Knowledge based cloud FE simulation of sheet metal forming processes

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques. This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions

Hot stamping of AA6082 tailor welded blanks for automotive applications

Friction stir welded (FSWed) AA6082 tailor welded blanks (TWBs), with gauge combinations of 2.0-2.5 and 3.0-5.0 mm, have been prepared and successfully formed into automotive panel components. Experimental results indicated that the post-form strength, in terms of hardness, varied from location to location on the final parts. The strength is highly dependent on the blank gauges, with the average hardness values being HV 110 and HV 98 for the 2.0-2.5 and 3.0-5.0 mm TWB parts, respectively. Conventional FE simulation was built in PAM-STAMP and the prediction results were validated from experimental data in terms of strain distribution and temperature evolution. A typical continuous cooling precipitation (CCP) diagram for AA6082 was implemented into the verified simulation data to explain the strength variations. It is deemed that the temperature history during the stamping and quenching stages has played a major role on the post-form strength of the final parts

Recent Achievements in Numerical Simulation in Sheet Metal Forming Processes

Purpose of this paper: During the recent 10-15 years, Computer Aided Process Planning and Die Design evolved as one of the most important engineering tools in sheet metal forming, particularly in the automotive industry. This emerging role is strongly emphasized by the rapid development of Finite Element Modelling, as well. The purpose of this paper is to give a general overview about the recent achievements in this very important field of sheet metal forming and to introduce some special results in this development activity. Design/methodology/approach: Concerning the CAE activities in sheet metal forming, there are two main approaches: one of them may be regarded as knowledge based process planning, whilst the other as simulation based process planning. The author attempts to integrate these two separate developments in knowledge and simulation based approach by linking commercial CAD and FEM systems. Findings: Applying the above approach a more powerful and efficient process planning and die design solution can be achieved radically reducing the time and cost of product development cycle and improving product quality. Research limitations: Due to the different modelling approaches in CAD and FEM systems, the biggest challenge is to enhance the robustness of data exchange capabilities between various systems to provide an even more streamlined information flow. Practical implications: The proposed integrated solutions have great practical importance to improve the global competitiveness of sheet metal forming in the very important segment of industry. Originality/value: The concept described in this paper may have specific value both for process planning and die design engineers

Hot stamping of AA6082 tailor welded blanks for automotive applications

Friction stir welded (FSWed) AA6082 tailor welded blanks (TWBs), with gauge combinations of 2.0-2.5 and 3.0-5.0 mm, have been prepared and successfully formed into automotive panel components. Experimental results indicated that the post-form strength, in terms of hardness, varied from location to location on the final parts. The strength is highly dependent on the blank gauges, with the average hardness values being HV 110 and HV 98 for the 2.0-2.5 and 3.0-5.0 mm TWB parts, respectively. Conventional FE simulation was built in PAM-STAMP and the prediction results were validated from experimental data in terms of strain distribution and temperature evolution. A typical continuous cooling precipitation (CCP) diagram for AA6082 was implemented into the verified simulation data to explain the strength variations. It is deemed that the temperature history during the stamping and quenching stages has played a major role on the post-form strength of the final parts

Hot stamping of AA6082 tailor welded blanks: experiment and FE simulation

An advanced forming technology, solution Heat treatment, Forming and in-die Quenching (HFQ®), has been employed to form AA6082 tailor welded blanks (TWBs). In comparison with conventional stamping of TWBs, the mechanical properties and formability of AA6082 laser TWBs could be improved under the HFQ® forming condition. The TWB was divided into three physical zones, i.e. base metal, heat affected zone (HAZ) and weld zone, based on the hardness distribution. It was found that the degraded hardness of the weldment can be restored after HFQ® forming. TWBs of AA6082 with different thickness ratios of 2 (2–1 mm), 1.3 (2–1.5 mm) and 1 (1.5–1.5 mm) were used to study the TWB thickness ratio effects on the forming behaviour. Hemispherical punch dome tests on the TWBs with varying thickness ratios demonstrated different formabilities, and indicated increased displacement of the weld line with increasing thickness ratio. Finite element (FE) modelling was adopted to analyse the weld line movement and strain distributions during HFQ® forming

Development of the Fast Light Alloy Stamping Technology (FAST) towards automotive applications: experimental studies

In order to improve fuel efficiency and reduce carbon emissions for the automotive industry, a novel forming technology Fast light alloy stamping technology (FAST) for high and ultra-high strength aluminium alloy thin wall components (such as AA7075) was developed with experimental studies in this thesis. The process consists of: rapid heating, forming and in-die quenching, and incubation. A hot Stamping Simulator tool set to study FAST was successfully developed and manufactured to work in conjunction with the Gleeble 3800 thermo-mechanical testing machine. Based on this Hot Stamping Simulator, the effect of forming parameters on the formability of material and post-form strength have been studied for AA7075 2 mm blank. The effects of contact pressure, lubricant, and tool material on the Interfacial heat transfer coefficient (IHTC) have also been studied, and a mathematical model was developed in order to calculate the quenching time, predict post form strength and optimise the tool design to secure a high quenching rate, enabling the full post-form strength to be retained. Verification tests for the FAST process utilising AA7075 2 mm blank were conducted by forming U-shape and M-shape components. A standard testing procedure was developed for different materials and manufacturer requirements and was verified by studying 6 test cases. Finally, as a new forming process, conclusions and recommendations are made outlining additional factors to be studied to enable the FAST process to be adopted in an industrial environment.Open Acces

Image-based Artificial Intelligence empowered surrogate model and shape morpher for real-time blank shape optimisation in the hot stamping process

As the complexity of modern manufacturing technologies increases, traditional trial-and-error design, which requires iterative and expensive simulations, becomes unreliable and time-consuming. This difficulty is especially significant for the design of hot-stamped safety-critical components, such as ultra-high-strength-steel (UHSS) B-pillars. To reduce design costs and ensure manufacturability, scalar-based Artificial-Intelligence-empowered surrogate modelling (SAISM) has been investigated and implemented, which can allow real-time manufacturability-constrained structural design optimisation. However, SAISM suffers from low accuracy and generalisability, and usually requires a high volume of training samples. To solve this problem, an image-based Artificial-intelligence-empowered surrogate modelling (IAISM) approach is developed in this research, in combination with an auto-decoder-based blank shape generator. The IAISM, which is based on a Mask-Res-SE-U-Net architecture, is trained to predict the full thinning field of the as-formed component given an arbitrary blank shape. Excellent prediction performance of IAISM is achieved with only 256 training samples, which indicates the small-data learning nature of engineering AI tasks using structured data representations. The trained auto-decoder, trained Mask-Res-SE-U-Net, and Adam optimiser are integrated to conduct blank optimisation by modifying the latent vector. The optimiser can rapidly find blank shapes that satisfy manufacturability criteria. As a high-accuracy and generalisable surrogate modelling and optimisation tool, the proposed pipeline is promising to be integrated into a full-chain digital twin to conduct real-time, multi-objective design optimisation.Comment: 32 pages, 11 figure

Hot stamping of titanium alloys

Demand for low density and high strength materials in the aviation sector has expanded greatly due to ambitious carbon emission and fuel consumption targets. In order to meet these targets, manufacturers have focused on weight reduction via the use of lightweight materials. In the aerospace sector, high strength structural components are made from titanium alloys. However, the forming of complex-shaped components from titanium alloys is time, energy and cost intensive. One promising solution to overcome these difficulties proposed in the literature is using the hot stamping process to form complex-shaped components from sheet metal with cold dies, and rapidly quenching the workpiece in the dies simultaneously. The hot stamping process promises to reduce the tool wear commonly found in conventional hot forming processes and be an overall more efficient and economical process when compared to conventionally used isothermal hot forming techniques. A novel hot stamping process for titanium alloys using cold forming tools and a hot blank was studied systematically in this thesis. This work aims to investigate the microstructural evolution and flow behavior of a titanium alloy (Ti6Al4V) under hot stamping conditions experimentally, and to model these parameters using the constitutive equations proposed. The material behavior was modelled using mechanism-based viscoplastic constitutive equations to replicate the material response of a two-phase titanium alloy Ti6Al4V under hot stamping conditions. Finally, the developed model's accuracy was validated by comparing to experimental uniaxial tensile tests and microstructural maps of the deformed alloy. Microstructural analysis revealed that the heating and soaking conditions are vital to the microstructure and post-form strength, whereas the plastic deformation during the hot stamping only has a negligible effect on both recrystallization and phase transformation due to the very short deformation time. The developed material model was implemented into the Finite Element (FE) simulation to study the deformation characteristics during the hot stamping process. The verified simulation data were analysed through a novel hot stamping technique with good agreements achieved between the predicted and experimental results. A complex shaped wing stiffener panel component was successfully formed from TC4 titanium alloy, demonstrating the great potential of investigated technology in forming complex shaped titanium alloys components. Finally, Fast light Alloys Stamping Technology (FAST) is proposed for titanium alloys, where fast heating to a twophase titanium alloy sheet with equiaxed microstructure is employed.Open Acces

Springback analysis of AA5754 after hot stamping: experiments and FE modelling

In this paper, the springback of the aluminium alloy AA5754 under hot stamping conditions was characterised under stretch and pure bending conditions. It was found that elevated temperature stamping was beneficial for springback reduction, particularly when using hot dies. Using cold dies, the flange springback angle decreased by 9.7 % when the blank temperature was increased from 20 to 450 °C, compared to the 44.1 % springback reduction when hot dies were used. Various other forming conditions were also tested, the results of which were used to verify finite element (FE) simulations of the processes in order to consolidate the knowledge of springback. By analysing the tangential stress distributions along the formed part in the FE models, it was found that the springback angle is a linear function of the average through-thickness stress gradient, regardless of the forming conditions used

Design Optimization of the Aeronautical Sheet Hydroforming Process Using the Taguchi Method

The aluminium alloy sheet forming processes forging in rubber pad and diaphragm presses (also known as hydroforming processes) are simple and economical processes adapted to aeronautical production. Typical defects of these processes are elastic recovery, necking, and wrinkling, and they present di culties in control mainly due to property variations of the sheet material that take place during the process. In order to make these processes robust and unresponsive to material variations, a multiobjective optimization methodology based on the Taguchi method is proposed in the present study. The design of experiments and process simulation are combined in the methodology, using the nonlinear finite element method. The properties of sheet material are considered noise factors of the hydroforming process, the objective being to find a combination of the control factors that causes minimal defects to noise factors. The methodology was applied to an AA2024-T3 aluminium alloy sheet of 1 mm thickness stamping process in a diaphragm press. The results allowed us to establish the optimal pressure values, friction coeficient between sheet and block, and friction coeficient between sheet and rubber to reduce the elastic recovery variations and the minimal thickness before noise facts