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Roll forming is increasingly used in the automotive industry for the manufacture of structural and crash components from ultra-high-strength steel (UHSS). Springback and end flare are common shape defects in roll forming and increase with material strength. The conventional roll forming process is limited to the manufacture of components with a uniform cross section while flexible roll forming can produce parts with variation in width and depth. In this paper, the flexible roll forming of an automotive component from three different high-strength sheets of steel is investigated. The experiments are carried out with a flexible roll forming prototyping facility and combined with finite element analysis. The study shows that the flexible roll forming of high-strength automotive components is possible. Springback and end flare depend on the material strength and the forming sequence and can be reduced with a flexible forming approach where the material is first overbent followed by bending back. Wrinkling of the flange was observed but the severity of wrinkling reduced with an increasing number of forming passes.

With the advantages of continuous bending, small bending diameter, and variable curvature, the spatial variable curvature (SVC) bent metallic tube (MT) is widely used in the aeronautics industry. Due to the complex characteristics of its central axis, SVC MT bending is prohibitive in terms of modeling and analysis, which results in a rather high calculation complexity. The springback is the primary detection that directly affects the axial forming accuracy. To achieve higher forming accuracy, this paper provides a numerical approximation springback prediction and compensation method considering cross-section distortion for SVC MT. The curvature and torsion mapping function of MT central axis before and after springback is constructed. According to the characteristics of different SVC MT, the differential equations in the SVC springback prediction model are solved by using three numerical approximation methods. The springback compensation method is subsequently obtained by inverse operation of the mapping relationship. To verify the feasibility of the proposed method, a 00Cr17Ni14Mo2 tube is bent with a multi-roll bender into the spiral shape. The results of the three springback numerical approximation methods and the numerical simulation result are compared. It illustrates that the Runge–Kutta method owns the highest prediction accuracy, so that we choose the Runge–Kutta method for bending compensation. The result indicates that the position deviation of each node is less than 1.4% along with the average position deviation of 0.80% after springback compensation.

Sheet springback and structural deformation of the folding mechanism are key issues in the sheet metal–forming process. Elastic-plastic bending theory and numerical simulation are applied to study the forming performance of sheet metal. First, a springback prediction model under general assumptions is established, based on the constitutive relationship of the elastic-plastic linear hardening material. In addition, the influences of processing parameters, such as sheet thickness and forming angle on springback, are analysed according to the theoretical model and verified by experiments. Then, a laser tracker is used to acquire the folding trajectory, and the structural deformation of the folding mechanism is confirmed by trajectory comparison. On this basis, numerical simulations are performed to collect deformation parameters, and a formula for mechanical compensation is obtained by linear fitting to the simulation data. Finally, experimental tests are carried out to verify the accuracy of the compensation model. The results show that the forming precision of the sheet metal can be controlled in the range of $\pm 10^{\prime }$ . The proposed method is generally applicable to linear hardening materials and operation conditions where the sheet thickness ranges from 0.8 to 3 mm.

The structure type of porthole die has a crucial impact on metal flow balance in die cavities, strength of seam weld, and die strength. At present, there was little industrial case for the application of protection-type porthole die. In this study, a novel combined porthole die which includes protection, upper, and lower dies was designed to manufacture a multi-cavity and thin-walled profile. The plastic deformation behavior and flow velocity distribution of metal in die cavities were examined by numerical simulation. Seam weld strength and porthole die strength were quantitatively analyzed. In order to eliminate extrusion defects, multiple structure modifications for protection-type porthole die were proposed to balance metal flow and improve seam weld strength. Extrusion experiments were carried out on the horizontal extruder to validate the accuracy of numerical model and the rationality of modified dies. The research results showed that the relative velocity difference at die exit corresponding to the theoretical flow velocity for the designed die is at the range of −54.96 ~ 5.86 mm/s. The weld strength at the outer edges of profile is larger than that at the connecting edges of profile. The comprehensive effect of above factors that leads to an uneven front end, bending defect and seam weld cracking in extruded profile. After optimization, the relative exit velocity difference is decreased to at the range of −1.478 ~ 1.641 mm/s. The welding pressures on the concerned welding planes are obviously improved. The maximum stresses on the optimized porthole dies are both far less than the yield strength of H13 tool steel. The simulated front end shape for extruded profile agrees well with experimental one as well as the grain size and distribution on different observation positions are relatively uniform, which validate the rationality of design method for protection-type porthole die.

With the rapid development of science and technology, the traditional manufacturing industry is facing huge pressure and therefore requires to make changes and to combine new technologies in the situation of the fourth industrial revolution. Digital twin, which is a virtual representation of a physical object or system across its lifecycle, using real-time data to enable understanding, learning, and reasoning, is the core technology of industry 4.0. Here in this paper, digital twin is applied in the deformation of the sheet metals based on the novel incremental bending process. First, the framework of the digital twin-based stamping system (DTSS) is illustrated, then the experimental related works, including the setup and the working principle, are presented, and last, DTSS is applied to the incremental bending process to achieve the metal plates with single curvature and variable curvature, respectively. Results show that the information on the loading path and punch speed can be obtained, and the real-time data about the punch force and the support force can be compared with the corresponding simulation results in DTSS. The proposed DTSS is proved to have good accuracy, high efficiency, and good feasibility. DTSS helps to better understand and judge the working situation of the incremental bending device, and therefore helps to make appropriate decisions on whether to make adjustments to the novel sheet metal-forming process.

In this paper, the method of limit analysis is adopted, and three kinds of self-bending extrusion dies controlled by combined function are presented. They are the sin-atan self-bending extrusion die, the sin-erf self-bending extrusion die, and the sin-tanh self-bending extrusion die. Through numerical simulation, self-bending profiles can be obtained from all three kinds of dies. These dies can make the billet flow closer to the real billet flow path and maximize the billet utilization rate. They also can reduce the extrusion load and reduce the local damage of the die and then prolong the die life. It is very effective to predict the bending deformation of the billet by analyzing the central flow line of the billet. It provides a theoretical reference for the design of the actual streamlined self-bending die.

Compared with the conventional drilling, the helical milling has obvious advantages in making holes of carbon fiber-reinforced plastic (CFRP). Nevertheless, the rapid wear of cutting edges readily causes some defects in the outlet holes, such as burrs and tearing. In order to improve the hole-making quality of CFRP, a comparative experimental study on conventional and ultrasonic-assisted bi-directional helical milling of CFRP was carried out. The wear mechanism of the forward and reverse cutting edges was analyzed in the two types of machining, and the change laws of cutting forces and hole wall quality were obtained by different machining means. The experimental results indicated that the flank face of forward and reverse cutting edges was dominated by the abrasive wear mechanism in the ultrasonic-assisted milling. With aggravation of the tool wear, no obvious coating peeled off the forward cutting edge, the reverse cutting edge remained relatively intact, and the wear form of neither cutting edge changed. Furthermore, in the ultrasonic-assisted reverse milling, the axial force and hole diameter deviation were restrained better than in the conventional milling, and especially when the tool wear occurred, the cutting force fluctuation varied slowly. In the ultrasonic-assisted milling, the shear fracture predominated over bending fracture. Meanwhile, the time variation of effective rake angles improved the chip breaking and removing performance of cutters, and thus, the machining quality of hole wall was enhanced obviously.

This paper presents a new forming technology for manufacturing the AZ31 magnesium alloy thin-wall tube. The direct extrusion process and continuous shearing-bending process are combined to produce thin-wall magnesium tube, abbreviated as “TESB” (tube extrusion-shearing-bending). The process has been studied based on the combination of experiments and numerical simulations, and the influences of temperatures, extrusion stresses, and friction factors on the forming process have been studied by Deform-3D simulation. And the mechanical properties and the grain size of the formed product have been tested. TESB technology has been proved to refine the grains of magnesium alloy tube effectively, and the mechanical property of the product can be improved. The better experimental extrusion conditions were also obtained by simulation, and the properties of the products under the condition of lubrication were better when the temperature was 400°C. Three-dimensional finite element modeling is used to investigate the plastic deformation behaviors of wrought magnesium alloy during TESB process. Numerical results indicate TES could increase the cumulative strains effectively by direct extrusion and additional shearings. Experiments show that microstructures of magnesium alloy fabricated by TESB process can be refined to 50% of the original grain size with more uniform distribution. TES process could improve hardness of magnesium alloy obviously by comparing with which fabricated by direct extrusion.

Warping is conventionally regarded as a drawback of asymmetrical sheet rolling caused by speed mismatch-induced cross-shear straining. But, in this paper, by utilizing the warping effect, we developed a novel roll bending process, named cross-shear roll bending (CSRB), for the manufacturing of tubular sections. In the process, the metal sheet is rolled and bended under cross-shear straining by mismatched circumferential speeds of two rollers. The process is capable of manufacturing continuously changeable curvature tubular sections with minimized springback and straight ends and also with increased strength through strain hardening. Experiments show that the CSRB process is effective in forming the tubular sections by the following aspects. (1) The curvature radius decreases as the circumferential speed differential rate increases, but it loses its sensitivity to a relatively larger circumferential speed differential rate. (2) The curvature radius evolves along with the change of thickness reduction rate of the sheet in a V-shape manner, which indicates the existence of a minimum curvature radius. (3) The change of radius ratio poses little effect on the curvature radius. Therefore, by exclusively regulating the circumferential speed differential rate and the thickness reduction rate, the curvature of the sections can be controlled.

How to improve the bonding ability and quality perform between heterogeneous plates has always been one of the difficult issues that have long been concerned in the field of high-performance heterogeneous composite plate forming and manufacturing. This paper proposes a new method for manufacturing heterogeneous composite panels—composite panels by hard-plate rolling (HPR). In addition to adding hard plates above and below the aluminum/magnesium/aluminum (Al/Mg/Al) composite slab, the research results of the hot rolling process of the composite plate with or without the hard plates at 40%, 60%, and 80% reduction show that the hard plates can be rolled During the manufacturing process, the shear stress in the rolling direction (RD) is partially converted into the compressive stress in the normal direction (ND), which then increases the welding pressure between the heterogeneous composite laminates, which can inhibit the occurrence of bending and edge cracks, and significantly improve the quality and shape of the board ability. At the same time, through the study of the interface structure of the composite plate, it can be known that metallurgical bonding can be achieved with a small reduction after the addition of the hard-plate, and two clear layers of Al3Mg2 and Al17Mg12 intermetallic compounds appear at the Al/Mg interface, and the thickness of the diffusion layer is uniform. Significantly larger than the traditional hot-rolled composite board, the thickness of the diffusion layer can reach 38µm under the condition of 60% reduction under the action of the hard-plate, the yield strength is 172.3MPa, and the elongation reaches 21.5%. In summary, the hot-rolled by hard-plate is high forming and manufacturing of performance heterogeneous composite panels provides a method.

Small-batched metal plates with free-form surfaces are widely used in different manufacturing industries; however, it is unrealistic to produce such metal plates based on traditional die stamping and rolling processes. Over the last few decades, numerous efforts have been adopted to produce the metal plates with free-form surfaces with acceptable quality, efficiency, and cost through flexible forming processes. In the present paper, a heat-assisted incremental bending process was proposed to manufacture metal plates with large unsymmetrical curvatures. The test metal plates were supported by some hydraulic cylinders, and the punch moved up and down to press the metal plates according to the loading path determined by the minimum energy method. In addition, an induction heating system was applied to heat the metal plates at the punching position. One objective metal plate with large unsymmetrical curvature is deformed based on the heat-assisted incremental bending experiments. The obtained results indicate that the proposed thermo-mechanical flexible forming process could produce complex metal plates with good accuracy and high efficiency.

Three-dimensional surface rolling with rigid arc-shaped rollers (TSRRAR), a new method for manufacturing double-curved metal sheets, can be used to realize the rapid forming of 3D surface sheets. The non-uniform roll gap is generated by a pair of rollers with different axial radii with appropriately reduced sheet thickness. After passing through the roll gap, a flat sheet is bent in the rolling direction. Meanwhile, it deforms perpendicular to the rolling direction, resulting in a three-dimensional surface part with curvatures in both directions. The work adopted the elastic-plastic finite element (FE) method to simulate aluminum alloy sheets with different maximum thickness reductions. The results showed that the longitudinal curvature of sheets rose as the reduction increased. Moreover, a slightly increased reduction caused a significant variation in the longitudinal curvature radius of sheets. Different bending curvatures of sheets could be obtained by changing the reduction, indicating the flexible forming of three-dimensional curved surface metal sheets. Also, the changing trend of longitudinal curvatures of testing parts obtained by rolling experiments was substantially in agreement with the FE simulation results. Therefore, the established FE models can be used for exploring the manufacturing process of TSRRAR.

Recent years have seen the wide diffusion of composite materials in many manufacturing fields and the rapid evolution of additive manufacturing. Lately, these technologies have been combined practically allowing the fabrication of continuous-fiber reinforced polymer parts via 3D-printing. This topic is gaining attention both in the research community and among industrial users. Because of their novelty, such manufacturing methods are, however, still not thoroughly understood, and their performance limits have not yet been fully characterized. This study aims at analyzing the mechanical resistance of components made with continuous carbon fiber (CCF) thermoplastic materials by means of fused filament fabrication (FFF), focusing on the influence of the fiber orientation on such properties. In particular, both the tensile and the bending characteristics are evaluated according to the relative test standards, in specimens with both unidirectional and mixed-isotropic configurations. The experimental findings are compared with a set of reference specimens made with a base polymer filled with chopped “short” carbon fibers, allowing one to appreciate the advantages or limitations of the different fiber arrangements.

High-strength aluminum alloy has been widely used in aerospace and other industries. In the traditional bending process, a large springback occurs for high-strength aluminum alloy sheet due to its higher yield strength and lower elastic modulus. In the past, many scholars found that electromagnetic forming (EMF) can significantly reduce the springback effect. However, the electromagnetic-assisted bending and low-yield-strength aluminum alloy were used in the past researches. If the electromagnetic force is used to bend the high-strength aluminum alloy, what is the different of plastic deformation laws and springback effect both in electromagnetic forming and traditional bending? Those are the research interest of this paper. Thus, we have studied the influence of electromagnetic direct forming, electromagnetic drive forming, and traditional stamping on deformation uniformity and springback of high-strength aluminum alloy sheets. The deformation and stress distribution were analyzed by numerical simulations. The accuracy of the simulation was verified by experimental results. The results reveal that both electromagnetic direct forming and traditional stamping endow a large springback effect. It must also be mentioned that the high-strength aluminum alloy sheet dented on the center after electromagnetic direct forming, which reduces the sheet deformation uniformity. However, a small springback occurs on sheets due to small residual stress and the final deformed sheet has a smooth profile by electromagnetic drive forming. Thus, the electromagnetic drive forming is an effective mean to reduce springback and enhance deformation uniformity for high-strength aluminum alloy sheets.

Hybrid machining-forming technology is a combination of two thin-structural machining and incremental forming manufacturing processes. A group of complex geometry parts in which a thick region is connected to a thin wall region can be manufactured through this technology with certain advantages. The parts made by this technology require less raw material compared to the ones created by means of machining. The major problem with this technology is the dimensional and geometric inaccuracy of its products which is mainly due to springback. The main purpose of this research was to study the effects of machining parameters and residual stresses induced by the machining primary stage on the subsequent springback after the forming stage. It was found by experiments that the parameters of cutting speed, axial depth of cut, mode of milling and milling path had a minor effect on springback. However, the workpiece fracture during the forming stage was observed to be sensitive to the prior machining feed rate. Both finite element simulations and experimental results confirmed that the compressive machining residual stresses increased with an increase in the machining feed rate. The compressive residual stresses postponed the onset of fracture at the workpiece lower end during the forming stage. Therefore, we could approach the forming tool closer to the bottom of the wall during forming and, as a result, springback decreased considerably.

The variable curvature local-induction-heating bending forming (VC-LIHBF) technology is commonly used in the automotive industry to lighten and stiffen the structure parts. This technology allows the simultaneously bending forming and hardening of ultrahigh strength steel tubes, and allows the tensile strength of B1500HS steel to reach 1500 MPa. By adjusting the bending curvature parameters of the experimental facility through the numerical control system, the production of the tubes with variable curvatures could be achieved without changing dies. However, the more major problem of wrinkling occurs when a small-radius bending is applied on thin-walled rectangular tubes. This paper focuses on improving of forming quality and forming limit of the thin-walled rectangular steel tube (TWRST) with mandrel supported. In this study, an analytical model of the mandrel is established and some reference formulas for the selection of the mandrel parameters are deduced. Based on the above analysis, a three-dimensional elastic-plastic finite element method (FEM) model of the LIHBF process of the B1500HS TWRST is developed using the dynamic explicit FEM code ABAQUS/Temp-disp/Explicit, and key technological problems are solved. Experiments are carried out to verify the accuracy of the analytical model and confirm the reliability of the FEM model. The influences of the mandrel on stress distribution during the local-induction-heating bending process are also investigated. The influence mechanism of the mandrel parameters on the minimum radius of the LIHBF without wrinkling and the forming quality is revealed. The appropriate process parameters for the B1500HS TWRST are obtained through experiments and simulations.

Machining workpieces made of fiber-reinforced composites (FRC) with edge tools have a large range of applications. However, one of the drawbacks is the resulting fiber-matrix debonding in a thin layer under the machined surface. This can decrease the operational properties of the machined composite parts. A number of techniques are available to minimize machining defects in FRCs, with varying degrees of effectiveness. Fiber-matrix debonding results from the fibers having higher strength than the matrix. Consequently, during machining, the fibers bend to a greater angle compared to the matrix areas. To minimize this bending and debonding, we propose fiber counter-deflection in front of the cutting zone through water-jet pressure on the work surface. We verified this proposal using two methods: a smoothed particle hydrodynamics (SPH) simulation of the cutting process and full-scale experiments with a robotized water-jet cutting device and a special edge cutting tool. Both the calculations and the experiments generally confirmed the hypothesis of minimizing fiber debonding. Planing a FRC workpiece using water-jet pressure on the work surface provided a decrease in the length of fiber debonding by only 13% on average. This decrease is not high, but the simulations and experiments are only the initial investigations into improving the surface quality using this approach. At present, quality improvement of FRC workpiece machining with edge tools can be achieved with water-jet pressure using additional water-jet nozzles in these tools. Therefore, this paper presents the results of theoretical and experimental studies of a new technique based on the use of water jet to reduce fiber-matrix debonding.

International audience; The stainless clad steel materials (particularly A283-Gr-C hot-rolled to austenitic stainless steel plate SA240 TP 316L) have become widely used in the fabrication of heat exchangers, pressure vessels, and other components owing to their very interesting properties and low production cost. These cladded materials are mostly joined using multi-pass welding techniques. The temperature distribution that supervenes during welding affects the microstructures and the mechanical properties and may generate residual stresses in the heat-affected zone of the welded plates. Since limited experimental data are available in the literature regarding the complex cases of multi-pass welding of cladded steel materials, a thorough experimental study was performed in order to evaluate the temperature distribution on the welded plates. In fact, eight K-type thermocouples were fixed at different distances from the weld centerline in order to record the temperature evolution along longitudinal, transversal, and thickness directions during the welding process. Due to the unavoidable effects of the generated heat fluxes that always follow the welding, several dimensional changes were occurred on the welded plates. In this study, the longitudinal shrinkage and the angular distortion generated during the welding process by the effect of the heat fluxes were investigated. Then, tensile and bending tests were performed in order to check the welded plate reliability. It was found that (i) the welded joint presents a higher mechanical tensile strength than the parent metal and (ii) no separations, fractures, or tearing appear on the weld joint surface after the bending test.

In order to realize the rapid forming of three-dimensional surface, a new process based on the continuous cold rolling with curved rigid roll is proposed. In this process, the transversal bending deformation of metal plate is caused by the rolls shape; at the same time, it is unevenly thinned by the symmetry uneven roll gap composed by the upper and lower roll; the longitude deformation is caused. With the rolls rotating, the metal plate is continuously formed; the three-dimensional surface is produced. The formation mechanism of three-dimensional surface is stated; the theory and method of three-dimensional surface rolling forming controlling are presented; the longitude bending deformation caused by unevenly thickness thinning is analyzed, and the formula of bending deformation in the longitude direction is deducted, and the calculation method of roll gap and roll contour curve is established. A small test device is developed to form the convex and saddle surfaces, and the forming results are measured and analyzed by numerical simulation. The results indicate that curved rigid roll rolling process is feasible and effective for forming three-dimensional surface.

Flexible stretch-bending of multi-point roller dies technology is a new three-dimensional forming technology for profiles. Compared with the traditional stretch-bending process, the three-dimensional deformation of the profile can be formed at one time, and the cost of the die is greatly reduced and the production efficiency is improved. The die is an important component of flexible stretch-bending of multi-point roller dies equipment. Discrete die is the focus of this paper. The finite element model of flexible stretch-bending of multi-point roller dies is established. Taking T-profile and L-profile as research objects, the effect of die arrangement on strain, shape error, thickness distribution, and springback error is studied. The non-contact area between profile and die is one of the important factors that affect the 3D deformation of profile. By comparing the numerical simulation results with the experimental results, the effect of the non-contact area length on the three-dimensional deformation of profile is analyzed. The results show that with the increase of the non-contact area length, the shape error of profile increases, the thickness of profile web becomes thinner more seriously, and the springback error of profile increases after unloading.

The increasing demand for a wider access to additive manufacturing technologies is driving the production of metal lattice structure with powder bed fusion techniques, especially laser-based powder bed fusion. Lattice structures are porous structures formed by a controlled repetition in space of a designed base unit cell. The tailored porosity, the low weight, and the tunable mechanical properties make the lattice structures suitable for applications in fields like aerospace, automotive, and biomedicine. Due to their wide-spectrum applications, the mechanical characterization of lattice structures is mostly carried out under compression tests, but recently, tensile, bending, and fatigue tests have been carried out demonstrating the increasing interest in these structures developed by academy and industry. Although their physical and mechanical properties have been extensively studied in recent years, there still are no specific standards for their characterization. In the absence of definite standards, this work aims to collect the parameters used by recent researches for the mechanical characterization of metal lattice structures. By doing so, it provides a comparison guide within tests already carried out, allowing the choice of optimal parameters to researchers before testing lattice samples. For every mechanical test, a detailed review of the process design, test parameters, and output is given, suggesting that a specific standard would enhance the collaboration between all the stakeholders and enable an acceleration of the translation process.

Machining distortion has been a long-term obstacle in the machining of aircraft monolithic parts. Furthermore, its stability has to be considered. The machining distortion stability represents the fluctuation degree of the machining distortion. This paper investigates the evolution of elastic energy induced by initial residual stress inside materials, revealing that this evolution directly affects machining distortion. In this paper, the concept of machining distortion stability and bending potential energy is defined. By analyzing bending potential energy releasing, this study proposes a novel method for improving machining distortion stability through optimization of material removal sequence. Numerical simulation and milling experiments are performed to verify and validate the model, respectively. The results indicate that the machining distortion stability is significantly improved when optimized material removal sequence is applied. By controlling the machining distortion stability, the final distortion can be further reduced via re-machining the machining datum at the beginning of the finishing stage.

Isogrid is a highly efficient stiffened plate structure which was developed in the aerospace industry for use in rocketry and space structures. Its current form is unviable outwith these applications, as the available production methods are expensive due to excessive machining time in addition to considerable material wastage. The method detailed in this body of work was developed to manufacture Isogrid in a more efficient manner, so that its weight-saving properties may become more widely accessible. This novel Isogrid manufacturing process uses a rolling mill with patterned rollers to imprint a 3D structure of ribs into the surface of a billet material. To validate this method, a patterned roller was designed, manufactured and fitted to a rolling mill to produce sheets of aluminium AA1050 Isogrid. This process successfully created Isogrid in a sustainable, rapid manner. The samples produced were tested in 3-point bending and compared against flat plate of the same material. They were found to be 100% stronger in bending compared to a neutral flat plate with a strength shape factor of 1.6 after discounting the effect of cold work.

Continuous flexible rolling is a novel plastic forming process for 3D curved parts. In this work, asymmetry forming technology was firstly applied in continuous flexible rolling process, which can effectively compensate the lack of longitude bending deformation caused by work hardening. In the process of asymmetry forming technology, by changing the relative longitude elongation between the tensile surface and compressive surface of the sheet metal, the adjusting of longitudinal bending deformation is achieved. In this paper, the finite element model with different friction ratio was designed; the effect of asymmetry forming technology on longitude curvature radius of 3D curved parts was studied. As results demonstrate that: When the friction ratio between the upper (compressive) and lower (tensile) surface are 0.2:0.2, 0.2:0.15, 0.2:0.10, 0.2:0.05 and 0.2:0.2, 0.15:0.2, 0.10:0.2, 0.05:0.2 in turn, the corresponding longitude curvature radiuses of convex curved parts are 226 mm, 236 mm, 254 mm, 272 mm and 226 mm, 219 mm, 207 mm, 199 mm in turn. When the friction ratio between the upper (tensile) and lower (compressive) surface are 0.2:0.2, 0.2:0.16, 0.2:0.12, 0.2:0.08 and 0.2:0.2, 0.16:0.2, 0.12:0.2, 0.08:0.2 in turn, the corresponding longitude curvature radius of saddle curved parts are 330 mm, 321 mm, 315 mm, 306 mm and 330 mm, 339 mm, 345 mm, 350 mm in turn. The longitude bending deformation of sheet metal can be effectively adjusted in the asymmetry forming technology, so the feasibility of this technology is verified.

With the development of the shipbuilding, chemical engineering, and military industry, the demand for bending the metal plates with large curvature is increasing dramatically. Take the shipbuilding as an example, the line heating method is widely applied. However, this traditional method has significant disadvantages. In order to improve the manufacturing efficiency and precision, a novel method called incremental bending has been presented by our team, which is based on the minimum energy principle and model-less control method. However, due to the limited formability of the metal plates at room temperature, the bending curvature of the plates during the incremental bending process cannot meet the requirements of the shipbuilding industry. Researches show that heating can reduce springback and improve the metal formability effectively. So here in this paper, a new method called heat-assisted incremental bending is presented. In this method, the metal plate is supported by several supporting pillars and the punch moves according to the loading trajectory, which is calculated by minimum energy method. In addition, the induction heating system is applied to heat the plates at the punching positions. The bending process continues step by step until the metal plate achieves the designed shape finally. During this study, the springback behavior of the metal plates during the heat-assisted incremental bending process was investigated based on theory, numerical simulation, and experiment. Then, the metal plates with large single curvature and variable curvature were deformed based on the novel thermal-mechanical coupled metal forming process. The experimental results show this new forming process can better control the springback behavior of the metal plates and achieve the objective metal plates with lager curvature with higher processing efficiency and accuracy.

Recently, eliminating the gap between design and formability analysis of sheet metal parts has been studied to simulate sheet metal stamping processes. In this regard, a transfer-based inverse isogeometric formulation has been proposed. This method has various advantages such as solving the governing equations in two-dimensional networks without any concern about the convergence; however, it neglects the bending effect which is a major contributor in die/punch profile radii. The present work aims to consider the bending effects by introducing a bending-dependent inverse isogeometric formulation. The developed model deals with the minimization of potential energy, deformation theory of plasticity, classical plate theory, and considering a yield criterion in stress-resultant space. In addition to all advantages of the transfer-based inverse isogeometric formulation, one major benefit of this study is that the bending effects are included with a slight increase in the computation time. This methodology allows for accurately predicting the effects of changing die/punch profile radii and initial sheet thickness on the formability of the final part by presenting a new material updating process. To assess the credibility of this approach, an experimental setup and forward FEM software have been utilized to form a rectangular box. The results acquired by the developed method and those achieved by experiment and forward FEM reveal acceptable accuracy in the presented model. Also, strains and thicknesses predicted by the developed method, membrane inverse isogeometric model, and forward FEM for nine different values of punch radius to the sheet thickness ratio have been compared. Considering forward FEM as a reference method, the average of calculated error in the presented model for prediction of thickness at the middle of punch radius zone is around half of that in the membrane model. In solving the studied problems, the presented model requires only slightly more computation time (around 2%) than the membrane inverse isogeometric model and much less computation time than forward FEM. Therefore, the presented method is a valuable inverse forming solver especially when the bending effects are significant.

With the increasing demand for parts with large sizes and complex cross-sectional shapes, the required target shapes are increasingly difficult to meet. In this paper, a flexible 3D stretch bending device has been developed, which can form complex cross-sectional 3D parts with 2 degrees of freedom at one time and can form large sizes 3D parts. Compared with traditional monolithic molds, discrete molds using in flexible 3D stretch bending forming are more convenient for shape adjustment of target profile. The multi-point roller dies are composed of multiple different roller-type die units. In order to better evaluate the forming accuracy of 3D parts, the influence of the number, shape, and surface of the roller dies on the forming results is discussed. The influence of different parameters on the forming accuracy is studied by numerical simulation, and the results are compared with the experimental results. From the perspective of forming accuracy, the influence of FSBR process and different parameters on the forming result is analyzed. Analysis of the dimple and shape errors of the FSBR parts shows that the number, shape, and surface of RDU directly affect the forming accuracy. By modifying the die parameters, the surface dimples can be reduced and the forming accuracy can be improved.

Springback compensation is considered as the best method to reduce springback error. In view of the springback defect of 3D deformed workpiece, a springback compensation method based on variable compensation factor is proposed. This method can accelerate the convergence speed of iterative compensation. In this paper, the 3D flexible stretch bending of multi-point roller die technology (3D FSB-MPRD) is introduced firstly, and then, the principle of the springback compensation method based on variable compensation factor is explained. In order to improve the springback compensation accuracy of workpiece, the total springback compensation process is divided into horizontal bending springback compensation and vertical bending springback compensation. Taking the T-shaped profile with variable curvature as the research object, the die surface is optimized and the optimal springback compensation factor is obtained by using numerical simulation after multiple iterations. Finally, the results of springback compensation are compared with the desired shape. And the effectiveness of the springback compensation method based on variable compensation factor is verified by comparing the simulation results with the test results.

A boring process based on electrostatic cooling is proposed, and the effectiveness of the cooling process is verified by simulation and experiment. First, the action mode of active gas in the cutting area is analyzed on the basis of the electrostatic cooling mechanism and metal cutting law. Second, a corona discharge device with an external gas path is designed, and the attenuation law of the length and bending degree of the external gas path on the concentration of active gas in the transmission process is analyzed as well. Third, the precision boring cutter is modified into an internal cooling precision boring cutter with an external gas path. The gas concentration attenuation value at the outlet of the boring head is also obtained. Finally, finite element simulation and experimental analyses are conducted. Results show that the error of main cutting force between simulated and theoretical calculation is less than 2.65%, which verifies the correctness of the simulation. Electrostatic cooling can obviously reduce the feed force and cutting temperature, improve the wear life of tools, and achieve the effect of wet boring compared with dry cutting. The results of this study can be applied to the cooling process modification of cylindrical holes, V-shaped grooves, end faces, and threads during boring. In addition, it can also provide theoretical support for the cooling effect of gear hobbing experiments, welding, and other processes.

Local heat clamp bending equipment for carbon fiber-reinforced thermoplastic (CFRTP) sheets has been developed. The equipment holds a CFRTP sheet with thin metal foils to heat the bending region to the resign melting temperature and then bends the sheet keeping the hold by the foils under continuous pressure application during cooling. Using this equipment, it has been revealed that even a unidirectional continuous carbon fiber sheet can be locally bent by the in-plane wavy deformation of the fiber in the inner plies, while keeping the same profile length of the outside ply. In contrast, in the bending of unidirectional carbon fiber sheets with cutting at constant length, a combination of the wavy deformation of the inside ply and expansion of the outside ply has been observed. The developed bending equipment will be useful for the bending of CFRTP sheets similar to how a press brake is used for sheet metal forming. The development of the local heat clamp bending equipment will expand a field of bending for mass production using CFRTP sheets.

High aspect ratio (HAR) structures are widely utilized in diverse applications, including the defense industries, medical treatment, and aerospace. Studies show that the micro-milling has superiorities such as high efficiency and high flexibility over other methods. Currently, the biggest problem of micro-milling is the influence of burrs on the milling performance, which is an enormous challenge to remove. In the present study, numerical simulations through the finite element method (FEM) and experiments are carried out to optimize cutting parameters of the specimen made of Cr12MoV alloy. Moreover, an improved constitutive model is proposed by considering the size effect of the micro-milling. The proposed model is based on the J-C constitutive model, and it is concluded that the cutting force error is 4.6% through the comparison of experiment and FEM, which further proves the convergence of the improved constitutive model. It is also found that the side burr of HAR slots and the top burr of shallow slots are the biggest factors affecting the surface quality. The depth of cut (DoC) affects the maximum bending angle of the tool, the feed per tooth (FpT) affects the size of the unremoved area, and the spindle speed (SpS) affects the dynamic balance of the micro-mill, through the exploration of the above cutting parameters which can effectively improve the cutting state of the tool and finally achieve the purpose of curbing burr.

Lightweighting is a need in many industrial fields and, in particular, in transports, to reduce energy consumptions and to promote more environmentally friendly solutions. In this context, the use of composite materials has become ever more strategic, and a design approach that effectively combines shapes and materials is by now mandatory. In this work, the Systematic Design Approach has been extended to include potentialities and constraints related to materials and manufacturing at the early steps of the design flow. The proposed approach, named systematic material-oriented design approach, enables designers to identify and to select, in a systematic way, design solutions where shapes are tailored to materials and where benefits and criticalities related to the manufacturing processes are considered. In the paper, each design phase of the approach is described and applied to design the carbon fiber-reinforced polymer (CFRP) motor wheel of the Emilia 4 solar vehicle. Optimization steps of geometry and materials complete the approach. The design of the wheel is fully detailed as well as its manufacturing and bending tests under static and fatigue conditions. In particular, strain fields were measured with a 3D digital image correlation (DIC) system during static tests to validate the numerical model.

The process for manufacturing automotive aluminum profiles is a multi-stage process, which includes porthole die extrusion, aging treatment, bending, and electrophoretic painting. Prediction and reduction of springback are essential in quality control of bent profiles. However, existing researches related to springback issues were mainly focused on bending process stage. This study aimed to investigate the springback behaviors of extruded aluminum profile during the whole manufacturing process by numerical simulations with experimental validations. Formation mechanism and rule of springback for aluminum profile at different process stages were revealed. The optimum process route for manufacturing bent aluminum profiles was proposed. The research results reveal that compared with the transient bending region, the springback of aluminum profile during bending process induced by the finished bending region and two straight regions is relatively small. Springback angle increases with increasing bending angle and aging time. After bending tools unloading, the stresses of the two straight zones are almost completely relaxed. However, large residual tensile and compressive stresses exist in the material adjacent to the neutral layer of aluminum profile in transient and finished bending regions. Consequently, residual stress relaxation causes additional springback of bent profiles during subsequent heat treatment processes. The additional springback angle shows linear correlation with bending angle and parabola correlation with aging time. The total springback angle is minimum for process route 3 that extruded profile is firstly bent to required shape, then treated by artificial aging and finally treated by electrophoretic painting.

With the increasing demand of the parts with multi-segment curvature, long length, and complex section shape, the required target shape is more and more difficult to meet. In this article, a flexible three-dimensional (3D) multi-point stretch bending processing method for a roller die is proposed, and a flexible 3D stretch bending equipment of a roller die is developed. With the application of flexible 3D stretch bending technology of roller dies, the complex 3D parts can be formed at one time with only two degrees of freedom. In order to better evaluate the springback deformation of 3D parts, the total springback process of the flexible 3D stretch bending parts of a roller die is divided into two parts: horizontal bending springback distance and vertical bending springback distance. The springback law of different length profiles is studied by numerical simulation and compared with the experiment. From the perspective of springback, this study analyzes the parts produced by the 3D FSBRD process and studies the influence of different process parameters on springback.

Laser shock forming (LSF) is an emerging method for metal sheet forming, and it can also be used to adjust the curvature of the curved metal. A series of laser shock adjustment experiments were conducted on 1-mm-thick curved aluminum 6061-T6 sheets using pulsed Nd3+:YAG laser operating at 1064-nm wavelength. The effects of various factors on the curvature adjustment were studied, including laser energy, impacted area, coverage rate of laser spots, and initial sheet shape. The mechanisms of curvature adjustment by LSF were studied by FEM simulation. The results have shown that the stress gradient mechanism and the shock bending mechanism were responsible for the two different kinds of deformation. The characteristic difference between the two mechanisms lies in whether the plastic deformation is directly induced on the bottom surface when the laser-induced shock wave is transmitted to the bottom surface. The curvature of the metal sheet can be adjusted conveniently within a certain range by changing the laser processing parameters, which is very useful for the engineering application.

The research is aimed at increasing the quality of a concast billet macrostructure by limiting static and dynamic longitudinal forces created in billets by electrical drives of withdrawal rolls during wear and bending of the withdrawal roll body and random and periodic slips of drives. The paper analyzes process requirements for electrical drives of withdrawal rolls: contains a procedure for calculating dynamic longitudinal forces created in billets by drives of withdrawal rolls, determines whether influence of operating modes of the said drives on changes in billet withdrawal force is relevant, contains developed techniques and algorithms of withdrawal roll drive automated control limiting static and dynamic longitudinal forces in billets, and includes the experimental analysis of efficiency of methods and technical solutions on operating drives. Research was carried out at the Russian large iron and steel works. When performing the research, the authors applied analytical and numerical methods of solving algebraic and differential equations and systems, methods for structural modeling. As a result of the research, the authors developed and experimentally confirmed methods for “soft” restoring of the contact between the withdrawal roll and the billet and adjusting phases of fluctuating changes in load currents of motor groups. The obtained results are transferred as technical specifications and taken for introduction, when revamping electrical equipment of existing continuous casting machines. Results of mathematical simulation and experimental research are used to design automated electrical drives of withdrawal rolls in the secondary cooling zone of the bow-type continuous casting machine. Impact dynamic loads were decreased by 3 times, resulting in an average increase of 8% in the quality of the billet center with regard to all types of defects.

Sequentially coupled thermo-mechanical model was used to simulate the residual stresses and residual distortions in the directed energy deposition additive manufacturing by laser. The proposed models were validated by comparison with experimental data. Different sizes of components were used to study the scaling effects. Results indicate that the residual stress can be controlled by the component sizes. This phenomenon can be explained by the bending deformation and the temperature fluctuations, especially the cooling rate, in the directed energy deposition additive manufacturing process. Both the bending deformation and the temperature fluctuations can be controlled by the ambient temperature and the designed process parameters. Analytical model was established to show how the components’ sizes affect the final residual states in combination with different design parameters.

The paper describes the investigation’s results of functional capabilities of the equipment testing systems as applied to the withdrawal roll drives provided with individual power supply using the frequency converter-asynchronous motor system. All the experimental investigations were carried out at the “Magnitogorsk Iron and Steel Works” (MISW). The statistical analysis of time diagrams and frequency-response curve of changes in instantaneous values of withdrawal roll drives load torques were used. The diagnostic signs of the withdrawal roll bending, occasional slippage along the slab, wear of ring seals, and teeth of the mounted gearbox on the basis of the analysis of the component range of spectrum density of changes in load torques were computed. It was found that variance inhomogeneity of scattering of load torque change for adjacent time intervals can be used as a diagnostic sign of the withdrawal roll occasional slippage along the slab. We considered the developed diagnostic methods for withdrawal roll drive equipment at continuous casting machines (CCMs) which provide the increase productivity due to decreasing of the CCM repair work downtime. A functional diagram and a generalized algorithm of the diagnostic system for equipment of the withdrawal roll were developed taking into account the characteristics of continuous casting of steel at a slab CCM. An experimental estimate was carried out to assess the efficiency of the developed diagnostic system.

Gear is an important power transmission part, which has been widely used in aviation, aerospace, vehicles, instruments, mining machinery, and other industries. The gear teeth are formed with two methods of chip removal processing and precision plastic forming. The plastic forming method overcomes the defects of chip forming; the internal metal flow line is continuous, the material utilization ratio is high, and the production efficiency is high. In order to avoid the defects of rabbit ear in gear roll forming, the forming process of rolling bevel gear is studied in this paper. Studies have shown below. In the process of forming the bevel gear, the defects of the rabbit ears will be generated, and finally, the defects of the folding are formed in the forging. The defects of the rabbit ears must be eliminated during the forming process. When the friction shear factor is 0.1, 0.3, 0.5, 0.7, and 1.0, the maximum increment of rabbit ear is about 0.51 mm. The left profile first forms the top of the tooth, and the tooth top of the left tooth profile forms the left rabbit ear under the extrusion of the convex tool. The right-hand contour of the tooth blank is finally formed, and the rabbit ear of the right tooth profile is formed by the bending extrusion of the convex tool. In the multi-pass roll forming method, the occurrence of rabbit ear defects in roll forming process is effectively suppressed when the big end tooth height of bevel gear is 3.2 mm, 6.5 mm, 9.8 mm, and 13.1 mm and rolling wheel feed is 1.9 mm, 3.5 mm, 5.2 mm, and 6.9 mm, respectively.

Electromagnetic forming (EMF) was used to conduct elongated hole flanging in this work. The investigation showed that the low geometry accuracy around the elongated hole flanging attributed from an uncoordinated deformation occurred, including unequal flanging heights and different rebound amounts between the straight edges and the circular edges. The uncoordinated flanging height resulted from different strain distribution. The strain distribution of the circular edges was similar to circular hole flanging, while the strain distribution of the straight edge regions was similar to sheet stretch bending. The uncoordinated rebound amount resulted from different deformation mechanisms, stress distribution, and structural stiffness within the forming regions. To improve the geometry accuracy of the elongated hole flanging, a two-step method combined geometric compensation electromagnetic forming (GC-EMF) and electromagnetic calibration (EM calibration) was proposed. GC-EMF was used to achieve equal flanging height by optimizing the prefabricated hole, while EM calibration after GC-EMF was used to improve the forming accuracy by reducing the amount of rebound. The difference in the flanging heights between the straight edges and the circular edges was only 0.1 mm after the GC-EMF process, when the compensation dimension on both sides of the straight edges of a prefabricated hole was 3.4 mm. The gap between the die and the straight edges was 0.2 mm, the gap between the die and the circular edges was 0.1 mm, after EM calibration. Therefore, the improved geometry accuracy of the elongated hole flanging was achieved by combining the GC-EMF with EM calibration. The results obtained and the method proposed in this work present significant guidance for the process of elongated hole flanging or other irregular hole flanging by EMF.

Longitudinal waves are the main flatness defects of metal sheets. This defect is typically eliminated by repeated elastoplastic bending via a multi-roll leveller to make the residual curvature of the sheet as small as possible. Therefore, an effective mathematical model is important for the leveller design and levelling parameter adjustment. In this paper, based on the basic principle of multi-roll levelling for the longitudinal wave of a metal sheet, a geometric model of multi-roll levelling was established via the curvature integration method; a bending-moment curvature model was also established to account for the residual curvature of reverse bending and the difference between the elastic section and the elastoplastic section. A coupled curvature integration model was constructed by combining the two models to systematically describe the multi-roll levelling process, and the variation of the curvature, surface profile curve and plastic deformation rate of the sheet during levelling were discussed; the influence of the intermesh of the work rolls on the levelling effect of the longitudinal wave was analysed. The results show that there are infinite intermesh combinations of the first work roll and the last work roll that make the residual curvature of the sheet close to zero after levelling. The results also show that the residual curvature is much more sensitive to the variation of the first work roll than to the variation of the last work roll.

This paper presents a novel technology called ‘double-action bending (DAB)’ to eliminate springback in hat-shape forming of advanced high-strength steel sheets (AHSS). It consists of four steps: (1) clamping of a sheet between an inner punch and a counter punch, (2) U-bending under a constant clamping force, (3) pushing-up the sheet by the counter punch from the bottom end, and (4) bending of the flange by an outer punch. A great advantage of this technology over other hat-bending processes, such as draw bending and crash forming, is that perfect hat-shaped channels are easily obtained for any type of AHSS just by determining two controllable process parameters, namely, the bottom pushing-up force and outer-punch stroke in flange bending. An accurate finite element (FE) simulation allows us to determine these process parameters prior to experimental tryout. The validation for this process was shown by performing the hat-shaped DAB experiments on a dual-phase 980-MPa AHSS and the corresponding FE simulation.

In the automotive industry, the demand for ultra-high-strength steel is increasing due to the CO2 emission and safety regulations. Hot-press forming (HPF) steels are a type of boron-alloyed high-strength steel fabricated via hot-press forming, which enables both high strength and elongation. Because HPF is conducted at high temperatures (900–950 °C) for a few minutes, its surface is coated with Al–Si or Zn to prevent surface oxidation and decarburizing. However, the coating layer often influences the properties of the welds. In this study, friction stir spot welding (FSSW) is used to weld dissimilar metals, i.e., an Al alloy and Al–Si-coated HPF steel. The effects of Al–Si coating on the mechanical and metallurgical properties of the hook formation on the weld are investigated. The shape of the hook, which is formed during FSSW, changes from bent to straight shape due to the presence of Al–Si and the HPF process. The joint strength of the straight hook-shaped specimens is demonstrated to be lower than that of the bent hook-shaped specimens. This difference in strength is because the hard Fe–Al–Si intermetallic (IMC) layer on the outer surface of the hook disturbs the bending of the hook during the welding. On the outer surface of the hook, a Fe–Al–Si IMC layer of chemical composition similar to that of the coating layer formed during HPF is observed. This formation is different from the inner surface of the hook, wherein a thin Fe–Al IMC layer is reconstructed between aluminum and steel. Thus, the hard Fe–Al–Si intermetallic layer transformed during the HPF process is the primary cause of the straight hook shape.

In this paper, the modified Mohr-Coulomb (MMC) ductile fracture criterion was adopted to analyze the fracture behavior of the AA6061-T6 aluminum alloy sheet during the U-bending process. Appropriate calibration procedures were employed using various tension tests. A finite element (FE) model was built using the commercial FE code Abaqus/Explicit incorporating the calibrated MMC fracture criterion. It was found that the MMC criterion calibrated by the uniaxial, plane strain, notched, and modified in-plane shear tension tests can predict the onset of fracture in the U-bending process with reasonable accuracy. The error of the predicted fracture displacement was about 2% as compared to experiments. Due to the dependency of the fracture prediction accuracy on the stress state, the effects of process parameters on stress triaxiality and normalized Lode angle parameter were investigated. The negligible effect of process parameters on the stress state confirmed that the calibrated fracture criterion (MMC) was able to predict fracture in different forming conditions with equal accuracy. Also, the proportional stress and strain state in the U-bending process indicate that, besides the high fracture prediction accuracy of the MMC’s damage accumulation function, the fracture forming limit diagram (under proportional loading assumption) can serve as a reliable tool for estimating the onset of fracture in the U-bending process. Therefore, a series of studies were also conducted on damage evolution, crack propagation, principal strains, and fracture displacement during the U-bending process under various forming conditions.

Wave defects are the main flatness defects in rolled metal sheets and typically must be eliminated via multi-roll levelling for further use. Convex work rolls are the key component of the levelling process. The effectiveness of the description of the work roll and its bending characteristics determines the efficiency and accuracy of the levelling numerical analysis, which is also the key problem to be solved in the current research. This paper proposes a finite element expression method for convex work rolls that is based on the beam-membrane method by using a beam element to express the mechanical characteristics of the work rolls and the membrane elements to express the contact characteristics between the work rolls and the metal sheet. An effective multi-roll wave levelling model was established based on the beam-membrane method, and the influence of the bending parameters of the work rolls on the wave levelling performance was analysed. The results demonstrate that work rolls that have a parabolic bending curve can substantially reduce, but not eliminate, residual waves. The residual stress and curvature simulation have been discussed, and the comparison shows that the proposed method is closer to the real experiment result.

At present, high straightness precision and good bar surface quality are difficult to meet at the same time in the straightening process of bar. In view of this problem, this paper puts forward a continuous variable curvature roll shape design method, and studies the straightening process setting method. The roll shape of the straightening roll is tangentially connected by multiple segments arc of uniform curvature changes, and the curvature decreases uniformly from the middle to both ends. The roll shape designed by this method can be in good contact with the bar and can effectively improve the surface quality of the straightened bar. In order to make the straightening process parameters more reasonable and effective, reduce the dependence of the production line on workers, and realize the full automatic straightening of the bar, a complete process straightening bending springback model of bar was established. Based on roll shape and bar specification, the optimization iteration model of upper and lower straightening roll angle is established. Then the setting method of the roll gap and the guide plate spacing is discussed. The field straightening process is simulated by finite element analysis. The process setting model is verified on the straightener after roll shape modification. The automatic control of two-roll straightening of bar can be effectively realized by using the roll shape and process model. The straightened bar has high straightness and surface quality.

To investigate the impact of the variations of different input parameters in the multi-stage hot forging process of a shackle, an analysis is carried out through numerical simulations of the whole manufacturing process. Due to the complexity of the process and the large number of factors influencing the thermo-mechanical forming process, the investigation is focused on the workpiece positioning, the temperature of the tools, the transportation time and the contact-friction conditions. The analysis is narrowed down to the key stages of the process that are closed-die forging and ram bending. Coupled with experimental measurements, a comparison of forging loads, functional dimensions and shackle geometry is presented. It is shown that the conformation of shackle geometry to the industrial specifications depends mainly on the workpiece positioning and the transportation time. The dispersion measured in the forging load and in the main dimensions can thus be explained and these observations can be used to improve the manufacturing process for shackles.

Due to the complicated deformation of the billet in roll forming process and the lack of the theoretical understanding, there are still no unified methods to design and optimize roll profiles. Theoretical analysis of the deformation in roll forming process based on mathematical method is efficient and necessary. A qualified roll profile optimization method should be based on the accurate calculation of the spatial configuration of the billet. However, the existing models for calculating the spatial configuration of the billet in roll forming process cannot calculate the springback of the billet. In this paper, according to the mathematical model established by the author for calculating the spatial configuration of the billet, a roll profile optimization method for high-strength V channel roll forming process was proposed by taking the maximum edge membrane longitudinal strain as constraint conditions. After optimization, the number of roll stands required for final V channels was reduced from 8 to 5. Through analyzing and comparing the deformation of the billet in simulation results of bending and roll forming process, it is found that bending tests can also be used to verify the feasibility of the roll profile optimization method proposed in this paper. The bending tests were carried out using the original and optimized process parameters, respectively. The results show that the shape of the V channel obtained by the optimized process parameters is much closer to that of the designed V channel.

Electromagnetic-assisted forming (EMAF) combining quasi-static stamping and electromagnetic forming (EMF) is a potential method for controlling the springback of aluminium alloy materials. In this study, to further promote the application of EMAF in the high-precision forming of aluminium alloy sheet parts, the springback during electromagnetic-assisted bending of aluminium alloy sheet was investigated using a custom-designed U-shaped bending tool with the optimised curved spiral coils. Two types of conditions to control springback were designed: gapless and gap conditions, and the springback under these conditions was studied both experimentally and using numerical simulations. In addition, the effects of the discharge parameters on springback were analysed. Finally, the mechanism for controlling springback under different forming conditions was revealed. The results showed that the efficiency of springback control was significantly higher under gap conditions compared with gapless condition. With increasing gap, the springback angle decreased, but negative springback easily occurred when using excessively wide gaps. As the discharge voltage or number of discharges increased, the tangential stress of the fillet area decreased, thereby reducing the springback angle. Stress oscillations under the gapless condition reduced the tangential stress of the fillet area to a certain extent, while inertial motions under gap conditions greatly reduced the tangential stress, which were the essential mechanism for the observed springback reduction.

3D printing has gained great popularity due to its main feature of manufacturing complex geometries. The building process by adding successive layers generates mechanical properties that depend on the printing parameters, where build orientation is one of the most relevant factors. Due to this, the characterization of the mechanical response of these pieces is a challenging task of practical importance to estimate their lifespan. The aim of this study is to characterize the mechanical behavior and define a 3D constitutive model of polymer materials commonly used in 3D printing manufacturing. Hence, ABS and PLA were used with a low-cost desktop printer with which specimens were manufactured in two orthogonal orientations: flat and upright. Tensile and compression tests were performed to this end, where the Young’s modulus, yield, and maximum stresses were determined. In the tensile tests, the samples with vertical (upright) orientation showed lower values in the evaluated mechanical properties than the corresponding to the horizontal (flat) orientation. However, no significant difference caused by the printing orientations was observed in the compression tests. Different values of Young’s modulus and maximum strength were found between tensile and compression tests for the same material and orientation. Moreover, in order to describe the observed material response, a linear isotropic bimodular model is proposed. This constitutive model, which is fed with the previously obtained tensile and compression data, is used in the simulation of a four-point bending test where it is found to adequately represent the experimentally measured elastic behavior in the load-deflection curve. Thus, the combination of experiments and a bimodular constitutive model contributes to making better predictions of the mechanical response of structures made with 3D printing.