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Deep drawing and ironing are the major processes used today in manufacturing of most beverage cans from aluminum. The same technology is utilized in manufacturing of steel cans for the food industry. The practical aspects of this technology are well known and gained through extensive experimentation and production know-how. The fundamental aspects of the processes, however, are relatively less known, especially regarding the temperature developed during deformation and the effect of deformation speed upon temperatures and lubrication. Thus, it is expected that process simulations using FEM techniques would provide additional detailed information that could be utilized to improve the process conditions. This paper illustrates the application of process modeling to deep drawing and ironing operations. The predictions agree well with the experimental results.

Predominant failure modes in the forming of sheet metal parts are wrinkling and tearing. Wrinkling may occur at the flange as well as in other areas of the drawn part and is generated by excessive compressive stresses that cause the sheet to buckle locally. Fracture occurs in a drawn material which is under excessive tensile stresses. For a given part and blank geometries, the major factors affecting the occurrence of defects in sheet metal parts are the blank holder force (BHF) and the blank holder pressure (BHP). These variables can be controlled to delay or completely eliminate wrinkling and fracture. Modern mechanical presses are equipped with hydraulic cushions and various advanced multi-point pressure control systems. Thus, the BHP can be adjusted over the periphery of the blank holder as a function of location and time (or press stroke).

Process simulation for product and process design is currently being practiced in industry. However, a number of input variables have a significant effect on the accuracy and reliability of computer predictions. A study was conducted to evaluate the capability of finite element method (FEM) simulations for predicting part characteristics and process conditions in forming complex-shaped, industrial parts. In industrial applications, there are two objectives for conducting FEM simulations of the stamping process: (1) to optimize the product design by analyzing formability at the product design stage and (2) to reduce the tryout time and cost in process design by predicting the deformation process in advance during the die design stage. For each of these objectives, two kinds of FEM simulations are applied.

Edge fracture is a common problem when forming advanced high strength steels (AHSS). A particular case of edge fracture occurs during a collar forming/hole extrusion process, which is widely used in the sheet metal forming industry. This study attempts to relate the edge stretchability in collar forming to the strain hardening along the pierced edge; thus, Finite Element (FE) simulations can be used to reduce the number of experiments required to improve cutting settings for a given material and thickness. Using a complex-phase steel, CP-W 800 with thickness of 4.0 mm, a single-stage piercing operation is compared with a two-stage piercing operation, so called shaving, in terms of strains along the pierced edge, calculated by FE simulation. Results indicated that strains were reduced along the pierced edge by shaving.

Springback affects the dimensional accuracy and final shape of stamped parts. Accurate prediction of springback is necessary to design dies that produce the desired part geometry and tolerances. Springback occurs after stamping and ejection of the part because the state of the stresses and strains in the deformed material has changed. To accurately predict springback through finite element analysis, the material model should be well defined for accurate simulation and prediction of stresses and strains after unloading. Despite the development of several advanced material models that comprehensively describe the Bauschinger effect, transient behavior, permanent softening of the blank material, and unloading elastic modulus degradation, the prediction of springback is still not satisfactory for production parts. Dies are often recut several times, after the first tryouts, to compensate for springback and achieve the required part geometry.

Designing the process sequence for deep drawing round cups is a trial and error process. The variations in the part geometry and processing conditions lead to a variety of problems that have to be solved after the dies and punches have been made. A system to design processes sequences is being developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM). The system would help designers in developing the sequences, evaluating these sequences, and in predicting possible problems before production of parts. This would lead to a substantial savings in time and money. This system has three modules, a design module to design the process sequences, a finite element analysis module to simulate the forming process to predict possible problems when forming the part, and an interface module to handle data transfer between the two modules. The design module of the system is documented here.