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Abstract: FE-simulation and optimization are widely used in the stamping process to improve design quality and shorten development cycle. However, the current simulation and optimization may lead to non-robust results due to not considering the variation of material and process parameters. In this study, a novel stochastic analysis and robust optimization approach is proposed to improve the stamping robustness, where the uncertainties are involved to reflect manufacturing reality. A meta-model based stochastic analysis method is developed, where FE-simulation, uniform design and response surface methodology (RSM) are used to construct meta-model, based on which Monte-Carlo simulation is performed to predict the influence of input parameters variation on the final product quality. By applying the stochastic analysis, uniform design and RSM, the mean and the standard deviation (SD) of product quality are calculated as functions of the controllable process parameters. The robust optimization model composed of mean and SD is constructed and solved, the result of which is compared with the deterministic one to show its advantages. It is demonstrated that the product quality variations are reduced significantly, and quality targets (reject rate) are achieved under the robust optimal solution. The developed approach offers rapid and reliable results for engineers to deal with potential stamping problems during the early phase of product and tooling design, saving more time and resources. [Copyright &y& Elsevier]

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Drawing die complexity is higher than conventional stamping operations, nowadays. It needs to decrease stamping die operation numbers for a part to reduce project budget consumption. Therefore, frequency of tearing, thinning, crack occurrence increase while this amendment. Force, blank cutting, blank location on the drawing die and process optimization were investigated to decrease tearing, thinning and crack occurrence in Transit bodyside inner panels which have over 110 mm. deep drawing process. Formability was improved at the end of this study. Thus production scrap, stoppage time of stamping line were decreased over 90%. This study was conducted at Ford Otosan. [ABSTRACT FROM AUTHOR]

The cam die is one of the most complicated types of automotive panel stamping dies. It is hard to achieve parametric and automated design of the non-standard cam, which determines the quality and cost of die design. The cam design process is extremely complex and requires a great deal of professional knowledge. A new design system for non-standard cams based on the feature reuse and group assembly technology was researched and developed in this paper for automotive panel dies. Taking the advantage of the well-organized historical knowledge base and features database of non-standard cam design cases and the seamless integration with the NX platform, the system was able to generate designs of the die substructure with cam in the form of assembly, including the driver, slider, stripper, cam base, and types of standard components such as nitrogen cylinders, guide plates, stopper seats, return hooks, safety pulling plates, and other parts. Finally, an engineering example of a cam trimming die for body side outer panel verified the feasibility and validity of this system. Comparisons with different design methods demonstrate that the newly developed system shows excellent performance in the design of complex non-standard cams for automotive panels. [ABSTRACT FROM AUTHOR]

Spot welds are widely used to join metal stamping parts in the automotive industry. The number and layout of spot welds have direct impacts on both the mechanical performances of the vehicle and the manufacturing cost. The traditional methods including the 0-1 programming method, the size optimization method, the direct optimization method, and the single-step topology optimization (SSTO) method all have major drawbacks and are not suitable or efficient for spot weld layout design of an automotive structure. In this work, we propose a new method called multi-step varying-domain topology optimization (MVTO) method for spot weld design of automotive structures to balance structural performance and manufacturing cost. Based on a multi-step topology optimization framework with adaptive and varying design domains, the MVTO method can find a better layout design of the spot welds in a more efficient way compared to the existing methods. Limited engineering experiences are required and adverse human factors are eliminated in the spot weld design process with MVTO. To assist the application of MVTO method and to realize design automation, a new modeling approach is also developed to connect the continuous connection elements (CCEs) of the spot welds to the shell elements of the welded structure. Two case studies involving a simple single-hat beam and an automotive B-pillar show that the proposed MVTO method is reliable and effective for spot weld design of automotive structures. It has also been demonstrated that the MVTO method is superior to the direct optimization method and the SSTO method in terms of spot weld number reduction and welded structure performances, thus has a great potential for spot weld design of complicated automotive structures. [ABSTRACT FROM AUTHOR]

In this paper, a kind of flow-solid sequence coupling technology for forming large aluminum alloy automotive covering parts was presented. Firstly, the numerical simulation of hydraulic bulging process was carried out. Then, the springback analysis and mold surface compensation for the simulation results were implemented. The hydraulic bulging test was made by using the optimized compensation surfaces of mold, and the hydraulic bulging parts with relatively accurate shape were obtained. The accuracy of the numerical simulation results was verified by comparing the experimental values and simulation values of the 3D deviation on the same measurement paths; then, in order to form the small fillet features in three different areas of the part, the numerical simulation and experiment research of the stamping technology were carried out on the part obtained by the hydraulic bulging process. The accuracy of the numerical simulation results was verified by comparing the experimental values and simulation values of the thickness distribution on the measurement path; finally, using the numerical simulation of fluid-solid sequence coupling forming process and the matching experiment, the changing rules of the first principal strain and the second principal strain in the small features were studied from the angle of the qualitative and quantitative analysis and it was fully verified that the small characteristics have deformed sufficiently at the end of local shaping process with the rigid die. [ABSTRACT FROM AUTHOR]

Fracture and wrinkling are two major defects in sheet metal forming and can be eliminated via an appropriate drawbead design. This article proposes to adopt a multi-objective particle swarm optimization (MOPSO) approach, which differs from traditional multi-objective optimization with construction of a single cost function. MOPSO shows a certain advantage over other single cost function or population-based algorithms. While radial basis function (RBF) has shown considerable promise in highly non-linear problems, there has been no report in sheet metal forming design. Here RBF is attempted to establish the metamodels for fracture and wrinkling criteria in sheet metal forming design. In this article, a sophisticated automobile inner stamping case is exemplified, which demonstrated that RBF provides a better surrogate accuracy and MOPSO is more effective than the other methods studied. The use of RBF driven MOPSO procedure significantly improved the formability and can be recommended for sheet metal process design. [ABSTRACT FROM PUBLISHER]

Friction stir welding is becoming increasingly desirable in many applications, including tailor-welded blanks in which two sheets of different thicknesses are joined together to form blanks that can be subsequently stamped into a final product shape. In this article, we have studied the static tensile and tension-tension fatigue behavior of friction stir welded joint in a tailor-welded blank of aluminum alloy 5754. It was observed that the yield and tensile strengths of friction stir welded specimens with weld located 90° to the tensile direction are close to the base material values, but its elongation is nearly half the elongation for the base material. The friction stir welded joints had relatively high-fatigue strength, and was even superior to that of the base aluminum alloy in the high-cycle region. Pre-straining caused by press forming lowered the elongation to failure, but improved the fatigue performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The initiation and growth of wrinkles are influenced by many factors such as stress ratios, the mechanical properties of the sheet material, the geometry of the workpiece, contact condition, etc. It is difficult to analyze wrinkling initiation and growth while considering all the factors because the effects of the factors are very complex and studies of wrinkling behavior may show a wide scattering of data even for small deviations in factors. The finite element analyses of wrinkling initiation and growth in sheet metal forming process provide detailed information about the wrinkling behavior of sheet metal. The direct analysis of wrinkling initiation and growth, however, brings about a little difficulty in complex industrial problems because it requires large memory size and long computation time. From the industrial viewpoint of tooling design, therefore, readily available information on the possibility and location of wrinkling is sometimes more preferable to detailed and time-consuming analysis results. In the present study, in order to give such readily available information on wrinkling initiation, the wrinkling factor, which shows the locations and relative possibility of wrinkling initiation, is proposed as a convenient tool of relative wrinkling estimation based on the energy criterion. The reliability of the wrinkling factor is verified through the buckling analyses of sheet strips. The location and relative possibility of wrinkling initiation are predicted by calculating the wrinkling factor in various sheet metal forming processes such as cylindrical cup deep drawing, spherical cup deep drawing, and elliptical cup deep drawing. Finally, the wrinkling factor proposed in the present study is also implemented in the prediction of wrinkling in the door inner stamping process. For verification of the calculated wrinkling factor, detailed zone analyses with fine meshes are carried out for the regions where wrinkling is predicted. [ABSTRACT FROM AUTHOR]

Energy efficiency improvement and environmental impact reduction are emerging issues in the manufacturing industry. Aside from cutting, metal forming is also an important process in manufacturing. Metal forming is energy intensive because of the low energy efficiency of the used metal forming press. Although many literature reviews focused on the energy reduction and energy efficiency of machine tools, a comprehensive literature review of metal forming processes remains lacking because of the great difference between cutting machines and forming equipment. In addition, methods for energy efficiency and energy-saving still need to be promoted in metal forming. In this review, a novel hierarchy of the metal forming system was presented to describe the relationship among the equipment, process, and manufacturing system, providing a guideline of methods for energy efficiency and saving in metal forming. Then, existing energy consumption modeling and estimation theories and methods were discussed from two aspects. One is energy monitoring and modeling of metal forming equipment, and the other is process energy analysis of metal forming based on different parameters. On the basis of the hierarchy of the metal forming system, the present methods and technologies aiming to promote energy efficiency and energy saving effects were discussed from the aspects of equipment design and control, process optimization, and scheduling management and use. Thus, this review may serve as a reference for the decision-making of producers and managers to realize energy efficiency and energy saving at the system level. In addition, the major points that need attention are accurate energy models and control of forming equipment as well as the integrated optimization of equipment, process, and scheduling. [ABSTRACT FROM AUTHOR]