International Journal of Material Forming最新文献

The extrusion speed and deformation temperature are important factors affecting the microstructure development during the deformation. Microstructure development plays a crucial role in the performance of the mechanical properties of materials. In direct extrusion, the homogeneous evolution of the microstructure in the length of the extruded bar could be affected due to its non-isothermal exit temperature evolution. Thus, a new set-up is suggested with real-time controllable speed and temperature to characterize the influence of temperature on the microstructure and obtain its homogeneous development for the magnesium alloy. During the extrusion, the temperature of the extruded bar is evaluated by using the infra-red camera, and the extrusion speed is simultaneously controlled in real-time depending on the temperature difference between a set temperature reference and the one obtained from the infra-red camera. This suggested set-up of extrusion is evaluated in terms of the microstructure and temperature evolution of the extruded bar.

During the high-speed forming processes, the metallic sheets are usually deformed under the biaxial tensile condition. The strain rate of metallic sheets often exceeds 10² s^− 1. It is essential to determine the strain-rate-sensitive hardening model of metallic sheets for accurate numerical simulation of the high-speed forming processes. Thus, an electromagnetic hydraulic bulge experiment is proposed to determine the strain-rate-dependent hardening model of metallic sheets under the biaxial tensile condition with the strain rate of 10² s^− 1. It is convenient to numerically simulate the electromagnetic hydraulic bulge processes. Hence, the strain-rate-dependent hardening models of metallic sheets can be determined by the inverse identification procedure of updating the numerical simulation. The electromagnetic hydraulic bulge experiments of SUS304 stainless steel sheet and AA5052-O aluminum alloy sheet were performed for the inverse identification of Johnson-Cook hardening model. The discrepancy between the experimental results and numerical simulation was minimized by optimizing the parameters of strain-rate-dependent hardening models. The dynamic flow stress curves of SUS304 stainless steel sheet and AA5052-O aluminum alloy sheet were higher than the static ones. However, the AA5052-O aluminum alloy sheet exhibits more significant strain-rate hardening effect than the SUS304 stainless steel sheet. The inverse identification of strain-rate-dependent hardening model of metallic sheet was validated by comparing the simulated and experimental results of electromagnetic micro-hydroforming of micro-channel.

The initial temperature of the preform has an important influence on the stretch and blowing step of the process to produce PET bottles. A complete 3D modelling of the heat part of the stretch blow molding machine including meshing is a long and complex task. Solving Navier Stokes equation coupled with the thermal problem takes more than one week using ANSYS/Fluent software. The numerical simulation of infrared (IR) heating taking into account the ventilation effect is very time-consuming. This work proposes a simplified approach to achieve quickly the numerical simulation in order to have an estimation of the temperature distribution in the preform. In this approach, the IR heating flux coming from IR lamps and the ventilation model are calculated in a semi analytical way and are applied as the boundary conditions of the simulation in COMSOL where only the preform is meshed. This approach is validated by comparing our numerical results with the experimental temperature distribution of PET preform.

Roll forming is a sheet metal forming operation that incrementally forms flat sheets into a desired profile geometry. The process is characterized by a high material utilization and a high output quantity. Concomitant with these advantages, profile defects such as bow and twist of the profile can occur. In the literature, an inhomogeneous longitudinal strain distribution across the profile cross-section is considered to be the cause of these defects. However, a quantitative cause and effect analysis is missing up to now. This paper presents an analytical model that shows a quantitative relationship between profile defects and the underlying longitudinal strain distributions. The model can be used to calculate the longitudinal strain distribution of a roll-formed profile across its cross-section based on given values for bow and twist or vice versa. It is compared with results from simulations and experiments and clearly reveals the cause for twist and bow in roll forming.

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Approximately half of global steel production is dedicated for manufacturing sheets. Due to global warming, geopolitical instabilities and rising raw material costs, recycling sheet metal is increasingly important. Conventional recycling has inefficiencies, therefore improving material efficiency and adopting circular economy strategies is necessary to halve CO₂ emissions by 2050. This paper presents a review of sheet metal reuse techniques and introduces an innovative remanufacturing framework of curved steel sheet, with a special focus on the automotive sector and car-body panels. To support the framework presented, an experimental procedure on small-scale samples was carried out. The material tested was DC 0.4 steel parts (0.8 mm thick) characterized by different curvature radii. The material was reshaped and flattened under different conditions to understand the effect of the process variables onto the final quality of the remanufactured parts. The experiments showed that even parts with small curvatures can be flattened and reshaped with success. Lastly, to support the general remanufacturing framework presented, some flattening simulations of a large car-body are presented, revealing the importance of implementing a dwelling stage in the process and the advantage of performing such process with heated tools.

Important developments have been achieved for self-pierce riveting with the utilization of a double-sided tubular rivet that is able to join sheets of similar and dissimilar materials with different and larger thicknesses, while remaining hidden in-between the sheets after the joining process is completed. Nevertheless, the performance of those joints can still be improved by an optimization of the rivet parameters, mainly the chamfered angle of the rivet ends and the ratio between the initial height and thickness of the rivet. In this paper, the correct parameter combination is established by the performance of the obtained joint to shear destructive tests, the requirements of force and energy, as well as the dimension of the protuberance produced above the sheets surface. The influence of the introduction of an additional rivet in the overall performance of the mechanical joint is also discussed. Joints of different thinner and thicker sheets are analysed, as well as the combination between those thicknesses, to extend the range of applications of the new joining by forming process.

The coupled biaxial tension and shear-biaxial tension deformation responses of a unidirectional non-crimp fabric (UD-NCF) was explored using a novel experimental test setup. A custom multiaxial loading system was used to subject multibranched fabric specimens to combined in-plane tension loads. Biaxial tension tests conducted with varying ratios of deformation along the orthogonal carbon fiber tow and supporting glass fiber yarn directions revealed minor tension-tension deformation coupling over the deformation range considered. Combined shear-equibiaxial tension tests were also conducted with different deformation rates along the fabric diagonal direction, where variations in the force-strain response revealed notable shear-extension coupling. A macroscopic finite element simulation model was developed for the fabric, which employed an available constitutive model that captured the anisotropic hyperelastic response of the fibers. The simulation model accurately predicted the fabric coupled shear-extension deformation for the combined shear-equibiaxial test cases and revealed that the shear angle at the specimen center was limited by the applied tension along the orthogonal fibers. The simulation model was also used to predict shear angle contours for multibranched specimens with different fiber orientations. It was demonstrated that the extent of shear deformation is sensitive to the direction of tension loads. These important findings provide an improved understanding of the coupled deformation modes for UD-NCFs, which will aid in future studies focused on their formability.

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