Drawing Operation Research Articles

Predicting Shear Fracture in Deep Drawing: Combined Yld2000-3D and Hosford-Coulomb Fracture Model

The proper numerical treatment of strain and stress distributions are an indispensable prerequisite of predicting the fracture initiation in deep drawing operations. The formability of sheet metal is generally limited by the so-called Forming Limit Curve (FLC) that is broadly accepted in forming community. However, fracture actually occurs at higher strains than the membrane instability predicted by the FLC. In the present paper, the results of the well-known Nakazima experiments (which are traditionally used to determine a FLC) are explored beyond the necking limit to determine the multi-axial fracture response. Indeed, the strains at the fracture initiation have been determined using a hybrid experimental-numerical approach, i.e. through the numerical simulation of each experiment. To increase the robustness of the hybrid experimental-numerical technique, we also measured the post-mortem thickness of all failed specimens. Moreover, in view of characterizing the local plasticity, the non-quadratic full stress constitutive model along a recently Hosford-Coulomb fracture criterion are employed. The candidate tests to determine the fracture parameters are the Nakazima test and a special configuration of the cup drawing test, which fails under the out-of-plane shear loading range. The obtained complex constitute model are then applied to predict the fracture in a new designed triangle shape part for deep drawing. This complex new triangular deep drawing shape is fabricated to validate the constitutive model and predict a crack initiation.

Cylindrical cup deep drawing of ZEK100 sheet at elevated temperatures

Cylindrical cup deep drawing experiments are performed on as-received magnesium rare-earth alloyed ZEK100 rolled sheet between room temperature and 250 °C. All tests are performed using warm tooling comprising a 101.6 mm (4”) diameter cylindrical punch and smooth die and blank holder. Both isothermal and non-isothermal experiments are performed with a draw ratio of 2.25. Warm temperature formability of ZEK100 is investigated through determination of draw depths of cylindrical cups under isothermal and non-isothermal conditions. The effect of sheet anisotropy during deep drawing operation is investigated by measuring the earring profiles by means of digital imaging as well as sheet thickness from the center to the outer diameter in the rolling direction. It is found that ZEK100 sheets exhibit significantly better warm temperature drawing performance over commercial wrought magnesium alloy sheet – e.g. a full draw of 203.2 mm (8”) blanks of ZEKIOO-O was achieved with tool temperature of 150 °C compared to a full draw for AZ31B-O with a tool temperature of 225 °C. Temperature process windows are used to present a direct comparison of forming behavior between ZEK100 and AZ31B. The increased forming performance of ZEK100 at elevated temperatures is attributed to the weakened texture resulting from alloying with Zr and Nd, respectively, allowing for elevated slip activity at lower temperatures.

Developing a progressive draw with ironing tool for manufacturing a solenoid casing

The present paper focuses on developing a progressive draw with ironing process for production of solenoid casings with the main aim of reducing the number of presses required to form the component thereby reducing the cost of the component and enhancing the productivity rate. The material used for the present study is extra deep drawing (EDD) steel. In progressive draw with ironing tool, the first draw operation takes place followed by the ironing operation in a single tool. The progressive draw with ironing tool consists of three different die inserts planned one below the other in single station. The solenoid casing is manufactured by using this progressive draw with ironing tool and the thickness is measured at the dome and wall regions using an ultrasonic thinning measuring device. Tensile tests were performed for EDD steel according to ASTM standards and mechanical properties were evaluated. Finite element method (FEM) simulations were performed using the mechanical properties evaluated from tensile tests to predict the thickness at the dome and wall regions by using the progressive draw with ironing tool. It is found that the simulated thickness is close to experimental results. It is also found that the surface finish on the component has improved and die life has increased due to use of internal lubrication with coolant supplied.

Experimental and numerical investigation of ironing in deep drawn parts

Majority of the industrially relevant deep drawn sheet metal parts undergoes an additional process after the drawing operations. Operations like flanging or hole extrusion are widely used especially in the automotive industry. In such industrial applications it is seen that process planers design the tools by using a clearance less than the sheet thickness. Due to this smaller gap between the forming steels and the post, sheet material is compressed in the thickness direction. This additional compression is definitely needed for collar forming and it is beneficial in flanging operations in terms of springback. Addition of compressive deformation state on flange regions reduces the bending effects on those parts. Ironing in sheet thickness direction is a challenging deformation state for numerical simulations. This effect can be modelled by 3D continuum elements. However, due to high computation times this solution is not feasible for industrial applications. On the other hand, shell elements are widely used in sheet metal forming problems due to their efficiency but the conventional shell elements cannot predict ironing effects since the formulation does not consider through-thickness deformation. In order to analyze the effect of ironing, cup drawing experiments were performed. Ironing level is controlled by changing the die diameter while keeping the punch diameter constant. DC04-SUPERMOD with 1.75 mm thickness was used in the experiments. The thickness distribution along the cup wall and height of the cups were measured after each operation. Same experimental procedure was modeled using new thick shell elements which accounts for the through-thickness deformation. Comparison with the experimental measurements show that the enhanced formulation of the shell elements can be used to simulate the ironing effects in deep drawn parts.

Perceived-Color Approximation Transforms for Programs that Draw

Human color perception acuity is not uniform across colors. This makes it possible to transform drawing programs to generate outputs whose colors are perceptually equivalent but numerically distinct. One benet of such transformations is lower display power dissipation on organic light-emitting diode (OLED) displays. We introduce Ishihara, a language for 2D drawing that lets programs specify perceptual-color equivalence classes to use in drawing operations enabling compile-time and runtime transformations that trade perceived color accuracy for lower OLED display power dissipation.

Drawbead uplift force analytical model for deep drawing operations

Drawbead uplift force calculation has been an open issue among the deep drawing tool maker and software developers in the last years. Starting from the original work of Stoughton (1988) many have been the models presented in order to improve the predictions. However, still nowadays, the main deep drawing software are not able to accurately predict the uplift force and clear example of that are the intensive effort of the software developers in that topic as well as the conversion factors used by the main OEM when acquiring a new tool. In this work, a new semi-analytic model of drawbead closing force calculation is presented. The model is not only able to predict the uplift force for different steps of the closing (very useful for the set-up process) but it has been validated when using a high strength steel (DP780) for different drawbead configuration.

A Review on Deep Drawing Process

Deep Drawing (DD) process is the one in which a punch forces a flat sheet metal blank into a die cavity. DD can also be described as the process which involves conversion of flat thin sheet metal blanks into parts of desired shape. Little work is available in the applications of DD processes at elevated temperatures which is going to be a very important manufacturing application in the coming decades. Deep Drawing (DD) is one of the sheet metal forming processes widely used in automobile, aerospace, electronics and allied industries to produce the hollow parts. The improvement in the deep drawing manufacturing process with latest methodologies leads to developments in the automobile and other sheet metal industries. Still today, this process of analysis and design is an art than science. Presently, the conventional deep drawing (CDD) operation is carried out at room temperature in industries. Although the deep drawing process of high strength / low formability metals has an extensive industrial application area, deep drawing at room temperature has serious difficulties because of the large amount of deformations revealed and high flow stresses of the materials. The present paper gives an overview of deep drawing process, its classification along with advantages, limitations and applications.

Mechanical behavior of HSLA350/440 and DP350/600 steels at different temperatures and strain rates

The present paper presents an experimental investigation of the mechanical behavior of HSLA350/440 and DP350/600 through uniaxial tensile tests, covering temperatures from 30 °C to 800 °C, and strain rates from 0.035 s−1 to 1.35 s−1 encompassing several conditions for the motor vehicle parts manufacturing process. Experimental data were analyzed and tensile flow curves were plotted. Yield strength (YS), ultimate tensile strength (UTS), and total elongation (EL) were determined. A severe reduction of formability was found at 600 °C for both materials. At 800 °C, the UTS was dramatically reduced to around 100 MPa for both materials. No benefit was detected for HSLA350/440 in hot working. On the other hand, the EL of DP350/600 had a straight increase at 800 °C according to the strain rate. The Hensel-Spittel coefficients were calibrated for experimental data to represent the materials in a finite element (FE) code in order to predict the springback. Experimental deep drawing operations were performed, and the results showed good agreement with the simulations. As a result, the calibrated Hensel-Spittel constitutive equation can predict the mechanical behavior of HSLA350/440 and DP350/600 through simulations in a wide range of temperatures and strain rates.

Effect of Annealing Treatment on the Anisotropy Behavior of Cold Rolled Stainless Steel 304 Sheets

Anisotropy of materials has harmful effects during deep drawing operations and reduce it will strongly enhance the productivity and quality of deep drawing yields. In this work the effect of annealing treatment on texture and anisotropy behavior of cold rolled stainless steel 304 sheets were investigated. Uniaxial tensile test samples cut at 0o, 45o and 90o to the rolling direction were prepared in order to measure the anisotropy parameters (normal anisotropy, r_n, and planar anisotropy, ∆r). Two annealing temperatures (1050, and 1150) °C were used to study their effects on anisotropy behavior. The results show that the normal anisotropy value of annealed samples at 1150°C increases by (31%) as compared to the received samples. This indicates that the annealed samples at 1150 °C have the highest formability. Also, results show significant reduction (about 88.7%) in planar anisotropy value for 1150°C annealed samples. This gave rise to an increase in deep drawing yield

VARNISH DELAMINATION IN TINPLATE CUTTING AND DRAWING OPERATIONS: MINIMIZATION THROUGH APPLICATION OF FRACTIONATED EXPERIMENT DESIGN

The aim of this work is to avoid varnish delamination during cutting and drawing operations, which are carried out in the manufacturing process of tinplate lids for cans intended for food storage. Delamination, which occurs in the periphery of tin discs during the cutting operation, generates a varnish “thread” that can be thicker than 200 ?m and may adhere to the cutting tool, compromising product quality and productivity. As a consequence, lengthy production downtimes for tool cleaning operations are required. By means of optical or electronical microscopy it is possible to determine the amount of varnish adhered to the tool, as it is directly related to the depth of the delamination layer. The experimental methodology followed a fractioned Design of Experiments with 8 factors, 2 levels and resolution IV. The research was carried out in an industrial scale and studied parameters were those inherent to the manufacturing process. It is concluded that the depth of the delamination layer is uneven and manifests two different behaviours depending on the direction: one in the direction of the fabrication line and other in the opposite direction. The factor with greater influence over the depth of the delamination layer is the stamping pressure. If the stamping pressure decreases, the thickness of the detached varnish thread also decreases. Tin plate thickness resulted to be another important process variable, being smaller thicknesses beneficial. A thicker varnish layer (amount of varnish applied) and a specific curing treatment are possible solutions to counter the deleterious effects of high stamping pressure and thicker tinplates respectively. Keywords: Varnish Delamination, Tinplate, Cutting, Drawing, Design of Experiments

A Study on DLC Tool Coating for Deep Drawing and Ironing of Stainless Steel

The trend in metal forming tribology is to develop new tribo-systems including new lubricants, tool materials and tool coatings in order to substitute environmentally hazardous lubricants by environmentally friendly tribo-systems. In preliminary testing the limits of lubrication of new tribo-systems for sheet forming production, it is advantageous to use dedicated simulative tribo-tests. This paper studies the influence of tool coatings on deep drawing operations using the Bending Under Tension (BUT) test and also under more severe tribological conditions by adopting the Strip Reduction Test (SRT) to replicate industrial ironing of deep drawn, stainless steel parts. Non-hazardous tribo-systems in form of a double layer Diamond-like coated tool applied under dry condition or with an environmentally friendly lubricant were investigated via emulating industrial process conditions in laboratory tests. Experiments revealed that the double layer coating worked successfully, i.e. with no sign of galling, when it was used with environmentally friendly lubricants, whereas the results were more prone to galling under dry condition.

Experimental Evaluation and Finite Element Simulation to Produce Square Cup by Deep Drawing Process

Deep drawing process to produce square cup is very complex process due to a lot of process parameters which control on this process, therefore associated with it many of defects such as earing, wrinkling and fracture. Study of the effect of some process parameters to determine the values of these parameters which give the best result, the distributions for the thickness and depths of the cup were used to estimate the effect of the parameters on the cup numerically, in addition to experimental verification just to the conditions which give the best numerical predictions in order to reduce the time, efforts and costs for producing square cup with less defects experimentally is the aim of this study. The numerical analysis is used to study the effect of some parameters such as die profile radius, radial clearance between die and punch, blank diameter on the length and thickness distributions on the cup, dynamic-explicit (ANSYS11) code based on finite element method is utilized to simulate the square deep drawing operation. Experiments were done for comparison and verification the numerical predictions. effective square cup with less defects and acceptable thickness distributions were produced in this study. It is concluded the most thinning appear in the corner cup due to excessive stretching occur in this region and also it is found the cup thickness and height prediction by numerical analysis and in general in harmony with experimental analysis.

Experimental Evaluation and Finite Element Simulation to Produce Square Cup by Deep Drawing Process

Deep drawing process to produce square cup is very complex process due to a lot of process parameters which control on this process, therefore associated with it many of defects such as earing, wrinkling and fracture. Study of the effect of some process parameters to determine the values of these parameters which give the best result, the distributions for the thickness and depths of the cup were used to estimate the effect of the parameters on the cup numerically, in addition to experimental verification just to the conditions which give the best numerical predictions in order to reduce the time, efforts and costs for producing square cup with less defects experimentally is the aim of this study. The numerical analysis is used to study the effect of some parameters such as die profile radius, radial clearance between die and punch, blank diameter on the length and thickness distributions on the cup, dynamic-explicit (ANSYS11) code based on finite element method is utilized to simulate the square deep drawing operation. Experiments were done for comparison and verification the numerical predictions. effective square cup with less defects and acceptable thickness distributions were produced in this study. It is concluded the most thinning appear in the corner cup due to excessive stretching occur in this region and also it is found the cup thickness and height prediction by numerical analysis and in general in harmony with experimental analysis.

Experimental Evaluation and Finite Element Simulation to Produce Square Cup by Deep Drawing Process

Deep drawing process to produce square cup is very complex process due to a lot of process parameters which control on this process, therefore associated with it many of defects such as earing, wrinkling and fracture. Study of the effect of some process parameters to determine the values of these parameters which give the best result, the distributions for the thickness and depths of the cup were used to estimate the effect of the parameters on the cup numerically, in addition to experimental verification just to the conditions which give the best numerical predictions in order to reduce the time, efforts and costs for producing square cup with less defects experimentally is the aim of this study. The numerical analysis is used to study the effect of some parameters such as die profile radius, radial clearance between die and punch, blank diameter on the length and thickness distributions on the cup, dynamic-explicit (ANSYS11) code based on finite element method is utilized to simulate the square deep drawing operation. Experiments were done for comparison and verification the numerical predictions. effective square cup with less defects and acceptable thickness distributions were produced in this study. It is concluded the most thinning appear in the corner cup due to excessive stretching occur in this region and also it is found the cup thickness and height prediction by numerical analysis and in general in harmony with experimental analysis.

Study on forming process and spring back control of high strength sheet based on Dynaform

The drawing process of a high strength steel part without blank holder force was numerically simulated based on Dynaform. In present investigation, the drawing velocity and velocity profile motion of punch was studied by simulating the drawing operation of high strength steel part. The results show that restricting drawing velocity and controlling velocity profile motion of punch could all reduce the spring back. The measure of restricting drawing velocity could reduce non-pressure forming spring back about 31% and Trapezoidal motion mode of punch is the most beneficial to reduce spring back.

Improvement of deep drawability of ultra-fine grained 6000 series aluminum alloy by tailored heat treatment

Among other approaches like alloying, it is possible to increase the strength of aluminum sheet material by the application of processing techniques like Accumulative Roll Bonding. However, the ductility will be reduced, which results in a limited formability in deep drawing operations. In this context, the Tailor Heat Treated Blanks technology is a well-known approach to enhance the forming limits of conventional precipitation hardenable aluminum alloys. The local softening of a blank can be achieved by a short-term heat treatment, which causes a dissolution of the MgSi-clusters in the heat treated zones. In a subsequent deep drawing operation, the material flow can be improved from the softened towards crack-critical areas. Within this investigation, the method of Tailor Heat Treated Blanks is transferred to a multi-layered, ultra-fine grained sheet material of the aluminum alloy AA6014 in order to investigate the effect of a local short-term heat treatment on the forming limits in deep drawing. In a first step, a material characterization in dependency of different heat treatment temperatures is carried out. The strength and ductility, as well as the bond strength of the multi-layered sheets, are investigated. Concluding, the effect on the formability is examined by deep drawing experiments on cylindrical cups in combination with a local heat treatment of the outer flange area prior to the forming step. The results regarding the limiting drawing ratio are compared with a conventional sheet material in the T4 temper condition and a multi-layered sheet material without heat treatment. The investigations indicate that the drawability can be enhanced significantly by the combination of both methods.

A silicon-impregnated carbon nanotube mat as a lithium-ion cell anode

Silicon is a widely researched material for the anodes of lithium-ion batteries due to its high practical charge capacity of 3600 mAh g−1, which is ~ 10 times the specific capacity of conventional graphitic materials. However, silicon degrades rapidly in use due to its volumetric changes during charge/discharge of the battery, which makes it necessary to use complicated or costly methods to ameliorate capacity loss. Here, we report a novel silicon anode fabrication technique, which involves winding an aligned carbon nanotube (CNT) sheet and commensurately infiltrating it in situ with an aqueous solution containing silicon nanoparticles and hydroxypropyl guar binder. The resulting infiltrated felts were processed, evaluated, and compared to conventional silicon–carbon black anodes with the same carbon, silicon, and binder content as a proof of concept study. The felts had a large initial reversible capacity and promising rate capability. It is likely that the conductive CNT structure improved the charge transfer properties while lessening the effects of silicon volumetric expansion during lithiation. The results demonstrate that this novel anode fabrication method is viable and may be explored for further optimization. A novel fabrication method is described for the negative electrode for a lithium-ion battery: a CNT mat is formed by a drawing operation from a CNT vertical array while simultaneously being impregnated with a solution containing silicon nanoparticles and hydroxypropyl guar gum binder. The resulting CNT–Si anode structure shows improved lifetime cycling performance compared to traditional slurry-based silicon anodes.

GPU rasterization for real-time spatial aggregation over arbitrary polygons

Visual exploration of spatial data relies heavily on spatial aggregation queries that slice and summarize the data over different regions. These queries comprise computationally-intensive point-in-polygon tests that associate data points to polygonal regions, challenging the responsiveness of visualization tools. This challenge is compounded by the sheer amounts of data, requiring a large number of such tests to be performed. Traditional pre-aggregation approaches are unsuitable in this setting since they fix the query constraints and support only rectangular regions. On the other hand, query constraints are defined interactively in visual analytics systems, and polygons can be of arbitrary shapes. In this paper, we convert a spatial aggregation query into a set of drawing operations on a canvas and leverage the rendering pipeline of the graphics hardware (GPU) to enable interactive response times. Our technique trades-off accuracy for response time by adjusting the canvas resolution, and can even provide accurate results when combined with a polygon index. We evaluate our technique on two large real-world data sets, exhibiting superior performance compared to index-based approaches.

On the die face design for stamping an automotive engine hood

Since the engine hood is mainly manufactured in the drawing operation, the die addendum design is the key to the success of manufacturing a defect free product. In this study, the existing die addendum designs corresponding to those engine hoods were reviewed and the design parameters were constructed. The preliminary study was then performed to examine the influences of the stamping die angle, binder surface shape, and die open line shape on the defects occurred in the part. Based on the simulation results, the optimum design for the die addendum face was then investigated and a systematic design guideline was proposed. In order to validate the proposed design guideline, actual engine hoods were stamped according to the finite element analysis and the production part shapes, thickness distributions, and the stretch at the central region were compared with those obtained from the finite element simulations. The consistent agreement between the product parts and the simulation results confirms the validity of the design guideline proposed in the present study for stamping an engine hood.

Strategy to prevent surface deflections for automotive sheet metal parts

Surface deflections are undesirable in automotive outer panels because they disturb their visual appearance. As a consequence, the geometry of the deep drawing tool is manually adjusted during tryout until the produced parts do not display any surface deflections. The aim of this paper is to reduce this time-consuming and cost-intensive tryout by slightly changing the geometry of the tool in an early state of the product development process to lower the risk of surface deflections. Therefore, this paper shows the influence of geometrical parameters of the deep drawing tool on the occurrence of surface deflections. A multiple curved outer panel with a door handle depression is chosen for the investigation. Typically, so-called “teddy bear ears” occur around the depression. The sheet metal material AA6016 with a sheet thickness of 1.0 mm is used. Numerical simulations of the draw operation and springback are performed in AutoForm. An analysis of the curvature before and after springback is used to detect surface deflections. The influence of the stresses and curvatures on the appearance of surface deflections is analyzed. For the experimental validation, stoning is used to detect surface deflections on a physical part. A very good agreement between the numerical and experimental results was obtained. The results show that the existence of surface deflections strongly depends on the initial curvature of the part and the appearance depends on the distribution of minor stresses. It is possible to reduce the risk of surface deflections during the design phase by changing the geometry.