Deep drawing is part of forming process in which sheet metal drawn into die cavity by action of a punch. Sheet metal drawing is a more complex operation than cutting or bending, and more things can go wrong. A blank holding force, punch... more
Deep drawing is part of forming process in which sheet metal drawn into die cavity by action of a punch. Sheet metal drawing is a more complex operation than cutting or bending, and more things can go wrong. A blank holding force, punch force, material property of sheet metal, thickness of sheet, velocity of punch, these are all affecting parameters in deep drawing process to regulate wrinkling effect, tearing effect and fracture defect. Nowadays composite material is extensively used in manufacturing industries due to its better strength. Die radius has the greatest influence on the deep drawing of stainless steel blank sheet followed by the blank holder force and the friction coefficient. Further, it is shown that a blank holder force application and local lubrication scheme improved the quality of the formed part. The present study aims to determine the optimum blank shape design for deep drawing of arbitrary shaped cups with a uniform trim allowance at the flange, i.e., cups without ears. The earing, or non-uniform flange, is caused by non-uniform material flow and planar anisotropy in the sheet. Drawing is sheet metal forming operation used to make cup shaped, box shaped, and complex curved and concave cup.
This paper presents finite-element analyses and analytical models of innovative, small-scale, prototype deck panels examined under monotonic bending. The deck panels consisted of two glass fiber–reinforced polymer (GFRP) facesheets... more
This paper presents finite-element analyses and analytical models of innovative, small-scale, prototype deck panels examined under monotonic bending. The deck panels consisted of two glass fiber–reinforced polymer (GFRP) facesheets separated by webs formed from E-glass–woven fabric placed around trapezoidal-shaped, low-density, polyurethane foam segments. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness than those of conventional sandwich panels. Analytical models were used to predict critical facesheet wrinkling in the sandwich panel. Furthermore, a three-dimensional model using simulation software was developed for analysis of the proposed panel system under monotonic four-point loading. The finite-element results in terms of strength, stiffness, and deflection were found to be in good agreement with those from the experimental results. A parametric study was also conducted to further evaluate the effects of the stiffness of the top facesheet fiber layers, the mass density of the polyurethane foam, the existence of web layers, and the introduction of an overlay above the top facesheet. A flexural beam theory approach was used to predict the flexural strength of the sandwich panel.
The aim of use blankholder gap (BHG) is to regulate the flow of material in the cavity of the die. In this paper, the effect of blankholder gap on parameters of process such as forming load, strains and stress distributions and occurrence... more
The aim of use blankholder gap (BHG) is to regulate the flow of material in the cavity of the die. In this paper, the effect of blankholder gap on parameters of process such as forming load, strains and stress distributions and occurrence of wrinkling in the cup wall were analyzed numerically. Finding thebest BH gap for the die and the material which use in this study. Different values of (BHG) to arrange (0.5 -3 mm) were used and also without (BHG). 3D model of deep drawing was used and analyzed based on FEM. The best forming distance for the blankholder is between 1 to 1.5 times sheet thickness. The results showed that when the gap is larger than 0.75 mm, the wrinkles will occur and the drawing force increased.
In this paper flame instabilities are analyzed utilizing the Sivashinsky equation in order to derive the flame wrinkling factor. This is a synthetic variable representing the excess of flame surface which is obtained for a wide range of... more
In this paper flame instabilities are analyzed utilizing the Sivashinsky equation in order to derive the flame wrinkling factor. This is a synthetic variable representing the excess of flame surface which is obtained for a wide range of hydrogen concentrations, considering the Darrieus–Landau and the Thermo-Diffusive instabilities, and also taking into account the effect of acceleration. Additionally, the time for the development of the cellularity is also analyzed. The study is carried out for a wide range of hydrogen–air mixtures as well as for a large domain of accelerations. Models representing both the wrinkling factor and the time of development of the instabilities are obtained.
For structures consisting of a thin film bonded to a compliant substrate, wrinkling of the thin film is commonly observed as a result of mechanical instability. Although this surface undulation may be an undesirable feature, the... more
For structures consisting of a thin film bonded to a compliant substrate, wrinkling of the thin film is commonly observed as a result of mechanical instability. Although this surface undulation may be an undesirable feature, the development of new functional devices has begun to take advantage of wrinkled surfaces. The wrinkled structure also serves to improve mechanical resilience of flexible devices by suppressing crack formation upon stretching and bending. If the substrate has a reduced thickness, buckling of the entire structure may also occur. It is important to develop numerical design tools for predicting both wrinkle and buckle formations. In this paper we report a comprehensive finite element-based study utilizing embedded imperfections to directly simulate instabilities. The technique overcomes current computational challenges. The temporal evolution of the wrinkling features including wavelength and amplitude, as well as the critical strains to trigger the surface undulation and overall structural buckling, can all be predicted in a straightforward manner. The effects of model dimensions, substrate thickness, boundary condition, and composite film layers are systematically analyzed. In addition to the separate wrinkling and buckling instabilities developed under their respective geometric conditions, we illustrate that concurrent wrinkling and buckling can actually occur and be directly simulated. The correlation between specimen geometry and instability modes, as well as how the deformation increment size can influence the simulation result, are also discussed.
