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Minimization of part variation has been a challenging topic for both researchers and engineers. Variations in final stamping parts could come from numerous sources such as incoming material, lubricant, processing parameters, environment, automation, etc. Identifying the cause of the variations is not only time consuming, but also a continuously changing process. In this paper, experiments are reviewed which were conducted to examine the feasibility of implementing closed-loop process control to reduce dimensional variations on an in-production 3D part. Specifically, the effects of punch force (PF) and binder force (BF) on part dimensions are studied. For our particular application, proper control of both PF and BF is necessary to control the dimensional variations of the part.

Tailor welded blanks (TWBs) offer an excellent opportunity to reduce manufacturing costs, decrease vehicle weight, and improve the quality of auto body stampings. However, tearing near the weld line and wrinkling in the die addendum often occurs when a traditional forming process is used to fabricate this type of blank. Cao and Kinsey [1] proposed a modification to the stamping process where a mechanism would clamp on the weld line during the deep drawing process to improve the formability of TWBs. Critical to the success of this proposed modification is the ability of the clamping mechanism to perform its intended function and avoid creating adverse effects in the forming process. In this paper, numerical simulations verify the ability of the clamping mechanism to hold the weld line in place during forming and not severely deform the blank in the area of the clamping mechanism.

Draw beads are widely utilized as a mechanism for providing proper restraining force to a sheet in a forming operation. In this paper, numerical simulations using the nonlinear finite element method are conducted to model the process of drawing a sheet through various draw bead configurations to study the mechanics of draw bead restraint. By examing the sensitivity of the draw bead restraining force due to the change of the draw bead penetration, the work shows that the penetration has the potential to be a very good element for varying and controlling restraining force during the process. A closed-loop feedback control of draw bead penetration using a proportional-integral controller is achieved by the combination of the original finite element simulation and a special element which links penetration to a pre-defined restraining force trajectory.

Advanced high strength steels (AHSS) are particularly attractive to automotive industry. Stamping AHSS parts, however, results in accelerated die wear problems which could emerge after few thousands of stampings. The existing wear testing methods are either not suitable for charactering die wear in stamping or requires significant capital investment. The first generation of strip-on-cylinder wear test apparatus which can efficiently and economically characterize die wear is introduced in this paper. Different measurement methods were compared and white light interferometer with nanoscale accuracy was chosen to determine the wear volume due to its overall advantages. Based on the strip-on-cylinder wear test apparatus, a design of experiments study analyzing the effects of contact pressure, sliding speed and hardness of the die material on die wear was conducted and the results were discussed.

Tailor welded blanks offer an excellent opportunity to reduce manufacturing costs, decrease vehicle weight, and improve the quality of sheet metal stampings. However, tearing near the weld seam is a concern in Tailor Welded Blanks due to material changes in the fusion and heat affected zones of the weld. Therefore, data is required such as the potential strain of the material in these areas to use in the process design. For example, Cao and Kinsey proposed a modification to the deep drawing process where segmented dies with local adaptive controllers clamp adjacent to the weld line during the forming operation thereby reducing the strain in the material near the weld seam and in turn the concern of tearing failure. In order to aid in the design process for this modification, an understanding of the effects of the welding process on material changes near the weld seam is essential.

Tailor welded blanks offer a unique opportunity to reduce manufacturing costs, decrease vehicle weight, and improve the quality of stampings through the consolidation of multiple formed, then welded, parts into a single stamping. However, tearing near the weld line often occurs in this type of blank when formed with a traditional deep drawing process. Therefore, some adaptation to the existing sheet metal forming process must be developed in order to reap the numerous benefits available from tailor welded blanks. In this paper, numerical simulation are presented for a newly contrived tailor welded blank forming process where several hydraulic mechanisms apply distinct clamping forces along the weld line during forming. Excellent results demonstrate the effectiveness of the proposed method.

In this paper we investigate the optimal forming of conical cups of AL 2008-T4 through the use of real-time process control. We consider a flat, frictional binder the force of which can be determined precisely through closed-loop control. Initially the force is held constant throughout the forming of the cup, and various levels of force are tested experimentally and with numerical simulation. Excellent agreement between experiment and simulation is observed. The effects of binder force on cup shape, thickness distribution, failure mode and cup failure height are investigated, and an “optimal” constant binder force is determined. For this optimal case, the corresponding punch force is recorded as a function of punch displacement and is used in subsequent closed-loop control experiments. In addition to the constant force test, a trial variable binder force test was performed to extend the failure height beyond that obtained using the “optimal” constant force level.

{Metal forming process is characterized by large deformation that poses a great challenge for the implementation of contact algorithm. Based on the meshless representation of the geometry, a new contact detection algorithm is presented in this paper. The advantage of this algorithm is that it can handle a wide variety of complicated geometry involved in the forming process. Because only a simple scalar criterion is used, the algorithm is applicable to parallel computing and detection of self-contact. Although the algorithm is derived based on the framework of meshless method, it can be implemented in both finite element and meshless methods.}