International Journal of Material Forming最新文献

Accurate prediction of the Forming Limit Curve (FLC) is essential for the design of sheet metal stamping processes; however, its experimental determination is costly and limited by data availability. This work investigates the use of Machine Learning techniques to predict the FLC of Dual Phase (DP) steels based on mechanical properties obtained from uniaxial tensile tests. To overcome the scarcity of experimental data, a synthetic database was developed based on statistical consistency and physical constraints, using Kernel Density Estimation, PCA projections, and controlled probabilistic interpolation, followed by the application of physicometallurgical plausibility criteria. The models use physics-based descriptors as input variables, which reflect known metallurgical mechanisms associated with plastic instability, without explicitly incorporating differential equations into the training process. The results show that all models were able to reproduce the characteristic geometry of the FLC, with errors on the order of 10⁻³–10⁻². Among the investigated techniques, Random Forest exhibited the best performance (MAE = 0.0052; MSE = 0.00011; R² = 0.943), followed by XGBoost, while the Neural Network showed greater variability and a tendency toward overfitting. The results demonstrate that the combination of physics-based descriptors, statistically validated synthetic expansion, and ensemble machine learning methods constitutes a robust and efficient strategy for modeling FLCs of DP steels.

Continuous fiber-reinforced polymers (CFRPs) offer high strength-to-weight ratios, which makes them an attractive choice for applications in transportation, biomedical devices, and sports equipment. Additive manufacturing presents new opportunities for producing CFRPs with improved geometric freedom and digital fabrication flexibility. However, achieving adequate fiber impregnation and strong interfacial bonding remains a major challenge. This paper presents a novel rotating impregnation die, patented by some of the authors, designed to produce fiber-reinforced polymer filaments at a die speed of 15 rad/s. These filaments, characterized by a final diameter of 0.65 mm and a fiber volume fraction of 5.4%, are compatible with fused deposition modelling for 3D printing. The die is engineered to improve polymer–fiber interaction during filament fabrication. Specifically, its rotating geometry induces a swirling flow pattern in the molten polymer, which enhances fiber wetting and promotes partial fiber interlacing. The performance of the system was evaluated through both numerical simulations and experimental tests. In the computational fluid dynamics analysis, an inlet velocity of 5 mm/s was imposed, showing that the rotational motion generates a tangential velocity component that improves fiber-polymer interaction and locally reduces viscosity at the fiber surface, leveraging the shear-thinning behaviour of the polymer. This results in improved impregnation efficiency without affecting the internal pressure of the die. Two filament configurations were produced for comparison: one using the rotating impregnation die PLAGF-B (PolyLactic Acid – Glass Fiber Braided) and one using a static die PLAGF-UB (PolyLactic Acid – Glass Fiber UnBraided). The produced filaments consisted of three glass-fiber bundles impregnated with PLA resin and were subjected to standard tensile testing, after being pulled at a controlled speed of 6 mm/s. The PLAGF-B samples exhibited higher tensile strength (~ 70 MPa vs. ~60 MPa) and elongation at break (~ 0.023 mm/mm vs. ~0.018 mm/mm), attributed to enhanced twisting and compaction induced by the die’s rotation.

To enhance the wear resistance and corrosion resistance of 42CrMo bearing steel and extend the service life of sliding bearing bushings in wind turbine gearboxes, this study used Laser Powder Bed Fusion (LPBF) technology to prepare a CuSn12Ni2 molten layer on the surface of 42CrMo bearing steel. Preliminary melting process parameters were determined through orthogonal experiments, and a Greenwood-Tripp (G-T) contact model was established for load analysis. Electrochemical corrosion tests were conducted in a 3.5% sodium chloride (NaCl) solution. Four laser scanning angles (0°, 45°, 67°, and 90°) were tested to analyze the density, microstructure, hardness, friction wear, and corrosion resistance of the molten layers. Results showed that as the scanning angle increased, the overall melting quality first improved and then declined, with 67° proving optimal for achieving high density, high hardness, and minimal porosity. Under a 40 N load, the sample at 67° exhibited the best relative wear resistance (1.35), with abrasive and oxidative wear as the main mechanisms. In the NaCl solution, the 67° sample showed fine and sparse corrosion pits. Its high density and uniformly distributed Sn and Ni elements formed a continuous passive film that effectively blocked Cl⁻ ion penetration. Polarization curves and Bode plots confirmed the corrosion resistance order: 67° > 45° > 90° > 0°. Comprehensive analysis indicated that the 67° scanning angle significantly improved the coating’s performance by optimizing track overlap, reducing defects, and promoting uniform microstructure formation. This research provides theoretical guidance and process references for applying LPBF technology to manufacture wind power sliding bearing bushings in low-speed, heavy-load, and corrosive environments.

The development of sustainable and efficient manufacturing strategies is accelerating the adoption of advanced forming processes for lightweight, high-performance components. Sheet-bulk metal forming (SBMF) enables near-net-shape production of thin-walled parts with integrated functional elements, offering advantages in material efficiency, process consolidation and geometric complexity. While the feasibility of straight-toothed gears has already been demonstrated, helical gears, which are widely used in industry due to their favorable load capacity and noise behavior, have not yet been experimentally validated. This study presents an experimental investigation into the SBMF-based production of helical gear structures. Starting from flat steel sheets, a combined process chain of deep drawing, upsetting and lateral extrusion is applied. The influence of material choice (DC04, CuZn37, DP600) is examined, complemented by reference tests on helix angle, punch stroke and lubrication strategy. Key process variables such as forming force, die filling and local strain hardening are analyzed and correlated with macroscopic defects and microstructural observations. The results demonstrate that the helix angle has negligible influence on process force or die filling, confirming the viability of transferring SBMF to helical gear geometries. Among the tested materials, DC04 exhibits the most advantageous forming response. Lubricant type and quantity exert minimal influence on die filling, indicating that global tribological adjustments are insufficient to steer material flow. Although high cavity engagement is achieved, localized defects such as folding, burrs and indentations highlight the need for improved material routing.

Dual-phase (DP) steels, particularly DP1000, are widely used in the automotive industry due to their excellent strength-ductility balance and crash performance. However, their high tendency to develop edge cracking during manufacturing processes such as blanking and trimming remains a significant challenge. This issue arises primarily from the sharp mechanical property contrast between the ferritic and martensitic phases. As a countermeasure, laser-polishing has been introduced to enhance edge quality by locally remelting and smoothing the cut surfaces, thereby eliminating burrs and micro-defects. This study investigates the effectiveness of laser-polishing in improving edge formability using a novel Diabolo test setup, which promotes pronounced deformation at the specimen edge due to its hourglass-shaped punch geometry. Experiments are conducted on 1.5 mm thick DP1000 sheets with varying edge morphologies, and surface strain evolution is captured using digital image correlation (DIC). To complement the experiments and gain insight into the multiple mechanisms behind the enhanced performance, a multi-scale simulation approach is applied. The model integrates the actual mechanical properties and topographical features of the laser-polished edge, incorporating both macroscopic and microscopic effects, including a calibrated surface factor. Results reveal a notable improvement in edge formability and global formability in laser-polished specimens compared to sheared specimens. The numerical predictions show both excellent agreement with the experimental force-displacement curves as well as strain fields.

This investigation focuses on determining the optimal concentration of multiwalled carbon nanotubes (MWCNTs) to enhance the compressive strength of pavement-grade high-volume fly ash (HVFA) concrete. The proportion of MWCNTs was systematically varied from 0% to 2% in 0.25% intervals, with the fly ash content held constant at 55% replacement. Experimental testing demonstrated that a 2% MWCNT dosage consistently yielded the highest compressive strength across all curing durations, reaching a maximum of 48.43 MPa at 90 days. 108 observations were recorded in the current study and was divided into training and testing sets for developing 11 different machine learning models: SVM with power, linear, and radial basis function (RBF) kernels; partial least squares (PLS); LASSO; Elastic Net; Ridge regression; gradient boosting machines (GBM); random forest (RDF); and neural networks. MWCNT dosage and curing age were used as input variable and compressive strength was the output variable. Model evaluation was conducted using parity and Taylor plots, alongside various statistical performance metrics. Among the eleven machine learning models evaluated, the SVM with radial basis function (RBF) kernel achieved the lowest test-set errors, with MAE = 0.70 MPa and RMSE = 0.87 MPa, outperforming Random Forest (MAE = 1.63 MPa, RMSE = 1.89 MPa) and Gradient Boosting models. Linear and regularized regression models showed notably higher errors (RMSE ≈ 4.5–4.7 MPa), indicating limited capacity to capture nonlinear strength development. To assess model generalization and reliability, regression error characteristic (REC) curves and area over the curve (AOC) values were also computed. Interpretability of the best-performing model was explored using partial dependence plots (PDPs), which showed that both MWCNT concentration and curing age positively influence compressive strength. Notably, curing age exerted a more substantial and nonlinear effect. Monotonicity analysis affirmed the model’s capability to reflect the steady increase in strength with prolonged curing, while the impact of MWCNT dosage remained comparatively consistent. Perturbation analysis revealed limited variation in predicted strength due to minor changes in MWCNT levels, contrasted with greater sensitivity to alterations in curing duration. Sensitivity analysis further emphasized curing age as the dominant factor driving compressive strength predictions in MWCNT-enhanced HVFA concrete.

In this study, the effects of lubrication mode, counter punch end face angle, and counterforce on the hydroforming of curved diagonal tee tube are investigated to address the wrinkling and rupture defects caused by structural spatial multi-directional asymmetry. The experiment uses a flexible punch with a 70° end face angle to offer counterforce and multi-directional differential lubrication to address the multi-directional asymmetry of the curved diagonal tee tube. By analyzing the friction forces in each zone, the best lubrication method is found. This results in a differential lubrication scheme where the ratio of the lengths of the left and right lubrication areas is the same as the ratio of the distances from the two ends of the tube blank to the axis of the branch tube, the lower bulging zone uses a MoS₂-PTFE combination lubrication, and the upper bulging zone is coated with PTFE film. By quickening the flow of material to the bulging zone, this technique avoids wrinkle faults at the branch tube’s bottom and lower bulging zone rupture. When compared to a 90° end face counter punch, the 70° end face counter punch greatly raises the branch height, hence minimizing rupture flaws and improving the forming effect. Furthermore, a counterforce of 4. 24 kN raises the branch height while preventing rupture at the apex of the branch caused by significant wall thickness thinning.

Material extrusion additive manufacturing technique faces challenges in products’ forming quality due to inherent limitations in polymer melt rheological property and interlayer bonding. This study introduces ultrasonic vibration-assisted machining (UVAM) to address these issues by actively modulating melt flow behavior and interfacial bonding mechanisms. A coupled theoretical framework integrating dynamic rheological properties (DRP) and bonding neck evolution (DBN) under ultrasonic excitation is established and validated by experimental analysis. Systematic parametric investigations reveal that UVAM significantly reduces key rheological parameters (i.e. pressure drop, apparent viscosity and shear stress), while enhancing bonding neck formation. With the increasing frequency or amplitude of UVAM, the effect is further strengthened.. The proposed theoretical model demonstrates UVAM’s potential to synergistically improve the melt flow behavior and interfacial bonding quality in material extrusion process.

Developing new technologies for producing long, deformed, industrial-grade semi-finished products from palladium-based alloys is a pressing need for high-value products that meet European quality and safety requirements. This study addressed the development of thermal deformation processing technology for producing rods and wire from new palladium-based alloys. The aim of the research was to develop energy- and resource-saving technologies for the thermal deformation processing of new palladium alloys to produce long, semi-finished jewelry and industrial products with high strength and performance properties. Two palladium alloys, patented by the authors, were selected for the study. The first is designed for the production of 0.3 mm diameter wire for jewelry chains, while the second is designed for the production of 0.5 mm diameter wire for contact manufacturing. A comprehensive study was conducted on these alloys using proprietary software and computer modeling to develop new reduction modes and processing routes for rolling and drawing processes. As a result, the characteristics of metal deformation, the stress-strain state were studied, and the force parameters of these processes were determined. It was established that the rolling force (92 kN) and drawing force (5 kN) are low, therefore the equipment load does not exceed permissible values. Moreover, the safety factor ηв for transitions for producing wire with a diameter of up to 0.5 mm is 1.7, which indicates high stability of the metal deformation process during drawing. Experimental studies were conducted to verify the modeling results, which confirmed the modeling results and made it possible to determine the strength properties and evaluate the metal structure during processing of the studied alloys. The level of strength properties of the metal (ultimate resistance σв) at maximum degrees of deformation of up to 92–98% is within the range of 829–847 MPa for the first alloy and 632–777 MPa for the second. This allows for the deformation of semi-finished products made from new palladium alloys without fracture, which is also confirmed by the Cockcroft-Latham index, which does not exceed the critical value of 1. Thus, comprehensive studies have been conducted that allow us to confirm that the developed technologies allow for the production of long semi-finished products in the form of rods and wires made from new palladium alloys with high strength and performance properties.

A double-wire median pulsed gas metal arc welding (GMAW) with a high-frequency pulse waveform was developed to study the influence of a high-frequency pulse on the droplet transfer process and weld formation in aluminum (Al) alloy. The droplet transfer process was recorded using a high-speed photography system. At the same time, the influence of a high-frequency pulse at the peak stage was investigated. The experimental results demonstrated that stable droplet transfer and continuous welds are obtained by incorporating high-frequency pulses. The high-frequency pulses increase electromagnetic force and facilitate premature detachment of droplets. Especially, at a high frequency of 20 kHz, one drop per pulse (ODPP) droplet transfer mode is achieved, which is the ideal mode. In addition, high-frequency pulses increase axial arc pressure, strengthen convergent flow, and reduce the effect of divergent flow, resulting in increased weld penetration while decreasing weld width and porosity.