International Journal of Material Forming最新文献

This work employs the hot oscillatory pressure (HOP) sintering technique for the first time to prepare AlCoCrNiFe high-entropy alloy at varying amplitudes, systematically investigating the influence of amplitude on their microstructure and properties. As the amplitude increased, the grain boundaries of HOP sintered alloy were disappeared, and significant improvements in density and microstructural uniformity were observed. Specifically, when the amplitude increased from ± 1 to ± 10 MPa, the density of the HOP sintered alloy was rose from 93.65% to 99.11%, achieving near-complete densification. The increased amplitude also effectively enhanced their hardness and corrosion resistance. At an amplitude of ± 10 MPa, the Vickers hardness of the HOP sintered AlCoCrNiFe high-entropy alloy was reached a maximum of 481.52 HV₁, which was significantly higher than that of the hot-press sintered samples. Moreover, its corrosion current density was minimized at 9.1 µA/cm², indicating the strongest corrosion resistance. The research results demonstrate that the increasing the HOP amplitude can produce high-entropy alloys with high density, well hardness, and excellent corrosion resistance in lower temperature.

Direct extrusion is a potential route for re-forming chipped carbon-fibre-reinforced thermoplastic composites (CFRTPs), but the influence of feedstock size on processing and final properties remains unclear. Unused commercial 2/2 twill-woven CFRTP sheets were cut into 4-, 8- and 12-mm square chips and used as a controlled model feedstock rather than as manufacturing scrap or end-of-life material. The chips were compression-moulded into 30-mm-diameter, 30-mm-long billets, reheated and directly extruded into 10-mm-diameter rods. As chip size increased from 4 to 12 mm, ram speed increased from 2.238 ± 0.091 to 2.713 ± 0.063 mm/s, whereas the pressure–ram-stroke slope decreased from 21.32 ± 1.40 to 16.43 ± 0.63 MPa/mm. Apparent flexural strength increased from 52.9 ± 10.9 to 108.4 ± 6.8 MPa and apparent flexural modulus from 2.02 ± 0.27 to 3.65 ± 0.35 GPa. Apparent shear strength varied only from 20.7 to 21.6 MPa. Structure tensor analysis of one longitudinal section per condition yielded global a₁₁ values of 0.976, 0.951 and 0.963 for the 4-, 8- and 12-mm conditions, respectively. The analysed 8-mm section showed the largest standard deviation of local a₁₁ and the largest misalignment. Under the present material, geometry and thermal conditions, chip size was associated with extrusion resistance, cross-sectional morphology, local orientation heterogeneity and apparent flexural performance. These results are condition-specific and require validation using practical recycled feedstock and independently sampled cross-sections.

Varying material thicknesses along the longitudinal axis of stringer profiles in aircraft structures serve to reduce weight, a goal that is currently achieved through chemical milling. To introduce this thickness variation in a more environmentally friendly manner, a new flexible rolling process for T-profiles has been developed. The flexible T-profile rolling is based on a novel roll gap geometry that enables the simultaneous rolling of the web and flange of the T-profile. The rolls have varying radii, which leads to different longitudinal strains across the profile’s cross-section, causing vertical bow in the profiles. The objective of this study is to straighten the bow by three different methods: varying the thickness ratio between web and flange, varying the ratio between angular speeds of the rolls and using a straightening roll. The feasibility of these straightening methods is first tested experimentally. The straightening roll has proven to be the most robust and easiest to implement, though slightly less effective than ideally tuned methods. However, a residual bow remains in the profile due to the difference in longitudinal strain, which is why a combination of the various straightening methods is being investigated. To this end, experiments and numerical simulations are being conducted using extruded T-profiles made of Al7075 O.

This study investigates the influence of moisture content in an epoxy-based thermoset moulding compound on process stability and scrap rate during injection moulding, motivated by seasonal performance variations observed in an industrial setting. A controlled trial production series was conducted using six discrete moisture levels (1.38% to 2.76%), prepared from a single material batch. Data from 1 524 parts produced across 254 cycles were collected, including machine parameters and 100% automated camera inspection of eight surface defect types. Statistical analyses comprised Kruskal–Wallis testing, linear and quadratic logistic regression, and correlation modelling. A pronounced non-linear, quadratic relationship between moisture content and scrap rate was identified. At low moisture levels (< 2.0%), scrap rates surged to 22–26%, driven by excessive slip surface, protrusion, and void defects, while peak injection pressures exceeded 2 100 bar. In contrast, an optimal moisture window of 2.0%–2.6% yielded scrap rates as low as 3%, accompanied by a stable switchover volume of 6.0 cm³ with zero variance and substantially reduced baric resistance. Quadratic logistic regression provided a significantly better fit than a linear model (ΔAIC > 10, where AIC is the Akaike Information Criterion) and confirmed the optimal operating range. Switchover volume was shown to be a more sensitive leading indicator of visual defects than pressure, and moisture levels above ≈2.7% introduced melt cushion instability without further quality gains. These findings challenge the common assumption that drier material always improves quality, instead demonstrating an optimal moisture window that maximizes yield. Practical recommendations include standardizing incoming material to 2.1% ± 0.2% moisture and using real-time switchover volume monitoring for predictive quality control. This work provides a data-driven framework for reducing scrap, lowering energy consumption, and extending tool life in thermoset injection moulding.

This study investigates the springback behavior in a roll forming process, with a particular focus on the sill-side inner component made of 1.5 GPa-grade steel. Springback was predicted using an anisotropic constitutive model that incorporates an advanced yield function along with nonlinear kinematic and distortional hardening models. The degradation of Young’s modulus, which is known to significantly influence springback in sheet metal forming, was also considered. The roll forming process, consisting of eighteen sequential roll stages, was simulated using the commercial software LS-DYNA3D, with both the Yoshida–Uemori and HAH constitutive models implemented using User MATerial (UMAT) subroutines. To replicate actual manufacturing conditions, a trimming simulation was performed following the roll forming process, considering that the formed part is typically cut to a length of approximately 300 mm. Springback analysis was then conducted by applying appropriate boundary conditions to suppress rigid body motion. The results were analyzed with respect to material anisotropy, hardening behavior, and the effects of nonlinear strain path associated with the overbending sequence in the roll forming process.

This study investigates a hybrid forming process for the simultaneous manufacturing of complex parts consisting of sheet metal and long fiber-reinforced thermoplastics (LFT), specifically glass fiber-reinforced polyamide 6 (PA6 GF40). This approach integrates sheet metal forming and LFT compression molding within a single tool and process step. Adhesive bonding between the metal and LFT was achieved during the process using a bonding agent previously applied to the sheet metal. Various tool concepts were developed and experimentally evaluated to form different open-ended, complex-shaped hybrid parts in a single-step process. Special attention was given to sealing concepts to prevent the press-out of LFT during forming. The manufactured hybrid parts were analyzed with respect to sheet metal forming behavior, geometrical accuracy, and LFT filling using optical measurement and cross-sectional analysis. Finally, a longitudinal control arm for the multi-link rear axle of the current VW Golf was manufactured and evaluated. The results demonstrate that the new integrated tool design enables reliable forming of hybrid parts with complex geometries. Excellent forming results were obtained for DC04 and DP600 steels, while DP800 steel showed localized thinning and partial underforming. The developed tool concepts ensured effective sealing and prevented LFT leakage, enabling full cavity filling when appropriate process parameters were selected, thereby proving the concept for real industrial parts. Thus, this process offers significant potential for lightweight multi-material structures in automotive applications by reducing process steps.

Explosive forming offers a flexible route for shaping metallic sheets into dies, but a single explosion at room temperature can limit formability and die filling. This study experimentally and numerically investigates underwater forming of a 3 mm thick plate into a female die using repeated blast loading. Metallic specimens were subjected to single, double, and triple explosions, and the outcomes were assessed in terms of sheet thinning and die-filling percentage. In single-shot forming, increasing the charge mass beyond 5 g caused reverse deflection in the central region, led to a maximum thinning of 36.7%, and still failed to achieve full die filling (81.4%). In contrast, the use of second and third underwater blasts enabled complete die filling with reduced thinning and a lower total explosive charge. A coupled Eulerian–Lagrangian (CEL) model in ABAQUS/Explicit was employed to examine deformation velocity, Von Mises stress (SMises), equivalent plastic strain (PEEQ), and the Johnson–Cook damage initiation parameter (JCCRT). Double-explosion tests showed higher SMises, PEEQ, and JCCRT, while no red (damaged) zones appeared on either face of specimens formed with triple explosions. Using a rupture limit of 29% based on the material’s elongation, the region with thinning beyond this limit was shorter for triple than for double explosions. These findings highlight the benefits of repeated, especially triple, underwater blasts for improving die filling while controlling thinning in explosive forming.

The bending response of metal foam shells is dictated by a complex interplay of geometric curvature and graded porosity, which complicates accurate modeling. To address this issue, we create a thorough Physics-Informed (PI) Machine Learning framework that integrates an improved higher-order shear deformation theory with a finite element formulation to forecast the bending behavior of multidirectional functionally graded (MFG) porous metal foam doubly curved shells. A four-node quadrilateral element is developed to model both hard-core and soft-core architectures with five different porosity distribution patterns. The model's predictions match up very well with the benchmark results, which shows that it is numerically strong across a wide range of geometries and boundary conditions. Five hybrid machine learning surrogate models, PI-ANN + GBM, PI-ANN + RF, PI-ANN + DNN, PI-ANN + DT, and PI-ANN + XGBoost are trained on simulation data to predict displacements and stresses. Among them, PI-ANN + XGBoost and PI-ANN + DNN achieve the highest predictive accuracy, with R² values exceeding 0.98 and the lowest RMSE values. These models effectively capture the nonlinear stress–strain relationships while maintaining physical consistency through embedded physics constraints. Overall, the proposed framework modeling exhibits advanced hybrid learning to make better predictions and make predictions that are physically accurate.

To solve the difficulty of forming complex parts of aluminium alloy, a method was proposed using local hardening by laser heat treatment (LHT) to improve the formability of the Al alloy sheet. In order to explore the influence of laser local hardening on deep drawing forming performance, the temperature field of laser treatment was simulated based on the measured data, and a sheet model coupled with mechanical property gradient was established. In addition, the mechanism of the improvement of material formability by the change of constitutive parameters was revealed by the combination of simulation and experiment. The results show that laser scanning can generate a stable gradient temperature field with little influence on the surrounding area. Furthermore, the multi-pass scanning allows for the design of property gradient differential sheets with varying ranges. It is proved that the LHT can effectively improve the plastic strength and the local hardening ability of Al alloy. The results of deep drawing simulations and tests show that the LHT mainly affects the forming ability of differential aluminium alloy sheets by regulating the gradient distribution of strain hardening exponent n and strain hardening coefficient k. The gradient decreasing distribution of n value from the heat treatment center to the surrounding area can not only improve the forming ability of the core area, but also alleviate the strain concentration in the periphery, so as to achieve a more uniform strain distribution in the large deformation zone. The gradient distribution of k can change the position and order of the yield behavior of the plate, and then change the material flow sequence, thus slowing down the material flow at the bottom fillet with higher k value and reducing the tendency of thinning and cracking. In particular, it is found that the gradient distribution of k value is the dominant factor to improve the forming ability of poor aluminium alloy sheet. When the gradient of k value distribution between the laser strengthening area and the surrounding material reaches the critical value, the fracture position of the deep drawing part will shift, which greatly delays the occurrence of necking and cracking processes and improves the overall forming ability of the sheet.

Plastic thermoforming relies heavily on uniform heating to ensure quality and efficiency, while uneven temperature distribution caused by improper thermal control remains a key engineering bottleneck. This paper presents a combined numerical and experimental investigation on the thermal heating characteristics of four typical thermoplastic sheets, namely polyethylene terephthalate (PET), polyvinyl chloride (PVC), polypropylene (PP) and polystyrene (PS), during infrared radiation heating. A transient thermal finite element model was established to simulate the temperature field evolution, and the Taguchi method was adopted to quantitatively evaluate the effects of heating temperature, heating distance, heating time and material type on temperature uniformity. The results show that heating distance exerts the most significant effect on sheet temperature uniformity, followed by heating temperature and material type, whereas heating time shows the least influence. Specifically, increasing the heating distance from 100 mm to 200 mm reduces temperature non-uniformity by approximately 24% relative to its initial value, which corresponds to a reduction of about 13% per 50 mm increment. A low temperature range between 250 °C and 300 °C contributes to better uniform heating. Among the four materials, PS exhibits the best comprehensive thermal response, while PP requires targeted optimization of heating parameters due to its combination of relatively low thermal diffusivity and high specific heat capacity. Furthermore, the dimensional change rate is positively correlated with temperature uniformity, suggesting that improving heating uniformity is essential to suppress thermally induced deformation. This provides theoretical guidance for the improved design of heating parameters and precise thermal control in plastic thermoforming.