International Journal of Material Forming最新文献

As cast whisker-reinforced Al matrix composites are prone to cracking in subsequent forming processes due to numerous micro defects and poor formability, which limits their application. This work investigates the healing effects of current-assisted rolling and upsetting on cracks and micropore defects in a 6061Al composite reinforced with a total of 20 vol% (SiCw and Al₁₈B₄O₃₃w), as well as the impact on the mechanical properties. The thermal compression behavior of the 20 vol% (SiCw + Al₁₈B₄O₃₃w)/6061Al composite was also analyzed systematically to investigate their thermal deformation characteristics. The results show that the combination of current with upsetting and rolling can improve interfacial adhesion between the matrix and the reinforcement phase, reduce internal micropores and microcracks, and increases the density of the composite to 1.009 and 1.053 times that of the die-cast state, respectively. The fracture mode partially transitions to ductile fracture, while the composite’s ultimate tensile strength increases by up to 101.63%. The formation of a high-temperature, high-pressure coupled field leads to crack closure is the main reason for defect healing in current-assisted forming processes. This work provides insights into solving the problem of poor formability of as cast whisker-reinforced Al matrix composites.

Advanced high-strength steels, particularly dual-phase (DP) steels like DP1000, are widely used in the automotive industry due to their exceptional strength and ductility. However, DP steels are sensitive to edge cracking caused by damage and edge surface roughness from conventional cutting processes such as punching. Laser-polishing has emerged as a technique to enhance edge quality by melting and reshaping the material, potentially improving formability. This study aims to investigate the enhanced formability of DP1000 steel achieved through laser-polishing using a multi-scale simulation approach. Hole expansion tests were conducted on DP1000 steel samples with varying edge profiles: punched and laser-polished edges with different geometries. Surface roughness profiles were characterized using white-light confocal microscopy. The modified coupled Bai-Wierzbicki damage model is used in the numerical calculations. Considering the effect of surface roughness, a surface factor is applied in the proposed damage and fracture locus to characterize the material behavior more accurately. Multi-scale FE simulations combined macroscopic modeling of the hole expansion test and microscopic modeling that incorporated actual surface roughness profiles. The numerically predicted force–displacement curves and hole expansion ratios for punched and laser-polished specimens align well with the experimental results. The inclusion of the surface factor in the MBW model effectively captured the influence of surface roughness and microstructural transformations on the material's formability.

Biomedical titanium alloys provide a unique mix of favorable biomechanical and biocorrosion characteristics and are lightweight, non-toxic, and highly biocompatible. These qualities make them highly desirable for the fabrication of medical implants. Hot working methods are crucial in producing titanium components as they break down the lamellar microstructure into a finer structure. This phase is essential in shaping the final microstructure and determining the qualities of the components. This review delved into the hot deformability, phase and microstructural evolution, and related constitutive equations used in biomedical titanium flow stress modelling. It describes the counteractive effect of the dynamic recrystallisation (DRX) and dynamic recovery (DRV) deformation mechanisms on the working hardening behaviour of the biomedical titanium alloys after hot deformation processing. It also discusses the effect of forming necklace structures and lamellar kinking structures. Notably, in biomedical titanium alloys, the hot deformation behaviour and dynamic softening effect are significantly influenced by the alloy composition and microstructural characteristics like dislocation movement and grain boundary diffusion. The use of processing maps to identify the instability regime—which includes cracks, flaws and flow instabilities that may arise as the biomedical titanium alloys are undergoing hot processing and to ascertain the best processing conditions is covered in the article. Finally, the article's conclusion includes suggestions for possible future research directions.

Forming small to medium composite parts with complex geometries presents significant challenges to engineers, primarily due to material-induced, in-process defects such as fibre bridging and wrinkling, leading to poor mould conformity. These issues are characteristic of continuous fibre preforms and the inextensibility of the fibres. HiPerDiF (High Performance Discontinuous Fibre) technology is a novel manufacturing technique to produce high-performance, aligned discontinuous fibre pre-preg materials. This study investigates the forming characteristics of prepreg manufactured using the HiPerDiF method, highlighting its viability for complex part manufacture where mould conformity is critical. Additionally, a previously developed finite element (FE) model, able to predict the behaviour discontinuous fibre preforms during double diaphragm forming (DDF), was used to obtain insights into the experimentally observed material deformation. The results demonstrated the advantage of the enhanced formability of the HiPerDiF preform, owing to its stretchability in the double-diaphragm vacuum forming process. The FE simulations were shown to be a powerful tool to gain understanding of preforms deformation and thickness variation which are otherwise difficult to measure experimentally.

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In this paper, a new method of the cogging process of a forging (type: shaft) consisting in the application of the multi-stage process composed of a preparatory shaping on three different kinds of convex anvils, and also in a primary forging on the flat anvils and the asymmetrical V-shaped ones, is presented. The new, implemented method of forging was subjected to tests in the aspect of the formation of conditions favourable for the location of the maximum values of effective strain in the particular zones of the forging being deformed whereas simultaneously marked by the absence of tensile stresses. That renders it possible to develop a scientific foundation for the development of the rational technology of the cogging process. The effective geometrical parameters of new convex anvils were determined, and the efficiency of different applied technological parameter was analysed, in the aspect of the intensity of the re-forging of the particular zones of an ingot. The investigations were complemented by prognosing the formation of ductile fractures in the course of forging with the application of the Normalized Cockcroft and Latham criterion. The analysis of the spatial strain state and stress was conducted with the application of the finite element method and of the DEFORM-3D software. The comparison between theoretical outcomes, and the outcomes of experiments, within the scope of the investigation indicates a good level of their commensurateness.

Laser forming (LF) is an advanced non-contact manufacturing technique that utilizes laser energy to induce controlled thermal expansion and plastic deformation in metal sheets, enabling the shaping of high-strength and brittle materials with minimal residual stresses. The effectiveness of LF is governed by three primary mechanisms Temperature Gradient Mechanism (TGM), Buckling Mechanism (BM), and Upsetting Mechanism (UM)) which are influenced by process parameters such as laser power, scanning speed, beam diameter, and material properties. This review presents a comprehensive overview of recent advancements in LF, beginning with an analysis of the governing deformation mechanisms and their role in achieving precision and control. It then explores critical microstructural changes including grain refinement, phase transformations, and heat-affected zones (HAZ) that directly impact material behavior and performance. Building upon these foundational aspects, the article highlights current innovations in LF process enhancement through machine learning (ML)-based optimization, real-time thermal feedback, and adaptive control strategies. Challenges such as edge effects, residual stresses, and process repeatability are discussed, along with mitigation approaches Like forced cooling and adaptive scanning. Experimental findings show that forced cooling can increase the bending angle by up to 35.2% and improve energy efficiency by 22.14%. The review Further examines the application of computational models such as ANNs, SVMs, and GAs in predicting bend angles and optimizing process parameters. ANN-based models, for instance, have achieved prediction accuracies of up to 98.9%. The AI tools offer a holistic perspective on future research directions aimed at enhancing process sustainability and broader industrial adoption.

This study systematically investigated the mechanical hammer forming of 7075 aluminum alloy driven by a voice coil motor through experiments and simulations, focusing on the effects of hammering force, offset distance, and thickness on forming behavior and surface quality. Parameter optimization, theoretical modeling of stress–deformation, stress relaxation analysis, and multi-contour plate forming were also explored. Results showed that increasing the force from 35 N to 65 N raised the maximum arc height by 53%, extending the offset distance from 1 mm to 1.6 mm increased it by 29%, and raising thickness from 2 mm to 5 mm yielded a 110% rise, identifying thickness as the dominant factor. Surface waviness and roughness were strongly influenced by force and offset distance but only slightly by thickness, with higher force and smaller offset distance leading to poorer quality. Offset distance most affected surface hardness, while thickness had the least influence. A BP neural network optimization identified optimal parameters (55 N, 1.2 mm, 3 mm) balancing deformation and surface quality. Furthermore, an arc height model was established to correlate residual stress redistribution with deformation, and stress relaxation was described using an exponential decay model with extracted relaxation time constants (τ). Finally, multi-contour plate forming was demonstrated through trajectory design, providing a reference for correcting deformed thin-walled parts.

This study investigates the effects of laser power, welding speed, and welding current on melt pool fluid dynamics, Keyhole stability, and porosity by developing a multiphysics coupled numerical model and validating it with high-speed imaging experiments. A single-variable controlled experimental design was employed to address porosity defects encountered in the laser-TIG hybrid welding of 12 mm-thick Invar steel. The study found that increasing the laser power from 4 kW to 6 kW significantly raises the Keyhole collapse frequency and porosity. This is attributed to the increased recoil pressure and melt pool depth, which hinder bubble escape. Increasing the welding speed from 0.008 m/s to 0.05 m/s reduces porosity by enhancing the melt pool’s kinetic energy, which offsets interfacial forces, and by lowering heat input to Maintain Keyhole stability. Welding current exhibits a nonlinear effect on porosity, In the range of 100 A to 150 A, electromagnetic forces enhance melt pool stability and extend solidification time, promoting bubble escape. However, when the current increases from 150 A to 225 A, excessive heat input leads to local overheating and intensifies Keyhole instability. Finally, 1,000 frames of keyhole morphology during the stable stage were extracted, and analysis of keyhole collapse frequency was conducted to reveal the influence of welding parameters on porosity.

In this research, the simulation and experimental control of crown formation in the rolling process of ultra-thin silver strip is comprehensively investigated, which is crucial for the applications in high-voltage circuit protection, particularly in new energy vehicles. The objective was to identify key factors influencing crown formation and develop control strategies to ensure product quality and consistency. A finite element model was constructed to simulate the fourteen-stand rolling mill system, integrating static and dynamic analyses to evaluate the rolled crown value under various process parameters. The simulation results were validated against actual rolling data, confirming the model’s accuracy. Factors affecting crown formation were identified through simulation and analysis, including reduction per pass, friction coefficient, lateral displacement of intermediate rolls, strip entry position, input strip crown, material strength, strip width, and entry/exit tension. Empirical formulas were derived to predict crown values based on these parameters, providing a scientific basis for process optimization. Optimization recommendations included adjusting intermediate roller lateral displacement, annealing before the final rolling pass, selecting narrow strip, implementing progressive reduction per pass and controlling strip entry position. An experimental investigation validated the simulation findings, Maintaining thickness tolerance within a stringent standard of less than 1 micron, demonstrating the feasibility of ultra-high precision rolling for silver strips. In conclusion, this study significantly contributes to the understanding and control of crown formation in ultra-thin silver strip rolling, offering a scientific basis for optimizing the rolling process and improving product quality. The research outcomes are expected to influence the development of advanced rolling technologies and the manufacturing of high-performance strips for various industries.