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Additive Manufacturing Methods and Modeling Approaches

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Simulation and Design".

Deadline for manuscript submissions: closed (31 January 2021) | Viewed by 38339

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Prof. Dr. Massimiliano Avalle

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DIME—Department of Mechanical, Energy, Management and Transportation Engineering Polytechnic School, University of Genoa, 16145 Genoa, Italy
Interests: materials characterization and modeling; design and optimization of AM structures; cellular materials
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Prof. Dr. Giovanni Berselli

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Department of Mechanical, Energy, Management and Transportation Engineering, University of Genova, 16145 Genova, Italy
Interests: compliant mechanisms; smart-material-based transducers; variable stiffness actuators
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Dear Colleagues,

Nowadays, materials and technologies related to additive manufacturing (AM) are quickly evolving, both in terms of production processes and in terms of available materials. Additive manufactured components have already started to represent final products rather than mere prototypes. Indeed, one should notice that the term AM has basically substituted the terms rapid prototyping and 3D printing, in order to underline a closer link to the end-use components.

Regarding AM of metal parts, the main challenges are represented by the costs and the capability to obtain good performances. As for plastic parts, the current issues are similar, although the 3D printing of some low-cost plastics is already widely available. In this case, several materials can now be employed, ranging from the well-known ABS and PLA up to soft, rubber-like polymers. As for composites, this technology is rather new and offers interesting challenges and perspectives (including, also, the potential to replace metal).

Within this context, this Special Issue aims to provide an opportunity for researchers from both academia and industry to share recent advances in the field, with special attention to material modeling, design methods and criteria, software tools, and case studies, in this case, including industrial applications.

Prof. Dr. Massimiliano Avalle
Prof. Dr. Giovanni Berselli
Guest Editors

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Keywords

AM materials: metals, plastics, and composites.
Material characterization, especially fatigue, fracture, aging.
AM product design and simulation methods and tools; design rules.
Process simulations; residual stresses.
Post-treatment: surface finish, heat treatment, and machining.
Case studies, industrial applications.
New technologies (e.g., hybrid AM, 4D printing).
Lattice and cellular structures.
AM-related standards and specs: materials, technologies, material recycling, and environmental issues.
Inspection techniques, defect identification, and characterization.

Related Special Issue

Additive Manufacturing: Alloy Design and Process Innovations in Materials (63 articles)

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Research

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16 pages, 28859 KiB

Open AccessArticle

Influence of Geometric and Manufacturing Parameters on the Compressive Behavior of 3D Printed Polymer Lattice Structures

by Rafael Guerra Silva, Cristóbal Salinas Estay, Gustavo Morales Pavez, Jorge Zahr Viñuela and María Josefina Torres

Materials 2021, 14(6), 1462; https://doi.org/10.3390/ma14061462 - 17 Mar 2021

Cited by 17 | Viewed by 2877

Abstract

Fused deposition modeling represents a flexible and relatively inexpensive alternative for the production of custom-made polymer lattices. However, its limited accuracy and resolution lead to geometric irregularities and poor mechanical properties when compared with the digital design. Although the link between geometric features and mechanical properties of lattices has been studied extensively, the role of manufacturing parameters has received little attention. Additionally, as the size of cells/struts nears the accuracy limit of the manufacturing process, the interaction between geometry and manufacturing parameters could be decisive. Hence, the influence of three geometric and two manufacturing parameters on the mechanical behavior was evaluated using a fractional factorial design of experiments. The compressive behavior of two miniature lattice structures, the truncated octahedron and cubic diamond, was evaluated, and multilinear regression models for the elastic modulus and plateau stress were developed. Cell size, unit cell type, and strut diameter had the largest impact on the mechanical properties, while the influence of feedstock material and layer thickness was very limited. Models based on factorial design, although limited in scope, could be an effective tool for the design of customized lattice structures. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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15 pages, 5710 KiB

Open AccessArticle

The Effect of Binder Loading on the Pore Size of 3D Printed PMMA

by Simon Riechmann, Odo Wunnicke and Arno Kwade

Materials 2021, 14(5), 1190; https://doi.org/10.3390/ma14051190 - 03 Mar 2021

Cited by 6 | Viewed by 1797

Abstract

Binder jetting is known to produce porous objects by depositing the binder selectively layer by layer on a powder bed. In this study, the pore size of printed parts and the correlating mechanical properties are investigated on a commercially available PMMA powder binder system. Pore sizes are measured via capillary flow porometry and mechanical properties via tensile tests. Porometry indicates that the pore size stays at a constant level of 22 µm at 5 to 10 wt% binder loading before decreasing to 6 µm at loadings of 30 wt% or higher. The results were compared with the mechanical testing and related to the agglomerate strength model of Rumpf. The highlights of the article are the application of a binder jetted part as a filter and the identification of a close relationship between porosity and mechanical strength, similar to phenomena in agglomeration science. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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21 pages, 4307 KiB

Open AccessArticle

Discrete-Event Simulation Thermal Model for Extrusion-Based Additive Manufacturing of PLA and ABS

by Sunil Bhandari and Roberto A. Lopez-Anido

Materials 2020, 13(21), 4985; https://doi.org/10.3390/ma13214985 - 05 Nov 2020

Cited by 17 | Viewed by 3662

Abstract

The material properties of thermoplastic polymer parts manufactured by the extrusion-based additive manufacturing process are highly dependent on the thermal history. Different numerical models have been proposed to simulate the thermal history of a 3D-printed part. However, they are limited due to limited geometric applicability; low accuracy; or high computational demand. Can the time–temperature history of a 3D-printed part be simulated by a computationally less demanding, fast numerical model without losing accuracy? This paper describes the numerical implementation of a simplified discrete-event simulation model that offers accuracy comparable to a finite element model but is faster by two orders of magnitude. Two polymer systems with distinct thermal properties were selected to highlight differences in the simulation of the orthotropic response and the temperature-dependent material properties. The time–temperature histories from the numerical model were compared to the time–temperature histories from a conventional finite element model and were found to match closely. The proposed highly parallel numerical model was approximately 300–500 times faster in simulating thermal history compared to the conventional finite element model. The model would enable designers to compare the effects of several printing parameters for specific 3D-printed parts and select the most suitable parameters for the part. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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25 pages, 2915 KiB

Open AccessArticle

Fast Detection of Heat Accumulation in Powder Bed Fusion Using Computationally Efficient Thermal Models

by Rajit Ranjan, Can Ayas, Matthijs Langelaar and Fred van Keulen

Materials 2020, 13(20), 4576; https://doi.org/10.3390/ma13204576 - 14 Oct 2020

Cited by 17 | Viewed by 2793

Abstract

The powder bed fusion (PBF) process is a type of Additive Manufacturing (AM) technique which enables fabrication of highly complex geometries with unprecedented design freedom. However, PBF still suffers from manufacturing constraints which, if overlooked, can cause various types of defects in the final part. One such constraint is the local accumulation of heat which leads to surface defects such as melt ball and dross formation. Moreover, slow cooling rates due to local heat accumulation can adversely affect resulting microstructures. In this paper, first a layer-by-layer PBF thermal process model, well established in the literature, is used to predict zones of local heat accumulation in a given part geometry. However, due to the transient nature of the analysis and the continuously growing domain size, the associated computational cost is high which prohibits part-scale applications. Therefore, to reduce the overall computational burden, various simplifications and their associated effects on the accuracy of detecting overheating are analyzed. In this context, three novel physics-based simplifications are introduced motivated by the analytical solution of the one-dimensional heat equation. It is shown that these novel simplifications provide unprecedented computational benefits while still allowing correct prediction of the zones of heat accumulation. The most far-reaching simplification uses the steady-state thermal response of the part for predicting its heat accumulation behavior with a speedup of 600 times as compared to a conventional analysis. The proposed simplified thermal models are capable of fast detection of problematic part features. This allows for quick design evaluations and opens up the possibility of integrating simplified models with design optimization algorithms. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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20 pages, 15264 KiB

Open AccessArticle

Numerical Simulation Development and Computational Optimization for Directed Energy Deposition Additive Manufacturing Process

by Abhilash Kiran, Josef Hodek, Jaroslav Vavřík, Miroslav Urbánek and Jan Džugan

Materials 2020, 13(11), 2666; https://doi.org/10.3390/ma13112666 - 11 Jun 2020

Cited by 32 | Viewed by 5543

Abstract

The rapid growth of Additive Manufacturing (AM) in the past decade has demonstrated a significant potential in cost-effective production with a superior quality product. A numerical simulation is a steep way to learn and improve the product quality, life cycle, and production cost. To cope with the growing AM field, researchers are exploring different techniques, methods, models to simulate the AM process efficiently. The goal is to develop a thermo-mechanical weld model for the Directed Energy Deposition (DED) process for 316L stainless steel at an efficient computational cost targeting to model large AM parts in residual stress calculation. To adapt the weld model to the DED simulation, single and multi-track thermal simulations were carried out. Numerical results were validated by the DED experiment. A good agreement was found between predicted temperature trends for numerical simulation and experimental results. A large number of weld tracks in the 3D solid AM parts make the finite element process simulation challenging in terms of computational time and large amounts of data management. The method of activating elements layer by layer and introducing heat in a cyclic manner called a thermal cycle heat input was applied. Thermal cycle heat input reduces the computational time considerably. The numerical results were compared to the experimental data for thermal and residual stress analyses. A lumping of layers strategy was implemented to reduce further computational time. The different number of lumping layers was analyzed to define the limit of lumping to retain accuracy in the residual stress calculation. The lumped layers residual stress calculation was validated by the contour cut method in the deposited sample. Thermal behavior and residual stress prediction for the different numbers of a lumped layer were examined and reported computational time reduction. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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14 pages, 6880 KiB

Open AccessArticle

Additively Manufactured NiTi and NiTiHf Alloys: Estimating Service Life in High-Temperature Oxidation

by Hediyeh Dabbaghi, Keyvan Safaei, Mohammadreza Nematollahi, Parisa Bayati and Mohammad Elahinia

Materials 2020, 13(9), 2104; https://doi.org/10.3390/ma13092104 - 01 May 2020

Cited by 16 | Viewed by 2976

Abstract

In this study, the effect of the addition of Hf on the oxidation behavior of NiTi alloy, which was processed using additive manufacturing and casting, is studied. Thermogravimetric analyses (TGA) were performed at the temperature of 500, 800, and 900 °C to assess the isothermal and dynamic oxidation behavior of the Ni_50.4Ti_29.6Hf₂₀ at.% alloys for 75 h in dry air. After oxidation, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to analyze the oxide scale formed on the surface of the samples during the high-temperature oxidation. Two stages of oxidation were observed for the NiTiHf samples, an increasing oxidation rate during the early stage of oxidation followed by a lower oxidation rate after approximately 10 h. The isothermal oxidation curves were well matched with a logarithmic rate law in the initial stage and then by parabolic rate law for the next stage. The formation of multi-layered oxide was observed for NiTiHf, which consists of Ti oxide, Hf oxide, and NiTiO₃. For the binary alloys, results show that by increasing the temperature, the oxidation rate increased significantly and fitted with parabolic rate law. Activation energy of 175.25 kJ/mol for additively manufactured (AM) NiTi and 60.634 kJ/mol for AM NiTiHf was obtained. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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19 pages, 11800 KiB

Open AccessArticle

Effects of Material Properties on Angular Distortion in Wire Arc Additive Manufacturing: Experimental and Computational Analyses

by Sang-Cheol Park, Hee-Seon Bang and Woo-Jae Seong

Materials 2020, 13(6), 1399; https://doi.org/10.3390/ma13061399 - 19 Mar 2020

Cited by 10 | Viewed by 2595

Abstract

In wire arc additive manufacturing (AM), as in arc welding, arc heat thermally deforms substrates and articles. For industrial applications, deformation characteristics of various materials must be understood and appropriate materials and methods of reducing deformation must be devised. Therefore, angular distortions of different materials were investigated through bead-on-plate welding and finite element analysis. A model that simplifies temperature-dependent properties was developed to establish relationships between thermomechanical properties and angular distortion. A simplified model of temperature-dependent properties was used, and angular distortion characteristics were extensively investigated for different material properties and heat inputs. Coefficient of thermal expansion, density, and specific heat all notably affected angular distortion depending on heat input conditions. Results showed that during wire arc AM, flatness of both substrates and articles could vary depending on material properties, heat input, substrate thickness, and bead accumulation. Study findings can provide insight into deformation characteristics of new materials and how to mitigate thermal distortions. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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15 pages, 12495 KiB

Open AccessArticle

Relationship between the Size and Inner Structure of Particles of Virgin and Re-Used MS1 Maraging Steel Powder for Additive Manufacturing

by Kateřina Opatová, Ivana Zetková and Ludmila Kučerová

Materials 2020, 13(4), 956; https://doi.org/10.3390/ma13040956 - 20 Feb 2020

Cited by 22 | Viewed by 3212

Abstract

Additive manufacturing (AM) is today in the main focus—and not only in commercial production. Products with complex geometry can be built using various AM techniques, which include laser sintering of metal powder. Although the technique has been known for a quite long time, the impact of the morphology of individual powder particles on the process has not yet been adequately documented. This article presents a detailed microscopic analysis of virgin and reused powder particles of MS1 maraging steel. The metallographic observation was performed using a scanning electron microscope (SEM). The particle size of the individual powder particles was measured in the SEM and the particle surface morphology and its change in the reused powder were observed. Individual particles were analyzed in detail using an SEM with a focused ion beam (FIB) milling capability. The powder particles were gradually cut off in thin layers so that their internal structure, chemical element distribution, possible internal defects, and shape could be monitored. Elemental distribution and phase distribution were analyzed using EDS and EBSD, respectively. Our findings lead to a better understanding and prediction of defects in additive-manufactured products. This could be helpful not just in the AM field, but in any metal powder-based processes, such as metal injection molding, powder metallurgy, spray deposition processes, and others. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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Review

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21 pages, 3153 KiB

Open AccessReview

Review of Tailoring Methods for Joints with Additively Manufactured Adherends and Adhesives

by Mattia Frascio, Eduardo André de Sousa Marques, Ricardo João Camilo Carbas, Lucas Filipe Martins da Silva, Margherita Monti and Massimiliano Avalle

Materials 2020, 13(18), 3949; https://doi.org/10.3390/ma13183949 - 07 Sep 2020

Cited by 26 | Viewed by 3271

Abstract

This review aims to assess the current modelling and experimental achievements in the design for additive manufacturing of bonded joints, providing a summary of the current state of the art. To limit its scope, the document is focused only on polymeric additive manufacturing processes. As a result, this review paper contains a structured collection of the tailoring methods adopted for additively manufactured adherends and adhesives with the aim of maximizing bonded joint performance. The intent is, setting the state of the art, to produce an overview useful to identify the new opportunities provided by recent progresses in the design for additive manufacturing, additive manufacturing processes and materials’ developments. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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21 pages, 5167 KiB

Open AccessReview

An Overview of Additive Manufacturing Technologies—A Review to Technical Synthesis in Numerical Study of Selective Laser Melting

by Abbas Razavykia, Eugenio Brusa, Cristiana Delprete and Reza Yavari

Materials 2020, 13(17), 3895; https://doi.org/10.3390/ma13173895 - 03 Sep 2020

Cited by 66 | Viewed by 7550

Abstract

Additive Manufacturing (AM) processes enable their deployment in broad applications from aerospace to art, design, and architecture. Part quality and performance are the main concerns during AM processes execution that the achievement of adequate characteristics can be guaranteed, considering a wide range of influencing factors, such as process parameters, material, environment, measurement, and operators training. Investigating the effects of not only the influential AM processes variables but also their interactions and coupled impacts are essential to process optimization which requires huge efforts to be made. Therefore, numerical simulation can be an effective tool that facilities the evaluation of the AM processes principles. Selective Laser Melting (SLM) is a widespread Powder Bed Fusion (PBF) AM process that due to its superior advantages, such as capability to print complex and highly customized components, which leads to an increasing attention paid by industries and academia. Temperature distribution and melt pool dynamics have paramount importance to be well simulated and correlated by part quality in terms of surface finish, induced residual stress and microstructure evolution during SLM. Summarizing numerical simulations of SLM in this survey is pointed out as one important research perspective as well as exploring the contribution of adopted approaches and practices. This review survey has been organized to give an overview of AM processes such as extrusion, photopolymerization, material jetting, laminated object manufacturing, and powder bed fusion. And in particular is targeted to discuss the conducted numerical simulation of SLM to illustrate a uniform picture of existing nonproprietary approaches to predict the heat transfer, melt pool behavior, microstructure and residual stresses analysis. Full article

(This article belongs to the Special Issue Additive Manufacturing Methods and Modeling Approaches)

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