Showing papers on "Stamping published in 2009"

Energy absorption of longitudinally grooved square tubes under axial compression

Abstract: This paper investigates the energy absorption characteristics of longitudinally grooved square tubes under axial compression by using explicit nonlinear finite element code LS-DYNA. The grooves are fabricated by stamping and the distributions of the effective plastic strain and the thickness variation from the stamping process are considered in the following crash analyses. From the simulation results, we find that when grooves are introduced on the sidewalls, the specific energy absorption of conventional tubes can be increased by up to 82.7% and the peak force can be reduced by up to 22.3%. The influences of several parameters, including the width of the tube, the length of the groove and the number of the grooves, are analyzed and the features of the deformation modes of grooved tubes are described. The introduction of groove is found to be an effective way to improve the crashworthiness of thin-walled structures.

Fabrication of multilayer organic solar cells through a stamping technique

Abstract: In this article, we demonstrate a simple and reliable stamping technique for fabricating multi-layer solar cells. A poly(di-methylsilane) (PDMS) stamp is used for transferring the active layers onto the substrate. An intermediate solvent treatment is introduced to temporarily modify the PDMS surface; therefore, the polymer film can be uniformly formed on top of the PDMS surface. This method is involves non-contaminative and non-invasive processes, therefore it can avoid possible degradation or contamination of the polymer film and the PDMS stamp can be reused. Devices realized through this stamping technique both by direct and inverted structures exhibited power conversion efficiencies of 3.2 and 2.83% respectively.

Experimental investigations on wear resistance characteristics of alternative die materials for stamping of advanced high-strength steels (AHSS)

Abstract: Newer sheet alloys (such as Al, Mg, and advanced high-strength steels) are considered for automotive body panels and structural parts to achieve lightweight construction. However, in addition to issues with their limited formability and high springback, tribological conditions due to increased surface hardness and work hardening necessitate the use of alternative microstructurally improved die materials, coatings, and lubricants to minimize the wear-related die-life issues in stamping of advanced high-strength steel grades. This study aims to investigate and compare the wear performances of seven different, uncoated die materials (AISI D2, Vanadis 4, Vancron 40, K340 ISODUR, Caldie, Carmo, 0050A) using a newly developed wear testing device. DP600 AHSS (advanced high-strength steel) sheets were used in these tests. It was concluded that the tested die materials demonstrated higher wear resistance performance when compared to the conventional tool steel AISI D2 die material.

Springback control of sheet metal forming based on the response-surface method and multi-objective genetic algorithm

Abstract: An automated optimization method by the integration of the response-surface method and an optimization algorithm is presented to control springback of stamping parts. In order to minimize both objective functions of springback and thickness deformation simultaneously, a multi-objective genetic algorithm is applied to find all the optimal solutions at one run instead of transforming multi-objective functions into a single objective function. The response-surface model is employed as a fast analysis tool to surrogate the time-consuming finite-element procedure in the iterations of the multi-objective genetic algorithm. An example is studied to illustrate the application of the approach proposed, and it is concluded that the proposed method is more efficient than the traditional manual finite-element procedure and the ‘trial and error’ approach for springback controlling.

Direct Forming of All-Polypropylene Composites Products from Fabrics made of Co-Extruded Tapes

Abstract: Many technologies presented in literature for the forming of self-reinforced or all-polymer composites are based on manufacturing processes involving thermoforming of pre-consolidated sheets. This paper describes novel direct forming routes to manufacture simple geometries of self-reinforced, all-polypropylene (all-PP) composites, by moulding fabrics of woven co-extruded polypropylene tapes directly into composite products, without the need for pre-consolidated sheet. High strength co-extruded PP tapes have potential processing advantages over mono-extruded fibres or tapes as they allow for a larger temperature processing window for consolidation. This enlarged temperature processing window makes direct forming routes feasible, without the need for an intermediate pre-consolidated sheet product. Thermoforming studies show that direct forming is an interesting alternative to stamping of pre-consolidated sheets, as it eliminates an expensive belt-pressing step which is normally needed for the manufacturing of semi-finished sheets products. Moreover, results from forming studies shows that only half the energy was required to directly form a simple dome geometry from a stack of fabrics compared to stamping the same shape from a pre-consolidated sheet.

Blank optimization for sheet metal forming using multi-step finite element simulations

Abstract: 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. In this research, a new method for optimum blank shape design using finite element analysis is proposed. The deformation process is first divided into multiple steps. A shape error metric is defined to measure the amount of earing and to compare the deformed shape and target shape set for each stage of the analysis. This error metric is then used to decide whether the blank needs to be modified. The blank geometry change is based on material flow. The cycle is repeated until the converged results are achieved. This iterative design process leads to optimal blank shape. To test the proposed method, three examples of cup drawing are presented. In every case converged results are achieved after a few iterations. The proposed systematic method for optimal blank design is found to be very effective in the deep drawing process and can be further applied to other sheet metal forming applications such as stamping processes.

Pressure Loss and Heat Transfer Through Heat Sinks Produced by Selective Laser Melting

Abstract: Heat removal from electronic packages is often assisted with the use of heat sinks whose heat transfer surfaces come in a variety of forms such as cylindrical pins, flat fins, and corrugated sheet. These conventional designs are manufactured by traditional methods such as forging, machining, casting, stamping and bending, or a combination of processes. This article introduces a novel manufacturing technique, selective laser melting (SLM), and demonstrates its ability to fabricate new designs of heat sink that have not previously been considered, primarily due to their geometric complexity. Three novel finned structures have been manufactured and their thermal and fluid flow characteristics have been determined experimentally. The three heat sinks demonstrate selective laser melting's ability to produce fine detail and consist of a staggered elliptical array, an elliptical array where the pins are angled in a direction perpendicular to the flow, and a densely packed diamond array. The novel heat sink desig...

Influence of Manufacturing Processes and Microstructures on the Performance and Manufacturability of Advanced High Strength Steels

Abstract: Advanced high strength steels (AHSS) are performance-based steel grades and their global material properties can be achieved with various steel chemistries and manufacturing processes, leading to various microstructures. In this paper, we investigate the influence of supplier variation and resulting microstructure difference on the overall mechanical properties as well as local formability behaviors of advanced high strength steels (AHSS). For this purpose, we first examined the basic material properties and the transformation kinetics of TRansformation Induced Plasticity (TRIP) 800 steels from three different suppliers under different testing temperatures. The experimental results show that there is a significant supplier (i.e., manufacturing process) dependency of the TRIP 800 steel mechanical and microstructure properties. Next, we examined the local formability of two commercial Dual Phase (DP) 980 steels during stamping process. The two commercial DP 980 steels also exhibit noticeably different formability during stamping process in the sense that one of them shows severe tendency for shear fracture. Microstructure-based finite element analyses are carried out next to simulate the localized deformation process with the two DP 980 microstructures, and the results suggest that the possible reason for the difference in formability lies in the morphology of the hard martensite phase in the DPmore » microstructure.« less

Stamping of Titanium Sheets

Abstract: In this paper, some technological problems (e.g. low drawability, high susceptibility to galling, spring-back) occurring in the sheet-titanium forming process are discussed. A numerical simulation of the stamping process was carried out with the Adina System v.8.3 based on the finite element method. The effects of friction, the holding-down force and tool geometry on the course of the stamping process were analysed. The mechanical and technological material data needed for the calculations were determined experimentally. The friction coefficients for the frictional pair: ”titanium – tool steel” for different lubricants and antiadhesive layers determined in the “strip drawing” test were found. The role played by lubrication and antiadhesive layers in preventing titanium “build-ups” on the tools is presented. The calculated results were then confirmed experimentally.

Tooling-integrated sensing systems for stamping process monitoring

Abstract: In-situ stamping process monitoring plays a critical role in enhancing productivity and ensuring part quality in sheet metal stamping. This paper investigates the realization of two sensing methods to create a tooling-integrated sensing system: mutual inductance-based displacement measurement for sheet draw-in, and distributed contact pressure measurement at the tool–workpiece interface. The two sensing systems are complementary in nature, and together, they significantly enhance the on-line observability of the stamping process. The performance of the draw-in sensor was evaluated using numerical simulations and experiments in a small-scale and a large-scale lab setup, and its effectiveness has been confirmed under the presence of wrinkled sheet. To study the spatial and temporal variations of the tool–workpiece contact pressure in a stamping operation, experiments were conducted on a customized panel stamping test-bed with an array of thin-film force sensors embedded below the die flange and die cavity. The force sensor data were then numerically interpolated to form the contact pressure distribution across the tool–workpiece interface, based on the thin plate spline (TPS) method. Comparison between the interpolated pressure obtained from the surface generation techniques and direct measurement using redundant sensors and a press mounted load cell confirms the validity of the new contact pressure sensing method. The integrated sensing technique provides insight into the stamping process by quantifying process variations and providing a reference base for process control to reduce product disparities. Additionally, new product and process designs can be created based on the quantified and referenced variations. Published by Elsevier Ltd.

Robust design of sheet metal forming process based on adaptive importance sampling

Abstract: Optimization methods have been widely applied in sheet metal forming area. However, the existence of variations during manufacturing processes significantly may influence final product quality, rendering non-robust optimal solutions. In this paper, experiments were conducted to investigate how a stochastic behavior of noise factors affected stamping quality. Robust design models for sheet metal forming process integrated adaptive importance sampling with response surface method, in order to minimize impact of the variations and achieve reliable process parameters. Support Vector Machine with nonlinear capability in both pattern recognition and regression was adopted to map the relation between input process parameters and part quality. A cup drawing example was employed to verify the feasibility of the proposed method. Comparisons were conducted between different optimization models to demonstrate robustness of the adaptive importance sampling method. Final results showed that the stamping part quality was optimized under the specified constraint requirements.

The Potential of a Clinch-Lock Polymer Metal Hybrid Technology for Use in Load-Bearing Automotive Components

Abstract: In order to help meet the needs of automotive original equipment manufacturers and their suppliers for a cost-effective, robust, reliable polymer-metal-hybrid (PMH) technology which can be used for the manufacturing of load-bearing body-in-white (BIW) components and which is compatible with the current BIW manufacturing process chain, a new approach, the so-called direct-adhesion PMH technology, was recently proposed (Grujicic et al., J. Mater. Process. Technol., 2008, 195, p 282-298). Within this approach, the necessary level of polymer-to-metal mechanical interconnectivity is attained through direct adhesion and mechanical interlocking. In the present work, a new concept for mechanical interlocking between the metal and plastics is proposed and analyzed computationally. The approach utilizes some of the ideas used in the spot-clinching joining process and is appropriately named clinch-lock PMH technology. To assess the potential of the clinch-lock approach for providing the required level of metal/polymer mechanical interlocking, a set of finite-element based sheet-metal forming, injection molding and structural mechanics analyses was carried out. The results obtained show that stiffness and buckling resistance levels can be attained which are comparable with those observed in the competing injection overmolding PMH process but with an ~3% lower weight (of the polymer subcomponent) and without the need for holes and for overmolding of the free edges of the metal stamping.

Composite cold-punching mould

Abstract: The utility model discloses a composite cold-punching mould, which comprises an upper mould and a lower mould, wherein an upper template (7) and an upper backing plate (24) are arranged in the upper mould, a lower template (1) and a lower backing plate (15) are arranged in the lower mould, the composite cold-punching mould is provided with a composite stamping structure of a stamping part which completes blanking, stretching and punching in one number of punching. By adopting the above technical proposal, an automobile structure part can achieve the blanking, the stretching and the punching in a set of composite moulds, and automatically pushes materials and head parts during the process, which leads products to be taken out more conveniently. Compared with the prior art, the composite cold-punching mould reduces the development cost of dies, increases the production efficiency and reduces the transport process of the dies, thereby reducing the production cycle of a single vehicle, and guaranteeing the relative position accuracy of each structure simultaneously, reducing the cost of blanking dies in a normal process, reducing the cycle of turnover of the dies, and being capable of increasing the production efficiency of the single vehicle.

Computer-aided structural design of drawing dies for stamping processes based on functional features

Abstract: This paper describes a structural design system for 3D drawing dies based on functional features using a minimum set of initial information. In addition, it is also applicable to assign the functional features flexibly before accomplishing the design of a solid model for the main parts of a drawing die, such as upper die, lower die, and blank holder. The initial information includes blank sizes, work strokes, die faces, punch open lines, and press data. The proposed system integrated the design knowledge of drawing die into functions of 3D computer-aided design (CAD) software to automate design and to shorten design time. This design system is constructed on a PC and integrated with a Pro/ENGINEER CAD system including feature selector, shape calculator, model generator, design coordinator, and user interface. The proposed system is demonstrated using the example of designing a drawing die for the roof panel of a vehicle within 1 h. The results reveal that it can dramatically improve the design quality and can save both time and costs with excellent design quality.

Two-stage cold stamping of magnesium alloy cups having small corner radius

Abstract: A two-stage cold stamping process for forming magnesium alloy cups having a small corner radius from commercial magnesium alloy sheets was developed In the 1st stage, a cup having large corner radius was formed by deep drawing using a punch having large corner radius, and the corner radius of the cup was decreased by compressing the side wall in the 2nd stage In the deep drawing of the 1st stage, fracture was prevented by decreasing the concentration of deformation with the punch having large corner radius The magnesium alloy sheets were annealed at 500 °C to increase the cold formability Circular and square cups having small corner radii were formed by the two-stage cold stamping For the circular cup, the height of the cup was increased by ironing the side wall in the 1st stage The radii of the bottom and side corners of the square cup were reduced by a rubber punch for applying pressure at these corners in the 2nd stage It was found that comparatively shallow magnesium alloy square cups used as cases of laptop computers and mobile phones can be satisfactorily formed at room temperature without heating by the two-stage stamping

Empirical modelling of the influence of operating parameters on the spifability of a titanium sheet using response surface methodology

Abstract: Single-point incremental forming (SPIF) has the potential to replace conventional sheet forming processes for customized and small batch size sheet metal products. In this research work, the operating parameters (i.e. step size, tool size, and forming speed) which can affect the formability during SPIF process were altered over wide ranges and their effect on the formability of a titanium sheet was investigated. A six-dimensional hyper-surface showing the influence of investigated parameters on the formability was developed by using a response surface methodology. The capability of the SPIF process to enhance the cold formability of titanium sheet was also examined. This was carried out by comparing the sheet formability in SPIF and stamping processes.

Selection of tool materials and surface treatments for improved galling performance in sheet metal forming.

Abstract: Galling is a known failure mechanism in automotive stamping. It results in increased cost of die maintenance and scrap rate of products. In this study, rectangular pan and U-channel stamping experiments are used to (1) investigate the effect of stress states on galling performance in sheet metal forming, (2) select proper tool materials and surface treatments for improved galling properties, and (3) differentiate galling performances of bare and coated steel sheets. The results indicate that problems with galling are of major interest at the regions where sheet materials deform under the action of compressive stress. For the four investigated tool materials, Mo–Cr alloy cast iron shows the best galling performance. A combination of hardening, surface polishing, and Cr coating is suggested as the optimum tool treatment in the forming of bare high-strength steel. Hot-dip galvanized steel shows better galling behaviors than galvannealed and bare steel sheets. Galling performances of hot-dip galvanized and bare steels are improved with increased hardness of the forming tool. However, galvannealed steel results in severe galling when the hardness of the forming tool is very high.

Large Shear Deformation of E-glass/ Polypropylene Woven Fabric Composites at Elevated Temperatures

Abstract: Stamping operation of textile composite sheets in industry involves a process of heating and cooling of the material. In the present article, the in-plane large shear deformation of woven fabric composite sheets at elevated temperatures is studied. Using the modified ‘picture frame’ test, the effects of temperature on the shear behavior of the material and the onset of wrinkling were investigated. In addition to the reduction in yarn width, the change of physical and mechanical properties of polypropylene (PP) fibers with temperature also plays a significant role. The initial shear stiffness of the composite sheets and the onset of wrinkling are reasonably explained by inter-yarn friction measurement. To simply consider the temperature effect, the introduction of a temperature-dependent factor for the simulation of stamping operation is suggested.

Dough cutting and stamping apparatus and method

Abstract: An apparatus is provided for forming, cutting and stamping a dough sheet into a plurality of uniformly stamped, imprinted dough pieces. The apparatus engages a leading portion of a dough sheet as it travels along a conveyor. The apparatus includes a drum rotatably disposed relative to the conveyor, a plurality of cutter molds disposed on the rotatable drum and a plurality of pattern imprinters formed within internal cavities defined by the plurality of cutter molds. Each of the cutter molds simultaneously cuts a dough piece received in the internal cavity and imprints on the dough piece to form a rounded edge roll. The pattern imprinter preferably has a star configuration for stamping the dough to form Kaiser-type rolls.

Producing technique of films for aluminized anti-fake wrapping paper

Abstract: The invention discloses a producing technique of films for aluminized anti-fake wrapping paper, sequentially comprising the following steps of: paint coating, holographic nickel plate stamping, aluminizing, rewinding, combining, peeling, and the like. The producing technique improves the transferring and temperature-proof performances of films, and polyester films can be reused for 3-5 times, thereby improving the economic benefit and achieving the energy-saving and emission-reducing effects. In addition, corresponding holographic patterns can be made based on requirements to play an anti-fake role.