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Using variable blank holding force, which is conventionally achieved by hydraulic or mechanical drive, can effectively reduce defects in the forming process. To overcome the obstacles of low response and high complexity of conventional drives, this paper proposes a holding system for variable blank holding force driven by the electro-permanent magnet. Focusing on the variable electromagnetic force, a control method based on grading voltage pulse width modulation and mode matching is addressed. The model of the transient electromagnetic force is first established, the relationship between electromagnetic force and current is obtained, and the migration law of the working point of the magnet with the change of current is analyzed. Then, the grading voltage pulse width modulation control, which regulates current by the pulse width and its amplitude, is developed for continuously increasing or decreasing force control. When force variations occur, mode matching is introduced to identify the working point and allocate matching parameters for better control. To validate the feasibility of the control method, the co-simulation based on Simulink-Simplorer-Maxwell and the experiment bench are built. Results of electromagnetic force show that the step response time is 0.13 s and the mean relative error is less than 1% for a given variable blanking force. The control method can reduce the thickness variations of sheet metal by 14–20% compared to the existing electro-permanent magnet blank holder. This work assists in realizing the loading of variable blank holding force driven by electromagnetics to improve the forming quality of parts. [Display omitted] • Transient model was built for the electromagnetic blank holding system. • Grading voltage PWM control was developed for quickly tracking of the system. • Mode matching was introduced for accurate control of the system. • Response and accuracy of the system was validated by experiments. • Better forming quality was revealed compared with the existing control. [ABSTRACT FROM AUTHOR]

Presently the lack of methods for fast quality evaluation of deep-drawn paperboard containers limit the industrial applicability of the deep-drawing process. This work presents an inline method for quality evaluation of deep-drawn paperboard containers. Two images of the deep-drawn sample are taken immediately after forming within the forming machine. The images are scanned and compared with a template of an ideal wrinkle structure. Calculation of the local cross-correlation of image sections and the template allows the detection and localization of wrinkles in the wall section of the deepdrawn paperboard container. The quantity of detected wrinkles and the evenness of the wrinkle distribution on the sample can be used as a quality measure. The accuracy of the method described in this work is validated against previously applied methods for wrinkle detection. The new method outperforms the previous methods in evaluation speed by a factor of 50 without significant loss of accuracy and thus is potentially applicable for laboratory and industrial applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Remote joining by plastic deformation in the process of linear flow splitting combines forming with simultaneously activated joining processes. While the forming process takes place in one region of a profile, the joining of the profile with another component occurs outside the forming zone. This approach promises a great potential with regard to joining multi-material units in a short process chain. Linear flow splitting is a rolling process which results in thin-walled and branched parts out of flat sheet metals without any heat treatment. As in other forming processes, residual stresses remain in the manufactured parts. They are used in the study at hand for a mechanical joining of the profile with other components. Based on numerical and experimental results, two models of joining mechanisms based on spatially distributed, uniaxial tensile and compressive stresses are presented and verified. The remote joining approach described in this paper accommodates two challenges of modern manufacturing: On the one hand, the increasing market demands for lightweight products which lead to various material combinations and hybrid structures in complex assembly units; on the other hand, the need for continuous optimization of process chains with regard to efficiency. [ABSTRACT FROM AUTHOR]

The additive manufacturing (AM) of fiber reinforced plastics has gained much interests in the design of lightweight structures with superior mechanical performance. Strong anisotropy can be induced during the extrusion process owing to the preferentially orientated fiber reinforced plastics with high aspect ratio. To make better use of AM-induced material anisotropy, an integrated material-structure-performance design strategy for AM-produced carbon fiber reinforced plastic (CFRP) structures was proposed, in which the microscopic material and mesoscopic structural anisotropies were integrated to achieve enhanced macroscopic mechanical performance of CFRP core structures and sandwich sheets. The effects of AM process parameters including the layer thickness and build orientation on microscopic material anisotropy of the AM produced CFRP were firstly investigated and the strong relationship between material anisotropy and AM process parameters was confirmed by extensive mechanical tests and microscopic observations. A new core structure possessing the arbitrary bending anisotropy was proposed and the relationship between structural anisotropy ratio and bending stiffness was clarified. In addition, the mechanical properties of core structures were tested and superior mechanical performance can be achieved by tailoring the combination of material and structural anisotropies. The effects of structural anisotropies on mechanical properties and face buckling behaviors of sandwich sheets were investigated and found that face buckling is the dominant failure behavior. The new finding that the integration of microscopic material anisotropy and mesoscopic structural anisotropy induced by AM could enhance the mechanical property and formability of CFRP core sandwich sheets is of great significance in the design of lightweight structures. • An integrated material-structure-performance design strategy for additive manufacturing (AM) produced fiber reinforced plastic structures. • The effects of AM process parameters including layer thickness and build orientation on microscopic material anisotropy of CFRP are clarified. • Structure that can achieve an arbitrary bending anisotropy is proposed. • The relationship between structural anisotropy ratio and bending stiffness is investigated. • Better mechanical performance can be achieved by the integration of material and structural anisotropies. [ABSTRACT FROM AUTHOR]

The present investigation is carried out to assess the suitability of the clinching process for production of plastic–metal hybrid joints. To this end, a prototypal apparatus was developed to preheat the sheets before joining. A campaign of experimental tests was carried out on aluminium alloy AA5053 and polystyrene. Experimental tests were conducted by varying the main process parameters, i.e. pre-heating conditions (heating time and temperature of heating air) and forming pressure. The joints produced under different operating conditions were observed using optical and stereoscope microscope. In addition, the mechanical behaviours of joints were assessed by conducting single lap shear tests on single joints. Based on the achieved results, the main failure modes were identified and the effect of process parameters on mechanical behaviours of the joints were clarified. [ABSTRACT FROM AUTHOR]

Abstract: Public demand for an efficient and sustainable use of energy and resources has led to new design criteria for technical products. An even more consequent use of light-weight construction and so-called smart structures are two examples of this. Both approaches lead to hybrid components consisting of dissimilar materials. Joining processes based on plastic deformation of at least one joining partner promise great potential regarding the production of multi material joints. This paper first examines in detail the basic plastic joining principles for force- and form-closed joints as well as for solid state welds and presents a systematic classification. Subsequently, the joining processes based on these principles are discussed along with their specific potentials and limitations. Additionally, industrial applications of these processes are presented. Future trends in joining by forming based upon current research developments are finally highlighted. Despite these extensive research activities the outlook shows that gaps of knowledge still exist and hinder a broad industrial application so far. [Copyright &y& Elsevier]

Abstract: Force-fit integration of piezoceramic fibers in micro-formed structures is a new approach for function integration in structural sheet metal parts. In a first step, a micro-structured surface is formed in a planar semi-finished sheet metal part by micro-impact extrusion. Piezoceramic fibers are then assembled into this micro-structured surface with a small assembly clearance. The fibers and the structured surface of the sheet metal are joined by a forming process. In the next step, the sheet metal with piezoceramic fibres within a locally micro-formed substructure is shaped by deep drawing into a 3D-geometry. In this paper, results of the micro-impact extrusion and the joining by forming experiments are presented. Furthermore, the design constraints for assembly and joining due to the dimensional and form deviations of the piezoceramic fibers are discussed. Results of a numerical study of micro-forming, joining by forming and the global loading during a deep drawing process step were in good agreement with the experimental investigations. The direct comparison between experiment and numerical simulation increases the process knowledge and shows further improvement potential. [Copyright &y& Elsevier]

Abstract: Tailored Blanks is the collective for semi-finished sheet products which are characterised by a local variation of the sheet thickness, sheet material, coating or material properties. With these adaptions the tailored blanks are optimised for a subsequent forming process or the final application. In principle four different approaches can be distinguished to realise tailored blanks: joining materials with different grade, thickness or coating by a welding process (tailor welded blanks), locally reinforcing the blank by adding a second blank (Patchwork blanks), creating a continuous variation of the sheet thickness via a rolling process (tailor rolled blanks) and adapting the material properties by a local heat treatment (tailor heat treated blanks). The major advantage of products made from tailored blanks in comparison to conventional products is a weight reduction. This paper covers the state of the art in scientific research concerning tailored blanks. The review presents the potentials of the technology and chances for further scientific investigations. [Copyright &y& Elsevier]

Abstract: Electromagnetic (EM) forming is a high-speed forming process that uses the forces induced on a conductive workpiece by a transient high frequency magnetic field to form the workpiece into a desired shape. This paper describes the results of a work undertaken to study the reduction of a 20mm radius to 5mm in 1mm AA 5754 sheet by conventional metal forming process and by electromagnetic forming. The combination of conventional and EM forming will be referred to as “hybrid forming”. The 20mm radius was pre-formed from flat sheet using a conventional die, punch and binder that allowed the material to draw in. The radius was then reduced to 5mm, with no draw-in allowed for either process. Sheets were studied in the as-received condition and were also pre-strained to 5%, 10% and 15% to simulate strain path effects in a multiple stage forming operation. The process was modelled numerically to gain insight into the stress, strain and strain rate histories. The research indicates that features that are not achievable using traditional stamping techniques can be obtained with the aid of EM forming. [Copyright &y& Elsevier]

Abstract: An increasing number of components in automotive structures are today made from advanced high strength steel (AHSS). Since AHSS demonstrates more severe springback behaviour than ordinary mild steels, it requires more efforts to meet the design specification of the stamped parts. Consequently, the physical fine tuning of the die design and the stamping process can be time consuming. The trial-and-error development process may be shortened by replacing most of the physical try-outs with finite element (FE) simulations of the forming process, including the springback behaviour. Still it can be hard to identify when a stamped part will lead to an acceptable assembly with respect to the geometry and the residual stress state. In part since the assembling process itself will distort the components. To resolve this matter it is here proposed to extend the FE-simulation of the stamping process, to also include the first level sub-assembly stage. In this study a methodology of sequentially simulating each step in the manufacturing process of an assembly is proposed. Each step of the proposed methodology is described, and a validation of the prediction capabilities is performed by comparing with a physically manufactured assembly. The assembly is composed of three sheet metal components made from DP600 steel which are joined by spot welding. The components are designed to exhibit severe springback behaviour in order to put both the forming and subsequent assembling simulations to the test. The work presented here demonstrates that by using virtual prototyping it is possible to predict the final shape of an assembled structure. [Copyright &y& Elsevier]

Abstract: The near-axisymmetric compression of high strength steel tubes by electromagnetic forming is studied both experimentally and analytically. Tubes with a nominal tensile strength of 440MPa, outer diameters of 75mm and wall thicknesses up to 2.3mm were compressed using a 9 turn helical actuator and discharge energies up to 24kJ. This can produce reduction in diameters beyond 15%. Experiments were instrumented for measurement of velocity, as well as primary and induced current during the experiments. These records were compared to those of a simple numerical model and found to be in close agreement both in final tube diameter as well as temporal behavior of current and velocity. The model is also exercised to consider system design outside the space examined experimentally. The present experiments also clearly demonstrated that by reducing the system capacitance, the rise time of the pressure pulse can be decreased and this reduces the tendency for Euler bucking in the tubes. This results in rounder tubes, which may be more useful as a manufactured product. [Copyright &y& Elsevier]

Abstract: Electromagnetic (EM) forming is a high-speed forming process that uses the forces induced on a conductive workpiece by a transient high frequency current to form the workpiece into a desired shape. This paper presents the results of an experimental and numerical study carried out to determine whether EM forming techniques could be used to obtain sharper radii in aluminum alloy AA 5754 compared to that attained using conventional stamping process alone. AA 5754 1mm sheet was formed into a v-shape with a 20mm outer radius and then the radius was reduced or “sharpened” to 5mm using EM forming. This “hybrid” process was modeled numerically to gain insight into the process and the challenges involved in the numerical simulation of the physical phenomena that are present in this process. As with any novel process, there are limitations and issues that must be addressed if this technique is to be implemented commercially; however; the research indicates that features that are not achievable using traditional stamping techniques can be obtained using EM forming. [Copyright &y& Elsevier]

Abstract: In this study, the influence of the die geometry on the introduced damage of the processed parts by ECAE is studied. It will be shown experimentally and by FEM simulations that the die geometry greatly influences the imparted damage, if the die geometry is not selected adequately. This could lead to obtain processed materials which could be useless for posterior mechanical applications because of cracks nucleated inside of them, which will decrease the mechanical properties such as fatigue resistance and formability among others. Several FEM models have been solved in order to obtain a mathematical model to predict the influence of the die geometry. Moreover, several parts have been processed using different die geometries in order to determine the damage within the processed material experimentally and also to validate FEM simulations. A 5083 aluminium alloy in (O) state, which means that has been fully annealed, has been selected and different die geometries have been manufactured for processing this aluminium alloy. [Copyright &y& Elsevier]

Abstract: A new hot forming system for high-alloy metals with poor workability is developed. This forming system is a direct combination of a forming machine and continuous electric resistance heating, and is capable of the high-speed forming of metals with flexible and precise control of elevated temperature. The prototype of the new forming system is applied to the forming of high-alloy metals with poor formability, such as a Ti–6Al–4V bar, and the basic characteristics of this forming system are clarified. Using this system, sound, high speed forming of high alloys becomes possible, and the Ti–6Al–4V bar is successfully formed without fracture. [Copyright &y& Elsevier]

Abstract: Incremental sheet metal forming is becoming an attractive technology for fast prototyping and small batch production of sheet metal parts. The majority of investigations are focused on the use of a rigid tool to incrementally form the sheet metal into a final shape. An interesting alternative is to substitute the rigid tool with a high velocity water jet (WJ). The comparison between using a rigid tool and a WJ shows that each method has its advantages and disadvantages. This investigation is aimed to identify the most influential parameters affecting the forming process through experimental comparison of the two observed methods. Technological windows based on non-dimensional values and relevant process parameters like force on the rigid tool and water pressure were defined. [Copyright &y& Elsevier]

Abstract: The Al2O3 structure ceramics have been investigated extensively in previous studies. In order to compare micron- with submicron-scale powder on forming and sintering behaviors, three commercial α-Al2O3 powders were studied: 0.15μm (denoted S as small in the paper) (granulating), 0.43μm (denoted M as middle) (granulating), and 1.8μm (denoted L as large) (granulate-free) at d 50 (median size). Although the (M) powder contains hard agglomerates, it forms more easily than the (S) powder. This is principally because the (M)''s soft agglomeration strength (0.03MPa) is weaker than (S) (7MPa). The (L) bulk formed easily with lower pressure 10MPa because of wider starting-particle size distribution, 0.2–15μm. The (S) primary particles rearranged before sintering, so it postponed its sintering onset temperature to about 1200°C. Additionally, its shrinkage rate becomes maximal and concentrated at the 2nd stage of sintering from 1300 to 1400°C. (M) bulk revealed the longest shrinkage range from 1000 to 1500°C because the sintering occurred with its hard agglomerates at first. Although (L) powder formed rather easily, its sintering was impeded by a much wider particle size distribution. [Copyright &y& Elsevier]

Abstract: The production of metallic junctions employing elastomers is an unconventional technique that has been in development in the last 20 years. The forming process gets successfull just if a simultaneous compression between the elastomers and the tube takes place. Exact solutions for problems involving forming with elastomers are quite difficult to determine. However, the upper-bound theory can be used in order to predict the necessary load for junctions forming. Thus, it is necessary to develop a model capable to provide an estimate of the total forming force, which is useful to set-up tools and equipments required for the process. In this work, Von Mises, Hill''s 1948 and Hill''s 1979 associated yielding theories, and the Hosford''s theory (1979) as well, were used in order to study the anisotropic behaviour on total forming force of junctions using elastomers, insuring the functionality of the proposed model. [Copyright &y& Elsevier]

Abstract: A phenomenological TRIP model is proposed. It has been developed especially for industrial numerical simulations combining forming, springback, assembly and crash modelling. After comparison with micromechanical model of the literature its performances are illustrated by modelling the different stages of a U-channel composing a crash absorber. The TRIP effect on shock absorption is revealed. More generally the influence of the process is shown on the structure functionality. [Copyright &y& Elsevier]

Abstract: Electro-magnetic pulse technologies use magnetic fields to move conductive material in extremely short time steps. Recent developments have demonstrated the application of these technologies to sheet metal forming, tubular space frames and drive shafts. The high velocity of the tube wall displacement under the influence of impulse-magnetic field pressure complicates the control of the deformation process. In this paper the forming process is divided into three basic stages: stage of free movement, stage of joint movement and stage of unloading. For studying the kinematics of the forming process, one of the programs of three-dimensional graphics is applied and then modeling is carried out with use of animation principles for basic stages of the process. [Copyright &y& Elsevier]

Abstract: In stamp forming of sheet materials, the quality of the part and the robustness of the process are determined by a number of variables. This study looks at the application of the stamping process to a fibre–metal laminate (FML) material system and the effect of the blankholder force, punch feed rate and tool radius on the quality of a channel formed laminate. The results indicate that increasing feed rate reduces shape error and delamination significantly and reduces the variation between repetitions of the same test. Furthermore, analysis of the bend radii reveals that the normalised deviation in bend radius from the tool radius is constant for the range of radii investigated. This suggests that FML materials can possess superior formability characteristics compared to monolithic aluminium. [Copyright &y& Elsevier]

Abstract: A series of high-rate electromagnetic-forming experiments are presented that consider free-forming and two configurations of cavity fill operations, one with a flat-bottomed die and the other with a hemispherical protrusion on the bottom of the die cavity. The experiments are performed on 1 and 1.6mm AA5754 and 1mm AA5182 aluminum alloy sheet; all of which are candidates for lightweight automotive structural applications. Increasing energy levels of discharge resulted in increased cavity fill and strain level in the formed parts. The effect of die geometry on formability, strain state and location of failure is examined. Numerical simulations of the high-rate deformation and structural impact that occur during electromagnetic forming are presented, and provide insight into the physics of the problem and the transient nature of this high-rate deformation process. A transient electromagnetic finite-element code is used to model the time-varying currents that are discharged through the coil in order to obtain the transient magnetic forces that are imparted to the workpiece. The body forces generated by electromagnetic induction are then used as the loading condition to model the high-rate deformation of the workpiece using an explicit dynamic finite-element code. A “two-way, loose coupling” of the electromagnetic analysis with the elastic-plastic structural analysis is utilized to account for the effect of changing workpiece geometry on the transient body forces. Validation of the numerical model is performed through comparison between predicted and measured strain distributions within the formed parts. [Copyright &y& Elsevier]

Abstract: The production and machining of micro parts were in the past mainly made by technologies developed from the electronic industry, which is particularly based on silicon etching technologies for the production of, e.g., sensor elements. Due to the increasing demand for micro products in other production area such as medical-, automotive-, optical- and chemical-industry, suitable processes for machining parts from non-silicon materials has become increasingly more important. Laser technology has been qualified for microtechnology because of its high lateral resolution by minimized focusability down to a few microns, low heat input and high flexibility. Some examples for laser applications are micro welding, soldering, selective bonding of silicon and glass, micro structuring and laser assisted forming. [Copyright &y& Elsevier]

Abstract: In sheet metal forming processes, any disturbance as a slight change in the mechanical properties of the material can be the reason for the occurrence of defects without changing any other of the process parameters. In order to avoid production breakdowns and to improve the reliability of the stamping process, an integrated automatic control has been designed and tested. This includes a system based on the use of sensors, artificial vision, and neural networks for the diagnosis and the prediction of the process results as well as a second system including the strategy and the devices for the automatic control system, based on fuzzy logic. [Copyright &y& Elsevier]

Abstract: Thixoforming studies have been developed, mainly in processes such as forging and die casting, due to the advantages that the semi-solid processing presents when compared to the conventional forming, such as reduction of the forming force, near net shape products, increase of die life. However, the knowledge is very poor in drawing of thixocast materials. This work analyses the behaviour of A5052 sheets with thixocast structure when submitted to drawing tests, comparatively to rolled sheets. Thixocast conditions were produced by partial melting. Deformations were measured by means of a digital camera coupled with the press. The method used allows measurements of deformations in plane samples trough a digital image correlation; samples with several widths—40–200mm (various strain paths) were strained until rupture and a special software was used to achieve the deformation values. Forming limit diagrams were built. Results show that rheocast sheets present deformations in the order of 25% larger than rolled material, at 40% lower pressures; forming limit diagrams show higher formability of the rheocast structures when compared to rolled structures. [Copyright &y& Elsevier]

This paper investigates the major difficulty associated with the bending of sheet steel products, namely that of material elastic recovery (springback). Key material, and loading factors that influence springback have been assessed from an experimental study of this phenomenon, using a variety of forming methods. The results of which, in conjunction with previously published data are used to derive an expression for predicting springback using a numerical algorithm method. In addition, comparison is made between the best performing analytical model and that of the numerical algorithm derived in this study. [Copyright &y& Elsevier]

With the development of modern automotive manufacturing technology, and the increased demands of automotive use, coated sheet steel has been applied in the manufacturing of large-scaled auto-panels more widely. It presents many challenges in characterizing, and understanding the behavior of coated products in terms of forming. In recent years, the increasing application of galvanized steels has highlighted the urgent need for work in this area in relation to both formability, and stamping technology. The forming characteristics of pre-phosphated electro-galvanized (EG) steel are analyzed in this paper, including the effect of a zinc coating on formability, zinc damage characteristics, and relationship between the coefficient of friction, and the viscosity of lubricants. In addition, the sensitivity of the material mechanical parameters of sheet steel to the stamping process of an auto-panel is discussed. It is shown that compared with other zinc-coated steel the application of pre-phosphated film to electro-galvanized steel prior to its being subjected to stamping operations will increase the formability, and reduce the coefficient of surface friction. With the increase of the viscosity of lubricants, the coefficient of friction of both pre-phosphated EG, and EG sheet steel decrease. Electro-zinc coatings have little influence on the mechanical properties, and the forming limit of sheet steel, but they will affect the strain distribution in the stamping process. Because of their relatively low hardness, the coatings of electro-galvanized, and pre-phosphated electro-galvanized steel are much easier to deform with the substrate than galvannealed steel, so that cracks occur later, and are to a lesser extent. It can be seen that the mechanical parameters, σs/σb, N value, R value, and δ, are relatively sensitive to the forming process under the bulging-deep drawing deformation of pre-phosphated electro-galvanized sheet steel. [Copyright &y& Elsevier]

Laminated steel sheets sandwiched with a polymer core are increasingly used for automotive applications to improve vehicle’s vibration-damping performance without adding additional weight. It has been observed that the laminated sheets are prone to wrinkling during stamping processes. Due to the significant difference in material properties between the polymer core and the skin steel, FEM prediction of the occurrence, the location, and the shapes of wrinkles in the forming of laminated sheets is still a great challenge.In this paper, the Yoshida buckling test and wedge strip test of laminated steel and its steel skins were conducted. The information of local strains, buckling heights and global wrinkling patterns were obtained in order to study the initiation condition of wrinkling and the post-buckling behavior of the sheets, and to provide verification data for numerical predictions. Rectangular panel forming tests were also conducted. The results showed that the 1.0 mm laminated sheet employed has a wrinkling tendency similar to that of its 0.5 mm skin panel and has a strain distribution similar to that of its 1.0 mm solid counterpart. [Copyright &y& Elsevier]

An Al–Ti–Mo experimental alloy was studied by compression tests at high homologous temperatures and different generalized strain rates. The material was processed to obtain two different starting microstructures, coarse and fine grained. The values of the experimental high-temperature deformation data T, ϵ˙, s (temperature, strain rate and stress, respectively) were analyzed by means of a newly developed algorithm. The different mechanisms controlling the creep process were identified. These mechanisms strongly depend on the microstructure present in the material. Garofalo’s relations for describing the material behavior of each starting microstructure were obtained. The materials constants that were determined for both equations are coherent. The apparent activation energy is slightly higher for the fine-grained material. On the other hand, a different stress exponent for each equation was related with a different mechanisms controlling the deformation process. Finally, a study of the material stability depending on the forming conditions was preformed. Stability zones were specified as a function of the starting microstructure. [Copyright &y& Elsevier]

The rigid–plastic integralless–meshless method is applied to the analysis of plane strain backward extrusion. The rigid–plastic integralless–meshless method, based on the moving least squares approximation and the partial differential equations of mechanical equilibrium, is a truly meshless method. In addition, since there is no any integration in the formulation of the rigid–plastic integralless–meshless method, this method is also an integralless method. Compared with the conventional rigid–plastic FEMs, the rigid–plastic integralless–meshless method has some advantages that are briefly no mesh generation, no remeshing and no integration. Compared with BEMs and FBEMs, the rigid–plastic integralless–meshless method is found to have some merits such as sparse matrix, no singularity, no integration and no fundamental solution. Contours of the equivalent strain rate, the equivalent strain, the equivalent stress and the shear stress, etc. of the backward extrusion analysis using the rigid–plastic integralless–meshless method are obtained successfully. [Copyright &y& Elsevier]

A visioplastic analysis was conducted on cold-forged samples which were part of the production of connecting bolts. Forming is carried out starting with a cylindrical blank that is pierced in two indirect extrusion passes to produce the tubular part. The strain gradients within each piece were determined using the flow lines of the material, put in evidence by metallographic means, as internal markers. The visioplastic analysis was complemented with microhardness indentation tests made on the pierced specimens and with compression tests made on specimens machined from an undeformed blank. It was found that the strain distribution was heterogeneous; the higher values of the normal components were located at the tubular walls of the pieces, whereas the higher values of the shear and equivalent components were found close to the changes in geometry of the specimens, where the material flow has to change its direction. A good correlation between the values of microhardness and equivalent strain distribution was observed. [Copyright &y& Elsevier]

In this paper, an adaptive model of grain size, has been established with the help of the fuzzy neural networks (FNNs), based on experimental results for Ti–6Al–4V titanium alloy with homogeneous deformation under various process technological parameters. The data of Teacher’s samples has been obtained from the experimental results. By the comparison of the calculated results with the experimental data of the Teacher’s samples and the testing samples, it has been verified that the model proposed in this paper can be applied to compute the grain size evolution during the deformation of Ti–6Al–4V titanium alloy. [Copyright &y& Elsevier]

Analysis and results of the high temperature forming of seamless pipe fittings produced at a local factory are presented in this work. The studies were conducted by recording the thermal evolution in different parts of the piece as it was being forged, which was done by placing a series of type K thermocouples within the part and logging the data into a computer driven system. The initial trials put in evidence the need to change the heating practice in order to ensure a greater thermal homogeneity. Metallographic evaluation was carried out on formed pieces to study variations in their microstructure before and after the changes in the heating practice were made. Modification of this practice resulted in improvements in quality, such as the reduction in the variation in microstructure and wall thickness, as well as an increase in productivity, as the pressing speed was augmented. [Copyright &y& Elsevier]

• Combination of AM by PBF-LB and sheet bulk metal forming as a new approach for manufacturing hybrid functional components. • Prove of manufacturing near-net shape tooth geometry on a sheet metal by PBF-LB. • Identification of critical part areas for hybrid parts manufactured by PBF-LB and sheet bulk metal forming. • The analysis of geometry, material flow, metallographic structure and hardness, provides process and design understanding. • Using the approach, part geometry is improved and flexibility increased compared to a conventional process chain 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. [ABSTRACT FROM AUTHOR]

NiAl alloy is an important lightweight and heatproof structural material used for the service temperature up to 1000 °C. However, there are huge challenges in fabricating NiAl alloy sheets and forming thin-walled components. In order to solve this problem, a novel process of integrated forming and reaction synthesis using laminated Ni/Al foils as the initial blank was developed for fabricating NiAl alloy curved shells. The laminated Ni/Al foils were first formed into a curved shell at room temperature, then the shell was in-situ heat-treated under a proper pressure until the pure Ni and Al were transformed into intermetallic NiAl by reaction synthesis. The microstructure, defects such as voids and mechanical properties of the shell were investigated in order to evaluate the feasibility of the integrated process. The influence of loading pressure for fabricating the shell on the void size was studied quantitatively. A theoretical model was proposed to predict the thickness distribution of the shell. It was shown that the shell can be successfully fabricated by the forming and reaction synthesis integrated process. Thinning occurred in the whole region of the shell with the minimum and maximum thickness strain locating at ±80° and 0°, respectively. The voids in the shell mainly exist in the original Al foil regions and original Ni foil regions. The voids in the central region of the NiAl 3 diffusion layers were inherited to the central region of fine-grained layers. The diffusion of Ni layers at high temperatures led to the appearance of linearly distributed voids in the central region of coarse-grained layers. Loading pressure facilitated microplastic deformation, leading to a maximum contact area between the mating surfaces, which further promoted the interdiffusion. Increasing the pressure enhanced the voids shrinkage while decreasing the size of voids. The difference in the displacement increment of each region prevented the edge region of the shell from achieving full densification, resulting in the uneven distribution of density and mechanical properties. [ABSTRACT FROM AUTHOR]

• Basic research on the joining of dissimilar metals via cold formed pin-structures. • Cold formed pin-structures are suitable to join dissimilar metals. • Caulking enables higher joint strengths compared to direct pin-pressing. • Significant increase of joint strength by using multi-pin-structures. • Inhomogeneous material flow complicates the forming of multi-pin-structures. Joining dissimilar materials brings established joining techniques to their limits due to different thermal expansion, unequal stiffness/strength and chemical incompatibilities. The use of pin-structures has proven an appropriate strategy to join multi-material-systems in laboratory scale. At present, the industrial application of this joining technology is limited due to the time-consuming pin manufacturing process and the inadequately researched achievable joint strengths. In this study, extrusion of the pin-structures from sheet metal is used to investigate an approach that can be directly integrated into existing production processes and does not require auxiliary joining elements. With direct-pin-pressing and caulking, two different joining strategies are analysed to join multi-material systems of sheet steel (DC04, t 0 = 2 mm) and aluminium (EN AW 6016-T4, t 0 = 2 mm). The basic feasibility of the joining technique is experimentally proven by using single-pin-structures. The joint strength is analysed by tensile shear tests, micro sections and failure patterns. Based on the experimental results, a failure criterion for the joint is defined. Parallel to the experiments, numerical finite element models (FE-models) for the single-pin-joint are developed and validated. In a further step, numerical investigations for multi-pin-structures are carried out in order to derive predictions on achievable joint strengths with this joining technique. It is shown that the form-fit is crucial for the joint strength. Thus, 93 % higher shear strength is achieved for caulked joints. By multi-pin-structures the strength can be increased considerably. For a 5 × 3 pin-structure, shear strength of 9.9 kN can be achieved. [ABSTRACT FROM AUTHOR]

Knowledge of geometry based forming limits would be beneficial early in the product development process to enable design for manufacture in sheet metal forming process. This paper investigates the influence of corner, die and punch radii on the limiting part depth for drawing an isolated flanged shrink corner from aluminium sheet with and without a blank holder. Trends are identified to establish whether complex component geometry can be analysed to provide a guide for process limits for drawing. The failure draw depth is determined experimentally with a configurable tool for 96 different drawing scenarios. A further 432 scenarios were analysed using a validated Finite Element model. The results demonstrated that a trend could be obtained through plotting the failure draw depth against the average radii of a shrink corner. Assuming this can be extrapolated to full parts, the trend could be useful in the early stages of component design to guide decision making for the components shape and selecting the most appropriate manufacturing process. [ABSTRACT FROM AUTHOR]