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Cold spraying has great potential for additive manufacturing, especially of oxidation-sensitive metals, because the material is not melted and significantly higher deposition rates can be achieved than with conventional additive manufacturing processes such as selective laser melting or direct metal deposition. Titanium is regarded as a high-performance engineering material due to its unique combination of properties, including good corrosion resistance, biocompatibility and high strength at comparatively low density. However, due to its high price, it appears reasonable for many applications to use material compounds in which titanium is only used on the surface of the workpiece, while less expensive materials such as aluminum are used for the remaining volume. In the present work, cold sprayed pure titanium coatings were deposited on Al substrates and then formed to defined 3-dimensional final contours by die forging and rotary swaging. Different porosities were selectively set in order to evaluate their influence on the coating adhesion and cohesion in the forming process. Pre-consolidation of the coatings and the use of Al/Ti interlayers proved to be promising strategies.

The striving for energy savings by lightweight construction requires the combination of different materials with advantageous properties. For joining sheet metal components, clinching offers a good alternative to thermal joining processes. In contrast to thermal joining processes, the microstructure in the joining zone remains largely unaffected. Conventional clinch joints, however, have a protrusion on the underside of the joint, which restricts their use in functional and visible surfaces. Flat-clinching minimizes this disadvantage by using a flat anvil instead of a die. Due to the flatness on the underside, it can be used in visible and functional surfaces. This paper deals with the increase of joint strength by using an auxiliary joining element (AJE) in the second forming stage. To achieve optimum improvement in the joint strength of an aluminum Al99.5 H14 sheet metal joint and to save costs, the AJE was varied numerically in terms of volume, material and basic shape. The geometric parameters (e.g., interlocking f and neck thickness tn) do not allow direct derivation of the joint strength. For this reason, the 2D clinch model was extended for the first time to include 3D load models (cross tension, shear tension). To validate the numerical results, optimized flat-clinch joints with AJE and the associated load tests were implemented experimentally. The numerical models were used to improve the process development.

Purpose This paper aims to numerical and experimental analysis on substrate deformation and plastic strain induced by wire arc additive manufacturing. Design/methodology/approach The component has the form of a hollow, rectangular thin wall consisting of 25 deposition layers of SS316L on an SS304 substrate plate. Thermo-mechanical finite element analysis was applied with Goldak’s double-ellipsoidal heat-source model and a non-linear isotropic hardening rule based on von Mises’ yield criterion. The layer deposition was modelled using simplified geometry to minimize overall pre-processing work and computational time. Findings A new material modelling of SS316L was obtained from the chemical composition of the evolved component characterized by scanning electron microscope/energy dispersive X-ray and further generated by an advanced material-modelling software JMatPro. In defining heat-transfer coefficients, transient thermometric analysis was first performed in the bead and on the substrate, which was followed by an adjustment of the heat-transfer coefficients to reflect the actual temperature distribution. Based on the adjusted model and boundary conditions, sensitivity analysis was conducted prior to the ultimate simulation of substrate deformation and equivalent plastic strain. Furthermore, this simulation was verified by conducting a series of automated wire + arc additive manufacturing tests using robotic gas Metal arc welding with distortion measured by coordinate-measurement machine and equivalent plastic strain measured by optical three-dimensional-metrology measurements (Gesellschaft für Optische Messtechnik). Originality/value It can be concluded that a proper numerical computation using the adjusted model and property-evolved material exhibits a similar trend with acceptable agreement compared to the experiment by yielding an error percentage up to 30% for deformation and up to 21% for equivalent plastic strain at each individual measurement point.

This paper is dealing with the comparison of the FEM result quality between a commercial tool and an open source software with regards to the numerical simulation of a single seam WAAM process. For this purpose, an experimental WAAM process was conducted by a welding robot on a 1.4404 (316L) base plate with a 1.4404 (316L) welding wire, connected with the associated measurement equipment. Furthermore, the equivalent setup was transferred in the FEM tools Simufact Welding and Elmer FEM, using the same parameters for both simulations. The calculations show, that both programs are able to generate high quality results with a good accordance to the temperature development within the experimental processes. In summary it can be said, that both programs offer advantages and the decision what tool has to be used depends on the requirements and the possibilities of the user.

The high heat input during fusion welding leads to transformations of the microstructure in the area subjected to welding, mostly resulting in a heterogene crystalline structure and an overall deterioration of the mechanical properties. To reduce the detrimental effect, posttreatment processes which are typically separated from the actual welding process are state of the art. The present work shows the new methodology, WeldForming, which intends to eliminate subsequent treatment processes. The new in-line process combination harnesses the synergies of a welding and a rolling process to ultimately prevent the typical zone formation of the heat affected zone. Experimental investigations combined with a detailed numerical simulation of the coupled welding and forming process indicate the functional proof of the new methodology. The validation of the numerical model is carried out with the aid of temperature profiles, cross sections, and microstructure analysis as well as flow curves determined by upsetting tests on thermomechanical simulation systems.

The description and modelling of the forming behaviour is essential for the numerical prediction of material flow and the applied forming force. A representative stress state as well as comparable strain rate and temperatures should be considered during material characterization. In the presented investigations, an extruded aluminium alloy (EN AW-6060 T6) was formed for different compression tests with diverse specimen geometries (cylinders, discs, flat rings, cuboids) and compared with the tensile and torsion tests under the same forming conditions and with one and the same initial microstructure with an average grain size of 50 µm. To ensure that no microstructural changes during the deformation process (recrystallization) affect the measurement results due to load-related material anomalies, all tests for the material characterization were started at room temperature. The comparison is based on the cylindrical compression test, because this is standardised for room temperature (DIN 50106) and, due to the compressive stress, is the most suitable material description for bulk forming processes. However, in the stacked compression tests without additional guide elements, a much higher friction between the layers is required than between the workpiece and the tool, so that the deformation is not concentrated on the centre of the specimen (with regard to height) and the middle layers won’t get out due to high tangential stresses. By consideration of these conditions the stacked tests are comparable to the cylindrical compression test. However, the friction between material and die must be taken into account for compression tests as well as the resulting forming heat when calculating the flow curve. Based on this, the forming behaviour can be modelled according to various flow curve approaches for cold forming processes. In general, it was found that all flow curves of the tensile tests, torsion tests and the compression test were in the range of ± 7.5 % based on the cylinder compression test.

Additive Manufacturing is an established process group that includes various technologies. In contrast to subtractive methods, complex components can be produced by applying layers of construction materials. In accordance with the standard VDI Guideline 3405, additive manufacturing technologies can be differentiated into wire- and powder-based technologies. The basis for these experimental investigations is a Wire Arc Additive Manufacturing (WAAM) process with a high build-up rate (Cold Metal Transfer - CMT) to produce a rectangular thin-walled component made of G4Si1 (1.5130). In order to analyze the influence of a subsequent forming process on the microstructural properties and the forming behavior of the components, compression tests were carried out. Therefore, cylindrical specimens were made out of the additively manufactured components by machining. To be able to take a possible anisotropy in the workpiece caused by the multi-layer welding into account, the samples were taken both along and across the welding direction. To evaluate the inhomogeneous component properties, cast specimens with a representative microstructure were produced by inductive melting of the filler material and subsequent a solidification with an appropriate cooling rate. In addition to the cold forming of the additively manufactured components, the investigation also includes hot forming and the influence of a corresponding heat treatment. The experimental examination was completed by the analysis of the microstructure of each material state. The aim of the research work was to prove the homogenization and optimization of the mechanical properties of additive manufactured components due to a subsequent forming process.

The joining of machine parts by plastic forming is a common method for transmitting forces and torque. In drive trains, the ‘knurled interference fit’ has a high transmission capacity through the combination of frictional connection and form fit. In the present study, the shaft specimen made of C45 steel material is joined with an inner knurled hub made of 16MnCr5 case hardened steel. The influence of the joining process parameters on the torsional fatigue strength of the shaft-hub connection is investigated by means of experimental studies. The most important parameter is the chamfer angle of the knurled hub, which determines the rate of strain hardening in the material and differs between the cutting and forming joining processes. This study shows that knurled interference fit connections joined by forming achieve a higher fatigue strength and a higher maximum static torque than connections joined by cutting.

The incremental forming process Radial Rotation Profile-Forming (RRPF) has been developed to enable the production of profiled hollow parts with low sheet thinning and high geometrical accuracy. As a result of low thinning, a smaller initial sheet thickness can be used, while material and weight can be saved.The two principal forming steps are the production of the preform by Rotational Swing-Folding (RSB) and the subsequent radial profile forming of the hollow part in one clamping position. The special feature are the purposed wrinkles in the first process step, which formed in the indentation of the profiled mandrel. This is an advantage, because of the additional thickening. Due to the radial profiled forming in the second process step, the axial profile can be formed with less thinning.The focus of the article is on the development of the forming tools for the second process step of RRPF. Based on the general law of gearing, the forming tools for the production of a component are developed. First, a forming simulation of an example component validates the approach. For this purpose, some simplifications have been made in order to consider the profile forming process separately. Afterwards, the experimental results of the incremental sheet metal forming process for the production of the profiled hollow parts are presented.

In this work, the influences of deviations of material properties (used material is aluminium for both metal sheets), hole geometry (diameter, chamfer at the bottom and rounding at the top) and offset between punch and hole on the quality of a clinched connection are analysed. The analyses were done with numerical forming simulations, which were validated by experimental tests. For each process parameter, models were built up to simulate the forming process. After simulation of the forming process, it was possible to measure the resulting undercut and to identify the dependency between process parameters and width of undercut. This shows the influence of each investigated parameter on clinch quality and enables to set tolerances as high as possible but small enough to get the required undercut in the clinched connection.

Modern production equipment is based on the results of quality control as well as process parameters. The magnetic anisotropy of materials is closely connected to internal mechanical stress by the Villari effect, and also to hardening effects due to plastic deformations, and could therefore provide an interesting basis for process control. Nevertheless, the analysis of anisotropic properties is extremely sensitive to sensor and workpiece misalignments, such as tilting. In this work, a novel eddy current sensor system is introduced, performing a non-contact measurement of the magnetic anisotropy of a workpiece and realizing a separation and correction of tilting effects. The measurement principle is demonstrated with the example of two samples with different magnetic anisotropy values induced by cold forming. Both samples are analyzed under different tilt angles between the sensor axis and the surface of the workpiece. In this work, digital signal processing is demonstrated on the acquired raw data in order to differentiate the effects of tilt and of anisotropy, with the use of preliminary results as an example of two prepared samples.

This fundamental research deals with the investigation of material property model influences on distortion induced by multi-layered Wire Arc Additive Manufacturing (WAAM) with synergic-pulsed gas metal arc welding (P-GMAW) process which was modelled and simulated by means of non-linear numerical computation. The material property models of stainless steel SS316L component to be compared stem from three different sources namely existing database, initial wire and evolved component. The new property models were generated with advanced material modelling software JMATPRO based on chemical compositions analysed at initial wire and component using SEM–EDX. The flow curve for each material model was taken with the strain rates ranging from 0.001 to 1.0 s−1. In the numerical simulation, a coupled thermomechanical solution was adopted including phase-change phenomena defined in latent heat. Goldak’s double ellipsoid was applied as heat source model and simplified rectangular bead with hexagonal element type and meshing was developed to avoid extensive pre-processing effort and to reduce the computational time at post-processing level. Temperature behaviour due to the successive layer deposition was simulated considering heat transfer effect coupled to mechanical analysis. The adjustment of simulative transient to experimental thermal distribution lead to new fitted heat transfer coefficient. Prior to execution of numerical simulation, a sensitivity analysis was conducted to find the optimal number of elements or mesh size towards maximum reached temperature. It can be concluded based on the adjusted model, selected mesh size and experimental validation that numerical computation of substrate distortion with evolved material property of component and initial wire of SS316L yield closer average result within the relative error ranging between 11 and 16% compared to database material giving more than 22%.

Wire-arc additive manufacturing (WAAM) complex components can be built-up layer by layer from metallic construction materials. In this investigation two different WAAM processes with high built-up rates (CMT and pulsed GMAW) were compared in terms of geometry formation and component properties. The reference is a rectangular thin-walled geometry made of the austenitic stainless steel 316LSi (1.4430). During the welding process, the temperature development in the weld layer was measured. The experimental comparison of CMT (\({\text{R}}_{\text{m}}=630 {\text{MPa}}\)) and pulsed GMAW (\({\text{R}}_{\text{m}}=605 {\text{MPa}}\)) is completed by the determination of the mechanical properties using micro-tensile tests. Furthermore, the additive-manufactured walls were cold rolled with a subsequent heat treatment or hot rolled to provide proof of formability and forming induced property improvement.

The incremental forming process Radial Rotation Profile-Forming (RRPF) has been developed at the Professorship Virtual Production Engineering of the Technical University of Chemnitz. The aim is to enable the production of profiled hollow parts with low sheet thinning and high geometrical accuracy. Because of low thinning due to the process, a smaller initial sheet thickness can be used, whereby material and weight can be saved. RRPF is a two-step forming process. The two principal steps are the production of the preform by Rotational Swing-Folding and the subsequent radial profile-forming of the hollow part in one clamping position. During the preform production, wrinkles occur and these wrinkles can be directly formed in the indentation of the mandrel. In the second process step, the wrinkles are used to form the finished profile of the component. However, due to the geometrical stiffness and the material behavior, there is no wrinkle formed in every indentation of the mandrel. An indentation without wrinkle lead to a high sheet thinning, wich occurs due to forming of the final profile. The best component with less sheet thinning and uniform properties is created for a preform with uniform wrinkles in each indentation of the mandrel. Therefore, the approach of a local laser heat treatment is carried out to control the wrinkling for the first time. This extends the original two-step forming process by a further process step. Before forming, local heat treatment creates a tailored blank with locally varying strength. Therefore, wrinkling occurs in the area with the lower strength of the basic material. The approach and experimental basic investigations of the laser heat treatment are shown in this paper.

A chained forming–welding process is to be investigated and analyzed using experimental verification and numerical simulation in which the material and mechanical properties are fully transferred between processes. The investigated part is in the form of a tube with dimension of 300 mm (l) × 20 mm (OD) × 1.5 mm (t) made of a low carbon steel material DC04 commonly used for automotive parts and support structure. At first, a series of experiment using industrial U-/O-bending machine and fully automated robotic gas metal arc welding (GMAW) process on longitudinal slot were sequentially conducted and analyzed towards final geometrical change, macrostructure, and residual stress. Further, numerical simulation method using specialized FEM software Simufact.Forming and Simufact.Welding is developed to predict the major properties following the actual process parameters during experimental forming and welding process. Throughout the simulation of forming and welding process, additive isotropic hardening plasticity model based on von Mises yield criterion is selected with a wide range of operating temperature and Goldak’s double-ellipsoid is defined as welding heat source model. Based on the analysis outcome, it can be concluded that coupled forming–welding process simulation can be suitably implemented to forecast major material and mechanical properties of tube manufacturing within accepted range of error under consideration of material history.

Cold-rolling processes are commonly used in industrial production. Rolling-induced residual stresses influence the behavior of the material significantly. Thus, the prediction of this state is of high importance. In this study, the influence of the initial residual-stress state on the final state after cold rolling is investigated by means of finite-element analysis simulations and X-ray diffraction. It is shown that the initial residual-stress state of DC04 is eliminated after two cold-rolling passes even for comparably low plastic strains.

Within this study, a new method for the determination of the Taylor-Quinney coefficient is presented. The coefficient was identified by measuring the force-displacement-behavior as well as the temperature change resulting from an adiabatic compression test. In order to deduce the global temperature increasing of the specimen from the local measured temperature a suitable specimen geometry was designed with the use of numerical simulation. The resulting specimen allows a friction-free compression and therefore precludes a temperature increase through friction. Finally, the Taylor-Quinney coefficient of C35 steel (1.0501) was experimentally determined in the initial state as well as after a heat treatment.

Inner cavities in cast ingots have to be closed by means of open-die forging to guarantee the integrity of the forged components during usage. In the paper a differentiation is made between the macroscopic and the microscopic closing of natural inner cavities. Special attention is paid to the dendritic structure of the surfaces of inner cavities and their impact on the microscopic closing behavior. Additionally, investigation showed that a closing on the microscopic scale is only possible if the cavities do not come in contact to the atmosphere during hot forming. For the analysis of the cavity closing, ingots of a heat-treatable, hot-working and a cold-working steel were used. The ingots were cast, forged and the surface of the inner voids was analyzed with the help of light-microscopy, SEM and EDS for the microstructure and by using tensile tests on macroscopic scale. Also, numerical investigations were a part of the work, whereby the parameters void size, void shape and anvil-shape were varied. As a result of the numerical investigation, a so called closing function was formed. This function enables the user to calculate the necessary height-reduction for closing of inner cavities of the regarded ingot format.

The aim is to realize a Q&P (Quenching and Partitioning) process for a hot forged component made of low-alloyed advanced high-strength steel (AHSS) 42MnSiCr. One advantage of this steel is the low alloy concept which is cost-effective. After forging, the component is cooled down to room temperature with a subsequent heat treatment to achieve the characteristic microstructure with martensite and retained austenite. The material is annealed and then quenched to just above the martensite finish temperature (MF-temperature). Hence, in the martensitic matrix about 10 to 15% retained austenite is included. Finally, the Q&Ped material is artificially aged at 250 °C to support the diffusion process of carbon from the over-saturated martensite into the austenite. Thereby, mechanical properties of 2000 MPa for tensile strength with fracture strains of 10% can be achieved. This paper provides details of the process and material behavior for a reduction of the process chain. The goal is to develop a technology for the quenching and partitioning treatment of forged components by using the thermal energy from forging. Ideally, the quenching step should be performed in the forming dies just above the MF-temperature with additional holding on the temperature level. The majority of forged parts have different cross sections. Therefore, the cooling conditions are inhomogeneous in each cross section of the components. This cooling behavior was analyzed in laboratory tests with a forged part. Furthermore, the heat transfer coefficients were determined for different cooling media (water, air). The cooling technology was experimentally and numerically simulated in a first step for the conventional process chain (forging, cooling to room temperature, austenitisation, quenching, artificial ageing) and correlated with the microstructural evolution in combination with the component’s mechanical properties.

The constructive design of a flow field layout and the channel cross section parameters from a metallic half- or bipolar plate can have a significant influence on the performance characteristics of a fuel cell. One important aspect in the dimensioning of the channel geometry of half plates is the technical forming feasibility. In this article, first an equation is presented, which enables an analytical calculation of the channel parameters. Hereby, continuing calculations with parameter variations will be possible. Furthermore, the formability of the channel geometry of metallic half plates is evaluated through numerical and experimental investigations. Based on the results, an analytical model approach will be derived that enables an appraisal of the formability from channel cross section contours in an early development state. As a final step, the results of the numerical investigations and the analytical calculation method are compared and evaluated with the results of experimental investigations and other publications. It will be shown, that the derived analytical model approach has a good approximation compared to the effects and results from the numerical and experimental analysis. In particular, the assessment of whether a channel cross section can be manufactured safely is a result with high probability of the analytical model approach. Imprecisions happen, especially in variants with extreme geometries, for example, with very small radii or a huge channel depth. For this kind of variations, the analytical model behaves too sensitively, which makes it more difficult to estimate the damage effects. However, at an early development state, the analytical model offers a good method to get a pre-evaluation of the formability of channel cross sections with a simultaneous parameter variation possibility.