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Die-less spinning can achieve the thin-walled parts with the regular shape of cone and cylinder or even some non-axisymmetric shapes. And it has advantages in forming some difficult demolding shapes. In this study, die-less spinning in a cone–cylinder combined hollow part and its forming mechanism were investigated. A ball-crown-shape roller was used to replace a conventional roller in the spinning process. The roller movement and spindle rotation were controlled by a computer numerical control spinning machine to achieve a planned roller path. The pass sets of tilted and horizontal lines were designed to form the cone and cylinder shape, respectively. Further, two methods were adopted to link the two forming pass sets and spin the cone–cylinder combined shape. One is to connect the cone and cylinder forming lines directly (Schemes A); the other is to connect the cone and cylinder forming lines by transition lines (Schemes B). The effects of two key parameters (roller path and feed ratio f) on the wrinkling and wall thickness distribution were analyzed. The product exhibited wrinkling on the wall using the roller path of Scheme A with f = 0.5 mm/r. f affected the occurrence of wrinkling considerably. Larger f made the flatness of the cylinder wall worse, no matter which roller path (in Scheme A or B) was used. When f was set to 0.25 mm/r (f was lower than LT1 in this study) with a blank thickness of 2.05 mm, wrinkling could be suppressed in the roller path of Scheme A. The product had an increasing thickness distribution on both the cone and the cylinder. The cylinder wall was even thicker than the disk blank with a blank thickness of 2.05 mm.

Deformation has a significant effect on the machining accuracy of the monolithic components. Fluctuant initial residual stress is one of the factors causing deformation. In this paper, initial residual stresses of six specimens of 7050-T7451 aluminum alloy plates with 65 mm thickness and 70 mm thickness are measured respectively. Fluctuant initial residual stresses are fitted by segmented polynomials of best uniform approximation. An analytical model in terms of the deformation and initial residual stress is established for single-sided stringer parts. The results show that the weight of web-induced deformation in the whole deformation of the part is about 74%–98.5% and the weight sidewall-induced deformation is about 1.5%–26%. Therefore, minimizing the web-induced deformation is the key to minimize the whole part deformation. The condition number calculated by coefficients matrix of initial residual stress inside the web is defined in the model. The value of condition number is determined by initial residual stress inside the web and its fluctuant degree, which is positively correlated with web-induced deformation when the structural stiffness is invariant. By selecting the blank with a small fluctuant amplitude of stress or changing the workpiece position, condition number will be decreased, and the deformation is minimized.

Flange wrinkling is one of the common defects that occur in conventional spinning process, severely restricting the improvement of forming quality and formability. How to universally determine the formability dependent on flange wrinkling is a critical issue in conventional spinning process. For this end, such a determining method for the formability in the process is proposed to rationally design the forming parameters to prevent flange wrinkling. The method is as follows: firstly, the maximum circumferential stress during the process is calculated at the outer edge of the flange, where the circumferential stress is considered as the combining result of the shrinkage of flange diameter and the bending of flange; then, the formability is determined by comparing the maximum circumferential stress to critical circumferential stress for wrinkling defect. Based on the method, a formability analytical model considering wrinkling defect in the first-pass conventional spinning process with a linear roller path is established. The formability model is validated by experiments and FE simulations at different spinning conditions. Sequentially, the influences of forming parameters and their interaction on the formability considering wrinkling defect are systematically analyzed. Furthermore, the forming diagrams considering wrinkling defect for the first-pass conventional spinning are established. It is found that the feed ratio has the most significant effect on the formability, followed by the blank thickness, the hardening exponent, the feed ratio-hardening exponent interaction and the feed ratio-sheet blank thickness interaction. The smaller feed ratio and hardening exponent, thicker sheet blank and greater relative sheet blank radius are helpful to increase the formability. The research results could provide a theoretical basis and guidance for the selection of forming parameters in the actual production of the first-pass conventional spinning.

The usage of modern materials in the automotive industry for the body in white construction leads to increasing requirements for the manufacturing process. Due to the limited formability of high-strength aluminium alloys and steels, joining by forming of these dissimilar materials is still a big challenge, which requires suitable and innovative manufacturing technologies. In sheet forming processes the Tailor Heat Treated Blank (THTB) technology allows enhancing the formability of high-strength aluminium alloys. Therefore, the applicability of the THTB technology for the shear-clinching technology is investigated in this paper. Up till now, this innovative joining by forming technology is only qualified to join ductile aluminium alloys and high-strength steels, but the combination of high-strength aluminium and high-strength steel has not been realized yet. In this research work, the limits of the shear-clinching process have been extended to successfully join the material combinations of AA7075 on the punch side and HCT780X, as well as press hardened 22MnB5 on the die side by using aluminium specimens with different heat treatment layouts. Further, this paper shows the possibility to adjust the material flow of the shear-clinching process by local and short-term heat treatment.

The manufacturing accuracy of the thin-walled parts is significantly affected by the residual stress in the blank and the resulting machining deformation. In recent years, the prediction and control of the machining deformation have received extensive attentions. A semi-analytical machining deformation prediction model is proposed for the thin-walled parts in terms of the equivalent bending stiffness calculated by finite element method (FEM) simulation and theory of plates and shells. Machining deformations of seven typical study cases are predicted by the semi-analytical model. Corresponding experiments and FEM simulations are conducted to validate the proposed model. Then, the influences of the initial residual stress and equivalent bending stiffness on the machining deformation are investigated based on the quantitative results of the proposed model, which is difficult to be obtained by the previous FE models. The results suggests that 1) improving the bending stiffness of the part can effectively reduce the machining deformation; 2) decreasing the stresses in the top part of the blank and in the length direction is more advantageous to reduce the deformation than other parts and directions; 3) the final machining deformation is basically determined by the residual stress within a certain thickness under the blank surface when the residual stress symmetrically distributes along the mid-plane in thickness direction.

The elbow push-bending process involves pushing a tube between a die and a mandrel to bend a tubular blank into an elbow shape. In this study, the yield was improved by minimizing the cutting loss at the ends of the elbow tube. This was achieved by developing an optimized method for the design of the tubular blank. The design method is based on the deformation behaviors during the push-bending process and was formulated to minimize the cutting loss. An analysis was done to develop design rules for determining the intrados and extrados lengths and the inclination angles at both ends. Given a radius of curvature and the target dimensions of an elbow tube, it is possible to provide the optimum dimensions of the tubular blank to be bent in the push-bending process. The proposed method was successfully implemented in an actual production line and showed improved dimensional accuracies with reduced cutting losses.

In order to reduce the die-roll size in the fine-blanking process, a modified die structure was proposed, which an indenter arranged along the die profile was set on the cutting edge. The indenter can be defined by four structure parameters. To investigate the effect of these four die structure parameters and evaluate their degree of importance on the die-roll size, three different levels of each die structure parameter were applied in the fine-blanking process of a specially designed triangular tooth using FEM. The optimized die structures were determined considering the effect of reducing die-roll size, the die lifetime and the prevention of crack on the cutting surface. Extra simulations were carried out to verify the effect of the modified die. To explain the mechanism of the modified die, a theoretical model was established according to the features of die structures. The former FEM results were taken as examples to demonstrate the theoretical model. To test the feasibility of this modified die, experiments were performed on the part of automobile synchronizer slipper. In addition, the relationship between the blank holder force and the die-roll sizes in the different fine-blanking processes was studied during the experiments.

Recently, various methods for the metal spinning of noncircular shapes have been proposed to overcome the limitation of its application range. In this study, a metal spinning method for noncircular shapes with oblique bottoms is proposed. This method is a combination of synchronous spinning and multipass spinning, in which the roller is synchronized with the mandrel rotation to track a noncircular cross section while the workpiece is gradually deformed without much thinning through some paths of the roller. The roller trajectory is calculated by linear interpolation in the radial direction and axial direction between the inclined blank shape and the inclined cross section of the product. A circular cup and square cup with an oblique bottom and vertical side walls are successfully spun using this method. As the wall thickness locally increases at the side edges of the square cup, the thickness distribution is equalized by using an intermediate circular shape. This method interpolates the roller trajectory between the blank shape and intermediate shape and between the intermediate shape and the product. The difference in the wall thickness is reduced since the square shape is formed via a cylindrical shape. In addition, the effect of the process parameters on the forming results is experimentally investigated.

As important structural freeform panels (FFPs) for medical implants and aerospace system, lightweight thin wall panels with lower ductility are conventionally produced by hot forming process by utilizing the die on the press, which is not efficient or cost-effective for small batch or customized manufacturing. The dieless incremental sheet forming (ISF) provides a promising solution with increased formability, but making sheet metal panels with low-ductility at room temperature is still a challenging work. Targeting to solve this puzzle, a novel ISF without edge constraint on the target blank between the two edge-fixed supporting layers is developed to get flexible and free plastic deformation for the target blank. To reveal the deformation mechanism of this new method, an analytical prediction model of sheet thickness in ISF process is developed to calculate the deformed thickness in severe thinning region, which indicates that the undesired severe thinning region of conventional ISF process is caused by different stress states near the constrained edge, and can be completely eliminated by this proposed method to obtain uniform plastic deformation and improved formability. Different FFPs of magnesium alloy AZ31 and titanium alloy TC4 are fabricated by FFISF to validate the improved formability, and compared with conventional ISF and three-sheet incremental forming. Experimental studies demonstrate that the proposed method provides potentials for flexible fabrication of FFPs with low ductility at room temperature. More importantly, the promising geometric accuracy without trimming can be obtained by this new method, and multiple axisymmetric parts can also be formed within a cycle time.

A type of gear rolling process using conical gear rollers was firstly proposed in this study. Different with the cylindrical gear rollers used in the traditional gear rolling process, the roller which looks like a conical gear with different tooth profile along the axial direction was adopted in the rolling process. Besides, the radial feed applied on the roller in traditional rolling process was replaced by the axial feed applied on the blank. The proposed rolling process was divided into three stages, viz., tooth graduation, tooth forming and tooth finishing. According to the function of the roller in each stage, the structure of the conical gear roller was designed. Importantly, the detailed formulas to calculate the essential parameters of the gear roller’s tooth in tooth forming stage were established, such as the diameter of addendum circle, the radius of addendum tip, the pressure angle, and the cone angle. Through the numerical simulation, the variation and forming mechanism of the tooth profile at different stages were analyzed. The results revealed that the proposed process achieves better uniform tooth graduation and refining of the tooth profile, which increase the forming accuracy of the tooth to some extent in rolling process. Moreover, the experimental device was developed and the feasibility of the conical gear rolling process was verified.

Al-2219 alloy belongs to the class of age-hardenable materials applied in many industrial applications. To impart strength in components, it is usually tempered to T6 condition through age-hardening process. However, during this process, the components experience distortion thus adversely affecting the form accuracy. The present work is aimed at devising an appropriate processing route to produce age-hardened components through Incremental Sheet Forming (ISF) with reasonable accuracy and formability. Three different processing routes namely P-ISF-ST-T6 (ISF followed by solution treatment which is followed by age-hardening), P-ST-ISF-T6 (solution treatment followed by ISF which is followed by age-hardening) and P-ST-T6-ISF (solution treatment followed by age-hardening which is followed by ISF) are applied to produce a pyramid shape. The tensile properties of the starting sheet blank are observed to have significant influence both on the form error and formability. Yield strength appears to control the error in the flat wall and corner of pyramid in a way that the error decreases with a decrease in strength. Low yield strength, however, contrarily promotes geometrical error in the bottom of pyramid. Corner in the pyramid geometry suffers from the maximum error. Regarding formability, it is found to be governed by the area reduction in tensile fracture. The least cumulative error with reasonably high formability is offered by the P-ST-ISF-T6 route. The processing route is found to influence the distribution of residual stresses as well. The nature/magnitude of stresses in the material is transformed when ISF is performed, which further experience transformation if exposed to heat treatment. The material processed through the P-ST-T6-ISF route endures the maximum residual stresses, the route that also induces the highest form error. This reveals that higher residual stresses could cause higher form error in ISF.

The aim of this study was to develop an incremental forming method for carbon fiber reinforced thermoplastics (CFRTPs) using an optical heating system. The developed forming machine was mainly composed of a vertically articulated robot to control the position of the blank sheet on the X-Y plane, a reciprocating mechanism to generate the reciprocating motion of the forming punch, an electrical cylinder to control the position of the reciprocating mechanism, and a halogen lamp for local heating. Discontinuous short-fiber CFRTP work sheets with thickness of 0.5, 1.0, and 1.5 mm were used for the experiment. Each work sheet was fixed to a blank holder and locally heated by a halogen lamp set under the work sheet. The heated region of the work sheet was formed using the reciprocating motion of a spherical forming punch with a punch radius of 0.5, 1.5, or 2.5 mm, which was located on the opposite side of the halogen lamp. In order to evaluate the fundamental forming characteristics of the developed system, simple spot-forming was performed without feeding a work sheet on the X-Y plane. The work sheet temperature was set to 200 °C at a distance of 3.0 mm from the optical axis of the halogen lamp for each work sheet thickness. This study examined the relationship between the pushing distance of the reciprocating forming punch to the work sheet and the forming height, which was the distance between the top of the formed concave portion and the flange region of the work sheet. The forming height was lower than the pushing distance of the forming punch, and this tendency was conspicuous when the work sheet was thin and the punch radius was small. Fractures in the formed part were caused by excessive thinning of the work sheet due to the tensile deformation at the sidewall of the formed shape. The symmetrical shape profile of the formed part following the forming punch shape could be obtained when the pushing distance did not exceed 7.0 mm with a work sheet thickness of 1.5 mm and punch radius of 2.5 mm. The shape profile of the formed product obtained by two-dimensional sheet-fed forming was also estimated to evaluate the advantage of the developed method. The forming characteristics in the two-dimensional sheet-fed forming were different from those in the spot-forming. The continuous formed shape according to the sheet-feeding path could be achieved by the two-dimensional sheet-fed forming, and the advantage of the developed method could be experimentally clarified.

Problems of estimation of pulse magnetic field strength distribution across the affected area is an important component in the design and use of inductor systems for the electro-magnetic technologies including forming, joining and welding. Using a sensor placed between the coil and the blank, it is possible to measure strength of magnetic field in one or few locations, but that way it is difficult to obtain a detailed distribution. In this work the method of obtaining a distribution of magnetic field using pressure sensitive film (PSF) is suggested and experimentally tested. The method is verified by comparing the PSF data with the results from an induction sensor and also with the results of numerical simulation performed using finite-element code LS-DYNA®. The developed method is used to obtain the detailed distribution of magnetic field of the rectangular planar coil.

Obtaining square cups with the radius at the bottom corner lower than the thickness of original plate via a single-step hot forming process is a challenge. In this paper, a processing way was proposed by combining local-thickened plate and friction control, to manufacture square cups with small corner radii. Through finite element (FE) simulations, the metal flow during hot forming of square cups was optimized by varying the shape of the local thickened section and adjusting the friction conditions at the interfaces between blank and tools. It was found that the filling ratio of the bottom corner can be significantly improved by increasing the friction coefficient at the interfaces between the blank and the upper punch, and that between the blank and the central zone of counter punch. The established flow dividing surface (FDS) model is capable for describing the variation of metal flow with the friction coefficients. Base on the simulation results, hot forming experiments were also carried out, and square cups with small radii of 2 mm at the bottom corners were successfully manufactured.

Flexible roll forming is an advanced sheet metal forming process that allows for the production of variable cross-section profiles. Longitudinal bow is one of the major shape defects found in roll-formed products. To characterize the degree of longitudinal bow during flexible roll forming, experiments were conducted on three different blank shapes: trapezoid, convex and concave. Symmetric U-sections with variable cross-sections were roll formed using the three sheet materials with different strengths from each blank shape. The effects of process variables on the longitudinal strain and longitudinal bow were analyzed both experimentally and by using finite element simulations based on ABAQUS-Implicit 6.14. The results show that the transversal nonuniformity of the longitudinal strain is one of the fundamental causes of longitudinal bow in roll-formed products. The bow height as a function of blank shape increases in the order of concave, trapezoid, and convex. The bow characteristics on the basis of blank shapes and material parameters provides a better understanding of the non-uniform longitudinal strain and bow height during flexible roll forming with high reliability. Furthermore, to reduce the longitudinal bowing, leveling roll is introduced. The effect of leveling roll on longitudinal bowing was investigated experimentally. The results show that longitudinal bowing was reduced with the use of three blank shapes when leveling roll was applied to a flexible roll forming process.

In this paper, the warm forming process of a turbine engine strut made of 17-4PH (precipitation hardening) stainless steel is investigated. The blank is heated to a desired temperature using an industrial induction heater. The temperature value of the blank was measured using thermocouples and a pyrometer. The forming process at elevated temperatures is realized for a wide range of heating temperatures of 20–800 °C. The effect of overheating of the blank due to transfer of the blank from the heater to the stamping die using an industrial robot on the dimensional deviation of the drawpiece is considered. The geometry of the drawpieces was measured using an Atos 3D optical scanner (GOM, Germany). The smallest shape deviation of the drawpiece is obtained in the case of forming at 680 °C. To study the change of temperature during the heating and forming process, thermocouples and an optical pyrometer were used. The analysis of the microstructure of the blank material at different temperatures indicates that plastic strain in the temperature range of 20–800 °C causes an increase of banding of phase components of the microstructure. No evident effect of strain rate on the change of the 17-4PH steel microstructure is observed.

A novel hot stamping technique known as ‘Solution Heat treatment, Forming and in-die Quenching (HFQ ® )’ was employed to manufacture lightweight structural components from AA6082 tailor-welded blanks (TWBs) of different thickness combinations: 1.5–1.5 and 2.0–1.0 mm. A finite element (FE) model was built to study the deformation characteristics during the hot stamping process. The FE model was successfully validated by comparing simulation results with experimental ones. Subsequently, the verified simulation results were analysed through a novel multi-objective FE platform known as ‘Knowledge-Based Cloud – Finite Element (KBC-FE)’. KBC-FE operates in a cloud environment and offers various advanced unique functions via functional modules. The ‘formability’ module was implemented in the current study to predict the limiting dome height and failure mode during the hot stamping process. Good agreements were achieved between the predicted and experimental results, from which studies were extended to predict the forming features of 2.0–1.5 mm TWBs. The ‘formability’ module has successfully captured the complex nature of a hot stamping process, featuring a non-isothermal and non-linear loading path. The formability of TWBs was found to be dependent on forming speed and blank thickness, out of which the latter has a dominant effect.

Shear cutting is used to separate a sheet metal into two parts. During the cutting process, the material is deformed by two moving parts until its formability is exhausted. When a material is sheared, a burr deformation can often be observed on the cutting edge. Due to different disturbing effects, the burr must often be deburred before the next process of machining. The objective of the paper is the production of sheets without a burr under industrial boundary conditions. Therefore a progressive die is built in order to perform the necessary experiments. In addition to the experiments the simulation tool Abaqus is used to reduce the number of experiments to a suitable minimum. Adjusting a notching with a cutting process a burr-free cutting edge should occur. The notching results in a local change of formability on the blank sheet. Subsequently, the sheet metal is cutted in a normal shear process at the same position of the sheet metal where the notch at first was pressed into the bottom of the sheet. Due to the lowered deformability at this part of the sheet, the cutting edges of the sheet metal cannot build up any burr. Therefore, the impact of different parameters on the cutting edge is analyzed to create a notch geometry as well as shear cutting parameters without burr deformation, furthermore continuous strokes are performed to show the impact of this new cutting process for industrial applications on the tool material. Additionally to the burr free cutting edge, the new method shows less wear than the normal shear cutting.

Reducing sheet metal yield losses in automotive manufacturing would reduce material demand, providing both environmental and financial benefits. Current literature is unclear on how yield losses can be reduced since there is limited knowledge of how much scrap is generated, the cost of scrap and why yield losses occur. Through an industry study, this paper estimates that yield losses account for 44% of sheet metal used in the production of passenger vehicles. Improving production material efficiency to 70% would reduce the embodied emissions and material costs of the sheet metal car structure by 26% and 24% respectively. This could provide a global annual saving opportunity of 25 million tonnes of CO 2 , and £8 billion. Evaluation of a case study vehicle reveals that yield losses occur when a blank is simplified to a regular shape, or increased in size due to the design of the part, blank holder and addendum surfaces. A study of business processes identifies that yield losses are increased to meet part design and manufacturing requirements. Results from the industry, vehicle and business process investigations are analysed to propose and evaluate nine strategies for sheet metal scrap reduction. Suggestions are made to enable immediate and long term implementation of yield improvement strategies.

The combination of additive manufacturing (AM) and forming offers new opportunities in part and process chain design. To show the potential of this process combination, a gear component with discrete tooth geometry is manufactured by powder bed fusion of metal using a laser beam (PBF-LB/M) and forming. Such gear components are manufactured conventionally in a process chain of several sheet bulk metal forming operations like orbital forming, deep drawing and upsetting. Orbital forming is used to manufacture a tailored blank to increase form filling in the subsequent forming operations. However, challenges are form filling and control of material flow. These severely affect whether the target geometry can be realized. To overcome these limitations, in this work PBF-LB/M is used to manufacture the tooth geometry close to the target on a flat sheet. Subsequently, the three-dimensional part geometry is realized by forming. The advantage is that the orbital forming step is not necessary. With that, the tooth geometry does not depend on material flow. A further benefit is geometric flexibility of additive manufacturing processes. Hence, diversity of variations can be increased over a wide range without additional cost intensive forming tools for each single part geometry. Besides, the potentials and challenges of the approach are discussed. The investigations include characterization of formability of sheet metal and AM material, metallographic analysis and hardness measurement. A process chain for manufacturing hybrid parts is presented and the final part geometry is evaluated by topography measurement. The major finding is that the tooth geometry manufactured by additive manufacturing and forming is closer to the target than for the conventional process chain. Additionally, a comparison of technological and economic advantages is drawn. Finally, an extension of the approach is presented by hybrid parts with additively manufactured structures on both sides of the sheet metal.

There has been a great increase in the applications of micro thin-walled parts in many fields, such as medical devices, aerospace and so on. The requirement of machining dimensional accuracy for micro thin-walled parts is very high. Inconel 718has the advantages of high strength and corrosion resistance, which can meet the requirements of micro thin-walled parts under poor applying working conditions. However, it is difficult to machine. Micro-milling is a potentially effective processing technique for processing Inconel 718 thin-walled parts. Because of the low rigidity, deflection of Inconel 718 thin-walled parts is easy to occur in micro-milling process, which affects the machining accuracy. So far, the research on the deflection of micro-milling Inconel 718 thin-walled parts is still blank. In this paper, a method of deflection prediction of micro-milling thin-walled parts is proposed. Firstly, a simulation model of micro-milling Inconel 718 thin-walled parts process is established, which realizes the prediction of milling force. Then, by using element birth/death technique, a deflection prediction model of micro-milling thin-walled parts is built based on the predicted value of milling force output by the simulation model, which achieves the more efficient and accurate deflection prediction of micro-milling thin-walled parts. Finally, the correctness of the built simulation model of micro-milling thin-walled parts process as well as the deflection prediction model of micro-milling thin-walled parts are verified by experiments. The research provides a feasible way for deflection prediction of micro-milling thin-walled parts, and lays foundation for deflection suppression and machining accuracy improvement of micro-milling thin-walled parts to a certain extent.

The extremely thin wall (0.25 mm) and the Ω-sectioned profile of the ring together with the difficult-to-deform superalloy bring difficulties to forming technology. To address this issue, a new external-internal composite spinning technology is proposed. External and internal spinning are to handle the necking-in zone and flanging zone, respectively, of the Ω-sectioned profile of the ring. During the spinning process, roller trajectory is crucial to determine whether the ring can be formed successfully. Therefore, two types of roller trajectory were proposed: circular-straight and involute, the effect of which on the forming were compared via finite element simulation. The results indicate that the involute roller trajectory tends to produce a lower wall thickness reduction and improve the anti-wrinkling ability of the blank. The involute roller trajectory and its parameters were then determined. Then the process parameters were studied. With the increase of the mandrel speed, roller feed ratio, and roller nose radius, lower wall thickness reduction of the blank was obtained, while the wrinkling factor increases rapidly. According to these results, a process scheme is designed, with which successful experiments have been performed. The external-internal composite spinning technology shows great capability on forming the thin-walled complex-sectioned ring part.

A 3D profiled blank (3D-PB) is a variable thickness in both the rolling direction (RD) and transversal direction (TD). A novel method of manufacturing 3D-PB is proposed in this paper. The method combines two processes: first, the workpiece of a normal blank is rolled into a tailor rolled blank (TRB) through variable gauge rolling (VGR), then the TRB is rolled into a 3D-PB through variable thickness rolling (VTR). A significant modification was made to VGR as the original VTR could not be adapted to the production of 3D-PB. The metal flow of the thick and thin areas of the 3D-PB was investigated with finite element simulation. The metal in the thin area mainly flows in the TD. The deformation of the workpiece was studied during the process. The workpiece was first bent and then thinned, resulting in a different width between the thick and thin areas. The thickness difference between the thick and thin areas of the 3D-PB was explained through simulation and controlled rolling experiments. The final 3D-PB has a variable thickness in both the RD and TD with good shape.

A single nozzle design with three lateral ports has been proposed to feed a beam blank mold. Techniques of physical modeling and computational fluid dynamics (CFD) were applied to evaluate the fluid flow as a function of port angle, immersion depth and flow rate. The overall features of the flow field are not affected by changing the values of these parameters. The proposed design is characterized by: increasing fluctuation intensity at the meniscus and high impact velocities in certain regions of the broad face of the flanges. The oscillation intensity increases with decreasing immersion depth, increasing inclination of the exit ports, and increasing flow rates. These values vary also along the free surface of the mold, being larger on the flange opposite to the submerged entry nozzle (SEN) for all configurations. The impact velocities at the flange were affected only by the flow rate, reaching a maximum value of 0.45 m/s.

The critical step during open die forging of a large crank throw for a marine engine is bending the preform into a V-shaped blank. The blank may be bent in an inaccurate fashion due to its asymmetric shape, temperature non-uniformities, and/or any misalignment between the preform and the die. Correcting a distorted asymmetrically bent blank is difficult. Therefore, controlling the deformation during bending of a large crank throw is required. In this study, a new bending process that makes it possible to form a non-distorted, symmetrically bent blank is described by introducing the concept of a floating die. The feasibility of the proposed method is confirmed using test cases obtained from finite element simulation and scaled down model tests using laboratory prototype tooling. This technology will increase the shape accuracy of the bent blank and will save time during post-machining of a large crank throw.

Excessive thinning of wall thickness caused by the unstable deformation of metals is the main failure mode in the manufacturing of thin-walled circular rings with complex section. A novel quasi-bulk forming method is proposed in this work to deal with this problem through achieving a stable state of metal flow. Metallic materials and viscous medium with different strain rate sensitive exponents (m) were respectively employed as core materials (i.e. pressure-carrying medium) in finite element analysis (FEA) to investigate the effects of core materials on the deformation behaviors of ring-shaped metal blank. Numerical results indicate that viscous medium and metal blank deform synchronously like a composite billet when appropriate viscous medium acts as core material. It is attributed to the adhesive attraction between viscous medium and metal blank caused by the high viscosity of viscous medium. In this condition, the composite billet easily fills the die cavity, which is similar to the way that round billets fill the die cavity in bulk forming processes. In order to verify the validity of quasi-bulk forming method, two types of thin-walled circular rings with corrugated meridians were formed through proposed method in the forming experiments. The maximum wall thickness reduction of formed parts is less than 8%. The present study demonstrates the quasi-bulk forming method can not only inhibit wall thickness thinning of thin-walled parts but simplify the process control. Thus, it may become a key process to fabricate thin-walled circular rings with large diameter variation per unit axial length ( ψ ).

This paper presents a method of flange compression using a stepped punch and die for effective production of an extremely deep cup with a flange from sheet metal. The proposed method was composed of initial stretching and flange compression, and fracture was prevented during the flange compression as the blank elongates by only compressive force. Optimum forming parameters, which are stepped lengths of the punch and clearance between the punch and the die, were investigated by finite element analyses and experiments. It was possible to produce a deep cup with uniform side wall thickness, which length-to-diameter ratio was 2.00, by the optimization of the forming parameters. In addition, two-step forming, which uses two punches, was proposed for producing an extremely deep cup with a thinner side wall. As a result, the deep cup, which length-to-diameter ratio was 9.23, was obtained.

Flange wrinkling is one of the most common defects affecting the forming quality of workpieces in conventional spinning. To this end, the flange wrinkling mechanism is analyzed and a new robust theoretical prediction model for the flange wrinkling is developed in this work. It is found that the initiation of flange wrinkling is closely related to the excessive circumferential compressive stress in the zone affected by the roller action rather than the whole flange. Then, a theoretical model for the critical circumferential stress producing flange wrinkling is developed based on the generalized variational principle of limit analysis. By comparing the instant maximum circumferential stress in the zone affected by the roller action with the calculated critical stress, the flange wrinkling can be predicted. Compared with the prediction model based on energy method, the main improvements of the new model can be summarized as follows. First of all, the incremental displacement amplitude of deflection mode in the effective compressive region, which dramatically affects the critical stress but overlooked in the model based on energy method, is considered in the new model. Secondly, the sheet blank is regarded as a rigid plastic material in the new model, so the calculation of elastoplastic matrix which is very sensitive to the mechanical states does not need to be considered, thereby avoiding the adverse effect of the extraction deviation of mechanical states on prediction accuracy. Thus, compared with the prediction model based on energy method, the new model has higher prediction accuracy and better robustness under the extraction deviation of mechanical states. In addition to realizing the prediction of flange wrinkling, the new model can also be used to analyze the influence of sheet blank geometric parameters and material parameters on the initiation of flange wrinkling under various forming conditions. In view of this, the new model is applied to reveal the influence of material parameters (material strengthening coefficient K, hardening index n and elastic modulus E) on the initiation of flange wrinkling by combining response surface methodology and central composite design (CCD). The results show that K has the greatest influence on the initiation of flange wrinkling, followed by E and n. Considering the interaction between the parameters, the interaction between K and E also has a greater effect on the initiation of flange wrinkling. The smaller E and larger K are helpful to reduce the risk of flange wrinkling. Changing the value of n has no significant effect on delaying the occurrence of flange wrinkling. The results can deepen the understanding on the prediction and rules of flange wrinkling in conventional spinning.

In this study, a novel method was proposed to evaluate high strain rate (HSR) formability of Al-Cu-Mg 2B06-O sheets by impact hydroforming (IHF). IHF was suitable to manufacture hard-to-form sheets, since it combined the advantages of flexible liquid and impact impulse loading. Both 2D and 3D HSR formability curves were established to describe the relationship between impact energy, drawing height ratio (DHR) and deep drawing ratio (DDR). Moreover, the novel evaluation method was realized by finite element (FE) modeling using fluid-structure interaction (FSI) algorithm. FSI modeling was used to deal with the interaction of structure solid and flexible fluid. This evaluation means of FE modeling characterized with guiding production practice, saving evaluation costs, improving efficiency compared with corresponding experiments. The results obtained from FE modeling were in a remarkable agreement with those obtained from IHF experiments in the aspects of part shape, failure feature, thickness distribution. FE modeling showed that the limit deep drawing ratio (LDDR) and limit drawing height ratio (LDHR) were 1.99 and 1.04, respectively when the blank was completely deep drawn into the cavity of the die in one step only. FE modelling is proved to be reliable and efficient to estimate high strain rate formability of low formability metal sheets.

Due to the rising lightweight construction, especially in the automotive industry, the demands focused on functional components are constantly increasing with a result of new challenges regarding the manufacturing technology. For an extension of the process limits of conventional sheet metal forming processes, semi-finished parts with a defined material pre-distribution, so-called tailored blanks, can be used to provide additional material volume in defined areas in order to achieve a proper die filling of functional elements like gearings or carriers used e.g. for synchronizer rings. However, due to the increasing component complexity and thus the forming of functional elements on both sides of the frame, a two-sided thickness profile is mandatory. As a result, the material thickenings on both sides of the tailored blank lead to an interaction, regarding the maximum achievable sheet thicknesses or dimensions of the material pre-distribution. For the manufacturing of such tailored blanks, an orbital forming process can be used. Prior investigations showed the general feasibility for the manufacturing of tailored blanks with a one-sided thickness profile. In this paper, the feasibility of using the orbital forming process to produce tailored blanks is fundamentally investigated. Therefore, a numerical model of the process was developed, with a subsequent validation by comparing the numerical with the experimental results. Afterwards, the material flow is analysed regarding different geometries of the material pre-distribution as well as the position of the thickness profile in order to allow a generally valid design.

Gear rolling has the advantage of efficient material application, contour-related fiber orientation, and can overcome forming difficulties of gear forging. In the initial stage of gear rolling, often the slipping phenomenon occurs. Slippage and the degree of slippage significantly affect the forming quality of the tooth shape. In this paper, the applied forces on a blank in the initial forming phase of the gear rolling were analyzed, and the main factors affecting slippage were determined. Then, the quantitative evaluation index of the slippage was established. The effect of initial bite depth, friction condition, and number of teeth on the gear roller on slippage was obtained using finite element analysis. The effect of different initial bite depths and number of teeth on the gear roller on the slippage was studied experimentally. Moreover, the reliability of the finite element simulation results of gear rolling was verified. The results can provide a scientific basis for establishing reasonable process parameters, control of slippage, and improving the forming quality in gear rolling.

Hybrid composite material was fabricated by stacking carbon fiber-reinforced plastic (CFRP) on CR340 plates, resulting in greater specific strength and stiffness than other stacked composites fabricated by a different laminating method. To assess its formability and potential use in vehicle parts, deep drawing tests were conducted for this hybrid composite material with various process parameters. The experimental results showed that with low blank holding force, the forming depth of the CR340/CFRPR* composites was higher than the forming depth of CR340/CFRP composites. However, the forming depth of CR340/CFRP and CR340/CFRPR* composites were virtually the same when the blank holding forces were increased to 30 and 90 kN. Further, the CFRP composites flowed abruptly toward the round part of the die as the punch velocity increased. The thinning rate in each position of the drawing product and the problems encountered during the deep drawing process were reviewed by comparing the experimental results.

Internally toothed gears have wide application as transmission components, for which spinning process is attracting increasing attention due to its high production efficiency and low cost. In this paper, a multi-pass stagger spinning process of internally toothed gear from plate blank was investigated through FEM simulation and process experiment. Two passes, i.e., drawing spinning and power spinning, were designed during stagger spinning. The deformation characteristics were analyzed, the mechanisms of spinning defects were revealed and the influences of process parameters were discussed. It is shown that the preform formed by drawing spinning in the first pass contributed to the filling of inner tooth cavity in the second pass. Underfilling and crack in the vicinity of the tooth were two typical defects, which could be effectively controlled through optimizing the spinning process. On this basis, the internally toothed gear was well formed with high productivity by stagger spinning on a CNC spinning machine, showing great potential for industrial application.

Hot stamping has been widely studied and increasingly applied in the automotive industry. This process is characterized by its ability to stamp high strength steels, yielding products with high mechanical strength, thus reducing the weight of stamped components and therefore the vehicles weight. It also demands less energy because steel sheets can be heated by induction, more efficient than electric furnaces. With controlled thinning, it is possible to manufacture thinner stamped parts with high mechanical strength, therefore it is necessary to know the formability limits to prevent failure and achieve the largest possible thickness reduction. In this work the hot formability of DIN 27MnCrB5 steel sheets 4 mm thick, under thinning conditions was evaluated by numerical simulation with the finite element (FEM) software Forge2008. Tensile tests were carried out at 500, 600, 700, and 800 °C and with strain rates from 0.1 to 4 s −1 . With the results of tensile tests, it was possible to calculate Hensel–Spittel coefficients to model the steel sheet and simulate the hot Nakazima test to evaluate the highest dome which could be formed without failure risks caused by sheet thinning. Simulation results obtained with specimens 200 mm long and 125, 150 or 200 mm wide that were stamped at 930 °C, showed the radial position and dome height associated to plastic instability as well provided the thickness distribution along the specimen. The numerical results were compared to experimental tests and showed a good agreement in terms of failure initiation and localization. As a result, a new numerical and experimental strategy was elaborated to define the hot formability based on the plastic instability and necking localization as a function of stamping temperature and blank dimensions. This strategy proved to be useful to define the safe formability region and therefore the larger thickness reduction that can be done during hot stamping to reduce vehicular components weight and to avoid cracks and failures usually observed in components like clutch covers.

Laser cutting has started to be used as an effective method for cutting out blanks from rolled sheet metals because of its high flexibility for cutting lines and high productivity. However, residual stresses, which are generated by laser cutting, have been the greatest obstacle for the popularization of laser cutting. One of the problems is the warp which appears in the sheet metal after being subjected to bending processes after laser cutting. The authors present a light press method for reducing residual stress generated by laser cutting. The method is to give a light press on the sheet metal edge and to reduce tensile residual stress generated near the laser cutting surface. In particular, this present paper especially focuses upon optimization of working conditions depending on mechanical properties of the blank and the effect of the heat affected zone in laser cutting. Experiments of U-bending after applying light press were conducted for usability of this method. The FEM analyses were carried out in order to investigate proper working conditions depending on various mechanical properties. As a result, the optimum press pressure of the light press method for various mechanical properties was found out for reducing residual stress which caused by laser cutting, by taking warp after U-bending as an evaluation parameter. The relationship between the optimum pressure and the proof stress was quantitatively and specifically clarified for several sets of mechanical properties. It was also found that the influence of heat-affected-zone area and intensity of residual stress by laser cutting on the optimum press pressure was small.

Sheet-bulk metal forming is an expedient approach to efficiently manufacture functional components out of sheet metal. In order to reduce weight of the component manufactured, an application-adapted approach was developed to replace the conventional steel blank by a semi-finished product consisting of two blanks with half the thickness to enable the tailored combination of different materials in a combined deep drawing and upsetting process. To establish a basis for the application of these hybrid semi-finished products, first of all multilayer steel semi-finished products are drawn and upset in the process combination. Thereby, the upsetting process induces a three dimensional material flow and at the same time an interlocking connection of the two blanks. The gained results are the transferred onto the combination of steel and aluminium alloys within one semi-finished product. Fundamental dependencies as well as the influence of the application of different steel grades are investigated.

This paper presents an experimental and numerical study on the hybrid process of polymer injection forming (PIF) developed to manufacture sheet metal-polymer structures in one single operation. Despite the wide potential application of the PIF process, several challenges have prevented conducting an in-depth analysis of the simultaneous injection/forming condition that occurs during this hybrid process. One such challenge is the lack of a special feature in the regular injection molding machine for an independent application and control of the blank holder force (BHF) from the preset clamping force. To enable such, a new concept-to-design tool is proposed in this work. Using this specialized setup, the influence of the BHF, injection rate and their interactions are experimentally determined focusing on the transient PIF process variables and the quality of the final hybrid product. The use of the fluid-structure interaction (SFI) method to perform a multi-physics simulation on the PIF process incurs such computational costs that it is unreasonable to conduct multiple simulations to investigate the effects of several process parameters and their interactions. To achieve both efficiency and accuracy, a new combined analytical-numerical approach is presented to enable fundamental understanding of the PIF process physics considering the interaction of filling, stretching and drawing mechanisms. The feasibility of the proposed numerical and experimental methodologies is demonstrated through a comparative analysis of the deformation of the AA1100 sheet during the injection of a Polypropylene compound with different injection rates and BHF settings.

In spinning process of large thin-walled aluminum alloy parts, the wrinkling phenomenon easily tends to appear on the blank flange. By applying a constraint condition to the flange, such as a backup roller, the flange stiffness can be increased, and the wrinkling tendency is delayed. In order to understand the deformation mechanics under the flange-constrained conditions, the effects of two kind of flange-constrained methods on the spinnability of an aluminum alloy hemispherical part are studied in this paper, and the effects of the flange-constrained conditions and process parameters on the wrinkling initiation at the flange are analyzed. At the same time, multi-pass flange-constrained spinning processes are completed. The spinnability test results show that the forming defect of the single-side flange-constrained(SSFC) spinning is wrinkling, and that of the double-side flange-constrained (DSFC) spinning is cracking; the two flange-constrained methods can both increase the spinnability of the hemispherical spun part. And the analysis of process parameter shows that with the increase of the feed rate and the operating angle, and with the decrease of the roller nose radius, the flange wrinkling initiation in the SSFC spinning occurs in advance. Besides, in the multi-pass forming of the hemispherical part, compared with the conventional spinning, the two flange-constrained spinning processes can not only make forming passes fewer, but also improve the wall thickness uniformity.

In recent years, greater attention has been given to predicting and controlling machining deformation (MD), with a major factor in this being residual stress (RS), a primary concern in the processing of aerospace monolithic thin-walled parts. This paper proposes an analytical model for frame parts MD that can predict deformation caused by RS; a slope method is then presented for measuring the distribution of the blank initial RS. Accuracy for the proposed model is validated via experiments and finite element simulations. Following this is a study of the effects of neutral layer offset and RS on the deformation, as well as a determination of the functional relationships between deformation and RS. Machining deformation is controlled by two methods, with the part’s best position in the blank being optimized to minimize deformation and strain energy. Datum correction is used to effectively control the MD during the finishing stage.

A new rotary forming process for rim thickening was proposed in this paper, which can be applied on sheet metals to produce parts with thin web plates and thick rims integrally. Via FE simulation, an orthogonal test was conducted to investigate the effects of forming parameters on γ max , which is the ratio of maximum blank size to thickness and indexes the stability of sheet metals while during forming. It is found that the incline angle of the upper roller groove surface, and the friction condition between the sheet metal and roller groove are the dominant factors affecting the process, while the influence of the feeding velocity and the groove arc radius are relatively slight. It is also proved that interactions exist among these factors. Furthermore, an optimized parameters group is obtained, and a process window plot showing the limits of the forming process is achieved. The facticity of FE simulation is verified by technological experiments.

Double-sided hydroforming has been widely used in production since it can improve the formability and surface quality of sheet metals significantly. This paper investigates the application of thick shell element in finite element analysis of sheet metal forming process with pressure reacting on both sides of the blank. The computational efficiency and accuracy of thick shell element is compared with that of solid element and traditional shell element based on a numerical example. Then a double-sided blank hydroforming experiment is carried out to validate the thickness prediction ability of thick shell element, and the results show that the normal stress in the thickness direction caused by double-sided pressure reduces the material thickness and increases plastic strain and effective stress in the forming zone. Thick shell element, which can reflect the influence of normal stress on sheet metal forming process, is effective in finite element analysis of double-sided hydroforming.

The main focus of the present work is the development of a global procedure for a complete characterization of sheet metal behavior, including anisotropy, evolution of hardening and rupture. This efficient procedure involves the mechanical characterization, at room temperature and in quasi-static conditions, of the material up to large strains by evaluating the local strain field. The initial anisotropy, hardening and rupture of DC04 mild steel are characterized using a complex phenomenological model composed by the non-quadratic Yld2004-18p yield criterion combined with a mixed isotropic-kinematic hardening law and a macroscopic rupture criterion. For this purpose, an inverse methodology for material parameter identification is implemented based on several experimental tests considered as homogeneous and also, a mixed experimental-numerical approach to calibrate the rupture criterion is performed. In order to validate the obtained results, a deep drawing test, leading either to full drawing or rupture of the blank, is carried out. Digital image correlation is used to acquire additional data information in the deep drawing test. Strain fields at several stages of the deep drawing experiment are evaluated leading to a better comparison between the experimental observations and the results of the numerical simulation.

Studies on quantitative formability estimation by using deformation processing map have been performed to estimate deformation characteristics of SAF2205 duplex stainless steel during ring rolling process. To develop deformation processing map, dynamic materials model has been used on the basis of stress-strain relationships from Gleeble compression test. As a quantitative formability index, summation of ηij (efficiency of power dissipation for i-th unit deformation group in j-th slicing plane) multiplied by area fraction of unit deformation group (Aij) has been suggested. ηij-value for unit deformation group was determined from deformation processing map of which temperature and strain rate can be obtained by finite element method. For the feasibility analysis, the optimum blank dimension at various operating temperatures has been determined on the basis of formability index. The analysis result strongly confirms that the proposed formability index can provide a reliable guide in process design of ring rolling process.

Dieless hydro-bulging of a spherical shell comprising welded hexagonal and pentagonal shaped panels, in the manner of a ‘soccer ball’ construction using ‘corner-cutting’ technique to improve shape accuracy, is described in this paper. The ‘corner-cutting treatment’ of the panels is used to decrease the roundness error of a bulged spherical ‘soccer ball’ shell with a diameter of 1300 mm. The strains on the surface of shell were measured versus the internal pressure and the equation for calculating the maximum internal pressure is given. The nonlinear commercial simulation software ADINA was used to simulate the forming process. During simulation, the thickness of welding seam was considered for the first time compared to previous research of shell hydro-bulging, because the thickness of welding seam is larger than that of sheet. In order to investigate the variation of the stress state during hydro-bulging, the trajectory of the principal stresses of typical points on the soccer shell was plotted on the yield locus by numerical simulation method. Simulation results suggest that the springback deformation and the residual stress after unloading of the internal pressure are small. The experimental and simulation results show that the plastic deformation of the hexagonal blanks is larger and occurs earlier than that of pentagonal blank in the hydro-bulging process. Moreover, the roundness error of the shell after ‘corner-cutting treatment’ is significantly decreased.

Electrohydraulic forming (EHF) is based upon the electro-hydraulic effect: a complex phenomenon related to the high voltage discharge inside the water filled chamber. The resulting shockwave in the liquid is propagated toward the blank, and the mass and momentum of the water in the shock wave accelerates the sheet metal blank toward the die. Methodology of numerical simulation of EHF processes was developed based upon LS-DYNA commercial code using Arbitrary Lagrange–Eulerian (ALE) Multi-Material formulation. The model incorporates energy deposition inside the plasma channel, expansion of the channel driven by high pressure inside of it, propagation of the pressure pulse through the water filled chamber in contact with the rigid walls of the chamber and with the sheet metal blank being deformed. Comparison of the numerical and experimental results was performed on maximum pressure measured on the wall of the cylindrical chamber employing the membrane method. The model was used to simulate multistage EHF of a complex geometry automotive part. Analysis of the results showed the complex nature of multistage EHF process: a clearly recognizable wave picture during the initial stage of the channel expansion which transitions to almost incompressible water flow during later stages.

FE simulation of elliptical bulge forming of AZ31 automotive magnesium sheet has been carried out based on a recent experimental study where a new method of simultaneously bulging of two clamped blanks of different geometries was successfully employed to experimentally obtain tension–compression side of the FLD. The present study complements the earlier experimental study by providing insight into material plastic flow and strain localization for various ‘double blank’ configurations. In addition, FE simulation results are utilized to predict the FLD of AZ31 sheet at 300 °C based on a recently proposed strain localization criterion and other material model assumptions. Good agreement has been observed between the experimental and predicted FLDs.

This paper proposes a new die design for deep drawing with high-pressured water jet. The authors had previously proposed a deep drawing method with high-pressured water jet. The water jet enables deep drawing without oil or other chemical lubricants, which might require some additional processes for lubricant removal and become a nuisance in the environment. One of the problems in the method using a prototype die with 8 nozzles in the hoop direction had been that the pump pressure had to be boosted significantly high for successful deep drawing, leading to scars on the surface of the deep drawn product. In the present paper, two new concepts of design were introduced with the help of computational fluid dynamics (CFD) for water film considering the blank deformation obtained by the finite element method (FEM). The first concept is that the number of nozzles should be increased from 8 to 16, and that the position of the added 8 nozzles should be positioned on the flange part of the die as a result of the CFD. The second concept is to shallowly engrave a looped ditch linking the nozzles. The CFD showed that while the die without the looped ditch generated an area of reduced pressure between the nozzles, the ditch-engraved die maintained the pressure, resulting in satisfactorily strong uplift force on the blank even at relatively low pump pressure. A series of experiments also verified the numerical results, and proved the excellence of the ditch-engraved die.

This study is an investigation into the effect of the different parameters of the pass set on the formability in synchronous multipass spinning. Synchronous multipass spinning is a metal spinning method that can produce a noncircular cylindrical shape with a noncircular bottom and vertical walls from a metal sheet. The radial position of the roller tool is synchronized with the spindle rotation while the work piece is formed from a flat disk into the shape of the mandrel step by step along varying trajectories. The tool trajectory is calculated by linear interpolation between the mandrel shape and the blank disk shape along a pass set. Here, a pass is the tool trajectory in the normalized two-dimensional space defined by the radial and axial directions of the mandrel. The aim of this study is to examine the effect of different parameters of the pass set on the formability of two sample shapes, a circular cup and a rectangular box. The formability was experimentally examined using a rotational pass set and a translational pass set as simple tool trajectories. The rotational pass set consists of curved passes with the same start point and a constantly increasing angle inclination. The translational pass set consists of passes with the same inclination and a start point that is moved by a constant amount. The angle of growth of the rotational pass set, the incremental movement of the translational pass set, and the nominal product height are varied for comparison in the experiments.

In order to achieve further weight reduction in automotive components, the technology of manufacturing of automotive panels from advanced high strength steels is being developed. Electrohydraulic trimming technology eliminates the necessity of accurate alignment of the shearing edges in trimming operation. Analysis of loads on the tool during high-rate EH trimming process has been performed. In order to investigate the effect of the process on the shearing edge performance, a dedicated finite element analysis procedure combining 3D shell and 2D solid models was developed. EH trimming experiments were carried out to validate the simulation model where elastic plastic deformation of the shearing edge was taken into account. The effects of the die geometry and number of trimming cycles on the tool contact loads and tool's plastic deformation were analyzed. This analysis was based on numerical simulation of deformation and fracture of the blank being trimmed in contact with the deformable shearing edge. Numerical analysis of the shearing edge deformation was performed in elasto-plastic formulation for the D2 tool steel inserts used in the experimental study and also in elastic formulation to define the maximum stresses which tool material needs to withstand to avoid its plastic deformation. The results of the analytical study indicate that the maximum contact pressure is applied to the trimming tool at the lower endpoint of the shearing edge, but the point of maximum plastic deformation in the tool is found on the vertical wall of the shearing edge where it contacts the area of the blank where separation takes place. The shearing edge of the EH trimming die experiences less contact pressure and less plastic deformation with increase of the radius of the shearing edge. The shearing edge of the EH trim die has a tendency to dull after a number of trimming cycles. In addition, when compared with conventional trim die, the shearing edge of the EH trimming tool experiences slightly higher (10–15%) contact loads than in conventional trimming. However, plastic deformations occurring in the conventional trim die for shearing of identical material are larger. Analysis of loads on the EH trimming tool was repeated for purely elastic tool material to formulate the requirements to the material of the shearing edge.

Since the deformation features of existing friction testing methods are not as similar as those of the closed die forging process of rib–web parts, the friction conditions evaluated by these methods are not consistent with the actual situation. In this paper, a new friction testing method, the T-shape upsetting–extruding process employing a rectangular blank, is proposed for evaluating the friction conditions during rib–web part forming process. It was found that rib height and the web width are both sensitive to friction conditions. Therefore, the ratio of rib height to web width was chosen as a criterion for friction evaluation. With the utilization of a commercial FEM program, DEFORM, the effects of the geometrical parameters and testing variables on the friction sensitivity were investigated, and the friction conditions between different interfaces were analyzed. In order to verify the proposed method, friction factors of a water-based graphite lubricant measured by three different methods (the proposed one, the ring compression test and the double-cup extrusion test) at 723 K were used to simulate the isothermal deformation process of a cross-rib part. The experimental results suggest that the proposed method is more accurate than the other two methods for rib–web part forming process.