Papers by Keyword: Deep Drawing

Abstract: Increasing waste streams of carbon fibers (CF) and carbon fiber reinforced plastics (CFRP) lead to increasing need for recycling and to growing amounts of recycled carbon fibers. A main issue in current research for carbon fiber recycling is the reuse of regained fibers. Carbon staple fibers such as recycled fibers hold big potential for mechanical properties of lightweight parts, if used properly. Applying recycled CF (rCF) as milled reinforcement fibers or as nonwoven in carbon fiber reinforced plastic leads to a poor yield of mechanical proper due to low fiber orientation, limitations in fiber volume content or due to short fiber length. The rC staple fiber tape presents a more efficient approach. Recycled carbon fibers are blended with 50 wt. % thermoplastic nylon 6 fibers and processed through a roller card to a sliver, which is a linear fibrous intermediate. The sliver is continuously drawn, formed, heated and consolidated to the thermoplastic rC staple fiber tape. The tape is similar to common carbon fiber tapes or to continuous tows but has different positive properties, such as high fiber orientation, homogeneous blend of fiber and matrix and suitability for deep drawing.

Abstract: Deep drawing is a complex process influenced by the geometric parameters of the die-punch system. In the present paper we study the behavior of the semi-finished product, in the process of drawing deep cylindrical parts, using the finite element method and the software package of the ANSYS program. In order to reduce the cost and design time, an analysis of the variation of the radius connection is carried out, resulting in low energy consumption, using the finite element method. By analysing the radius of connection of the plate, we identify future directions useful in substantiating the elaboration of a judicious experimental program and optimizing the geometric shape of the finished parts.

Abstract: The aim of this work is to study the plastic instabilities occurring on the stamped sheets during deep drawing process. The analysis of the plastic deformation of the material showed that the deformation occurs in bi-axial extension at the bottom of the punch due to thinning of the sheet, in local necking together at the vertical wall level of the sheet and below the blank holder due to thickening of the sheet. As a first step, an experimental characterization of the material is undertaken, whose experimental tests made it possible to determine the fundamental characteristics of the material. In the second step, a study of the material behaviour during forming process by numerical simulation using Abaqus finite element code is proposed. The various simulations undertaken showed the variation of the two parameters; the blank holder force and the friction effect. The blank holder force and friction, applied respectively to the blank flange region and between the tool-blank surfaces, make it possible to optimize the deformation limits and to repel any instability which may appear on the material in deep drawing. The simulations carried out on Abaqus code allow to visualize the material behaviour during deformation, by locating the thinning and necking zones on the sheet and from there, in order to locate areas at risk of failure. An optimization of the process is proposed by varying the considered parameters in a validated numerical model. Satisfactory results have been obtained which clearly show the failure and the safe zones.

Abstract: The typical textures developed in aluminium alloys for deep drawing applications are less favourable as those in competing steel sheet material. The {111} fibre texture in steel, associated to high r-values, is favourable to this purpose, but the typical textures of the aluminium materials, the {001}<100> "cube" texture component and the β-fibre component, are not. Asymmetric rolling (ASR) as part of the production process generates a shear component at the expense of the unfavourable components. Modelling was tried out as a possible tool to fine-tune the process parameters. A multiscale FEM model (with a built-in polycrystal deformation model to predict the texture) was used to this purpose. The effect of the shear component on the resulting texture is discussed in function of the values of the process variables, as well as its effect on the resulting plastic anisotropy parameters (r and q values).

Abstract: Cladding is the bonding together of dissimilar metals. One of clad products is the titanium clad steel sheet. It is effective to cover with pure titanium sheet to improve the corrosion resistance of the steel sheet. Titanium clad steel sheets are often achieved by rolling sheets together under high pressure. In the current study, the blank comprising three laminar non-bonded sheets, such as the titanium/steel/titanium sheet, is arranged in the die. The formability of pure titanium clad sheet by multistage deep drawing was investigated to enhance corrosion resistance of steel cup. In the experiment, the blanks were pure titanium sheets JIS1-TP270, JIS2-TP340, ultralow-carbon steel SPCC, and stainless steel SUS316L. The initial thickness of the sheet was 0.2 to 0.5 mm in thickness. The blank diameter was 70 mm. The blanks are merely adjacent sheet; however, not joined with each other. In the deep drawing process, a hydraulic press was used in the experiment and the forming speed for the press was about 10 mm/min. The lubricant used was the solid powders of molybdenum disulfide. For the prevention, pure titanium blank was treated by oxide coating. The conditions of heat treatment were annealed at 973 K for 3.6 ks to 7.2 ks. By oxide coating, the titanium sheet has sufficient ability in preventing the seizure in multistage deep drawing. The drawn cups of the three-layer laminated sheet were formed. The seizure did not cause. The oxidatively-treated titanium sheets have sufficient ability in preventing the seizure. In addition, the clad cups until 6th stage were formed by multistage deep drawing. Long clad cups were successfully formed in multistage deep drawing process.

Abstract: The planar anisotropy (PA) and tension-compression asymmetry (TCA) of the commercially pure titanium (CP-Ti) were investigated through uniaxial tension and compression experiments at room temperature. By deep drawing experiment, the formability and the earing profile for the CP-Ti were studied at room temperature. The deep drawing simulations using the hardening rules of uniaxial tensile or compression curves were compared with experimental results. The results show that the CP-Ti has obvious PA, and the plastic strain ratios r₀, r₄₅ and r₉₀ are 1.47, 1.64 and 2.05, respectively. The CP-Ti sheet shows the tension-compression asymmetry of yielding and hardening. The TCA also shows obvious PA. The tension-compression yield strength ratio of 0°, 45° and 90° to the rolling direction are 1.12, 1.08, 1.04, and the tension-compression hardening exponent ratio are 0.86, 0.8 and 0.62, respectively. The simulative results without considering TCA indicate that the forming force, the wall thickness and earing profile are not in good agreement with the experimental ones. Therefore, the earing appeared in 45° is contribution of the PA and TCA. The TCA will reduce the thickness of the deep drawing parts, increase the earing ratio and affect the drawing force.

Abstract: The object of this study is to highlight one the most encountered problems in the sheet metal forming. Cases of rupture on the mild steel sheet were recorded in a deep drawing workshop, during the forming operation of the wheelbarrows. The phenomenon appearance, led us to carry out a study of the material behavior during the metal forming. A characterization of the material is proposed and 3D simulations of the forming operation were performed on the finite element code Abaqus/CAE Explicit. The objective is to highlight the influence of the different deep drawing parameters on the sheet behavior during the deformation, especially the holding force, the die radius, the coefficient of friction between the contact surfaces and the punch velocity.The results are summarized in a representation of the strain curves in the three directions of the drawn part at the end of deep drawing operation, localization of the sheet areas which present a risk of tearing and the proposals to avoid this phenomenon depending on the variation of the operating parameters.

Abstract: Hot stamping process has been developed to produce the steel automobile parts with an ultra-high-strength of 1500 MPa. The effect of scale thickness on the formability in hot stamping was investigated by a hot deep drawing test in our previous research. The draw-in lengths of flange increased with decreasing the scale thickness. It is supposed that thin scale thickness resulted in low coefficient of friction at the flange area. The other reason is the temperature of wall zone would become low according to decreasing the scale thickness or increasing of the thermal transfer coefficient and it slightly inhibits local deformation at the wall area. It is difficult to separate these phenomena. To quantify the effect of scale thickness on the friction at the flange area during hot deep drawing, the coefficient of friction was directly measured. The coefficient of friction decreases with decreasing scale thickness.

Abstract: The finite element simulation has become an essential tool for the proper design of big size automotive components stamping tooling and their process optimization. Although big improvements have been made in the last years in terms of material and tribological modelling, the accuracy of the current models should be further improved to estimate the final post-forming springback of these components, in both AHSS and mild steels.In the present paper the forming of a B-Pillar reinforcement is numerically analyzed using a DX54D mild steel and a TRIP800 high strength steel. In the first part, the influence of the elastic behavior including variable young modulus, the yield criteria and the hardening law on the final springback is studied for both materials. Secondly, the friction coefficient is defined constant and pressure dependent and springback variation is analyzed in function of this variable.In order to stablish the material and friction variables and their typical deviation, results obtained from material characterization and strip drawing tests are used.

Abstract: Based on elastic stress and strain states after forming and joining processes, single and assembled parts show deviations regarding their dimensional accuracy. Therefore an analysis of selected influencing factors and their influence on the dimensional accuracy of assembled parts is performed in this paper. In this article a novel approach is presented that characterizes the impact of three geometrical shapes (convex/concave/straight) and different sheet thicknesses on the dimensional accuracy along a linked forming and joining process chain. The process chain consists of a deep drawing and a clinching process. Depending on sheet thickness, material and geometrical shape, the dimensional accuracy of single parts and joined assemblies varies. For the single parts the geometry of the specimen S-rail is used. Several types of assemblies are used for the proposed approach combining this specimen with a plane sheet or a second S-rail. The FEM-tools LS-DYNA and Abaqus, are used to demonstrate this approach. Simulations and experiments with aluminum alloy 6014, mild steel CR3 and sheet thicknesses of 0.7, 1.0 and 2.0 mm are conducted for single and assembled parts. In summary, a significant improvement of the dimensional accuracy of an S-rail assembly is demonstrated using two non-dimensional accurate single parts. Future work will be to analyze frequently occurring part segmentations for the joining technologies and to optimize material mix and sheet thicknesses in order to improve deviations of the assembly to the nominal CAD geometry.