Special Issue "Additive Manufacturing: Topology Optimization and Cellular Microstructures"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: 10 March 2022.

Special Issue Editors

Prof. Dr. Georgios E Stavroulakis
E-Mail Website
Guest Editor
Institute of Computational Mechanics and Optimization, School of Production Engineering and Management, Technical University of Crete, 73100 Chania, Greece
Interests: computational mechanics; smart structures; identification; structural control
Special Issues, Collections and Topics in MDPI journals
Dr. Loucas Papadakis
E-Mail Website
Guest Editor
Department of Mechanical Engineering, Frederick University, Nicosia 1036, Cyprus
Interests: manufacturing processes; additive manufacturing; thermomechanical modelling’ vehicle structures
Dr. Ioannis Ntintakis
E-Mail Website
Guest Editor
Department of Mechanical Engineering, Hellenic Mediterranean University, 71410 Heraklion, Greece
Interests: design engineer; material process; industrial design; additive manufacturing; topology optimization

Special Issue Information

Dear Colleagues,

Topology optimization (TO) is a mathematical method that spatially optimizes the distribution of material within a defined domain, by fulfilling predefined constraints and, if required, the cost function. However, topology optimization results are characterized by high complexity. The proposed optimized structures are difficult to manufacture with subtractive technologies. Additive manufacturing (AM) is a well-established technology already applied for the fabrication of structural components with nearly no geometric constraints. The combination of TO and AM allows for the creation of optimized parts with reduced mass and increased stiffness. Additive manufacturing leads to new structural design constraints and manufacturing defects, such as porosity and unmelt regions, shape inaccuracy after support structures removal, degradation of material properties, etc. Additionally, defects induced during additive manufacturing processes including unmelt regions and pores are the main cause of fatigue failure. These defects may cause crack initiation under cyclic loading.

Developments in AM techniques enable the fabrication of materials with intricate cellular architectures. A rapidly growing research area of cellular structures is auxetic materials with negative Poisson’s ratio (NPR). These materials expand in the lateral direction when stretched longitudinally or contract laterally under uniaxial compression. These materials possess a combination of high stiffness and strength with significant weight savings and demonstrate a series of particular characteristics over conventional materials, such as excellent indentation resistance, high shear stiffness, remarkable fracture toughness, and unique acoustic energy and impact absorption abilities.

The purpose of this Special Issue is to encourage the two scientific communities of additive manufacturing and topology optimization to focus on this novel and rapidly growing research area. In addition to the above fields, example topics may include new auxetic materials applications, machine learning applications, and novel algorithms linking topology optimization with additive manufacturing. This issue will publish original research papers, short reports, and reviews related to cellular structures fabricated with 3D printing and topology optimization methods for additive manufacturing.

Prof. Dr. Georgios Ε Stavroulakis
Dr. Loucas Papadakis
Dr. Ioannis Ntintakis
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • design for AM
  • lightweight, topological, lattice, and cellular structures
  • auxetic structures
  • materials for AM
  • surface finish and post processing operations
  • thermomechanical analysis for shape distortion prediction and compensation
  • reverse engineering methods
  • integrated computational materials engineering (ICME) in additive manufacturing
  • defects and stress inspection of 3D printed structures
  • support structures
  • artificial intelligence and machine learning for AM

Published Papers (3 papers)

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Research

Article
Experimental and Numerical Analysis of 3D Printed Polymer Tetra-Petal Auxetic Structures under Compression
Appl. Sci. 2021, 11(21), 10362; https://doi.org/10.3390/app112110362 - 04 Nov 2021
Viewed by 459
Abstract
Auxetic structures possess a negative Poisson ratio (ν < 0) as a result of their geometrical configuration, which exhibits enhanced indentation resistance, fracture toughness, and impact resistance, as well as exceptional mechanical response advantages for applications in defense, biomedical, automotive, aerospace, sports, consumer [...] Read more.
Auxetic structures possess a negative Poisson ratio (ν < 0) as a result of their geometrical configuration, which exhibits enhanced indentation resistance, fracture toughness, and impact resistance, as well as exceptional mechanical response advantages for applications in defense, biomedical, automotive, aerospace, sports, consumer goods, and personal protective equipment sectors. With the advent of additive manufacturing, it has become possible to produce complex shapes with auxetic properties, which could not have been possible with traditional manufacturing. Three-dimensional printing enables easy and precise control of the geometry and material composition of the creation of desirable shapes, providing the opportunity to explore different geometric aspects of auxetic structures with a variety of different materials. This study investigated the geometrical and material combinations that can be jointly tailored to optimize the auxetic effects of 2D and 3D complex structures by integrating design, modelling approaches, 3D printing, and mechanical testing. The simulation-driven design methodology allowed for the identification and creation of optimum auxetic prototype samples manufactured by 3D printing with different polymer materials. Compression tests were performed to characterize the auxetic behavior of the different system configurations. The experimental investigation demonstrated a Poisson’s ration reaching a value of ν = −0.6 for certain shape and material combinations, thus providing support for preliminary finite element studies on unit cells. Finally, based on the experimental tests, 3D finite element models with elastic material formulations were generated to replicate the mechanical performance of the auxetic structures by means of simulations. The findings showed a coherent deformation behavior with experimental measurements and image analysis. Full article
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Article
Cost-Aware Design and Fabrication of New Support Structures in Laser Powder Bed Fusion: Microstructure and Metallurgical Properties
Appl. Sci. 2021, 11(21), 10127; https://doi.org/10.3390/app112110127 - 28 Oct 2021
Viewed by 397
Abstract
This study investigates the effect of support structures on the properties of Inconel 718 (i.e., IN718) parts produced by the laser powder bed fusion (LPBF) additive manufacturing process. Specifically, the effects of support structure shape (i.e., pin-type, angled-type, cone-type) and geometry (i.e., support [...] Read more.
This study investigates the effect of support structures on the properties of Inconel 718 (i.e., IN718) parts produced by the laser powder bed fusion (LPBF) additive manufacturing process. Specifically, the effects of support structure shape (i.e., pin-type, angled-type, cone-type) and geometry (i.e., support wall thickness, and gap) on their composition, hardness, microstructure, and material/time consumption are investigated and compared to the conventionally fabricated Inconel 718. From the microstructural analysis, the deepest melt pools appeared to be formed in the sample fabricated on top of the pin-type support structure having a relatively low wall thickness. The XRD results conveyed that a proper selection of geometrical variables for designing support structure results in elevated levels of the strengthening phases of IN718. The sample fabricated on top of the pin-type support structure showed the highest Vickers hardness value of 460.5 HV, which was even higher than what was reported for the heat-treated wrought Inconel 718 (355–385 HV). Moreover, for the thinner support wall thickness, an improvement in the hardness value of the fabricated samples was observed. This study urges a reconsideration of the common approach of selecting supports for additive manufacturing of samples when a higher quality of the as-fabricated parts is desired. Full article
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Article
Low Thermal Expansion Machine Frame Designs Using Lattice Structures
Appl. Sci. 2021, 11(19), 9135; https://doi.org/10.3390/app11199135 - 30 Sep 2021
Viewed by 391
Abstract
In this work, we investigated tessellating cellular (or lattice) structures for use in a low thermal expansion machine frame. We proposed a concept for a lattice structure with tailorable effective coefficient of thermal expansion (CTE). The design is an assembly of two parts: [...] Read more.
In this work, we investigated tessellating cellular (or lattice) structures for use in a low thermal expansion machine frame. We proposed a concept for a lattice structure with tailorable effective coefficient of thermal expansion (CTE). The design is an assembly of two parts: a lattice outer part and a cylindrical inner part, which are made of homogenous materials with different positive CTEs. Several lattice design variations were investigated and their thermal and mechanical performance analysed using a finite element method. Our numerical models showed that a lattice design using Nylon 12 and ultra-high molecular weight polyethylene could yield an effective in-plane CTE of 1 × 10−9 K−1 (cf. 109 × 10−6 K−1 for solid Nylon 12). This paper showed that the combination of design optimisation and additive manufacturing can be used to achieve low CTE structures and, therefore, low thermal expansion machine frames of a few tens of centimetres in height. Full article
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