International Journal of Material Forming最新文献

Developing and optimizing manufacturing processes for composite components is commonly supported by finite element (FE) simulations. Initial concepts are modeled and parametric studies are conducted to determine optimum process parameters. Built-in application programming interfaces (APIs) typically allow for a script-based automation of systematic model modifications for many FE solvers. However, the evaluation of simulation results typically depends on a manual inspection by experts, despite its repetitive nature. This study aims to use APIs to develop a fully-automated method for identifying and evaluating critical features and thus, the quality of draping simulations. The focus thereby lies on providing a validated framework for the automated evaluation of draping simulation results, rather than claiming perfect virtual representation of experimental draping. Three different metrics (deviations of fiber angles, the boundary contour and topological defects) are used to determine the overall draping quality of simulation results. With the developed routine, all quality metrics can be estimated quite well for simulation results. The routine is designed to be extended for the use with experimental data for a reliable real-life quality assessment.

Formability is the ability of a material to undergo plastic deformation without being damaged. In sheet metal forming, materials are known to experience deformation in biaxial stretch mode. In order to simulate the common failure strains in sheet metal forming process, numerous formability test methods can be used. A material’s formability can be altered in several ways, one of which is post-weld heat treatment. In this study, the effect of post-weld heat treatment on the formability of aluminum alloy 6061 and SAE1020 mild steel tailor welded blanks fabricated by friction stir welding was evaluated using limiting dome height test. It was found that the specimens which underwent post-weld heat treatment recorded a lower springback and higher value of plane strain, indicating a better formability. The improved formability is attributed to microstructural homogenization, defects elimination, residual stresses relieve and IMC layer growth control from the post-weld heat treatment process.

The objective of the paper is to analyze the fundamental influence of the tool design on the in-plane torsion test in order to create a common basis for carrying out tests that enable the characterization of comparable material parameters between various test setups. The clamps have a major influence on the process limits wrinkling and slippage of the in-plane torsion test. The size and the surface structure of the clamping on the process limit of slipping and wrinkling is investigated. Results show that a ring-shaped clamping surface can transmit up to 50% more torque at the same clamping force compared to a full-circle clamping surface. Investigations show that torque transmission through plain clamping surfaces is not possible for thin sheets (t = 0.5 to 3.0 mm). In order to enable torque transmission in spite of this, the structuring of the clamping surface is necessary. Therefore, radial serrations are well suited, to ensure a homogenous torque transmission over the circumference. An analytical approach was developed and numerically validated, that can determine the indentation depth, the maximum transmittable torque and the necessary clamping force for radial serrations. The geometrical and material specific influence on the process boundary of wrinkling was analyzed and a material independent recommendation for the geometrical shape of the clamps was proposed. This publication is an extended version of the paper “In-Plane Torsion Test—Analysis of the Tool Design”, which was published in the Proceedings of the 14th International Conference on the Technology of Plasticity—Current Trends in the Technology of Plasticity (ISBN 978–3-031–41022-2).

The demand for bent hollow parts, particularly those with larger diameters and smaller bending radii, has significantly increased in industries such as automotive, energy, and aerospace. However, manufacturing these components presents substantial challenges, primarily due to the risk of defects such as wrinkling or cracking caused by excessive wall thinning. This study investigates the combined manufacturing process of Rotary Draw Tube Bending (RDTB) followed by Tube Hydroforming (THF) to address these challenges. Through numerical simulations and experimental validation, the process parameters of both forming techniques, as well as key defects including wrinkling, wall thickness reduction, and die filling rate, were thoroughly examined. The findings reveal that excessive thinning in the extrados during RDTB is mitigated during the subsequent THF operation. Similarly, excessive thickening in the intrados during RDTB is counteracted by the stretching and thinning effects of THF. The results demonstrate that the proposed process, with optimized parameters, enables the production of high-quality elbow parts, confirming the method's effectiveness and its potential as a reliable manufacturing solution for complex elbow geometries.

In the dynamic forming process of profile during roll bending, the downward pressure parameters at different times exert a nonlinear coupled effect on the final curvature radius, making it difficult to predict the ultimate curvature radius accurately. This has become a challenging issue in the field of industrial precision forming. To address this problem, a CNN-TCN-TPA neural network model is proposed to model the complex coupled relationships during the dynamic roll bending forming process. Firstly, a multi-scale CNN is employed to extract the implicit features of roll bending at different time scales, enabling the model to understand the inherent patterns of roll bending data comprehensively. Subsequently, TCN is utilized to learn the influence relationships before and after roll bending forming. Finally, a temporal attention mechanism is adopted to learn the impact of different historical moments on the final outcome, thereby establishing the CNN-TCN-TPA roll bending forming curvature radius prediction model and achieving accurate prediction of the roll bending forming curvature radius. The prediction performance of the CNN-TCN-TPA model is compared with traditional neural network models, TCN models, and TCN-TPA models. The results indicate that the CNN-TCN-TPA model exhibits higher prediction performance compared to other neural network models, with mean square error and mean absolute error of 5971.65 and 24.42, respectively.

Pin structures extruded from the sheet metal plane have numerous industrial applications. For instance, they can be used in bulk microforming to solve handling difficulties or in joining technology to connect dissimilar materials to overcome challenges of different chemical, thermal and mechanical properties of materials. Due to the absence of material flow restrictions in the direction of the sheet metal plane, pin extrusion is affected by numerous process-, workpiece- and tool-related parameters, which have a huge impact on the material utilization and the obtainable pin geometry. Within the scope of this study, a combined numerical-experimental research approach is used to analyze the influence of the material and its condition on the achievable pin height and the occurrence of the mostly undesired funnel formation at high punch penetration depths. For this purpose, elastic-ideal plastic and elastic-real hardening model materials are first investigated numerically, which are subsequently validated and verified in experiments by using the materials Cu-OFE and DC04 on a laboratory scale. Based on the results, recommendations for the material selection and its properties are derived in order to maximize the material utilization. In addition, a pin joining process with locally modified extrusion conditions to increase the load-bearing capacity, especially under axial load, is being investigated with DP600 and AA 6014-T4. This process is a new type of two-stage mechanical joining process without an auxiliary joining element in which pin structures extruded from the sheet metal plane are used to join dissimilar materials in a subsequent step. In this work, test specimens are locally pre-punched before pin extrusion to create an enhanced pin geometry in order to achieve an improved undercut in the subsequent joining process. As a result, a new type of pin geometry was realized and investigated, which shows a significant increase of up to 82% in load-bearing capacity under axial load compared to the existing reference pin geometry.

This paper presents an extensive benchmark study conducted across eight European research centres, focusing on the high-temperature testing of the Alloy 625 nickel-based superalloy to evaluate its flow behaviour and microstructural evolution, including grain growth (GG) and dynamic recrystallization (DRX). Uniaxial compression tests were performed at 1050 °C and three strain rates (0.1 s⁻¹, 1 s⁻¹, and 10 s⁻¹) using six testing facilities categorised into three types: two conventional thermomechanical machines equipped with electrical resistance furnaces, two deformation dilatometers with induction heating, and two Gleeble machines with Joule heating. Flow curves were compared, and EBSD analysis was conducted to examine DRX. Virtual twins of tests were developed to estimate the thermomechanical history at the centre of the samples, where microstructural observations were conducted. The study methodically discussed the variability in thermomechanical behaviour and DRX results. Additionally, GG was investigated through heat treatments at 1150ºC for various hold times, using the three heating methods mentioned. Significant effects of the heating methods on GG were identified. In-situ synchrotron analysis at PETRA III DESY provided deeper insights into microstructural evolution. Considering the extensive findings of this research, this paper aims to establish guidelines and define best practices for high-temperature testing to characterise the thermomechanical behaviour and microstructural evolution of materials, while providing insights for advancing experimental mechanics and optimising constitutive model development.

Ceramic fused filament fabrication (CF3), a type of ceramic additive manufacturing technology, uses ceramic powder/polymer composite filament as raw material to fabricate densified ceramic parts through shaping-debinding-sintering (S-D-S) process, and it owns broad application and development prospects. However, the existing study on the static mechanical properties of CF3 parts is still in the basic stage, lacking comprehensiveness and systematicity. In this paper, self-made zirconia/polymer composite filament with a five-component binder system was developed, and the ME equipment was used to shape the green specimens with different processing parameters (layer thickness, solid loading and infill angle) in order to verify the formability of the composite filament; They were then debinded and sintered using the box sintering furnace so as to obtain the sintered CF3 specimens; Finally, experimental studies on their physical and static properties were carried out to investigate the effects of processing parameters. The results showed that increasing the solid loading of zirconia significantly reduced the dimensional shrinkage of the sintered specimens; When the layer thickness increased from 0.2 to 0.3 mm, the compressive strength decreased from 358.66 to 213.40 MPa, and the bending strength decreased from 456.01 to 293.12 MPa; When the infill angle increased from 0° to 90°, the bending strength of the specimens decreased from 456.01 to 120.08 MPa; The Vickers hardness of the sintered specimens was independent, and it has the characteristic of isotropy.

Flexible skew rolling (FSR) of hollow shafts with a mandrel represents a novel near-net-forming technology for hollow shafts. Surface quality, particularly the presence of spiral mark defects, poses a significant challenge in achieving precision forming. In this paper, the formation mechanism of spiral marks of hollow FSR shaft with mandrel was studied through experimental methods and finite element (FE) simulations, and the morphology of spiral marks under different rolling parameters is analyzed. Our findings indicate that the initiation of spiral marks occurs at the point where the rolled piece separates from the rolls. The outer spiral marks are attributed to the mismatch between the radial and axial metal flow; when the rolled part separates from the rolls, the metal that has exited the rolls is influenced by the deforming metal still within the rolls, resulting in an accumulation of excess material that takes on a spiral shape, mirroring the profile of the rolled piece. The intensity of spiral marks increases with higher swing angles, greater reduction ratios, and larger mandrel diameters, while decreasing with an increase in relative wall thickness. The spiral mark defect could be mitigated by extending the sizing section length, incorporating the unloading fillet and selecting appropriate rolling parameters. When the roll sizing length increased from 20 to 30 mm and the unloading fillet is set at 5 mm, the depth of spiral marks was improved by 21.8%. The results elucidate the causes of spiral marks on hollow shafts produced by FSR with a mandrel and provide theoretical guidance for selecting process parameters in production applications.

Incremental sheet metal forming (ISF) process is an established agile forming method wherein the blank of the sheet metal is deformed into a preferred geometric by the sequence of bit-by-bit local deformation produced by the forming tool. There is no need for a die to shape the sheet metal, which is the principal strength of this process. The review made on the ISF process and particularly the different deformation mechanisms that are generated on the sheet metal during the ISF process are discussed broadly in this paper. The effects of this deformation mechanism on the ISF process are also discussed. The recent developments in ISF processes, such as Heat Assisted ISF process, Water Jet ISF process, Electromagnetic ISF process for sheet metals and Multi-stage ISF process, are also discussed in detail. Each of these processes possesses its distinct merits and demerits which are also listed. The ISF process is performed on different materials that were also discussed.