International Journal of Material Forming最新文献

Robo-forming is a flexible version of Incremental Sheet Forming (ISF) that utilizes industrial robots to guide the forming tool along a desired trajectory on a blank surface. ISF is particularly suitable for rapid prototyping and low-volume production; however, the process is limited by a critical wall angle, beyond which the material fails by necking. Geometric shapes that exceed this critical wall angle have to be formed in multiple stages, adhering to the maximum limit of wall angle in each of the intermediate stages. Since the final outcome depends upon the intermediate shapes formed, it is essential to optimize the design of pre-form shape(s). The existing methods for multi-stage forming rely heavily on intuition and other heuristics for preform design. The current work proposes a frequency decomposition based approach using Fourier transform to generate preforms. The proposed multi-stage methodology presents a more standardized, algorithmic approach, ensuring an effective and reliable methodology that can be applied to any new complex shape. Experimental results demonstrate that the forming depth of the target geometries has improved significantly up to (235%) for the human cranial implant shape (a freeform shape) and by (155%) and (173%), respectively, for hemispherical and elliptical components compared to the case without preform, ensuring successful forming of the components without fracture.

Research results for the production of strips from a platinum‒rhodium alloy for the manufacture of spinneret feeders are presented. Using the author’s software, an analysis of the process of rolling strips of the investigated alloy with a thickness of 1 mm from a forged workpiece with a thickness of 28 mm, which is currently used in industrial conditions, was carried out. The number of rolling passes and the number of annealing steps decreased. Experiments for the process of cold sheet rolling of strips from the platinum‒rhodium alloy were carried out. The proposed compression mode was tested under industrial conditions, and it was found that for the studied process of cold sheet rolling of a platinum‒rhodium alloy, it is possible to increase the unit degree of deformation to 0.3–0.4 mm, which leads to a decrease in the fractional deformation, a decrease in the number of anneals and passes in the absence of strip destruction.

Galvanized steel has been widely used in industrial fields such as automobiles, ships, and household appliances. Due to its anti-corrosion properties, galvanized steel samples have lower corrosion rates and toughness losses. Therefore, using galvanized steel sheets is an effective way to improve the quality of welded joints. Nowadays aluminum alloy is gradually replacing steel as the raw material for industrial products due to its lightweight and corrosion-resistant properties, aluminum alloys have disadvantages in terms of cost and mechanical properties. Multi-material structures in industrial products (especially in automotive components) to fully utilize the advantages of steel and aluminum alloys. There are many ways to achieve steel/aluminum dissimilar metal connections. Due to the high welding temperature and poor welding environment, a high volume fraction of Al-Fe-Si intermetallic compounds precipitates at the welding interface, resulting in higher hardness at the welded joint and strong local corrosion. High-speed impact welding can effectively avoid these problems. At low welding temperature and high impact speed, minimal metal melting occurs at the interface while the base material deforms in solid state, forming a characteristic wavy bond morphology. Therefore, the coating will affect the morphology and component content of the welding interface during the impact joining process. In this paper, the effects of Zn coating on the welding interface will be investigated and the joint interface formation process will be clarified by using a method that combines numerical simulation and experiment, in order to instruct the processing design.

The Single Point Incremental Forming (SPIF) technique has received considerable recognition for its improved formability, versatile process capabilities, and diminished forming forces. Nevertheless, its widespread industrial adoption remains limited due to challenges in accurately predicting fracture during forming. This study addresses these challenges by examining the formability and damage mechanisms of a ferritic steel matrix composite reinforced with TiB₂ ceramic particles. By leveraging advanced materials and computational methods, our research focuses on optimizing the SPIF process for these composites, renowned for their exceptional mechanical properties. We analyze three critical process parameters—blank thickness, forming tool diameter, and wall angle of the cone—to evaluate their influences on deformation mechanics and process performance. Numerical simulations generate response surfaces to optimize forming parameters, focusing on punch force, equivalent plastic strain, Von Mises stress, and final forming depth. Employing a desirability function approach, we tackle this multi-objective optimization, providing a robust framework for parameter selection. This study demonstrates the potential of TiB₂-reinforced steel matrix composites in advanced forming applications and highlights the optimal SPIF conditions for achieving superior formability while minimizing damage. The findings offer valuable insights for industries working with innovative composite materials and advancing manufacturing efficiency.

Magnesium alloys are known for their poor plasticity at room temperature, making them difficult to form. Typically, heating is required to enhance their formability. However, even heat-assisted forming has limitations when it comes to improving the quality of the formed components. To further enhance the forming quality of magnesium alloys, this study explores the use of vibration in conjunction with heating, specifically through a multi-pass incremental forming process for magnesium alloys under combined thermo-vibratory effects. The research integrates thermal-vibration parameters with forming process parameters for comprehensive analysis. Initially, orthogonal experiments were conducted to examine the influence of different thermal-vibration parameters, such as temperature, vibration frequency, and amplitude, on the wall thickness and geometric accuracy of the workpiece. This analysis led to the determination of an optimal combination of thermal-vibration parameters. Subsequently, under these optimal thermal-vibration conditions, the effects of single-process parameter variations, including inter-pass angle, tool diameter, and layer spacing were examined, and their interactions on forming quality. Experimental validation confirmed the accuracy of the simulation model used in this research. The results revealed that the optimal thermal-vibration parameter combination consists of a forming temperature of 250 °C, a vibration frequency of 30 kHz, and an amplitude of 0.01 mm. Under these conditions, the minimum wall thickness of the workpiece improved by 3.24%. Furthermore, among the process parameters, the inter-pass angle had the most significant impact on forming quality, followed by the tool diameter, while layer spacing showed the least influence.

This study investigates the influence of natural aging on the formability and plastic deformation behavior of AA 2198, a third-generation Al-Li alloy, under W-temper conditions to address its low formability. Mechanical tests, including uniaxial tensile, bulge, and Nakazima tests, were performed to evaluate the evolution of mechanical properties, anisotropy, and formability during natural aging. A phenomenological hardening model was developed and validated through yield surfaces and finite element simulations, incorporating insights from forming limit tests. During natural aging, yield strength and ultimate tensile strength increased, while elongation decreased. Natural aging was completed within 7.6 days, with solute and precipitation strengthening identified as primary mechanisms. Anisotropy appeared during early natural aging but remained stable, attributed to the aluminum crystal structure and rolling-induced crystallographic texture, independent of natural aging effects. The proposed hardening model effectively predicted the evolution of yield strength, anisotropy, and formability across natural aging conditions. The forming limit curve for natural aging at 0.5 h was significantly higher than other conditions, demonstrating enhanced formability through W-temper heat treatment. Finite element simulations and forming tests revealed that natural aging at 0.5 and 6.0 h supported stable forming, with natural aging at 6.0 h offering optimal thickness distribution and safety margins. Beyond 24.0 h of natural aging, formability diminished significantly due to wrinkling and fractures. This study highlights the utility of the hardening model and numerical framework as efficient virtual tools for optimizing the W-temper forming of aerospace components.

Hydroforming is an advanced technology that enables integrated forming for complex components and promotes lightweight construction and high reliability. However, the hydroforming process can result in a strain gradient at the wall thickness of tubes, which directly determines the deformation order in the thickness and is closely linked to the occurrence of defects like springback and wrinkling of tubular components. In this study, a geometric model of tube hydro-bulging that considers wall thickness was established, and the effects of length-diameter and diameter-thickness ratios on the radial strain gradient were studied through theoretical analysis and numerical simulations. Higher strains are experienced on the inside and lower on the outside during tube bulging. The strain disparity increases with greater length-diameter ratios and decreasing diameter-thickness ratios. In the case of a tube with an outer diameter of 78 mm and a wall thickness of 4 mm, the maximum equivalent strain difference observed was 0.03. Additionally, a tube hydro-bulging test was carried out to confirm the microstructural gradient, with high-density dislocations concentrated near the inner surface, resulting in noticeable strain localization. This study reveals the radial deformation mechanism of hydroformed tubular components, essentially providing a reliable scientific basis for controlling defects in tubular parts.

In this study, a finite element simulation strategy was developed to analyze the green tire building process, with the goal of identifying existing defects and guiding the refinement of process parameters. The mechanical behaviors of uncured rubber in various tire components were investigated through cyclic loading and unloading experiments conducted at two different strain rates. A viscoelastic constitutive model was adopted to describe the nonlinear elasticity and hysteresis effects of uncured rubber under large deformation. Then the finite element models including a two-dimensional (2D) axisymmetric model for lamination step and a three-dimensional (3D) model for the remaining building steps were constructed to simulate the whole process. The green tire cross-section profile obtained from simulation is in good agreement with the actual one obtained through 3D scanning, thereby verifying the reliability of the simulation. Additionally, the deflection angle of cords was simulated and verified through green tire cutting experiments. Finally, factors affecting cord deflection were identified, including an intrinsic factor (radial displacement) and an extrinsic factor (deflection angles of nearby cords). Two improvement measures, reducing the radial displacement of cords and the influence from nearby cords, were proposed to reduce the misalignment of the carcass cords, and the effectiveness of measures was validated by simulation.

Friction stir welding (FSW) is a renowned joining technology for creating difficult-to-be-welded or non-weldable dissimilar material joints engendering viscoplastic flow at the interface. The present work compares the evolution of the material flow and properties during FSW of extremely different materials, viz., Aluminum alloy 6156 and commercially pure Ti Grade 2 with the help of numerical simulation and practical. The necessity of the appropriate heat flux to be achieved through balancing parameters was realized through simulation and experimental outcomes. In this paper, a specialized numerical model specifically designed to account for the presence of two distinct alloys, was employed to examine the effects of process parameters on temperature distribution, strain distribution, and material flow through velocity vectors. Valuable insights relating to material flow patterns observed while altering the mutual skin stringer positions have been elaborated. Macrostructural and microstructural characterizations were carried out to understand the localized material microstructural evolution comprising grain refinement, intermetallic, defects, etc. The parametric influence on grain morphologies, intermittent phases, joint strengths, and hardness are discussed in depth. Interestingly, the joint strength values recorded for prepared T-joints are comparable with the ones found for butt joint configurations reported in the literature.

Thin-walled 304 stainless steel tubes with annular inner ribs have high strength, high stiffness, and light-weighting characteristics, and have wide applications in the aviation, aerospace, and navigation fields. In this study, stainless steel thin-walled tubes with inner ribs were manufactured by hot power backward-spinning. The microstructural morphology, microhardness, and main texture evolution of typical regions of the tube were characterized and tested. The influence of different stress-loading conditions on the microstructure and mechanical properties of the tube was mainly studied. The numerical simulation for the hot spinning forming process of 304 stainless steel was carried out to analyze the material flow rules in the regions of inner rib and wall-thinning, as well as predict the height of inner ribs with different spinning parameters. The results showed that the thinning of the wall of the tube region is obvious, and the material in the inner rib region fills into the groove of the mandrel, and the loading paths of stress on the materials in these regions are different, and the wall-thinning region is subjected to axial and radial loads accuring plane strain, which leads to the transformation from the original equiaxial crystalline to elongated grains. The microstructure of the sample presented strong < 111>//AD texture for the reason of acutely axial load born from rotating tools during spinning. This study provides a reliable theoretical basis and technical reference for the optimization of the spinning forming process of stainless steel thin-walled tubes with annular inner ribs.

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