Initial Blank Shape Research Articles

Automatic Optimization of Initial Blank Shape in Production of All Kinds of Rectangular Parts in Computer Aided Hydroforming Process

Automatic Optimization of Initial Blank Shape in Production of All Kinds of Rectangular Parts in Computer Aided Hydroforming Process

Process-based surface flattening method for laser peen forming of complex geometry

Laser peen forming (LPF) is a novel flexible forming process with several advantages, such as noncontact and high controllability, but it lacks a method to obtain the initial blank geometry based on its specific deformation behavior, limiting the application of the process. This study proposes a process-based surface flattening method to determine an optimal initial blank of complex geometry to accommodate the precise forming requirement. The process-based surface flattening method is developed based on the deformation behaviors of the laser-peened (LPed) and non-LPed zones with equal-strain and equal-area criteria, respectively. The objective surface is first flattened with the equal-area criterion, then the in-plane strain in LPed zones is loaded into the equal-area flattened blank. Because the in-plane strain is unknown before flattening, an optimization model is conceived to solve the in-plane strain in LPed zones based on the proposed equal-strain flattening method. Experiments are designed to validate the surface flattening methods regarding the LP-formed saddle surface as the objective with a known initial blank. The flattening blanks are quantitatively compared with the initial blank. The process-based flattening method presents the blank geometry with a mean absolute error (MAE) of 0.027 mm, while the geometry-based flattening method presents the result with a MAE of 0.398 mm, illustrating the process-based method can provide a more effective initial blank shape.

INCREASING THE ROBUSTNESS OF AN INVERSE STAMPING ALGORITHM

Inverse stamping is a useful tool in engineering. It can be used to find the initial blank shape of stamped parts. It is also useful for quick and easy analysis of a forming process and its impact on the design of a component. Algorithms for inverse stamping are commonly available, but in some situations these algorithms can collapse or may provide confusing results. This article describes improvements to a newly designed inverse stamping algorithm which lead to an increase in its robustness.

Optimization of process parameters for rectangular cup deep drawing by the Taguchi method and genetic algorithm

Abstract This article presents the optimization of process parameters in reducing the risk of failure due to wrinkling and fracture in deep drawing of a rectangular cup. Blank holder force, friction coefficient, punch radius and initial blank shape were chosen as design parameters. Wrinkling and fracture criteria were used as objective functions. Two-stage optimization approach was used. In the first stage optimization, optimum blank shape was determined using the Taguchi optimization method. In the second stage optimization, optimum parameter values were determined for the selected blank shape by the first stage optimization using genetic algorithm. In the second stage of optimization, response surface models based on 3-level full factorial design of experiments were constructed. Finite element simulation results were used for creating response surface models. Parameters obtained from optimization study were confirmed by conducting deep drawing simulations using commercial code DYNAFORM 5.9.2. Optimum results showed that proposed optimization methodology can solve wrinkling and fracture problems in the sheet metal forming process.

Feasibility of one-shot forming for manufacturing of steel/CFRP hybrid B-pillar

ABSTRACT In this study, the feasibility of one-shot forming for manufacturing of steel/CFRP hybrid B-pillar was investigated using a steel sheet with a CFRP patch. The design of one-shot forming process has been described in three stages. First, CFRP reinforcement was designed to substitute for the steel reinforcements for weight reduction. The thickness of CFRP reinforcement was determined through structural analysis by comparing the strengths of the conventional and hybrid B-pillars. Second, the stamping of B-pillars using only the steel sheet was preliminarily designed to determine a proper blank shape that could be used as an initial blank shape in one-shot forming. Third, one-shot forming of the steel/CFRP hybrid B-pillar was designed by finite element (FE) simulation to investigate if fracture and wrinkling occur during the forming process. The feasibility of the designed one-shot forming was evaluated by experimentally manufacturing a steel/CFRP hybrid B-pillar. The FE simulation and experimental analysis indicated that one-shot forming is efficient and suitable for manufacturing steel/CFRP hybrid structures and can be used for mass production of automotive parts at low cost without an additional assembly process.

Effect of blank holding forces and drawbead on various blank shapes for complex geometry using FE simulation

To obtain better quality parts in the stamping process, the important parameter is the flow of material into the die cavity. This flow is controlled by adapting appropriate blank holding force, initial blank shape, and geometry of drawbead. In this paper, a comparative study is carried out using blank holding force and different blank shapes such as rectangular, oblongated, and oval shapes on thinning of the formed part using hyperform as simulation software. From the simulation, it is observed that more thinning is in rectangular blank shapes as compare to oblongated and oval shapes. Formation of oblongated or oval shape blank required extra blanking die which adds more cost. Hence the use of rectangular blank is most preferable along with drawbead. Further research work is carried out to get an optimized solution on rectangular blank using circular drawbead. The result of drawbead with rectangular blank size will give a less thinning with minimum blank holding force compare to oval and oblongated blank shapes. The results obtained by finite element simulation are in good agreement with the experimental results with a permissible error of an average of 6.70%.

Numerical forming limit prediction for the optimisation of initial blank shape in hot stamping of AA7075

The prediction of failure and optimisation of the initial blank shape of a component formed under the complex thermal and mechanical conditions could not simply rely on its thinning or strain. In contrast, the prediction of forming limit of material as a comprehensive result of temperature, strain rate and loading path is an essential indicator in a non-isothermal hot stamping process. However, it is challenging to implement an advanced forming limit model into conventional finite element (FE) software to simulate the failure of the formed component and thus optimise its initial blank shape. In this work, a unified viscoplastic-Hosford-MK model was developed to post-process the simulated evolutionary thermomechanical characteristics and then numerically predict the forming limit criterion of AA7075 in a hot stamping process, of which results were demonstrated on a dedicated visualiser that independent of FE software. Subsequently, the initial blank shape was optimised by analysing the evolutionary temperature, strain rate and loading path of failure regions. Furthermore, the developed forming limit model and optimised initial blank shape were experimentally verified with an error of less than 10%.

Manufacturing of a hemispherical component combining incremental forming and superplastic forming

The interest towards magnesium (Mg) alloys for the fabrication of light weight components has been continuously increasing, especially for transportation, since the payload is strictly related to the energy (fuel or electricity) consumption. Super plastic forming (SPF) and single point incremental forming (SPIF) are viable processes for manufacturing light weight parts since they allow to produce components with superior characteristics and quite complex geometries, even in the case of the poorly formable Mg alloys. But, since both the processes are characterized by stretching, thinning is a key issue to be addressed. On the other side, in order to fulfil the structural and corrosion resistance characteristics required by aerospace and automotive applications, components with a uniform thickness distribution have to be produced. Such an aspect is even more important when the shape complexity of the component increases. SPF and SPIF have never been combined or hybridized so far but, in order to produce parts with a uniform thickness distribution, a possible strategy based on the blank pre-forming by SPIF prior to the SPF has been proposed in the present paper. In particular, the initial blank shape to be obtained by SPIF was designed using a numerical optimization approach and effectively created using the sine law to predict the wall angle and design the tool path. A hemispherical component in AZ31B-H24 was used as case study. The thickness profile of the component obtained by SPF revealed to be highly uniform in a large area (the portion from the centre of the sample to its periphery corresponding to about 70%) being characterized by a thickness equal to about 0.5mm. The quality in terms of finishing of the component produced by SPF resulted to be good, irrespective of the roughness increase exhibited by the blank after the pre-forming by SPIF.

Optimization of initial blank shape for flexible micro deep drawing of square parts

Micro flexible tool-assisted sheet metal forming is one of the forming techniques that have increasingly attracted extensive attention of researchers. Due to its simplicity, low overall production cost, feasibility of prototyping, this forming process seems appropriate for producing micro components. This work presents an evaluation study on using flexible deep drawing process to produce micro stainless steel 304 square cups. The influence of initial foil thickness and blank shape are investigated in details. An optimization of blank shape is implemented to provide micro square products with net-shape and flange free. The finite element simulations are achieved using the commercial code Abaqus/Standard. The results showed that the initial foil thickness affects the thinning and thickening values of the formed cup wall. As well as, the optimization method is feasible to indicate the optimum initial blank shape for producing free flange- micro square parts.

Influence of Process Variables on the Stamping Formability of Aluminum Wing Nose Rib

Ribs are the forming components of the framework of an airplane wing. The nose ribs studied have a U-shaped geometry that consisted of a flat plate, a curved flange with various radius of curvature, and straight flange, and were produced by a stamping process. During stamping, some defects such as thinning, thickening, wrinkling, and springback may occur. To design a forming tool that produces good quality, it was essential to understand the influence of process variables. This study evaluated the influence of stamping process variables on the formability of the nose rib for prevention of excessive thinning and control of the springback phenomenon. Three important process variables namely, blank holder gap, die corner radius, and clearance between the die and the punch were analyzed during an Al-2024-O nose rib stamping. The stamping simulation was a nonlinear problem in nonlinear behavior of solid materials and contacts, which was applied to an elastic–plastic material employed with contact behavior conditions. A DOE design matrix was generated by a full factorial design with every combination of the design variables. The main process variables affecting the multi-objective function, i.e., thickness reduction ratio and springback amount were suggested through main effect analysis, along with the stamping simulation. An experiment was performed to verify the validity of the simulation results. Results indicated that the thickness reduction rate and the springback amount predicted by the simulation were in good agreement with the experimental results. The locations where the maximum thickness reduction occurred, the maximum deformation amount caused by springback, the blank holder force, and the initial blank shape were suggested in this paper. The influence of the process variables will be considered as a reference for improving the quality of the nose rib.

Optimization of Initial Blank Shape for Minimizing the Trimming Process in Hot Stamping of T-Shaped Parts

Blank optimization in stamping is a way to reduce the cost of unnecessary material consumption or subsequent trimming operations by acquiring the final target part in a single forming process. There have been many studies on blank optimization in room temperature stamping, but few studies have yet been conducted in hot stamping. In this study, a blank shape optimization was conducted for a T-shaped part simulating a body center pillar. A finite element analysis (FEA) for the hot stamping process was performed using an appropriately assumed initial blank shape, and the blank shape was updated based on the shape error between the outline of the deformed blank obtained from the FEA and that of the target part. The shape error was calculated by applying the modified radius vector method. Hot stamping test was carried out using the optimal shaped blank predicted by the FEA. It was confirmed that the outline of the deformed blank obtained by the actual test was very close to the outline of the target part. From the results of this study, it can be seen that the blank optimum design technique at room temperature stamping can be applied to the case in hot stamping.

Forming limit prediction for AA7075 alloys under hot stamping conditions

In this paper, the forming limits of AA7075 demonstrators with different initial blank shape under hot stamping conditions were predicted using the developed model, named the viscoplastic-Hosford-MK model. The developed model enables the representation of non-isothermal conditions, changes in strain rate and loading path for AA7075 material. Additionally, the developed model was calibrated using the fundamental experiments including uniaxial and formability tests. To assess the capability of the proposed model, the forming limit of AA7075 with different initial blank shape designs were predicted, and the optimal initial blank shape was verified by applying it to the practical forming of a demonstrator AA7075 component.

深絞り加工におけるブランク形状と分割可変ブランクホルダー力の同時最適化

深絞り加工におけるブランク形状と分割可変ブランクホルダー力の同時最適化

深絞り加工における耳最小化を目的とした初期ブランク形状と分割可変ブランクホルダー力の同時最適化

深絞り加工における耳最小化を目的とした初期ブランク形状と分割可変ブランクホルダー力の同時最適化

타원형 다단 딥 드로잉 제품의 성형성 향상을 위한 초기 소재 형상 최적 설계

다단계 딥 드로잉(multi-stage deep drawing)은 산업현장에서 대형의 금속 제품 뿐만 아니라 소형의 제품에 까지 많은 제품으로 확대되고 있는 제조 공정 중 하나이다. 예를 들어, 스마트 폰에 사용되는 USB-C형 소켓은 매우 작고, 정밀하며 세장비가 큰 부품이며, 이 제품은 타원형 다단계 딥드로잉 방법으로 제조된다. 다단계 딥 드로잉에 최종 제품의 두께 분포를 보장하기 위해서 다단계 딥드로잉 전체 공정에서 제품의 두께 분포가 균일하게 유지되어야 한다. 따라서 첫 번째 드로잉 작업 후에 타원형 제품의 장변과 단변쪽 측벽의 높이 차를 최소화하는 것은 최종 제품의 균일한 두께를 보장하는 가장 중요한 공정 설계 인자이다. 본 연구에서는 첫 번째 드로잉 공정 후 소재가 균일한 높이를 지속적으로 유지될 수 있도록 하기 위해서 유한요소해석을 기반으로 초기의 타원형 소재 형상 결정에 대한 최적 설계를 수행하였다. 최적 설계된 초기 블랭크 형상으로 성형된 제품의 경우 전체 균일한 두께 분포를 가질 뿐만 아니라 드로잉 후 제품의 장변과 단변의 높이 단차가 최소화 되었다. 최종적으로 최적 설계로 예측된 초기 소재 형상은 실제 실험 결과와 비교하여 검증되었고, 매우 양호한 결과의 일치를 보여주었다. Multi-stage deep drawing is a widely used industrial manufacturing process, and its applications are gradually expanding to both small products and large metallic products. The USB C-type socket used in smart phones, for example, is manufactured using oval multi-stage deep drawing. The socket is very small and slender and it requires precise manufacturing. The thickness distribution of the final product is guaranteed only if it is uniform throughout the overall process. Therefore, minimizing the height difference between long and short sidewalls after the first operation is important for this goal. An initial blank optimization was performed for an oval-type drawing process based on finite element simulations. The goal was to determine an initial blank geometry that can maintain uniform height and thickness after the first draw operation. The initial blank shape of the sheet metal was optimized, and the results show that it satisfied the conditions of minimal thickness reduction and even thickness distribution. The geometry from the optimized simulation was compared with experimental results, which showed good agreement.

Genetic Algorithm optimization of initial blank shape in deep drawing of a stepped work piece

This study considers the effect of forging direction on the initial shape of sheet to create a stepped work piece. The purpose of this study is to consider rolling direction in 0°, decreasing the waste while producing workpieces and so decreasing total cost of process. To this end, the assumed workpiece was made of a low carbon and anisotropic st14 steel sheet. To find the most appropriate direction and the shortest modification steps for final shape, the expansion level of the sheet was first imaged in the rolling direction and then the piece was shaped by the geometry. This approach was based on the coupling between the simulation and Genetic Algorithm. A Genetic Algorithm based approach is developed to optimize dimensions through integrating a finite element code running to compute the objective functions for each generation. Those points with a few materials modified through Genetic Algorithm yielded better results.

금형보정 모듈을 이용한 초고강도강 자동차부품용 프레스금형의 자동보정

Abstract In the current study, automatic tool compensation is accomplished by using a finite element stamping analysis for a center roof rail made of UHSS in order to satisfy the specifications for shape accuracy. The initial blank shape is calculated from a finite element inverse analysis and potential forming defects such as tearing and wrinkling are determined by the finite element stamping analysis based on the initial tool shape. The blank shape is optimized to meet the shape requirements of the final product with the stamping analysis, and die compensation is determined with the information about springback. The specifications for shape accuracy were successfully achieved by the proposed die compensation scheme using the finite element stamping analysis. The current study demonstrates that the compensation tendency is similar when the proposed scheme is used or when the compensation is performed by trial and error in the press-shop. This similarity verifies that the automatic compensation scheme can be used effectively in the first stage of tool design especially for components made from UHSS.

Development of L-sectioned ring for construction machines by profile ring rolling process

Recently, there is an increasing commercial interest in manufacturing rings with a complicated cross-sectional shape directly by a metal forming process instead of by machining. Profile ring rolling is one of the advanced metal forming technologies to manufacture large or small seamless profile rings. Compared with plain ring rolling, profile ring rolling can yield considerable savings in material cost and a shorter cycle time for additional machining. In this study, a profile ring rolling process for producing large-scale profile rings with an L-section for construction machine parts is developed. The manufacturing process of large-scale profile rings with L-section consists of a forging stage and a profile ring rolling stage. In the forging stage, the raw material is formed to initial blanks for profile ring rolling. The forged initial blanks are then formed to the final product shape in the profile ring rolling process, which is designed to occur in a single pass to minimize the cycle time. The design of the blank shape is very important, to enable the design of a profile ring rolling process without forming defects, such as fishtails, underfilling, and distortion of the ring. A finite-element (FE) analysis was performed to optimize the blank ring shape, with the objective of minimizing forming defects. After determination of the initial blank shape, the effects of process variables such as feed conditions of mandrel and axial rolls on the final product shape was investigated to improve the dimensional accuracy. Also, forming experiments were conducted based on the results of the FE analysis. The experimental results were in good agreement with the results of the FE analysis.

可変ブランクホルダー力を用いたプレス成形加工における初期ブランク形状の最適化

可変ブランクホルダー力を用いたプレス成形加工における初期ブランク形状の最適化

311 耳削減のための初期ブランク形状及び分割ブランクホルダー力の最適設計(OS1-2 最適設計と解析)

311 耳削減のための初期ブランク形状及び分割ブランクホルダー力の最適設計(OS1-2 最適設計と解析)