•Measured monotonic tension, compression, and load reversals data for three steels are used to adjust parameters of the FE-EPSC model.•Geometrical shape changes after U-draw/bending forming are ...predicted using the FE-EPSC multi-level simulation framework.•Accounting for backstress fields is revealed as critical for the accurate predictions of part geometries upon U-draw/bending.•Hardening and carrying over residual stress fields are essential for predicting part shape changes involving pre-strained sheets.•Increase in the amount of springback with sheet strength is determined by simulating U-draw/bending of DP 590 and DP 1180.
This work is concerned with predicting geometrical shape changes in sheet metal forming using a multi-level simulation framework that considers the directionality of deformation mechanisms acting at the single-crystal level and microstructural evolution. The multi-level model is an elasto-plastic self-consistent (EPSC) homogenization of single-crystal behavior giving the constitutive response at each finite element (FE) material point. Numerical solution of a boundary value problem over geometry is then obtained using continuum finite elements at the macro-level. First, a set of model parameters for the evolution of slip resistance of ferrite and martensite and backstress are established by fitting a comprehensive set of mechanical data for dual-phase (DP) steels 590, 780, and 1180 using one-element model. Next, the potential of the FE-EPSC modeling framework is illustrated by carrying out a set of hat-shaped draw-bending simulations of the steel sheets. The evolution of geometry after hat-shaped draw-bending and springback is predicted and verified with experimental measurements for as-received DP 780. In doing so, the role of accounting for backstress is revealed as critical for the accurate prediction of the part geometry. The same process simulation involving a pre-strained sheet of DP 780 is compared with a corresponding experiment to reveal the role of strain hardening and residual stress on the subsequent part shape changes after the hat-shaped draw-bending test and springback. Finally, the same process simulations involving DP 590 and DP 1180 are performed to confirm the effect of strength on the geometrical shape changes of the sheets after springback.
The simulation of manufacturing processes has significant importance. The research and development of metal forming simulation started in the 1960s from the elastoplastic analysis of a simple plastic ...deformation, and it now covers a wide range of forming processes. The accuracy and applicability of metal forming simulation have significantly progressed, driven by the development of plasticity theory and numerical methods such as the remeshing technique and contact analysis algorithm. Now the targets of metal forming simulations are undergoing a transition from the macroscale analysis of deforming bodies to coupled analyses of deformations of deforming bodies and tools, and multiscale analyses of microstructure and texture. Past achievements of metal forming simulation show that it has reached the level of ‘visualizing forming phenomena’, but it will continue to evolve in the digital era, impacting the digital society and factories of the future, where machines work autonomously without human intervention. Emergent technologies require advanced materials, augmented reality, and, of course, metal forming simulation. In this paper, we reinforce the role of simulation as a means of performing computational (virtual) experiments and as a tool for the high-fidelity numerical visualization and quantification of unknown, unmeasurable, and invisible phenomena in formed components and their assembly. We will also discuss simulation–machine interactions, such as online simulation with process operation, to realize the triad of ‘process operation – data – simulation’ in the near future.
Lightweight sheet metals are attractive for aerospace and automotive applications due to their exceptional properties, such as low density and high strength. Sheet metal forming (SMF) is a key ...technology to manufacturing lightweight thin-walled complex-shaped components. With the development of SMF, numerical simulation and theoretical modelling are promoted to enhance the performance of new SMF technologies. Thus, it is extraordinarily valuable to present a comprehensive review of historical development in SMF followed by state-of-the-art advanced characterization and modelling approaches for lightweight metallic materials. First, the importance of lightweight materials and their relationship with SMF followed by the historical development of SMF are reviewed. Then, the progress of advanced finite element technologies for simulating metal forming with lightweight alloys is covered. The constitutive modelling of lightweight alloys with an explanation of state-of-the-art advanced characterization to identify the constitutive parameters are presented. Then, the formability of sheet metals with major influencing factors, the techniques for measuring surface strains in SMF and the experimental and modelling approaches for determining the formability limits are clarified. Finally, the review is concluded by affording discussion of the present and future trends which may be used in SMF for lightweight metallic materials.
The energy demand and CO2 emissions of the steel processing industry are a global challenge. During conventional steel processing, the treatment of iron ore and steel in a molten state heavily ...contributes to this problem. This paper provides an in-depth investigation of the benefits and technical requirements of an alternative processing pathway with minimal energy and CO2 burdens. Our proposed method, scrap metal consolidation (SMC) by rolling, is adapted from roll bonding, a scalable metal bonding technique, commonly used for niche composite applications to achieve material properties unattainable by monolithic alloy design. SMC transforms steel scrap into hot rolled steel in solid state without melting. Based on pre-published high-fidelity industrial data, we determined that processing hot rolled steel from scrap in the solid state would consume 94% less energy compared to the primary steel processing route with 94% less CO2 burden. Compared to conventional recycling methods, the energy savings of SMC would be 86%, with an 84% decrease in CO2 emissions. The proposed method is described in detail, and the process windows for AISI 1008 mild steel and SS304 stainless steel were determined in terms of rolling temperature and reduction using a lab-scale rolling mill at a temperature range of 700–1100 °C. The formability of the consolidated mild steel is also evaluated via the hemisphere punch test, a standard industrial test for assessing the formability of sheet metals. While the fracture height of consolidated specimens is in the 9.27–10.62 mm range, the monolithic sample has a fracture height of 10.34 mm. The test results show that the consolidated sheets have comparable formability to monolithic specimens. These investigations altogether demonstrate that SMC-by-rolling is a feasible and environmentally sustainable alternative for conventional steelmaking or recycling processes.
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•Solid-state consolidation of steel scrap uses 94% less energy than primary processing.•Compared to recycling, scrap metal consolidation saves 84% of process CO2 emissions.•Process boundaries for mild and stainless steel follow a reverse S-curve trend.•Test results exhibit comparable formability for roll-bonded and monolithic samples.•Most sheet metal forming operations don't cause opening stress, reducing failure risk.
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•Weakening the strong basal texture produced by extrusion.•It can achieve significant shear-compression deformation with large strain.•The physical simulation under different strain ...rate ranges can be satisfied.•The ideal thermal deformation parameters for pure Mg can be predicted.
In this study, the deformation behavior and microstructure evolution of pure Mg under hot shear-compression deformation conditions are investigated using the “Shear-Compression Specimen” as a model, which provides theoretical guidance for the investigation of the principles of surface defects in the hot extrusion process. The results showed low flow stress corresponded to a high temperature and a low strain rate, temperatures between 350–450 °C and strain rate at 5 s−1 are the perfect hot deformation parameters. The deformation generates a special texture that is bent by 45° along the extrusion direction, weakening the strong basal texture structure created by extrusion. The deformed microstructure is fine and uniformly distributed. In summary, the surface of the material is forced to undergo a complex shear-compression deformation during the hot extrusion process, while the core belongs to a simple uniaxial extrusion deformation. In some specific deformation conditions, the difference between these two may produce some defects.
Due to the change from mass production to mass personalized production and the resulting intrinsic product flexibility, the automotive industry, among others, is looking for cost-efficient and ...resource-saving production methods to combining global just-in-time production. In addition to geometric manufacturing flexibility, additive manufacturing offers a resource-saving application for rapid prototyping and small series in predevelopment. In this study, the FDM process is utilized to manufacture the tooling to draw a small series of sheet metal parts in combination with the rubber pad forming process. Therefore, a variety of common AM polymer materials (PETG, PLA, and ABS) is compared in compression tests, from which PLA is selected to be applied as sheet metal forming die. For the rubber pad forming process, relevant processing parameters, i.e., press force and rubber cushion hardness, are studied with respect to forming depth. The product batch is examined by optical evaluation using a metrological system. The scans of the tool and sheet metal parts confirm the mechanical integrity of the additively manufactured die from polymer and thus the suitability of this approach for small series in sheet metal drawing processes, e.g., for automotive applications.
A model for the evolution of ductile damage in the sense of void fractions using artificial neural networks (ANN) is proposed. In contrast to constitutive damage models, the damage prediction is ...solely based on experimental data and has no underlying assumptions for the damage evolution law. This guarantees that the experimental observations are captured correctly. High resolution experimental void data obtained by scanning electron microscopy with a minimum single void area of 0.02 μm2 are used as training data. The loading state is obtained from finite element simulations. The equivalent plastic strain is used to describe the load amplitude and the triaxiality as well as the normalised Lode angle are utilised to characterise the loading type. Different strategies for the training of the model as well as the prediction are analysed. The model is used to visualise the loading state-dependent damage evolution. Furthermore, it is applied to two different bending processes. It is shown that the prediction quality highly depends on the experimental and numerical data used for training. If the loading states of the application problem are within the domain of the training data, the prediction quality is good and even better than constitutive models used in literature.
In this work, a blank of galvanized steel blank with 80 mm diameter and 0.7 mm thickness and the hydromechanical deep drawing process to make a hemispherical and complex cup. Hydraulic oil was used ...to apply different amounts of fluid pressure. The work of this study was done in the following three states: In the first state, the experimental work was done without fluid pressure, so the product has wrinkles. In the second state, flaws like wrinkles were fixed by adding 1N/mm2. At a pressure of 1.7 N/mm2, the third state was done. The results show that a product with a blank holder force (BHF) that is neither too high nor too low may be free of defects. When BHF is low, faults in the cylinder cup look like wrinkles, and when BHF is too high, the cylinder cup breaks. So, the BHF value should change depending on the material, thickness, and nature of the product.
Isogeometric analysis (IGA) has been used with great success when combined with incremental methods to simulate sheet metal forming. In this paper, we present the development of one-step inverse IGA ...based on the total deformation theory of plasticity. For a large number of industrial stamping parts, the membrane effects are dominant. Thus, we adopted an isogeometric membrane element to predict the flattened contour of the initial blank from the energy-based initial solution estimation approach. In addition, we used the Newton–Raphson algorithm for nonlinear plastic iterations to evaluate the thickness and equivalent strain and stress of the final stamping parts. We applied our framework to square box and S-rail surface models for demonstration. The results for these two examples illustrate the performance of one-step inverse IGA and its applicability to the integrated design of sheet metal forming.
•We develop a one-step inverse isogeometric analysis method for simulating sheet metal forming.•The isogeometric membrane element is adopted to predict the flattened contour of initial blank.•We use Newton–Raphson algorithm to evaluate the thickness and equivalent strain/stress of the final stamping parts.•Numerical examples illustrate the performance of one-step inverse IGA and its applicability to the integrated design of sheet metal forming.
Commercially pure titanium exhibits strong anisotropy, strength differential as well as texture evolution, which make the development of predictive simulation models a challenging task. A new ...modeling approach is proposed based on the homogeneous distortion of well-established yield surface descriptions, in order to achieve a flexible tool to capture all the mentioned effects. The models are calibrated based on uniaxial tensile and compression tests and are validated based on the earing profile and thickness distribution of cup drawing experiments.
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