scholarly journals Retraction: Continuum model for effective properties of orthotropic octet-truss lattice through additive manufacturing

2021 ◽  
pp. 1-1
Keyword(s):  
Additive Manufacturing ◽  
Continuum Model ◽  
Effective Properties ◽  
Octet Truss

On the Effective Properties of 3D Metamaterials

2016 ◽  
Author(s):  
Mohamed Abdelhamid ◽  
Aleksander Czekanski
Keyword(s):  
Elastic Modulus ◽  
Effective Properties ◽  
Lattice Structure ◽  
Surface Elasticity ◽  
Geometric Parameters ◽  
Stiffness Tensor ◽  
Loading Direction ◽  
Octet Truss ◽  
The Impact ◽  
Effective Mechanical Properties

A continuum-based model is developed for the octet-truss unit cell in order to describe the effective mechanical properties (elastic modulus) of the lattice structure. This model is to include different geometric parameters that impact the structural effects; these parameters are: lattice angle, loading direction, thickness to diameter ratio, diameter to length ratio, and ellipticity. All these geometric parameters are included in the stiffness matrix, and the impact of each parameter on the stiffness tensor is investigated. Specifically, the effect of the lattice angle on the elastic moduli is discussed, and the loading direction of the highest elastic modulus is investigated for different lattice angles. Furthermore, the Gurtin-Murdoch model of surface elasticity is used to include the size effect in the stiffness tensor, as well as anisotropy of this model is investigated.

Stress-Strain Behavior of an Octahedral and Octet-Truss Lattice Structure Fabricated Using the CLIP Technology

2017 ◽  
Vol 1142 ◽  
pp. 245-249 ◽  
Author(s):  
Anil Saigal ◽  
John Tumbleston
Keyword(s):  
Additive Manufacturing ◽  
3D Printing ◽  
Lattice Structure ◽  
Liquid Interface ◽  
Layer By Layer ◽  
Stress Strain ◽  
Strain Behavior ◽  
Octet Truss ◽  
Continuous Liquid Interface Production ◽  
Similar Density

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the stress-strain behavior of an octahedral-and octet-truss lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. Continuous Liquid Interface Production (CLIP) is a breakthrough technology that grows parts instead of printing them layer by layer. Lattice structures such as the octahedral-and octet-truss lattice have recently attracted a lot of attention since they are often structurally more efficient than foams of a similar density made from the same material, and the ease with which these structures can now be produced using 3D printing and additive manufacturing. This research investigates the stress-strain behavior under compression of an octahedral-and octet-truss lattice structured polyacrylate fabricated using CLIP technology

Design for Additive Manufacturing: Effectiveness of Unit Cell Design Guidelines As Ideation Tools

2019 ◽  
Author(s):  
I’Shea Boyd ◽  
Mohammad Fazelpour
Keyword(s):  
Additive Manufacturing ◽  
Effective Properties ◽  
Cellular Materials ◽  
Design Guidelines ◽  
Unit Cell ◽  
Cell Design ◽  
Recent Approach ◽  
Wide Range ◽  
Unit Cells ◽  
High Flexibility

Abstract The periodic cellular materials are comprised of repeatable unit cells. Due to outstanding effective properties of the periodic cellular materials such as high flexibility or high stiffness at low relative density, they have a wide range of applications in lightweight structures, crushing energy absorption, compliant structures, among others. Advancement in additive manufacturing has led to opportunities for making complex unit cells. A recent approach introduced four unit cell design guidelines and verified them through numerical simulation and user studies. The unit cell design guidelines aim to guide designers to re-design the shape or topology of a unit cell for a desired structural behavior. While the guidelines were identified as ideation tools, the effectiveness of the guidelines as ideation tools has not been fully investigated. To evaluate the effectiveness of the guidelines as ideation tools, four objective metrics have been considered: novelty, variety, quality, and quantity. The results of this study reveal that the unit cell design guidelines can be considered as ideation tools. The guidelines are effective in aiding engineers in creating novel unit cells with improved shear flexibility while maintaining the effective shear modulus.

Continuum Model for Effective Properties of Orthotropic Octet-Truss Lattice Materials

2014 ◽  
Author(s):  
Adithya Challapalli ◽  
Jaehyung Ju
Keyword(s):  
3D Printing ◽  
Heat Dissipation ◽  
Effective Properties ◽  
Lattice Structure ◽  
Principal Direction ◽  
Base Material ◽  
Shear Moduli ◽  
Lattice Materials ◽  
Structural Applications ◽  
Octet Truss

Cellular materials, often called lattice materials, are increasingly receiving attention for their ultralight structures with high specific strength, excellent impact absorption, acoustic insulation, heat dissipation media and compact heat exchangers. In alignment with emerging additive manufacturing (AM) technology, realization of the structural applications of the lattice materials appears to be becoming faster. Considering the direction dependent material properties of the products with AM, by directionally dependent printing resolution, effective moduli of lattice structures appear to be directionally dependent. In this paper, we develop a constitutive model of a lattice structure, which is an octet-truss with a base material having an orthotropic material property considering AM. One case study is conducted with an orthotropic property of a base material in 3D Printing. A polyjet based 3D printing material having an orthotropic property with a 9% difference in the principal direction provides difference in the axial and shear moduli in the octet-truss by 2.3 and 4.6%.

scholarly journals CAD TOOLS AND FILE FORMAT PERFORMANCE EVALUATION IN DESIGNING LATTICE STRUCTURES FOR ADDITIVE MANUFACTURING

2018 ◽  
Vol 80 (4) ◽  
Author(s):  
Abdul Hadi Azman ◽  
Frédéric Vignat ◽  
François Villeneuve
Keyword(s):  
Performance Evaluation ◽  
Additive Manufacturing ◽  
Computer Aided Design ◽  
Data Exchange ◽  
Lattice Structure ◽  
Lattice Structures ◽  
File Size ◽  
Element Analysis ◽  
Computer Aided ◽  
Octet Truss

Additive manufacturing has opened the door to the creation of lightweight lattice structures. However, present Computer-Aided Design (CAD) and Computer-Aided Engineering (CAE) software are unsuitable for these types of structures. The objective of this research is to examine the performances of current CAD and CAE software to design lattice structures and to demonstrate their limitations and propose requirements for future developments. A performance evaluation of a case study for lattice structure designs was conducted. The criteria used for the evaluation were CAD human-machine-interface, RAM consumption, data exchange between CAD, CAE and CAM tools and finite element analysis (FEA) duration and file sizes. The CAD tool was incapable of executing a repetition function for octet-truss lattice structures of 150 x 150 x 150 mm dimensions or larger and the software stopped working. For 70 × 70 × 70 mm octet-truss lattice structure, the FEA computation file size reached 36.6 GB. The CAD file size of a 200 x 200 x 200 mm octet-truss lattice structure reached nearly 290 MB. In conclusion, this study exposes the performance inadequacy of current CAD and CAE tools and CAD file formats to design lattice structures for additive manufacturing parts.

Design of Stochastic Lattice Structures for Additive Manufacturing

2020 ◽  
Author(s):  
Matthew McConaha ◽  
Sam Anand
Keyword(s):  
Additive Manufacturing ◽  
Design Space ◽  
Volume Fraction ◽  
Effective Properties ◽  
Strength Properties ◽  
Lattice Structures ◽  
Design Engineers ◽  
Material Efficiency ◽  
Strength And Stiffness

Abstract With recent development of additive manufacturing methods, topology optimization, an increased focus on the generation of designs which maximize material efficiency by lightweighting has gained considerable interest. Lattice structures are one of the popular methods chosen by design engineers for constructing highly complex, functional geometries which are only manufacturable by additive processes. Stochastic lattices have been finding their way into additively manufactured geometries due to their strength at low volume fraction, as well as the ease of implementation with various generative design tools on the market. However, optimization of these stochastic lattices for maximizing part strength and stiffness is a research topic that has been largely overlooked. By tweaking stochastic lattice generation procedures, non-isotropic structures can be generated and these directional strength properties can be exploited. This paper describes a method for homogenizing the effective properties of non-isotropic stochastic lattices generated using stretched Voronoi tessellations, optimization of the stretching aspect ratio and angle within a part design space, and generation of the non-isotropic and smoothly graded Voronoi-based stochastic lattice structures for that design space. The method was applied to a case study of a cantilever beam with nine different Voronoi lattice configurations. Stiffness of parts designed using this procedure was found to be significantly higher than parts designed using an isotropic design.

scholarly journals Influence of the Miniaturisation Effect on the Effective Stiffness of Lattice Structures in Additive Manufacturing

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1442
Author(s):  
Guillaume Meyer ◽  
Florian Brenne ◽  
Thomas Niendorf ◽  
Christian Mittelstedt
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Mechanical Performance ◽  
Effective Properties ◽  
Weight Ratio ◽  
Effective Stiffness ◽  
Analytical Models ◽  
Lattice Structures ◽  
Thin Walled ◽  
The Impact

Thin-walled and cellular structures are characterised by superior lightweight potential due to their advantageous stiffness to weight ratio. They find particular interest in the field of additive manufacturing due to robust and reproducible manufacturability. However, the mechanical performance of such structures strongly depends on the manufacturing process and resultant geometrical imperfections such as porosity, deviations in strut thickness or surface roughness, for which an understanding of their influence is crucially needed. So far, many authors conducted empirical investigations, while analytical methods are rarely applied. In order to obtain efficient design rules considering both mechanical properties and process induced characteristics, analytical descriptions are desirable though. Available analytical models for the determination of effective properties are mostly based on the simple advancement of beam theories, mostly ignoring manufacturing characteristics that, however, strongly influence the mechanical properties of additive manufactured thin-walled structures. One example is the miniaturisation effect, a microstructural effect that has been identified as one of the main drivers of the effective elasto-plastic properties of lightweight structures processed by additive manufacturing. The current work highlights the need to quantify further microstructural effects and to encourage combining them into mesostructural approaches in order to assess macrostructural effective properties. This multi-scale analysis of lattice structures is performed through a comparison between effective stiffness calculated through an analytical approach and compression tests of lattice structures, coupled with an investigation of the arrangement of their struts. In order to cover different potential loading scenarios, bending-dominated and stretch-dominated lattice structures made of the commonly used materials 316L and Ti6Al4V are considered, whereby the impact of microstructural phase transformation during processing is taken into account.

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