Showing papers on "Stamping published in 2010"

Numerical failure analysis of a stretch-bending test on dual-phase steel sheets using a phenomenological fracture model

Abstract: Advanced High Strength Steels (AHSS) are increasingly used in automotive industry due to their superior strength and substantial weight advantage. However, their compromised ductility gives rise to numerous manufacturing issues. One of them is the so-called ‘shear fracture’ often observed on tight radii during stamping processes. Since traditional approaches, such as the Forming Limit Diagram (FLD), are unable to predict this type of fractures, great efforts have been made to develop failure criteria that could predict shear fractures. In this paper, a recently developed Modified Mohr–Coulomb (MMC) ductile fracture criterion ( Bai and Wierzbicki, 2010 ) is adopted to analyze the failure behavior of a Dual Phase (DP) steel sheet during stretch-bending operations. The plasticity and ductile fracture of the present sheet are fully characterized by a Hill’48 orthotropic model and a MMC fracture model, respectively. Finite element models with three different element types (3D, shell and plane strain) were built for a Stretch Forming Simulator (SFS) test ( Shih and Shi, 2008 ), numerical simulations with four different R / t values (die radius normalized by sheet thickness) were performed. It has been shown that the 3D and shell element simulations can predict failure location/mode, the upper die load–displacement responses as well as wall stress and wrap angle at the onset of fracture for all R / t values with good accuracy. Furthermore, a series of parametric studies were conducted on the 3D element model, and the effect of tension level (clamping distance), tooling friction, mesh size and fracture locus on failure modes and load–displacement responses were investigated.

Stamping tool, casting mold and methods for structuring a surface of a work piece

Abstract: A simple, cost-effective stamping or molding in the nanometer range is enabled using a stamping surface or molding face with a surface layer having hollow chambers that have been formed by anodic oxidation.

Thermo-mechanical finite element analysis incorporating the temperature dependent stress-strain response of low alloy steel for practical application to the hot stamped part

Abstract: The isothermal stress-strain responses of a low alloy steel sheet (0.2C-0.1Si-1.4Mn-0.5Cr-0.01Mo-0.002B steel, 1.2t) at elevated temperature, which simulates the material response in the hot stamping process, were measured by the Gleeble3500 thermo-mechanical simulator. The measured stress-strain responses fitted to the Swift equations discretized within the deformation temperature were used for the practical finite element simulation of the hot stamping process, in which the complicated effects of the volumetric mismatch between phases and phase transformation inducing plasticity were effectively ignored due to the significant constraints by the press stamping. The material parameters for the thermo-mechanical FE simulations were determined by considering the effects of plastic work and phase transformation on the temperature history. A mini-sized b-pillar reinforcing part was used as the simulation model. In spite of the simplified approach adopted in this paper, the finite element procedure could provide important information on the temperature distribution, martensitic phase distribution (or final product hardness), and the effect of process parameters such as punch force on the performance of the final hot stamped product.

Influence of material properties variability on springback and thinning in sheet stamping processes: a stochastic analysis

Abstract: A very critical issue for stamping operations is the improvement of process robustness. The reliability of final results, in fact, strongly depends on the intrinsic variability due to stochastic behavior of many parameters, namely, operative ones and material properties. A given process performance may undergo a variation around the value which would be obtained neglecting stochastic behaviors of the operative or material parameters (i.e., considering a deterministic parameters behavior). Such variation introduces a significant source of uncertainty within the process design: a possible consequence may be the rejection of some stamped parts. In this paper, reliability analyses aimed to evidence and quantify the effects of material coil-to-coil variations on springback and thinning phenomena is proposed. In particular, an aluminum alloy typical of automotive applications was considered and an S-shaped U-channel process was investigated. The stochastic analysis was performed within several operative windows at the varying of restraining forces. Formerly, a sensitivity analysis was carried out in order to evaluate the single effect of each selected material parameter and to screen the most influent ones. Subsequently, a finite element method-response surface methodology-Monte Carlo simulation-integrated approach was implemented to quantify such effects. The proposed methodology provides the possibility to powerfully analyze material variability effect on the final process quality, assisting the designer in a subsequent process optimization.

Integral forming method of large size thin-walled titanium alloy cylindrical part without welding line

Abstract: The invention provides an integral forming method of a large size thin-walled titanium alloy cylindrical part without a welding line. The integral forming method comprises the following steps of: (1) tube blank preparation by stamping; (2) high-temperature vacuum heat treatment; (3) heating power spinning thinning; (4) unheating power spinning diameter expanding; (5) repetitive and alternate conduction of steps (3) and (4) for 2-3 times; (6) high-temperature vacuum heat treatment; (7) finish turning treatment; and (8) stabilizing treatment. The integral forming method prepares the large size thin-walled titanium alloy cylindrical part without the welding line (wall thickness is 1-7mm) which has high precision and high performance by utilizing titanium alloy plates and adopting a compositetechnique combining a stamping method, a spinning method and a stabilizing treatment method, and solves the problems of low material utilization ratio, having longitudinal welding lines, low precisionof tube performance and the like in the forging and roll bending welding forming of the large size titanium alloy thin-walled tubes.

Photovoltaic devices with an active layer from a stamping transfer technique: single layer versus double layer.

Abstract: In this study, organic photovoltaic devices with single or double-layered active film were prepared from a stamping transfer technique A P3HT/PCBM single-layered active layer and a ratio-controlled P3HT/PCBM double-layered active can be successfully fabricated with the help of ultraviolet curable polycarbonate films via a stamping transfer technique The maximum conversion efficiency values 285 for a single active layer transferred device and 324% for an optimized double active layer transferred device Even though transferred double layers should have a sharp interface boundary, an intermixed zone with a concentration gradient was generated by the interpenetration of a donor-rich layer and an acceptor-rich layer in a thermal annealing process The generation of the intermixed zone is confirmed by Auger electron spectroscopy The enhanced conversion efficiency levels are attributed to the increased efficiency of the carrier transporting process, which is due to the fact that the concentration gradient is combined with the efficient charge generation from the bulk heterojunction layers

Design and Testing of a Thin-Flexure Bistable Mechanism Suitable for Stamping From Metal Sheets

Abstract: We present a new technique for fabricating compliant mechanisms from stamped metal sheets. The concept works by providing thinned segments to allow rotation of flexural beams 90 deg about their long axis, effectively providing a flexure as wide as the sheet's thickness. The method is demonstrated with the design and fabrication of a metal bistable mechanism for use as a threshold accelerometer. A new model based on elliptic integral solutions is presented for bistable mechanisms incorporating long, thin flexures. The resulting metal bistable mechanisms are tested for acceleration threshold sensing using a drop test and a vibration test. The mechanisms demonstrate very little variation due to stress relaxation or temperature effects. The force-displacement behavior of a mechanism is also measured. The mechanisms' switching force is less than the designed value because of out-of plane motion and dynamic effects.

An experimental analysis of effects of various material tool’s wear on burr during generator sheets blanking

Abstract: Blanking is one of the most frequently used processes in sheet metal forming. Unlike other forming processes, such as stamping, blanking not only deforms the metal plastically to give the appropriate size and shape, but also ruptures the sheet metal in the desired zones. Among the others, blanking enables manufacturing of electric motor components, such as rotor or stator parts. The parts of the low power commutator motor of rotor and stator are made of generator sheets, which are really difficult to do from the machining point of view. The shock loads and high reaction of the sheet metal of separation surface to the punch surface are presented during the blanking process. In this paper, an investigation has been made to study the effects of punch–die clearance, tool materials, and tool coatings on the wear of blanking tools. In the paper, the feasibility analysis for various materials used for production of the tools for punching the generator sheets is presented.

Consolidation Process in Near Net Shape Manufacturing of Armstrong CP-Ti/Ti-6Al-4V Powders

Abstract: This paper summarizes our recent efforts to develop the manufacturing technologies of consolidated net-shape components by using new low-cost commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy powders made by the Armstrong process. Fabrication processes of net shape/ near net shape components, such as uniaxial die-pressing, cold isostatic pressing (CIP), sintering, roll compaction and stamping, have been evaluated. The press-and-sinter processing of the powders were systematically investigated in terms of theoretical density and microstructure as a function of time, pressure, and temperature. Up to 96.4% theoretical density has been achieved with the press-and-sinter technology. Tensile properties of the consolidated samples exhibit good ductility as well as equivalent yield/ultimate tensile strengths to those of fully consolidate materials, even with the presence of a certain amount of porosity. A consolidation model is also under development to interpret the powder deformation during processing. Net shape components made of the Armstrong powder can successfully be fabricated with clearer surface details by using press-and-sinter processing.

Human-induced particle re-suspension in a room

Abstract: A large-eddy simulation/immersed boundary method for particulate flows in an Eulerian framework is utilized to investigate short-term particle re-suspension due to human motion. The simulations involve a human walking through a room, stopping, and then walking in place, causing particles to be re-suspended from a carpet. The carpet layer is modeled as the porous medium and a classical adhesive force model is applied to model the resistance of the carpet-bound material to hydrodynamic forcing. The effects of parameters such as the foot penetration depth and adhesive force coefficient on mass re-suspended during the foot stamping events are examined. Simulations of particulate re-suspension experiments conducted in a room within a U.S. Environmental Protection Agency test house are also described. The simulations vary the type of human motion (stamping in place versus stamping in place with rotation). The results indicate that significant amounts of particulate material are re-suspended from the carpet laye...

Experimental and Numerical Determination of Limiting Drawing Ratio of Al3105-Polypropylene-Al3105 Sandwich Sheets

Abstract: Sandwich structures are gaining wide applications in aeronautical, marine, automotive, and civil engineering. Since such sheets can be subjected to stamping processes, it is crucial to characterize their forming behavior before trying out any conventional forming process. To achieve this goal, sandwich sheets of Al 3105/polymer/Al 3105 were prepared using thin film hot melt adheres. Different sandwich specimens with different thickness ratios (of polymer core to aluminum face sheet) were prepared. Throughout an experimental effort, the limiting drawing ratios (LDRs) of the sandwich sheets were determined. Besides, the LDR of the sandwich sheets were predicted using finite element analysis simulations by considering Gurson-Tvergaard-Needleman damage model. The results show the capability of the damage model to predict the LDR and the location of damaged zone in a workpiece during a forming operation.

Numerical study on thermo-stamping of woven fabric composites based on double-dome stretch forming

Abstract: Through the international corporative benchmark works, the material characterization of the woven fabric composites has been examined to better understand their mechanical properties and to provide the process design information for numerical analysis. As the second stage of the benchmark work, the double-dome geometry has been used to illustrate the effect of numerical schemes on the forming behaviors of the woven composites parts. To account for the change of fiber orientation under the large deformation, the non-orthogonal constitutive model was utilized and nonlinear friction behavior was incorporated in the simulation. The equivalent material properties based on the contact status were used for the thermo-stamping process. Furthermore, we incorporated a recently developed non-orthogonal model which captures the dependency of shear behavior of woven fabric composites on the tensions in yarns. Simulation results showed the effect of coupling on the predicted forming behavior for the double-dome parts. As numerical results, blank draw-in, punch force history and fiber orientation after forming have been compared based on various numerical models and methods.

Thermal contact resistance estimation at the blank/tool interface: experimental approach to simulate the blank cooling during the hot stamping process

Abstract: In the present paper, an experimental device designed and developed to estimate the thermal contact resistance (RC) at the blank/tool interface is presented along with the simulation chain used to validate the experimental results. The designed stamping tool is composed of a die and a punch made in Z160CDV12 steel and presenting an omega shape. Sample and tools are thermally instrumented with thermocouples type K sheathed with silky glass, forming heat flux-meters in the most interesting locations in the tools. Hot stamping tests are carried out under different contact pressure values covering the range from 5 to 30 MPa. Tested blank material is a C-Mn steel, named Usibor 1500P. Temperatures measurement in the tool and the blank allow the estimation of Rc evolution for every contact pressure. Experiments were carried out in the same conditions of the industrial process. The recorded blank temperature shows systematically a slope change around 400°C; it is linked to the microstructure transformation from austenite to martensite. This metallurgical transformation is also observed on the RC evolution curve. Linked to the microstructure transformation, this singularity tends to vanish with increasing pressure. That is due to the increasing of the cooling velocity with the stamping pressure increasing. Results have been established as correlation of type: RC = RC(P) to be used for numerical simulation through Pam-Stamp and Abaqus. Experimental and numerical parameters have been compared and the small temperature difference shows the good quality of results.

Full-automatic punching machine

Abstract: A full-automatic punching machine comprises a host machine, a material bracket, and a material suction and emptying device, wherein, the host machine comprises a host machine oil cylinder, a stamping upper plate, a lower stamping ejection plate, a cavity, an ejection cylinder and a transmission device; the bottom end of the host machine oil cylinder is connected with the stamping upper plate; the cavity is formed on the stamping table of the host machine; the ejection cylinder is arranged in the cavity; the lower stamping ejection plate is arranged at the upper part of the cavity; the ejection cylinder is connected with the lower stamping ejection plate; the lower stamping ejection plate is provided with a station A and a station B; when the lower stamping ejection plate is in the station B, the ejection cylinder is extended out of the cavity; when the lower stamping ejection plate is in the station A, the ejection cylinder is arranged in the cavity, and the stamping upper plate is right opposite to the lower stamping ejection plate; the material suction and emptying device, which is arranged at the head of the host machine and is extended forward, comprises a lifting air cylinder mounting rack, a first material suction and emptying set, and a second material suction and emptying set; and the lifting air cylinder mounting rack is mounted on the transmission device The full-automatic punching machine provided by the utility model can fulfill material taking and receiving processes, thereby avoiding high work intensity and industrial accidents caused by manual material taking and receiving operation

Middle-duty and heavy-duty automobile knuckle stamp forging extruding compound technology

Abstract: A middle-duty and heavy-duty automobile knuckle stamp forging extruding compound technology overcomes the disadvantages of low material utilization and large device investment of the traditional production technology, utilizes flexibility of preforming by a stamping hammer and structure characteristic of a press extrusion die and adopts stamping hammer production technology and press extrusion compound technology. The main technical scheme includes a series of technical measures of vertically splitting of blank material by mould with V-shaped cutting edge and locally enclosed structure, preforging of cavity damping stripe, finish forging of locally enclosed structure, hot extrusion forming of steering space and the like, parameter requirements and corresponding moulds and devices. The invention has the characteristics that device investment of stamping hammer production technology is small, structure is simple, and equipment manufacturing period is short; production technological flowis reasonable and processing is easy; and the invention also has the characteristics that product quality is good and productivity is high; and material utilization is obviously higher than that of any original knuckle processing technology and production cost is greatly reduced.

Knowledge-based Engineering for Process Planning and Die Design for Automotive Panels

Abstract: This work automates process planning and die design in automotive panel production using a novel knowledge-based engineering (KBE) methodology. Automotive panels are more complicated than common stamped parts because automotive panels are composed of groups of freeform surfaces. Stamping process planning identifies and sequences the necessary operations, finally producing the appropriate press dies. Case-based reasoning (CBR) is integrated into ordinary process planning and die design processes to generate a hybrid KBE system. Utilizing the CBR methodology to plan stamping process and design stamping dies for automotive panels reuses existing designs to develop new designs. In the proposed flexible system, process-planning and die-design functions can adapt existing designs or generate new designs based on stamping knowledge. Tacit knowledge of stamping parts is preserved and automotive panel manufacturing is accelerated by design automation when using the proposed KBE system.

Producing method of thermoforming martensitic steel parts

Abstract: The invention provides a high security, high accuracy and thermal forming martensite steel part preparing method, which belongs to the field of obtaining controlling and cooling technology of the hotstamping forming part of the alloy steel plate, the martensite works as the matrix structure of the alloy steel plate. The method adopts the processes as follows: a steel plate is heated to 20 to 250DEG C above the Ac3 temperature, therefore an austenite structure can be obtained, then the steel plate is transferred to the stamping die for forming by stamping; simultaneously, the temperature of the stamping die is controlled in a range of 100 to 400 DEG C, 5 to 60 seconds later after stamping forming, the formed component parts can be taken out of the stamping die. The method has the advantages that a well ductility and security can be obtained, and the anti-susceptibility of the steel can be greatly enhanced.

Low-carbon ultra-deep punching cold-rolling steel sheet and production method thereof

Abstract: The invention relates to a low-carbon ultra-deep punching cold-rolling steel sheet and a production method thereof, belonging to the technical field of steel smelting and calendaring. The steel sheet comprises the following chemical components in weigh percentage: 0.006%-0.012% of C, 0.15%-0.20% of Mn, 0.030%-0.070% of Als, 0.015% of Si or less, 0.012% of P or less, 0.010% of S oe less, not more than 0.0030% of N or less, 0.0035% percent of O or less and the balance of Fe and inevitable impurities. Based on a ZSP sheet blank continuous casting and rolling process, the production method comprises the following working procedures of steel smelting, continuous casting, heating, hot rolling, cooling and curling, acid washing and cold rolling, and annealing and flattening. The steel sheet has excellent mechanical property and stamping forming property and simple chemical component and is suitable for punching products needing ultra-deep punching, such as fuel tank caps of automobiles; and the production method has the advantages of easy operation, low production cost, energy saving and consumption reduction and is beneficial to generalization and application.