IVth International Conference on Simulation for Additive Manufacturing (Sim-AM 2023)

Additive manufacturing (AM) is evolving as one of the most promising manufacturing technologies for creating solid structures of virtually any shape. AM can produce more complex shapes than those obtained through classical manufacturing techniques. As a consequence, areas of engineering applications for AM products include design models, lightweight components for the automotive or aerospace industry, patient-specific medical implants, civil engineering structural and/or architectural ... show more

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Design of Graphical Symbols for Shape Transformations of 4D Printed Parts
E. Pei, C. Leung

SIM-AM2023.

Abstract
The term “4D Printing” (4DP) is defined as the ability for a part produced using an additive manufacture process to change its shape when activated by or exposed to one or more stimuli over time. This emerging technology offers unique advantages over conventional Additive Manufacturing (AM) by extending the three dimensions of space into the fourth dimension of time. 4DP parts can be programmed to actuate passively without the need for an external power source such as an electromechanical or other active system, thereby reducing the probability of failure and the complexity of components. This work attempts to address some of the challenges faced by the design engineer in a project team when producing technical documentation to specify the desired shape transformation of a 4DP part with a structured graphical representation at an appropriate level of abstraction. In this paper the requirements for a shape transforming 4DP part are represented as the allowable variation in dimensional size and tolerance in geometric form of the functionally critical features on the part for each function that the transformed shape serves. In this paper, the authors describe how the proposed standard to specify the desired shape transformations of a 4DP part could use graphical symbols in a structured specification by means of a Transformation Control Frame (TCF) to define the rules of transforming between shapes and a Bill of Transformations (BoT) to enumerate all the Transformation Control Frames (TCF) necessary to describe the intended sequence of shape transformations. To illustrate how the graphical symbols could be applied, a SMA actuated gripper is presented as a use-case.
Abstract
The term “4D Printing” (4DP) is defined as the ability for a part produced using an additive manufacture process to change its shape when activated by or exposed to one [...]
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Thermal model for laser-based powder bed fusion of metal process: modelling, calibration, and experimental validation
M. Carraturo, P. Breese, S. Oster

SIM-AM2023.

Abstract
In the present contribution, we propose an effective numerical thermal modeling solution for melt pool simulations in Laser-based Powder Bed Fusion of Metals processes. The proposed model employs an anisotropic conductivity to represent melt pool dynamics effectsin a homogeneous material model. The numerical implementation of the proposed physical model is first experimentally calibrated and then validated with respect to a series of melt pool measurements as acquired by using a short-wave infrared (SWIR) camera monitoring system.
Abstract
In the present contribution, we propose an effective numerical thermal modeling solution for melt pool simulations in Laser-based Powder Bed Fusion of Metals processes. The [...]
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Cellular Automata Simulation of Fully Equiaxed Microstructure Formation in Scalmalloy® during Additive Manufacturing with Adjustable Ring Mode Laser
M. Mohebbi, V. Ploshikhin

SIM-AM2023.

Abstract
We utilized an Adjustable Ring-Mode (ARM) laser to achieve an almost fully equiaxed microstructure in powder bed Fusion-laser beam Scalmalloy®. ARM laser-built specimens exhibited over 90% fine-grained material, while circular laser-built specimens yielded less than 50% fine-grained material, using the same laser power, speed, and hatch spacing. To gain insights into these interesting results, we employed a Cellular Automata (CA) solidification simulation, incorporating the nucleation role of L12 Al3(ScxZr1-x) precipitates through a particle-based nucleation model. The simulation was coupled with the corresponding temperature field derived from finite difference analyses of the circular and ARM laser beams. The simulation results revealed a significantly thicker precipitation zone (equiaxed grains) under the ARM laser compared to the circular beam, primarily attributed to reduced temperature and cooling rates. The excellent correlation between simulation and experimental results demonstrates promising potential for the predictive application of the developed model. It can be effectively utilized to optimize heat source modulation and process parameters, thereby enabling the adaptation of microstructure and mechanical properties
Abstract
We utilized an Adjustable Ring-Mode (ARM) laser to achieve an almost fully equiaxed microstructure in powder bed Fusion-laser beam Scalmalloy®. ARM laser-built specimens [...]
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The Effect of Geometrical Imperfections on the Mechanical Properties of Lattice Structures Produced by the Powder Bed Fusion (PBF) Process
K. Hamasaki, K. Ushijima

SIM-AM2023.

Abstract
In this paper, the effects of geometrical imperfections observed in a lattice structure fabricated by metal 3D printer on the compressive response were investigated by using FE simulation. Geometrical imperfections which are due to excessive heat transfer and the melting of unnecessary metal powder during the fabrication process was observed using a 3D X-Ray microscope (XRM) machine. Based on the observation, two types of geometrical imperfections (strut diameter deviation and the center-axis offset) were measured, and the quantities of these imperfections on the mechanical properties of lattice block were discussed. By introducing imperfections to the FE model, a likelihood of reduced mechanical properties can be potentially adverted. In addition, by comparing the amount of geometrical imperfections, the initial stiffness and plastic collapse strength in the models based on different strut diameters, we proposed appropriate manufacturing conditions for the lattice blocks that would minimize the reduction of their mechanical properties.
Abstract
In this paper, the effects of geometrical imperfections observed in a lattice structure fabricated by metal 3D printer on the compressive response were investigated by using [...]
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Numerical Investigation of Vibration Properties of Chiral Structures with Artifical Structural Anisotropy
S. Noguchi, K. Ushijima

SIM-AM2023.

Abstract
The dynamic vibration response of sandwich beams with an anti-tetra-chiral lattice as a lightweight sandwiched core have been studied by using a nonlinear finite element analysis (FEA). Since the anti-tetra-chiral structure has a weak shear stiffness, its vibration response is strongly affected by the shear deformation. In our calculation, a 3-point bending flexural test was conducted for calculating the effective shear stiffness as well as the effective Young’s modulus of the chiral core. The natural frequency of the sandwich beam has been calculated by FEA, and predicted by using the Rayleigh-Ritz method, assuming that the sandwich beam is composed of composite continuum materials with equivalent Young’s modulus and shear modulus. Moreover, the natural frequency and damping ration of the sandwich beam produced by a 3D printer bas been measured through a vibration test, and compared with numerical results in order to clarify the effectiveness of the chiral sandwich beam as a mechanical component.
Abstract
The dynamic vibration response of sandwich beams with an anti-tetra-chiral lattice as a lightweight sandwiched core have been studied by using a nonlinear finite element analysis [...]
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Towards neuronal network enhanced finite element simulations in additive manufacturing
C. Behrens, V. Ploshikhin

SIM-AM2023.
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Parametric Study of Directed Energy Deposition Of Duplex Stainless Steels To Optimize Ferrite-Austenite Phase Ratio And Residual Stresses
D. Weisz-Patrault

SIM-AM2023.

Abstract
Optimal material properties of duplex stainless steels generally require near 50-50 ferrite-austenite microstructures. The development of additive manufacturing of duplex steels is hindered by difficulty in controlling cooling conditions to ensure a balanced phase ratio. In addition, non-uniform phase distribution is usually observed. Thus, sufficiently fast part scale process simulations are interesting to optimize process parameters to better predict and control the temperature history during fabrication and therefore solid-state phase transitions. Furthermore, stresses should also be taken into account in the optimization of the phase field in order to avoid cracking, buckling or excessive distortions. Numerical results obtained from a fast modeling of directed energy deposition including thermal analysis, diffusion of alloying element to account for phase transitions, and stress computation are analyzed. On this basis, we investigate the effect on stresses of an optimized fabrication strategy designed to target uniform and balanced ferrite-austenite ratio with respect to a reference printing strategy
Abstract
Optimal material properties of duplex stainless steels generally require near 50-50 ferrite-austenite microstructures. The development of additive manufacturing of duplex [...]
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Closed-walled topology optimization of an additively manufactured motor bracket for an unmanned cargo aerial vehicle
J. Rieser, M. Zimmermann

SIM-AM2023.

Abstract
Compared to conventional intuition-based design, topology optimization (TO) provides considerable mass savings by clearing excess material from lightly loaded regions of a structural part. The remaining material may be distributed in a purely truss-like fashion, or in the form of a closed-walled design consisting of flat plates or curved shells with variable thickness. Unless buckling is of critical concern, closed-walled designs are in general more efficient than trusses which makes them particularly interesting for challenging applications in lightweight design. However, closed-walled designs obtained by topology optimization are still the exception rather than the rule. This paper investigates the applicability of the recently developed selective penalization approach to the design of a motor bracket for an unmanned aerial vehicle (UAV) to deliver defibrillators which is currently being developed by the HORYZN student initiative at the Technical University of Munich. The optimization results are closed walled designs as desired. A comparison to a truss-like design as well as to a conventional off-the-shelf motor bracket reveals that the closed-walled design even outperforms the topology optimized truss-like design by additional 3% in terms of stiffness-to-weight ratio. Moreover, it provides a streamlined housing protecting the motor cables and contributing to the reduction of aerodynamic drag at cruise speed. Another key finding of this case study is: Depending on the specific optimization problem, and a suitable build orientation provided, closed-walled designs may lower the amount of necessary sacrificial support structures or may even be almost self-supporting. For the closed-walled motor bracket design we found a reduction by more than 25% compared to the truss-like design. This did not require limiting the freedom of design by imposing any additional constraints. The motor bracket was successfully manufactured from aluminium alloy using laser powder bed fusion (LPBF) followed by removal of support structures and CNC machining of functional surfaces.
Abstract
Compared to conventional intuition-based design, topology optimization (TO) provides considerable mass savings by clearing excess material from lightly loaded regions of a [...]
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Incremental Viscoelasticity for 3D Concrete Printing: Finite Strain Modeling and Parametric Studies
B. NEDJAR, Z. Awada, J. Torrenti

SIM-AM2023.

Abstract
Within a 3D concrete printing process, concrete is still fresh and possible collapse may occur due to its own weight and lack of formwork. On the other hand, the mechanical characteristics of the material are continuously evolving due to hydration during curing. Withina predictive theory, the constitutive relation of the early age concrete is to be defined in rate form. In this contribution, and due to the soft nature of the problem at hand, a finite strainincremental viscoelastic modeling is adopted. A generalized Maxwell rheological model is used together with a Saint-Venant-like incremental elasticity. A parametric study is conducted on simulated slump-tests to highlight the abilities of the present framework. Clearly, the early age rheology and mechanical properties have a great impact on the buildability of the fresh concrete. A set of simulations is then given for the purpose of demonstration.
Abstract
Within a 3D concrete printing process, concrete is still fresh and possible collapse may occur due to its own weight and lack of formwork. On the other hand, the mechanical [...]
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Effect of Residual Stresses on the Mechanical Properties of TPMS Lattice Structures Manufactured Using 316L Stainless Steel
H. Mapari, H. Kruse, E. Escobar, A. Matei, J. Schleifenbaum

SIM-AM2023.

Abstract
In recent years, the use of Triply Periodic Minimal Surface (TPMS) lattice structures has gained popularity due to their advantages like high surface to volume ratio and their lightweight potential. Nowadays, TPMS lattice structures can be seen in many fields, including aerospace and medical applications, which can be fabricated using AM methods like Laser Powder Bed Fusion (PBF-LB/M) process. During the PBF-LB/M process, the transient emperature change is caused by the cyclic nature of the thermal load resulting in the accumulation of residual stresses (RS). These RS can cause dimensional inaccuracies, warpageand have a severe impact on the loading capacity and quality of the PBF-LB/M part. In this paper, the effect of RS on the mechanical properties of primitive and gyroid TPMS lattice structures of volume fraction 20%, 30% and 40% undergoing compression testing is studied using Finite Element Analysis (FEA) and experiments. The sequentially coupled thermomechanical finite element model is used to account for the RS accumulation and its effect on Young’s modulus, yield strength and Specific Energy Absorption (SEA).
Abstract
In recent years, the use of Triply Periodic Minimal Surface (TPMS) lattice structures has gained popularity due to their advantages like high surface to volume ratio and their [...]
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SAMPLE3D: A Versatile Numerical Tool for Investigating Texture and Grain Structure of Materials Processed by PBF Processes
Z. Yang, Y. Kuesters, R. Logvinov, M. Markl, C. Körner

SIM-AM2023.

Abstract
Powder Bed Fusion (PBF) not only enables the fabrication of metal parts with complex geometries in near-net-shape, but also offers the potential to tailor the microstructure and, consequently, the mechanical properties of the final product. In this contribution, we present our in-house developed simulation software SAMPLE3D (Simulation of Additive Manufacturing on the Powder scale using a Laser or Electron beam in 3D), which is designed specifically for simulating grain structure evolution during PBF processes. The core of SAMPLE3D is composed of a finite difference model and a cellular automaton model. The finite difference model is used to obtain the temperature field caused by an electron or laser beam. This temperature field is further used in the cellular automaton model to simulate grain structure development where grain selection as well as nucleation is considered. A range of information can be extracted from the simulation results, such as texture, grain morphology, and grain boundary arrangement. SAMPLE3D provides a way to get insight into the relationship between PBF process strategies and microstructures. SAMPLE3D has been employed to investigate the texture and grain structure evolution of various materials in different research projects.
Abstract
Powder Bed Fusion (PBF) not only enables the fabrication of metal parts with complex geometries in near-net-shape, but also offers the potential to tailor the microstructure [...]
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Multi-Scale Topology Optimization of Bodies with TPMS-based Lattice Structures and Mortar Contact Interfaces
N. Strömberg

SIM-AM2023.

Abstract
The combination of topology optimization, lattice structures and 3D printing has quickly emerged as a potential alternative for the design and manufacturing of lightweight components. However, the size of the building chamber restricts the size of this kind of lightweight designs. A possibility to overcome this limitation is to design assemblies of 3D printed lightweight components put together with contact interfaces. To design such an optimal lightweight assembly, the components should not be optimized separately, but the wholeassembly should be optimized simultaneously with all components including their unilateralcontact interfaces. This is the topic of the following work. In this paper, a framework formulti-scale topology optimization of assemblies of bodies with triply periodic minimal surfaces(TPMS)-based lattice structures and unilateral contact interfaces is developed and implementedin 3D. The contact interfaces are formulated for finite element bodies with non-matching meshesusing the mortar approach which in turn is solved by the augmented Lagrangian formulationand Newton’s method. The multi-scale topology optimization formulation, suggested in [1],is set up by defining two density variables for each finite element: one macro density variablegoverned by RAMP (Rational Approximation of Material Properties), and a micro densityvariable governed by representative orthotropic elastic properties obtained by numerical finiteelement homogenization of representative volume elements of the TPMS-based lattice structure. Thus, the macro density variable defines if an element should be treated as a void or be filled with lattice structure, and the micro density variable sets the local grading of the lattice. The potential energy of the system is maximized with respect to the design variables, in such manner no extra adjoint equation is needed for the sensitivity analysis. Both density variables are treated with a density filter, and the macro density variable is also passed a Heaviside filter. The final optimal assembly design is realized by transforming the optimal density fields to implicit surface-based geometries using a support vector machine and Shepard’s interpolation method, which then can be 3D printed as the corresponding stl-file obtained by applying the marching cube algorithm. The implemented framework is demonstrated for three-dimensional benchmark problems.
Abstract
The combination of topology optimization, lattice structures and 3D printing has quickly emerged as a potential alternative for the design and manufacturing of lightweight [...]
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Fluid Flow-Based Topology Optimization of Internal Channels of a LPBF-Manufactured Calibrator Side Lath
F. Gallego-Bordallo, H. Erdelyi, W. Six, I. Marco, B. Van Hooreweder

SIM-AM2023.

Abstract
In this study, a method is presented to design embedded cooling channels in an additively manufactured metal part. A fluid flow-based Topology Optimization (TO) methodology was applied on a specific industrial case study with thermal objectives and constraints. The resulting design was 3D-printed and assessed numerically. In addition, the cooling efficiency is compared against that of the original design, which is machined. This work was performed using commercial software tools Simcenter STAR-CCM+ to perform the thermal and fluid flow optimization and simulations; NX to generate a final geometry from optimization results and 3DXpert to assess part printability.
Abstract
In this study, a method is presented to design embedded cooling channels in an additively manufactured metal part. A fluid flow-based Topology Optimization (TO) methodology [...]
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Thermal and Mechanical calibration of multi-material DED AM process simulations on part-scale
J. Vroon, A. van der Eems, W. van der Brink

SIM-AM2023.

Abstract
Additive Manufacturing (AM) processes, such as Directed Energy Deposition (DED), offer great potential for producing complex and customized components. To optimize these processes, accurate simulations and numerical modeling techniques are essential. This paper presents a study on the thermal and mechanical calibration of DED AM process simulations on a part-scale. The research aims to develop a comprehensive finite element model that incorporates the multi-physics nature of the DED process, accurately predicting thermal behavior, internal stresses, and distortion of manufactured components. The calibration process involves experimental measurements and simulations using Abaqus software. The thermal calibration involves calibrating parameters such as emissivity, absorptivity, and convection coefficients, while the mechanical calibration focuses on plastic strain properties. Additionally, the study explores the simulation of multi-material prints and functionally graded materials. The results demonstrate that the models can accurately represent thermal and mechanical phenomena, with calibration of material properties playing a crucial role. The paper concludes with recommendations for further validation, including demonstrator prints and investigations into simulation parameters. This research contributes to advancing the understanding and application of DED AM simulations, enabling more accurate and reliable predictions for industrial applications.
Abstract
Additive Manufacturing (AM) processes, such as Directed Energy Deposition (DED), offer great potential for producing complex and customized components. To optimize these processes, [...]
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Simulation-Based Process Optimization Towards Homogeneous Ti6Al4V L-PBF Components
T. Koenis, M. Montero-Sistiaga, M. De Smit, E. Amsterdam

SIM-AM2023.

Abstract
In this study, macro-scale thermal simulation of the laser powder bed fusion (LPBF) process is employed to predict and limit geometry-induced overheating of complex Ti6Al4V components. First, the overheating effect is reproduced in tensile specimens. Overheating is found to increase the local oxygen content by almost 80% and lower the elongation at break by over 70% in overheated regions. By employing macro-scale thermal simulations, an automated routine is developed to efficiently optimize the L-PBF process to prevent local overheating. Variable interlayer wait times are numerically optimized to allow cooling of the material without adding manufacturing time where this is not required. In this way, local overheating can successfully be prevented resulting in a more homogeneous temperature distribution during the L-PBF process. This method was found to fully restore the mechanical properties in geometries prone to overheating, resulting in more homogeneous and predictable Ti6Al4V components.
Abstract
In this study, macro-scale thermal simulation of the laser powder bed fusion (LPBF) process is employed to predict and limit geometry-induced overheating of complex Ti6Al4V [...]
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Numerical model for the laser metal deposition additive manufacturing process: Multiphysics modeling and experimental validation
G. Dali

SIM-AM2023.

Abstract
Metallic Additive Manufacturing (AdM) technologies (3D printing) is rapidly spreading to a variety of industrial applications. In recent years, advances in AdM have gradually transformed the way in which manufactured products are designed and produced. It enables easy manufacturing of complex shaped parts with high performance, less material waste and short development cycle. Laser Metal Deposition (LMD) is one of the processes in this growing field. This process can produce high performance parts by the injection of powders into a melt-pool created by a laser heat source. However, the LMD is complex and several defects may appear during the printing process. In this context, numerical simulation could be a helpful tool to describe the involved physical phenomena and then to predict the impact of process parameters on the material state. Such numerical tool can predict the heat exchanges and the fluid flow within the molten pool enabling defect prediction and process optimization. In this work, a multi-physics numerical model of the LMD process, at a mesoscopic scale, (i.e. at the layer thickness scale) is developed to predict thermal cycles during fabrication, as well as the complex relationships between part construction and operating parameters. For this purpose, the finite element code COMSOL Multiphysics is used. The developed model takes into account fluid flow and heat transfer in the different phases (gas, substrate and melt pool). As a key feature, the developed model simulates the growth of the track using the generation of droplets when the powder flow is intercepted by the laser beam. Material addition, interface tracking, and strong topological changes are handled using the level set technique. The numerical results are compared to the experimental results for validation purposes. This validation includes the comparison between the predicted molten pool cross-section and measurements from macrographs and high-speed videos.
Abstract
Metallic Additive Manufacturing (AdM) technologies (3D printing) is rapidly spreading to a variety of industrial applications. In recent years, advances in AdM have gradually [...]
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Design of Graphical Symbols for Shape Transformations of 4D Printed Parts

Thermal model for laser-based powder bed fusion of metal process: modelling, calibration, and experimental validation

Cellular Automata Simulation of Fully Equiaxed Microstructure Formation in Scalmalloy® during Additive Manufacturing with Adjustable Ring Mode Laser

The Effect of Geometrical Imperfections on the Mechanical Properties of Lattice Structures Produced by the Powder Bed Fusion (PBF) Process

Numerical Investigation of Vibration Properties of Chiral Structures with Artifical Structural Anisotropy

Towards neuronal network enhanced finite element simulations in additive manufacturing

Parametric Study of Directed Energy Deposition Of Duplex Stainless Steels To Optimize Ferrite-Austenite Phase Ratio And Residual Stresses

Closed-walled topology optimization of an additively manufactured motor bracket for an unmanned cargo aerial vehicle

Incremental Viscoelasticity for 3D Concrete Printing: Finite Strain Modeling and Parametric Studies

Effect of Residual Stresses on the Mechanical Properties of TPMS Lattice Structures Manufactured Using 316L Stainless Steel

SAMPLE3D: A Versatile Numerical Tool for Investigating Texture and Grain Structure of Materials Processed by PBF Processes

Multi-Scale Topology Optimization of Bodies with TPMS-based Lattice Structures and Mortar Contact Interfaces

Fluid Flow-Based Topology Optimization of Internal Channels of a LPBF-Manufactured Calibrator Side Lath

Thermal and Mechanical calibration of multi-material DED AM process simulations on part-scale

Simulation-Based Process Optimization Towards Homogeneous Ti6Al4V L-PBF Components

Numerical model for the laser metal deposition additive manufacturing process: Multiphysics modeling and experimental validation

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