sandwich panels subjected to impact loading was conducted by using a commercial software package, LS-DYNA (version 971). The FE model was verified by experimental results conducted previously. Good agreement was achieved between the FE and experimental results. Parametric study was conducted to investigate the effects of skin thickness, core thickness and boundary conditions on the deformation modes and energy absorption of sandwich panels with aluminum foam core.