In order to use incremental sheet forming (ISF) in an industrial context, it is necessary to provide fast and accurate simulation methods for virtual process design. Without reliable process ...simulations, first-time right production seams infeasible and the process loses its advantage of offering a short lead time. Previous work indicates that implicit finite element (FE) methods are at present not efficient enough to allow for the simulation of AISF for industrially relevant parts, mostly due to the fact that the moving contact requires a very small time step. Finite element methods based on explicit time integration can be sped up using mass or time scaling to enable the simulation of large-scale sheet metal forming problems. However, AISF still requires dedicated adaptive meshing methods to further reduce the calculation times. In this paper, an adaptive remeshing strategy based on a multi-mesh method is developed and applied to the simulation of AISF. It is combined with subcycling to further reduce the calculation times. For the forming of a cone shape, it is shown that savings in CPU time of up to 80 % are possible with acceptable loss of accuracy, and that the simulation time scales more moderately when the part size is increased, so that larger, industrially relevant parts become feasible.
The second-generation aluminum-magnesium-scandium (Al-Mg-Sc) alloy, which is often referred to as Scalmalloy
, has been developed as a high-strength aluminum alloy for selective laser melting (SLM). ...The high-cooling rates of melt pools during SLM establishes the thermodynamic conditions for a fine-grained crack-free aluminum structure saturated with fine precipitates of the ceramic phase Al₃-Sc. The precipitation allows tensile and fatigue strength of Scalmalloy
to exceed those of AlSi10Mg by ~70%. Knowledge about properties of other additive manufacturing processes with slower cooling rates is currently not available. In this study, two batches of Scalmalloy
processed by SLM and laser metal deposition (LMD) are compared regarding microstructure-induced properties. Microstructural strengthening mechanisms behind enhanced strength and ductility are investigated by scanning electron microscopy (SEM). Fatigue damage mechanisms in low-cycle (LCF) to high-cycle fatigue (HCF) are a subject of study in a combined strategy of experimental and statistical modeling for calculation of Woehler curves in the respective regimes. Modeling efforts are supported by non-destructive defect characterization in an X-ray computed tomography (µ-CT) platform. The investigations show that Scalmalloy
specimens produced by LMD are prone to extensive porosity, contrary to SLM specimens, which is translated to ~30% lower fatigue strength.
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•The addition of Ti and Cr promote grain refinement by primary precipitation of (Al,Cr)3Ti in the melt.•Near-eutectic Fe addition decreases the solidification temperature range of the ...alloy, further inhibiting hot cracking.•High nanohardness values up to 300 HV are achieved.
Wrought 2xxx aluminum alloys are difficult to process by laser powder bed fusion (LPBF) because of the hot cracking susceptibility caused by their large solidification range. Although several studies on Ti and Zr additions to 2xxx Al-Cu alloys show improved processability in LPBF, only few explore the addition of alternative alloying elements such as Cr and Fe. There is thus little knowledge on the ability of these elements to avoid hot cracking. In the present work, a new Al-Cu alloy with Ti, Cr and Fe additions is put forward and the mechanisms impeding hot cracking formation are analyzed. (Al, Cr)3Ti_L12 precipitates are formed during the solidification process, promoting heterogenous nucleation and grain refinement. Cr not only contributes to solid solution strengthening but also supports the stabilization of the Al3Ti metastable cubic phase. The addition of near-eutectic Fe decreases the solidification range, further reducing the susceptibility for hot cracking. Nano-hardness mapping reveals the solidification path of the alloy, with higher values associated with the highly dense areas of precipitates forming at the melt pool boundaries. A novel printable alloy with hardness values exceeding those of existing Al alloys for LPBF was designed.
ABSTRACTThe critical role that numerical simulation plays in additive manufacturing has stimulated research on the effectiveness and potential applications of mesh-free, particle-based discretisation ...techniques. These methods excel at handling fluid flows and are viable alternatives to the mesh-based techniques typically used in commercial simulation software. In this paper, we review recent advances in developing computational models for metal additive manufacturing (MAM) processes using particle methods, in the theoretical understanding of the fundamental mechanisms that control such processes at the powder (or melt pool) scale, and in the predictability of physics-based modelling approaches. The paper explores the applicability and performance of particle-based methods in simulating powder bed fusion, directed energy deposition, and binder jetting processes. Since the progress of MAM relies on systematic material-process-structure realisations which are often impossible to sense or observe experimentally, developing efficient particle-based and multiscale simulation tools can be essential to achieving this objective through in-situ process control and optimisation.
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•The densification behavior of CuCrZr and nickel upon spark plasma sintering is analysed for different sintering conditions.•The difference in sintering behavior of both materials is ...quantified using the concept of Master Sintering Curves.•A strategy for co-sintering both materials is developed using pressure-dependent master sintering surfaces.•Co-sintered 3D multi-material structures show a density of 99.9% in CuCrZr and 99.8% in Ni and diffuse sound interfaces.
The present work focuses on the possibility of manufacturing multi-material structures by spark plasma sintering (SPS), thereby broadening the field of application of this process by taking full advantage of the specific properties of individual materials. As a combination of dissimilar materials to be co-processed, CuCrZr and nickel are of particular scientific and technological interest. For the processing of complex 3D multi-material geometries made of highly dissimilar materials, the sintering behavior of each individual material should however be as identical as possible. Since both materials have different physical and mechanical properties, the sintering behavior of the two individual powder materials is first characterized at different uniaxial pressures, heating rates and holding times. A strategy to determine optimal sintering conditions for the processing of multi-material structures is then developed, based on representation of the densification data of each material in the form of master sintering curves (MSC) and surfaces (MSS). From the MSS, an optimal uniaxial pressure of 35 MPa was determined and the holding time to achieve dense multi-material structures at a temperature of 1223 K was estimated. Different configurations of CuCrZr-Ni multi-material samples were successfully sintered using these parameters and microscopic analyses showed that the relative density in these parts is >99.8, in both CuCrZr and Ni.
This paper presents an efficient mesoscale simulation of a Laser Powder Bed Fusion (LPBF) process using the Smoothed Particle Hydrodynamics (SPH) method. The efficiency lies in reducing the ...computational effort via spatial adaptivity, for which a dynamic particle refinement pattern with an optimized neighbor-search algorithm is used. The melt pool dynamics is modeled by resolving the thermal, mechanical, and material fields in a single laser track application. After validating the solver by two benchmark tests where analytical and experimental data are available, we simulate a single-track LPBF process by adopting SPH in multi resolutions. The LPBF simulation results show that the proposed adaptive refinement with and without an optimized neighbor-search approach saves almost 50% and 35% of the SPH calculation time, respectively. This achievement enables several opportunities for parametric studies and running high-resolution models with less computational effort.
Silicon alumina nitride (SiAlON) and alumina toughened zirconia (ATZ) ceramics are applied for ceramic cutting tools to machine, e.g., cast iron, nickel base alloys and other difficult-to-machine ...materials. The state of the art technology for manufacturing of the cutting tool geometry is grinding. Laser processing of ceramics is already studied in terms of ablation rate and roughness evaluation with the application of dental implant manufacturing. In the present study, laser machining of the mentioned ceramics is explored with a laser beam source of 1064 nm wavelength and 10 ps pulse duration (FWHM). The angle dependent energy specific removal rate is described in a model and the optimal pulse fluence for the different materials and the irradiation angles can be derived. For processing at irradiation angle of up to 75° no decrease of the relative absorption could be observed. For ATZ, lowest surface roughness is determined for both, orthogonal and quasi-tangential processing angle. For SiAlON, the roughness decreases constantly for higher tilt angles. A significant difference in the material answer with change of the sample composition can be detected and the results show the potential of further developing SiAlON ceramics towards machineability for laser ablation.
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•High laser energy density in the L-PBF technology induces the crystallization in the melt pool.•Low laser energy density reduces the crystallization but increase the contribution of ...large pores.•On the fusion line crystalize mainly the primary α-Fe(Si) phase.•In the pool area during the L-PBF process a nanocomposite consisting of α-Fe(Si) solid solution and amorphous matrix is formed.
Fe-based metallic glasses (MG) have become the subject of extensive research in recent years due to their favorable mechanical and magnetic properties. In particular, the production of this type of materials in Laser Powder Bed Fusion (LPBF), also known as Selective Laser Melting (SLM) technology, is a kind of breakthrough, as it has become possible to produce elements of any shape. An important factor influencing the properties of the manufactured parts is their microstructure. For metallic glass Fe79Zr6Si14Cu1 with low glass-forming ability, produced in SLM technology, tests were carried out in the field of structural X-ray diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy. In addition, porosity analysis was compared with process parameters such as laser power and scanning speed. The paper shows that the fusion line comprises a solid solution α-Fe(Si) and low fraction of intermetallic Fe23Zr6 and FeZr2 phases. Furthermore, in the melt pool area, a nanometric α-Fe(Si) phase and an amorphous matrix was observed. The presented research results of the Fe79Zr6Si14Cu1 alloy produced for the first time in SLM technology will undoubtendly contribute to further optimization of parameters for elements produced in Additive Manufacturing technology using Fe-based MG.
In this work, two Twinning-Induced Plasticity (TWIP) steels, an Fe–17Mn–1.5Al–0.6C (alloy I) and an Fe–23Mn–1.5Al–0.3C (alloy II), were processed by a simple combination of cold rolling and recovery ...annealing that resulted in a high yield strength along with appreciable ductility. The potential and limitations of recovery-annealed TWIP steel were assessed by comprehensive mechanical characterization and comparison with a conventional dual-phase Advanced High Strength Steel (AHSS). The energy-absorption capacity, a key parameter for the application of TWIP steel as crash-relevant structural components, was determined by uniaxial tensile testing and dynamic crash testing. The recovery-annealed TWIP material revealed superior properties compared to its fully recrystallized counterparts and to the AHSS due to improvement of the yield strength. These properties can be tailored by varying the chemical composition and the processing parameters. In addition, the formability was investigated using Nakajima and deep drawing tests. Critical issues and limitations of the recovery-annealed TWIP steels are discussed.
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