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A hot stamping process of quenchable steel tubes using a mandrel reinforced with eco-friendly fibers was developed to produce ultra-high strength steel hollow parts having enhanced lightweighting and crashworthiness. High internal pressure was generated to improve the die quenchability and shape accuracy of the formed parts by the fiber reinforcement. Wood sawdust, shredded copy paper, and plant fiber made of recycled toilet paper were chosen as the fibers, and not only the strength was evaluated from a uniaxial compression test but also the melting behavior of the mandrel was examined. The influence of the fiber reinforcement on the shape accuracy and die quenchability of hot-stamped parts was investigated. The generated internal pressure with the fiber-reinforced ice mandrel was higher than that with the pure ice mandrel without the reinforcement, and thus, the shape accuracy and die quenchability of hot-stamped parts were significantly improved even for a comparatively small change in internal volume of tubes. [ABSTRACT FROM AUTHOR]

In the die-less spinning of the conical part, the forming state changes during the spinning process and depends on the forming parameters, which has a critical effect on the forming quality of the spun part. In this paper, a criterion of the forming states is established, and its dependence on the forming parameters is investigated. It is found that the formed wall thickness changes during die-less spinning. According to the formed wall thickness variation degree, three forming states are defined: shear spinning state ( t f = t 0 s i n α , where t 0 and t f are the initial and formed wall thicknesses, respectively, and α is half-cone angel), the conventional spinning state ( t f > 0.9 t 0 ), and transition state between the shear and conventional spinning states ( t 0 s i n α < t f ≤ 0.9 t 0 ). The distribution of stress and strain in three forming states is obviously different. The die-less spinning always proceeds in the sequence of shear spinning state, transition state, and conventional spinning state. The initial forming state may be any one of them, which is mainly determined by the diameters of the blank and general mandrel. Thus, the quantitative dependence of initial forming state on the diameters of blank and general mandrel is further analyzed, and a criterion for the initial forming state is correspondingly established. In addition, the influence of forming parameters, including the blank parameters, mold parameters, and process parameters, on the criterion for the initial forming state in die-less spinning is revealed. This paper could improve the understanding of the deformation mechanism in die-less spinning. [ABSTRACT FROM AUTHOR]

Mandrel is an indispensable tool for manufacturing hollow curved components with large diameter by rotary draw bending. In this paper, an analytical model of mandrel parameters in numerical control (NC) rotary bending of a large diameter tube using a spherical hinge mandrel was proposed, and then the mandrel extension length and core number were preliminarily determined. A nonlinear 3D elastoplastic finite element (FE) model for simulating the NC rotary bending was established. The influences of mandrel-cores on the tangential stress, strain, and bending deformation characteristics were systematically studied. The results show that the maximum prediction errors of wall thicknesses and cross-section distortion are all less than 10%, and the simulated wrinkling position and number also showed good agreements with experimental ones, which indicate that the established FE model is accurate and reliable. Compared with the tube bending without mandrel-cores, the difference between maximum tangential tensile and compressive stresses, as well as the shift of stress and strain neutral layers, was smaller for tube bending with mandrel-cores, which had a good inhibitory effect on cross-section distortion and wrinkling. During tube bending with mandrel-cores, the compressive deformation zone was only located within the zone from the bending tangent point to the section position of 30°, and the tangential compressive strain reached peak value at the section position of 30°. Among the mandrel parameters, core number has a significant influence on cross-section distortion, while mandrel extension length is more sensitive to the wall thickness thinning. The cross-section distortion decreased while the wall thinning rate increased with increasing mandrel extension length, core number, and decreasing the clearance between mandrel and tube. A low friction between the mandrel and tube can decrease cross-section distortion and wall thinning rate. The appropriate mandrel extension length, core number, and clearance between mandrel and tube in NC rotary bending of ⌀ 76 × 1.2 × R150 mm tube were 9 mm, 3, and 0.2 mm, respectively. [ABSTRACT FROM AUTHOR]

With the increasing demand for customization and personalization, the manufacturing industry faces new challenges related to cost-effective, low batch size production. Additive manufacturing (AM) is among the promising technology to address this problem. AM has however some limitations in metal structure fabrication, including high surface roughness, porosity, and poor mechanical properties. Electroforming on an AM mandrel could be a potential alternative solution for low batch production and complex structures with high aspect ratios. This process takes advantage of both high design freedom from AM and better structural control with electroforming. However, the uniformness, deposition quality, and end-geometry of the electrodeposition on a mandrel are not always guaranteed. In this paper, a method and an algorithm are proposed to improve the geometric precision of the deposition on the mandrel. The desired net-shape can be achieved by a corrected mandrel that takes the variable electrodeposition thickness into consideration. Therefore, the dimensional accuracy of the outer surface can be improved for applications requiring the dimensional accuracy of the outer shape, and a uniform part thickness is less important. In addition, a method that allows the forming of parts with controlled multiple thicknesses on the same mandrel is proposed. As one of the potential applications, the manufacturing of high-aspect-ratio flexures is demonstrated. [ABSTRACT FROM AUTHOR]

HCWR (hot cross wedge rolling) of hollow shafts has been investigated while there are few investigations on CWR (cross wedge rolling) of hollow shafts at other temperatures. Because of the severe oxidative decarburization of HCWR and large deformation resistance of CCWR (cold cross wedge rolling), the WCWR (warm cross wedge rolling) was proposed for forming hollow shafts to compromise these limitations. In this paper, relevant investigations about a WCWR process of hollow shafts with corrugated surface were carried out. At first, the parameters and the geometry of the WCWR rollers of hollow shafts with corrugated surface were designed. Then, the finite element (FE) model of the WCWR process was established and verified by the laboratory test. Next, the FE results with various mandrel diameters were presented, and the influence of the mandrel diameter on the distribution of stress, effective strain, and temperature and the rolling force and torque was analyzed. Finally, the experiment results with various mandrel diameters were presented, and the effect of the mandrel diameter on the forming quality was discussed. The results show that as mandrel diameter increases, the temperature of the workpiece after rolling decreases, while the effective stress and strain and the rolling torque increase. The maximum dimensional deviation at the symmetric cross section is not larger than 0.3 mm when there is no mandrel or the relative mandrel diameter is 0.7, and the roundness is gradually worse as mandrel diameter increases. [ABSTRACT FROM AUTHOR]

Aluminum alloy profiles are widely used in traffic transportations. Both enough strength and precise shape are needed in these profiles. A novel ECAP with rubber mandrel is used to strengthen complex U-groove profiles. This ECAP is comprehensively researched by analytical and simulation as well as experimental methods in all the three situations "N," "U," and "C." The shape control mechanism will be received by analytical method. The thicknesses vertical to the deformation plane can be controlled by plane deformation, while the thicknesses parallel to the deformation plane can be controlled by the constant thickness ratio. The simulations and experiments will be both used to verify the shape control effects. Finally, there will be more stresses in situation "U" based on the stress nephograms. The shape control results in situation "C" are better than these in situations "N" and "U" from both simulations and experiments. Based on the research in this paper, U-groove aluminum profiles are suggested to be formed by ECAP with rubber mandrel in situation "C." This may be a strategy for U-groove aluminum profiles formed by ECAP. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, rotary draw bending (RDB) process is used to bend the rectangular ribbed (日-shaped) section profiles into commercial vehicle anti-collision beams. But the bottom plate of the profile will inevitably produce wrinkling defects in the actual processing. Therefore, ABAQUS finite element (FE) software is used to simulate the profile with no mandrel in RDB process to obtain the formation mechanism of the defects. Based on the above result, a novel type of mandrel-novel flexible cores (NFC) is designed. Its innovation is not only perfect for RDB of the rectangular ribbed (日-shaped) section profile but also can play a good role in occasions where the use of ordinary mandrels is limited. All in all, the working occasions are not limited. Moreover, changing the parameters of the mandrel core can achieve any angle bending under the premise of ensuring accuracy, and the cross-sectional distortion is small. Finally, the wrinkling rate at the bending area of the actual anti-collision beam product is measured and calculated, and the result shows that the wrinkling rate Q is less than the standard value that defines the presence or absence of wrinkling, which is regarded as no-wrinkling. And there is a good agreement between simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, rotary draw bending (RDB) process is used to bend the rectangular ribbed (日-shaped) section profiles into commercial vehicle anti-collision beams. But the bottom plate of the profile will inevitably produce wrinkling defects in the actual processing. Therefore, ABAQUS finite element (FE) software is used to simulate the profile with no mandrel in RDB process to obtain the formation mechanism of the defects. Based on the above result, a novel type of mandrel-novel flexible cores (NFC) is designed. Its innovation is not only perfect for RDB of the rectangular ribbed (日-shaped) section profile but also can play a good role in occasions where the use of ordinary mandrels is limited. All in all, the working occasions are not limited. Moreover, changing the parameters of the mandrel core can achieve any angle bending under the premise of ensuring accuracy, and the cross-sectional distortion is small. Finally, the wrinkling rate at the bending area of the actual anti-collision beam product is measured and calculated, and the result shows that the wrinkling rate Q is less than the standard value that defines the presence or absence of wrinkling, which is regarded as no-wrinkling. And there is a good agreement between simulation and experimental results. [ABSTRACT FROM AUTHOR]

As an important engineering material, aluminum alloy profile is widely used in each department of national economy. With polyurethane mandrel in the hollow of the profiles, equal channel angular pressing (ECAP) can be used to refine mechanical properties of these hollow materials with good shape control effects. However, based on existing researches, the hollow profiles are only limited to circular ones. In this paper, a mechanical analysis of a square tube in ECAP with polyurethane mandrel is provided. Through the slab method in different deformation planes, the mechanical mechanism of shape control effects is found. The thicknesses can be maintained as its initial ones after ECAP. Both simulations and experiments are used to verify the calculated results by the analysis. After calculating, most errors between the final and initial thicknesses in both simulations and experiments are less than 10%. [ABSTRACT FROM AUTHOR]

Thin-walled (D/t > 30; D, initial outer diameter; t, initial wall thickness) bent tubes with large diameter (D > 100 mm) and small bending radius (R/D < 3; R, centerline radius) are difficult to form integrally using traditional bending methods. In this paper, using a novel loading method, a modified push-bending (MPB) process with polyurethane as mandrel was developed. A stainless steel bent tube with extreme geometrical specification (D = 144 mm, D/t = 72, and R/D = 1.94) was formed integrally by MPB. Based on analytical and finite element (FE) method, the internal pressure, i.e., contact pressure between polyurethane and tube (CPPT) were investigated. The results show that the CPPT decreases linearly from the back end to the front end of polyurethane rod and increases with smaller μ1 (the coefficient of friction between polyurethane and tube) and larger L (the center axis length of polyurethane rod), and the increase of CPPT is helpful to decrease the ovality of the bent tube. [ABSTRACT FROM AUTHOR]

It is important for the thin-walled tube with relative bending radius of 1 to be bent with mandrel in order to avoid the defects such as wrinkling and cross-section distortion. In this paper, a novel push-bending method using sectional elastomers as mandrel was proposed to form the 5A02 thin-walled aluminum alloy tube with relative bending radius of 1 and 90° bending angle. Cylindrical polyurethane rubber (CPR) with shore hardness of 80A was chosen as the sectional elastomers. The influence of diameter (d), thickness (t), total length (L), and arrangement of CPR filler on the push-bending deformation of tube was first explored by means of simulations and experiments. According to the simulation results, 5A02 thin-walled aluminum alloy tube with relative bending radius of 1 was successfully fabricated with the sectional CPR as mandrel in the self-developed equipment of push-bending. The experimental results were in good agreement with the simulation results. The optimum parameters of CPR filler in push-bending process were obtained as follows: 37 mm diameter, a piece of CPR with 20 mm thickness contacted with the punch, and other 12 pieces of CPR with 10 mm thickness. [ABSTRACT FROM AUTHOR]

In the small-radius rotary draw bending (RDB) process of thin-walled rectangular tubes, push assistant matching consisting of pressure die and booster die is proposed to improve the forming quality of tube in this paper. Based on ABAQUS platform, the reliable 3D-FE models without and with booster die were established, and the cross-sectional deformation and wall thickness variation under different push assistant levels were analyzed. The results show that: (1) Adding the booster die or increasing push assistant level can reduce the cross-sectional deformation and wall thinning ratio of tube during small-radius RDB process. (2) The influence of adding the booster die or increasing push assistant level on the cross-sectional deformation in mandrel support zone (MSZ) is smaller than that in non-mandrel support zone (NMSZ), while the influence of that on wall thickness variation is opposite. (3) Increasing the push assistant level not only results in the variation of deformation degree of tube, but also makes the distribution zone of wall thickness thinning and thickening changed. Besides, the reasonable push assistant matching conditions are obtained. [ABSTRACT FROM AUTHOR]

In the application of the 13.5-nm extreme ultraviolet (EUV) collector optics of the discharge produced plasma (DPP) source, the Wolter-I structure based on the X-ray grazing incidence optical design is usually adopted. The requirement of the surface roughness of this collector optics is demanding, which should reach to several nanometers. Currently, the mandrel replication is the main fabrication technology of this collector optics. Obviously, the requirement of the surface roughness of the mandrel used for the replication process should reach to the same level of the collector optics. However, the fabrication of the Wolter-I mandrel with high surface quality requirement still faces great challenge. In this paper, we propose a method that applies an elastic spherical tool to polish the surface of the Wolter-I mandrel, in which the shape of the elastic sphere can be changed relatively easily to accommodate the aspherical surface of the Wolter-I mandrel. A mathematical model regarding the movement trace of the polishing tool was established. Based on this model, the contact force between the polishing sphere and the aspherical surface can be controlled to point from the center of the polishing sphere in the normal direction to the polishing point. The influence of the polishing parameters on the material removal thicknesses is simulated and analyzed. The polishing experiments of ellipsoid and hyperboloid are carried out considering the difference of the diameter of each radial section on the Wolter-I mandrel surface. The proposed method is proved to reduce the surface roughness of the mandrel coated with chemically deposited nickel-phosphorous (NiP) alloy after diamond turning effectively. The root mean square (RMS) roughness of the mandrel surface after polishing can be reduced to 1.56 nm. It indicates that this method is suitable for further polishing of nickel-plated Wolter-I mandrel after ultra-precision turning. As a result, the manufacturing precision and efficiency of the Wolter-I mandrels can be improved by using the proposed polishing approach in this study, and the manufacturing cost can be reduced accordingly. [ABSTRACT FROM AUTHOR]

Cold profiled ring rolling (CPRR) is an advanced local incremental forming process with complexity and high nonlinearity. In this process, the feed rate of mandrel is a key factor affecting the expanding speed of ring outer radius and the filling behavior; thus, it is very significant to rationally design the feed rate for precise controlling the deformation process. Aimed at the CPRR process, the problem of feed rate planning under two variable feed patterns, which are constant expanding speed of ring outer radius ( P ) and constant feed amount per ring revolution ( P ), has been solved successfully by using the hypothesis-testing approach in this paper. First, according to the relation between the ring outer radius R and the ring reduction ΔH, a novel mathematical solution for planning the feed rates under P and P has been proposed, in which a series of points of ( R, Δ H) under constant feed rate ( P ) pattern have been taken into consideration. Second, two differential equations obtaining variable feed rate curves under P and P have been built and their solving processes have also been given, and subsequently a new quantitative planning flow of variable feed rates has been presented. Third, an example of three feed rates planning under P , P , and P for a practical closed cold T-shaped ring rolling process in the design phase has been realized, and their validity has been proven by three-dimensional finite element numerical simulation. The achievements can provide a guideline for planning the feed rates of the relevant complex profiled ring rolling processes to improve efficiency and reduce cost. [ABSTRACT FROM AUTHOR]

Rotary draw bending is usually applied to round tubes, since their axisymmetric cross section helps reduce any type of distortion. In the present paper, we investigate rotary draw bending of rectangular tubes employing a novel elastic parallelepiped mandrel. For this purpose, tubes, manufactured by cold forming flat rolled sheets of steel S235JR into rectangular tubular shapes and electric resistance welded into solid wall tubing, were bent, both the 'hard way' and the 'easy way,' to form a nominal angle of 90°. A finite element (FE) model was developed to perform the process simulation based on an explicit dynamic time integration scheme using the commercial code ABAQUS. The FE outcomes have been validated by comparison with experimental results. Specifically, a coordinate measuring machine was used to determine the degree of bend as well as the radius, the profile, and the wall thickness of the bent sections. The obtained results showed the capability of the FE modeling to predict the material deformation process. Implementing the stiffness of the welding seam into the FE model of the tube dramatically increases the accuracy of the numerical simulations. The validated model is adopted for investigating the effect of mandrel position, clearance, and friction and how they can be set to minimize the tube distortions. [ABSTRACT FROM AUTHOR]