Search Results (263)

Microstructural analysis of hot-compressed magnesium alloys is crucial for understanding the plastic formability of magnesium alloys during thermo-mechanical processing. Thermal compression tests and finite element simulations were conducted on a low rare-earth (RE) Mg-1.8Nd-0.4Zr-0.3Ca alloy. Multiple microstructural characterization techniques were employed to analyze slip systems, twinning mechanisms, dynamic recrystallization (DRX), and precipitate phases in the hot-compressed alloy. The results demonstrated that the equivalent strain distribution within compressed specimens exhibits heterogeneity, with a larger equivalent strain in the core. After thermal compression, the original microscopic structure formed a necklace-like structure. The primary DRX mechanisms comprise continuous dynamic recrystallization (CDRX), twin-induced dynamic recrystallization (TDRX), and particle-stimulated nucleation (PSN). Pyramidal slip and recrystallization constitute primary contributors to peak texture weakening and tilting. Mg₄₁Nd₅ and α-Zr phases enhanced dislocation density by impeding dislocation motion and promoting cross-slip activation. Hot compression provided the necessary thermal activation energy and stress conditions for solute atom diffusion and clustering, triggering dynamic precipitation of Mg₄₁Nd₅ phases. Full article

This article presents a study on symmetric cyclic torsion with the application of electric pulses and their effect on the formability of α-brass CuZn30 at room temperature. Preliminary tests were carried out using a conventional monotonic torsion test. The obtained results served as a reference for the subsequently conducted symmetric cyclic torsion tests. Then, under analogical deformation conditions, tests were conducted with the application of electric pulses featuring various parameters: different pulse durations and different periods, i.e., intervals between successive pulses. Microstructural studies of the deformed material were conducted, including examinations using a microscope equipped with an electron backscatter diffraction (EBSD) detector. Based on the results, it was found that the application of electric pulses during cyclic torsion tests consistently leads to a reduction in stress compared to cyclic torsion tests conducted at ambient temperature without current flow. In most cases, it also results in an increase in strain compared to tests without the application of electric pulses. The electroplastometric torsion tests carried out in this study within the bulk forming process are the first of their kind to combine cyclic torsion with electrically assisted forming (EAF). The proposed combination may lead to the development of new deformation methods in real manufacturing processes. Full article

430 stainless steel exhibits soft magnetic properties, excellent formability, and corrosion resistance, making it widely used in industrial applications. This study investigates the effects of different cold working rates on the properties of 430 stainless steel subjected to various magnetic annealing atmospheres (F-1.5Si, F-1.5Si-10%, F-1.5Si-40%, F-1.5Si-10% (MA), F-1.5Si-40% (MA), F-1.5Si-10% (H₂), and F-1.5Si-40% (H₂)). The results indicate that increasing the cold working rate improves the material’s mechanical properties; however, it negatively impacts its magnetic and corrosion resistance properties. Additionally, the magnetic annealing process improves the mechanical properties, while atmospheric magnetic annealing optimizes the overall magnetic performance. In contrast, magnetic annealing in a hydrogen atmosphere does not enhance the magnetic properties as effectively as atmospheric magnetic annealing. Still, it promotes the formation of a protective layer, preserving the mechanical properties and providing better corrosion resistance. Furthermore, regardless of whether magnetic annealing is conducted in an atmospheric or hydrogen environment, materials with 10% cold work rate (F-1.5Si-10% (MA) and F-1.5Si-10% (H₂)) exhibit the lowest coercive force (286 and 293 A/m in the 10 Hz test condition), making them ideal for electromagnetic applications. Full article

In response to increasing sustainability demands, the packaging industry is shifting toward paper-based alternatives to replace polymer packaging. However, achieving complex, three-dimensional geometries comparable to plastics remains challenging due to the limited stretchability of paper. This study investigates advanced preconditioning techniques to enhance the formability of paper materials for deep-draw packaging applications. A custom-built test rig was developed at Syntegon Technology GmbH to systematically evaluate the effects of ultrasound-assisted moistening and segmented radiative heating. Under optimized conditions, 2.67 s moistening, 70.00 °C punch temperature, and 2999 W radiation power, maximum stretchability increased from 13.00% to 26.93%. The results confirm the effectiveness of ultrasound in accelerating moisture uptake and radiation heating in achieving uniform thermal distribution across the paper substrate. Although prototype constraints, such as the absence of inline conditioning and real-time measurement, limit process stability and scalability, the findings provide a strong foundation for developing industrial 3D paper forming processes that support sustainable packaging innovation. Full article

The heating rates and forming temperatures during the hot forming process of titanium alloys cause significant differences in phase transformation, grain size, and dislocation evolution. The formability and service performance of titanium alloy formed components are affected by these factors. This study investigated the hot flow behaviors of Ti-6Al-4V at temperatures ranging from 800 to 900 °C and heating rates ranging from 0.1 to 10 °C/s. These were tested via Gleeble hot tensile experiments, and the grain size and phase evolution were quantitatively characterized via EBSD and XRD. The results suggest that a higher heating rate decreases the β-phase transformation and dislocation density and inhibits grain coarsening, leading to better formability. The heating rate was introduced into the viscoplastic constitutive model for the first time to achieve accurate predictions of the microstructure and hot flow behavior under different heating rates. The prediction accuracy of the hot flow behavior and phase volume fraction reaches 92.93% and 94.97%. The current-assisted hot stamping experiments and finite element (FE) simulations of Ti-6Al-4V irregular cross-section components were carried out at temperatures of 800 and 900 °C and at heating rates of 1 and 3 °C/s. The results show that the rapidly heated formed components exhibit better thickness uniformity and yield strength. The FE simulation guided by the optimized constitutive model has achieved a 96.96% and 92.76% prediction accuracy for the thickness distribution and β-phase volume fraction, respectively. Full article

In recent decades, the automotive industry has faced challenges around improving energy efficiency, reducing pollutant emissions, increasing occupant safety, and reducing production costs. To solve these challenges, it is necessary to reduce the weight of vehicle bodies. In this way, the steel industry has developed more efficient metal alloys. To combine vehicle mass reduction with improved performance in deformations in cases of impact, a new family of advanced steels is present, AHSS (Advanced High-Strength Steels). However, this family of steels has lower formability and greater springback compared to conventional steels; if it is not properly controlled, it will directly affect the accuracy of the product and its quality. Different regions of a stamped component, such as the flange, the body wall, and the punch pole, are subjected to different states of stress and deformation, determined by numerous process variables, such as friction/lubrication and tool geometry, in addition to blank holder force and drawbead geometry, which induce the material to different deformation modes. Thus, it is understood that the degree of work hardening in each of these regions can be evaluated by grain morphology and material hardening, defining critical regions of embrittlement that, consequently, will affect the material’s stampability. This work aims to study the formability of the cold-formed DP600 steel sheets in the die radius region using a Modified Nakazima test, varying drawbead geometry, followed by a nanohardness evaluation and material characterization through the electron backscatter diffraction (EBSD). The main objective is to analyze the work hardening in the critical blank regions by applying these techniques. The nanoindentation evaluations were consistent in die radius and demonstrated the hardening influence, proving that the circular drawbead presented the most uniform hardness variation along the profile of the stamped blank and presented lower hardness values in relation to the other geometries, concluding that the drawbead attenuates this variation, contributing to better sheet formability, which corroborates the Forming Limit Curve results. Full article

The aim of this work was to study the influence of temperature and strain rate on the formability and structure of C22 steel. This study was based on tensile and compression tests. In the case of the compression test, the study of the influence that the process parameters (temperature and strain rate) have on the nonuniformity of the deformation was taken into account. This work presents an experimental analysis of the effects of temperature and strain rate on the mechanical and structural properties of C22 mild steel. Uniaxial tension and compression testing at high temperatures (800 °C, 900 °C, 1000 °C, and 1100 °C) and strain rates 0.001 1/s, 0.012 1/s, and 0.089 1/s for tension and 6.35 1/s, 5.72 1/s, 4.67 1/s and, respectively, 0.106 1/s for the compression hammer and hydraulic press served as the foundation for the studies. Analysis was carried out on how temperature and strain rate affected yield stress, strain to fracture, hardness, and structural evolution. Additionally, the nonuniformity of the deformations obtained at various temperature and strain rate values was examined. The fracture behavior of C22 steel can be enhanced by raising the deformation temperature and lowering the strain rate. In the tensile tests, the study of stress and strain distribution and the variation in the normalized Latham–Cockroft failure criterion was performed by numerical simulation using FORGE^® NxT 4.1 software. Full article

Incremental sheet forming technology is finding increasing application in the production of components in many industries. This article presents the analysis of the formability of 0.68-mm-thick Zn-Cu-Ti alloy sheets during the single-point incremental forming (SPIF) of pyramid-shaped drawpieces. Basic mechanical properties of sheets were determined in a uniaxial tensile test. Formability tests were carried out using the Erichsen and Fukui methods. SPIF tests were carried out under the conditions of variable process parameters: tool diameter (12 and 20 mm), feed rate (500–3000 mm/min), tool rotational speed (250–3000 rpm), and step size (0.1–1.2 mm). The effect of SPIF process parameters on the value of basic mechanical parameters, maximum deviation of the measured wall profile from the ideal profile, limit-forming angle, and surface roughness of pyramid-shaped drawpieces was determined. It was found that increasing the step size resulted in a decrease in the value of the limit-forming angle. Both the step size and the tool rotational speed contribute to the increase of the maximum wall deviation. However, the use of higher feed rates and a larger tool diameter caused its reduction. Higher values of arithmetic mean surface roughness Ra were found for the outer surface of drawpieces. The use of a smaller step size with a larger tool diameter caused a reduction in the Ra value of the drawpiece wall. Based on the obtained results, it can be concluded that the Zn-Cu-Ti alloy demonstrates good suitability for SPIF when proper process parameters and sheet orientation are selected. An appropriate combination of tool diameter, feed rate, step size, and sample orientation can ensure the desired balance between dimensional accuracy, mechanical strength, and surface quality of the formed components. Full article

Magnesium (Mg) alloys are gaining widespread use in the automotive and construction industries for their potential to enhance performance and lower manufacturing costs, making them ideal for lightweight structural applications. However, despite these advantages, extruding Mg alloys remains technically challenging due to their inherently limited formability and the strong crystallographic textures that form during deformation. This study aimed to comprehensively characterize the ductile fracture behavior of ZM51M Mg alloy round bars under various stress states and to improve the reliability of ductile failure predictions through the application and calibration of multiple uncoupled damage criteria. Tensile and compressive tests were conducted on specimens of varying geometries (dogbone, notched R5, shear, uniaxial compression, and plane strain compression specimens) and dimensions, meticulously cut along the extrusion direction of the round bar. These tests encompassed a wide spectrum of stress–strain responses and fracture characteristics, including uniaxial tension, uniaxial compression, and shear-dominated states. An inverse analysis approach, involving iterative numerical simulation coupled with experimental data, was employed to precisely determine fracture strains from the test results. The plastic deformation behavior was accurately modeled using the combined Swift–Voce hardening law. Subsequently, three prominent uncoupled ductile fracture criteria—Rice–Tracey, DF2014, and DF2016—were calibrated against the experimental data. The DF2016 criterion demonstrated superior predictive accuracy, consistently yielding the most accurate fracture strain predictions and significantly outperforming the Rice–Tracey and DF2014 criteria across the tested stress states. The findings of this work provide significant insights for improving the assessment of formability and fracture prediction in Mg alloys. This research directly contributes to overcoming the challenges associated with their inherent formability limitations and complex deformation textures, thereby facilitating more reliable design and broader adoption of Mg alloys in advanced lightweight structural solutions. Full article

This work investigates the role of friction in the numerical prediction of formability for ultra-thin aluminum sheets made of the EN AW 8006-O alloy. Nakazima-type hemispherical punch stretching tests were conducted under lubricated conditions to assess the influence of interface tribology on thickness distribution and failure behavior. The experimental activity included tensile testing for material parameter identification and coefficient of friction (COF) measurements according to ASTM D1894 to characterize interface friction. These parameters were then implemented into a finite element model developed in PAM-STAMP. The simulation results were compared with experimental thickness profiles, and showed good agreement when calibrated friction coefficients were used. The analysis highlights the sensitivity of sheet deformation to frictional conditions, and demonstrates that accurate tribological input significantly improves predictive accuracy. The proposed workflow offers a reliable and efficient methodology for simulating forming processes involving ultra-thin aluminum foils, with potential applications in the food packaging industry. Full article

This study proposes a novel octagonal starfish-inspired roller imprinting control for multi-space and multi-axial microstructure replication, featuring a roller printing system with a controllable mold structure for multi-space and multi-axis applications. First, a microstructure was made and a micro mold was replicated to develop and simulate a negative Poisson ratio structure as a special structure to control the polymer microstructure mold. Meanwhile, a spatial axial roller imprinting system was designed as a roller imprinting replication system for the replication and roller imprinting of microstructures to research and conduct a roller imprinting testing experiment. The experiment results showed that the multi-space and multi-axial roll imprinting processing system with a controllable mold in this research had high replication formability. The results proved that the high replication formability of the microstructure obtained through white light scanning after subsequent roller imprinting was up to 98.75%. The diameter of the microstructure reached 99.025%, and the development of this innovative system and method of new technology could obtain the expected replication formability of the microstructure. Meanwhile, good achievements were obtained through optical preliminary validation. The results of this research could provide a reference about continuous microstructure component roll forming processing for academic and technological development. Full article

This study investigates how moisture preconditioning and thermal parameters affect the stretchability of paper in 3D forming, with the goal of extending geometric forming limits and enhancing process stability. Multidimensional tensile tests were performed on FibreForm Duo (310 g/m²) using a hemispherical punch. Key variables included water bath dwell time, punch temperature, and contact time, simulating industrial conditions in high-speed packaging. A short duration of water bath immersion (1–3 s) led to rapid moisture uptake (−20%), resulting in significantly improved formability. Compared to unconditioned samples, the maximum stretch increased by up to 3.5 percentage points. The process window identified (3.03 s dwell time; 70 °C punch temperature; 1.08 s contact time to punch) yielded a predicted stretch of 16.5%, representing a notable expansion of the material’s geometric forming capacity. Regression analysis (R² = 0.8946) confirmed the strong statistical significance of all parameters. Full article

Understanding the formability limits of thin-walled tubes with square cross-sections and L-section profiles is crucial for improving manufacturing efficiency and ensuring structural reliability in industries such as automotive and aerospace. Unlike the usually studied circular tubes, square tubes and L-section profiles geometries present unique deformation and fracture behaviours that require specific analysis. To address this gap, this research establishes a novel methodology combining digital image correlation (DIC) with a time-dependent approach and precise thickness measurements, enabling accurate strain measurements essential to the onset of necking and fracture strain identification. Two experimental tests under different forming conditions allowed capturing a distinct range of strain paths leading to failure. This approach allowed the determination of the forming limit points associated with necking and the fracture forming lines associated with crack opening by tension (mode I) and by in-plane shear (mode II). The findings highlight the strong influence of geometry on the fracture mechanisms and provide valuable data for optimizing tube-forming processes for square tubes and L-section profiles, ultimately enhancing the design and performance of lightweight structural components. Full article

Variations in the warm formability of AA7075 sheets are primarily attributed to differences in precipitate morphology resulting from distinct thermal histories. To better understand this relationship, this study systematically investigates the influence of precipitate characteristics—quantified by the product of precipitate volume fraction and average radius—on forming limits across various thermal routes in warm forming processes. A modified Cockcroft–Latham ductile fracture model incorporating this microstructural parameter was developed, calibrated against experimental data from warm isothermal Nakajima tests, and implemented within a finite element framework. The proposed model enables the accurate prediction of forming limit curves with minimal experimental effort, thereby significantly reducing the reliance on extensive mechanical testing. Building upon the validated FE model, a practical methodology for rapid R-value estimation under warm forming conditions was established, involving the design of specimen geometries optimised for isothermal Nakajima testing. This approach achieved R-value predictions within 5% deviation from conventional uniaxial tensile test results. Furthermore, experimental results indicated that AA7075 sheets exhibited nearly isotropic deformation behaviour under retrogression warm forming conditions. Overall, the methodology proposed in this study bridges the gap between formability prediction and process simulation, offering a robust and scalable framework for the industrial optimisation of warm forming processes for high-strength aluminium alloys. Full article

Due to the need for weight reduction in the automobile structure, effective and accurate forming is demanded to take advantage of ultrahigh-strength steels. Research on the deep-drawing formability of Usibor^®2000 has an important impact on the application of lightweight automotive bodies. The microstructure and formability of Usibor^®2000 sheets at different temperatures were investigated by the Swift test. The positive effects of increasing the temperature on improving the forming limit and forming quality of Usibor^®2000 were demonstrated by LDR results, thickness, and hardness measurement. The microstructure evolution of Usibor^®2000 steel plates under warm forming and hot forming conditions was discussed in terms of microstructure characterization and precipitate morphology. The phase composition of the sample deformed at 860 °C is analyzed by two-step etching metallographic analysis and numerical simulation, which provides a reference for the application of Usibor^®2000 ultrahigh-strength steel in automotive lightweight. Full article