International Journal of Material Forming最新文献

Ceramic fused filament fabrication (CF3), a type of ceramic additive manufacturing technology, uses ceramic powder/polymer composite filament as raw material to fabricate densified ceramic parts through shaping-debinding-sintering (S-D-S) process, and it owns broad application and development prospects. However, the existing study on the static mechanical properties of CF3 parts is still in the basic stage, lacking comprehensiveness and systematicity. In this paper, self-made zirconia/polymer composite filament with a five-component binder system was developed, and the ME equipment was used to shape the green specimens with different processing parameters (layer thickness, solid loading and infill angle) in order to verify the formability of the composite filament; They were then debinded and sintered using the box sintering furnace so as to obtain the sintered CF3 specimens; Finally, experimental studies on their physical and static properties were carried out to investigate the effects of processing parameters. The results showed that increasing the solid loading of zirconia significantly reduced the dimensional shrinkage of the sintered specimens; When the layer thickness increased from 0.2 to 0.3 mm, the compressive strength decreased from 358.66 to 213.40 MPa, and the bending strength decreased from 456.01 to 293.12 MPa; When the infill angle increased from 0° to 90°, the bending strength of the specimens decreased from 456.01 to 120.08 MPa; The Vickers hardness of the sintered specimens was independent, and it has the characteristic of isotropy.

Flexible skew rolling (FSR) of hollow shafts with a mandrel represents a novel near-net-forming technology for hollow shafts. Surface quality, particularly the presence of spiral mark defects, poses a significant challenge in achieving precision forming. In this paper, the formation mechanism of spiral marks of hollow FSR shaft with mandrel was studied through experimental methods and finite element (FE) simulations, and the morphology of spiral marks under different rolling parameters is analyzed. Our findings indicate that the initiation of spiral marks occurs at the point where the rolled piece separates from the rolls. The outer spiral marks are attributed to the mismatch between the radial and axial metal flow; when the rolled part separates from the rolls, the metal that has exited the rolls is influenced by the deforming metal still within the rolls, resulting in an accumulation of excess material that takes on a spiral shape, mirroring the profile of the rolled piece. The intensity of spiral marks increases with higher swing angles, greater reduction ratios, and larger mandrel diameters, while decreasing with an increase in relative wall thickness. The spiral mark defect could be mitigated by extending the sizing section length, incorporating the unloading fillet and selecting appropriate rolling parameters. When the roll sizing length increased from 20 to 30 mm and the unloading fillet is set at 5 mm, the depth of spiral marks was improved by 21.8%. The results elucidate the causes of spiral marks on hollow shafts produced by FSR with a mandrel and provide theoretical guidance for selecting process parameters in production applications.

Incremental sheet metal forming (ISF) process is an established agile forming method wherein the blank of the sheet metal is deformed into a preferred geometric by the sequence of bit-by-bit local deformation produced by the forming tool. There is no need for a die to shape the sheet metal, which is the principal strength of this process. The review made on the ISF process and particularly the different deformation mechanisms that are generated on the sheet metal during the ISF process are discussed broadly in this paper. The effects of this deformation mechanism on the ISF process are also discussed. The recent developments in ISF processes, such as Heat Assisted ISF process, Water Jet ISF process, Electromagnetic ISF process for sheet metals and Multi-stage ISF process, are also discussed in detail. Each of these processes possesses its distinct merits and demerits which are also listed. The ISF process is performed on different materials that were also discussed.

A crystal plasticity model that can describe the complex work-hardening behavior and a homogenization method that is both accurate and computationally inexpensive are required for crystal plasticity-based sheet metal forming simulations. This study investigated several crystal plasticity models and homogenization methods for linear and nonlinear strain paths. In the experiments, the work-hardening behavior of an A5083-O sheet was measured under reverse and cross loadings. The anisotropy of the flow stress and plastic strain path was also measured in uniaxial tension and biaxial stress tests. The biaxial stress test included tension–tension and tension–compression combined stress states. The experimental and simulation results showed that the proposed crystal plasticity model accurately predicted the work-hardening behavior and texture evolution of the specimen. Furthermore, the two-grain cluster-type homogenization method captured the plastic anisotropy of the specimen as accurately as the finite element-based homogenization method. The computational speed of the two-grain cluster model was approximately 250 times faster than that of the finite element-based homogenization method. Therefore, the two-grain cluster model in conjunction with the proposed crystal plasticity model is an effective approach to predict the plastic behavior of polycrystals in large-scale sheet metal forming simulations.

Compared with traditional smelting technology, the GH4068 alloy prepared by electron beam smelting layered solidification technology (EBS-LST) has a more uniform microstructure and lower microsegregation. To further optimize the as-cast microstructure of GH4068 alloy, the element volatilization, microstructure and microsegregation of GH4068 alloy prepared by EBS-LST of different second layer smelting powers were studied. The experimental results show that element volatilization gradually aggravates with the increase of smelting power, and the volatilization of Cr element is the most obvious. By analyzing the cross-sectional microstructures of ingots, it is found that the dendrite zone gradually reduces, while the cellular dendrite zone and cellular structure zone gradually increase with the increase of smelting power. The secondary dendrite arm spacing of ingots with the smelting power of 10 kW, 12 kW and 14 kW are 55.9 μm, 48.1 μm and 42.1 μm, respectively, which are all smaller than the ingot prepared by traditional duplex melting is 65.8 μm. The microsegregation of ingots in the dendrite zone is the most serious, and the size of precipitated phases in the cellular structure zone is the biggest. Therefore, considering the above experimental results, this paper believes that 12 kW is the better second layer smelting power.

Predictive simulations of the press forming process for thermoplastic composites are invaluable tools for designing tool geometry and determining processing parameters. Ensuring the reliability of these simulations requires thorough validation, which can be challenging due to the wide range of possible geometries and the time and costs associated with obtaining validation data. This study presents and interprets press forming results for thermoplastic composites, with a specific focus on their application to simulation model validation. Experiments were conducted by forming blanks made from two unidirectional fiber-reinforced thermoplastic composite materials over a dome-shaped geometry. By varying the blank width and layup, the deformations and wrinkling behavior were systematically influenced. It is demonstrated that a careful selection of the forming conditions enables targeted analysis and validation of individual deformation mechanisms, including in-plane shear, bending and interply friction. Finally, a structured strategy is proposed for using these experimental results to validate forming simulations, offering an approach to evaluate the used constitutive models.

Die cast is a promising metal forming process that could potentially replace powder metallurgy for producing high Sc-contained Al-Sc sputtering targets. However, die cast of Al-Sc alloys with Sc contents more than 2 wt.% are not yet investigated. This work optimized the die-casting process parameters of Al-Sc alloys based on the air entrainment ratio and shrinkage porosity through numerical simulation and explored the microstructure and mechanical properties of Al-Sc die castings with Sc contents of 2 wt.%, 5 wt.%, and 10 wt.% by experiments. The results show that the influence weighting of parameters on defects is die temperature > pouring temperature > injection velocity, and the optimum parameter combination is pouring temperature of superheat of 60 ℃, die temperature of 240 ℃, and injection velocity of 3 m/s; The solidification structure of Al-Sc die castings comprised equiaxed grains, deformed and partially fragmented columnar grains, and uniformly distributed Al₃Sc precipitates. An increase of Sc content led to grain refinement and a rise in the size and volume fraction of Al₃Sc precipitates. The elongation and tensile strength of Al-Sc die castings were significantly higher than those of gravity castings, whereas these properties diminished with increasing Sc content.

A multilevel analysis of deformation and structure formation processes was carried out on powdered iron aluminide products obtained by different DPF technological schemes. At the macroscopic level, the analysis was carried out using rheological models of porous body compaction. The compaction curves are conventionally divided into three stages: at the first stage, the deformed volume decreases due to the deformation of the holder, at the second stage—due to the compaction of the porous workpiece, at the third stage—due to the plastic deformation of the dense workpiece realized due to the formation of a flake. When the compaction temperature and deformation pattern change, the staged compaction is maintained. At the meso level, the distribution of stresses and strains in the moulds and the kinetics of their changes during compaction were analysed by the finite element method. To predict the effect of structural changes on the complex of physical and mechanical properties, local processes of structure formation are analysed. It was established that the effect of porosity on electrical resistance and yield strength should be determined by the volume content of pores, consider planar pores, which are a characteristic feature of hot forging powder technology. During the strength analysis, special attention is paid to the areas around the triple joints, where defects of the maximum size are formed. The fracture toughness parameters and fracture pattern are sensitive to the presence of segregation clusters in the boundary region.

In the cutting process of nickel-based superalloy (Inconel718), the cutting deformation is complicated, forming sawtooth chips, and the study of its deformation mechanism has always been a hot issue in the academic circle. Numerical simulation provides an effective analytical means for in-depth understanding of the cutting process, but the current simulation methods still have some limitations in terms of cross-scale simulation ability. The dislocation evolution and deformation process in the cutting deformation of Inconel718 are still not well understood. In this paper, we propose a cross-scale material plasticity deformation simulation framework in which three-dimensional discrete dislocation dynamics (3D-DDD) coupled with base dislocation density (BDD) equations. Finite element simulations were performed by this simulation framework to study the stresses, strains, cutting forces, and temperatures during machining, as well as the microstructure evolution under different cutting conditions, such as grain size and dislocation density distribution evolution. In the process of cutting Inconel718, high-density dislocation movement and grain refinement mainly occur in the primary deformation zone and the second deformation zone, and the grain refinement degree of the machined surface is relatively weak. With the progress of cutting, the average grain size of chips is significantly smaller than that of the workpiece matrix, and the grain refinement in the chip shear zone is the most obvious. Strain rate plays a leading role in grain refinement. At the same time, due to the temperature rise, thermal softening occurs, grain deformation and dislocation accumulation in the shear zone cause cracks and holes, and accelerate the formation of sawtooth chips. Through experiments and simulation, the deformation mechanism of nickel-based superalloy is demonstrated, which further promotes the understanding of the microstructure evolution of Nickel-based superalloy during high-speed cutting.

The objective of this study is to propose a bulged bottom process as a means of reducing the amount of springback from a U-shaped channel in advanced high-strength steel sheets. The recently proposed method is based on the U-bending process, but it employs modified tooling, specifically a punch head with a shallow groove and a bottom die plate with a bulgy shape. Two distinct types of steel sheets, each exhibiting an ultimate tensile strength of 980 MPa and a thickness of 1.2 mm, were subjected to investigation. The efficacy of the process in reducing springback was examined by comparing it to the springback observed in the conventional U-bending process. A finite element analysis was conducted to evaluate the proposed processing technique, considering the effects of plastic anisotropy and the elastic modulus degradation with increased plastic deformation. Furthermore, the anisotropic hardening law was employed to account for the Bauschinger effect and the associated strain hardening behavior during loading path changes. The results of the experiments and simulations were evaluated and examined to gain insight into the effect of anisotropic hardening on springback under specific loading conditions and to interpret the mechanisms of springback reduction.