Shape Design of Periodic Cellular Materials Under Cyclic Loading

2011 ◽  
Author(s):  
Ehsan Masoumi Khalil Abad ◽  
Sajad Arabnejad Khanoki ◽  
Damiano Pasini
Keyword(s):  
Fatigue Strength ◽  
Cellular Materials ◽  
Unit Cell ◽  
Cellular Material ◽  
Cellular Solid ◽  
Lattice Materials ◽  
Cell Topology ◽  
A Cell ◽  
Continuous Curvature ◽  
Geometric Changes

This paper presents a method to improve the fatigue strength of 2D periodic cellular materials under a fully-reversed loading condition. For a given cell topology, the shape of the unit cell is synthesized to minimize any stress concentration caused by discontinuities in the cell geometry. We propose to reduce abrupt geometric changes emerging in the periodic microstructure through the synthesis of a cell shape defined by curved boundaries with continuous curvature, i.e. G2-continous curves. The bending moments caused by curved cell elements are reduced by minimizing the curvature of G2-continuous cell elements so as to make them as straight as possible. The asymptotic homogenization technique is used to obtain the homogenized stiffness matrix and the fatigue strength of the synthesized cellular material. The proposed methodology is applied to synthesize a unit cell topology described by smooth boundary curves. Numeric simulations are performed to compare the performance of the synthesized cellular solid with that of common two dimensional lattice materials having hexagonal, circular, square, and Kagome shape of the unit cell. The results show that the methodology enables to obtain a cellular material with improved fatigue strength. Finally, a parametric study is performed to examine the effect of different geometric parameters on the performance of the proposed cellular geometries.

Micromechanical Modeling of Two-Dimensional Periodic Cellular Materials

2013 ◽  
Author(s):  
K. Alzebdeh ◽  
A. Al-Shabibi ◽  
T. Pervez
Keyword(s):  
Elastic Moduli ◽  
Cellular Materials ◽  
Unit Cell ◽  
Cellular Material ◽  
Micromechanical Modeling ◽  
Beam Model ◽  
Essential Boundary Condition ◽  
Representative Unit Cell ◽  
Structural Applications ◽  
Equivalent Continuum

The mechanical behavior of 2-D periodic cellular materials is investigated using a continuum-based modeling approach. Two micromechanical models are developed on the basis of representative unit cell concept in which skeleton of cellular material is modeled as elastic beams. The ANSYS finite element code is used to solve the beam model of skeleton. Elastic moduli of square and triangular networks comprising the microstructure of the cellular material are calculated based on an equivalent continuum model. This is achieved by equating the stored energy in skeleton of a unit cell to the strain energy of the equivalent continuum under a set of prescribed boundary conditions. A proper displacement-controlled (essential) boundary condition generates a uniform strain field in both models which corresponds to calculation of one elastic modulus at a time. Then, effective Young’s modulus and Poisson’s ratio of continuum are extracted from the calculated elastic moduli. The dependence of effective elastic constants on relative density and thickness to length ratio of the microstructure is investigated. Furthermore, the in-plane behavior of cellular solids in compression is explored with the help of current modeling. The proposed models may contribute to optimal designs of a new class of materials with tailored geometry and material properties which could be useful in a broad range of structural applications.

Developing Design Guidelines for Meso-Scaled Periodic Cellular Material Structures Under Shear Loading

2016 ◽  
Author(s):  
Mohammad Fazelpour ◽  
Prabhu Shankar ◽  
Joshua D. Summers
Keyword(s):  
Design Process ◽  
Effective Property ◽  
Design Guidelines ◽  
Shear Loading ◽  
Unit Cell ◽  
Cellular Material ◽  
Plane Shear ◽  
Unit Cells ◽  
Cell Topology ◽  
Shape Characteristics

Much research has been conducted on effective elastic properties of meso-scaled periodic cellular material (MPCM) structures; however, limited research is found in the literature for design guidelines to develop a unit cell (UC) topology and shape for multiple loading conditions. The current methods to design topology of unit cells has experienced limitations including numerical modeling challenges and trial-and-error associated with topology optimization and intuitive methods, respectively. To address this limitation this paper aims to develop guidelines for redesign of unit cell topology and shape under in-plane shear loading. The guidelines are intended to use design knowledge for helping engineers by providing recommendations at any stage of the design process. In this paper, the guidelines are developed by changing topology characteristics to achieve a desired effective property of a MPCM structure. The effect of individual members such as side connection and transverse connection of MPCM structure when subjected to in-plane shear loading are investigated through conducting a set of numerical simulation on UCs with similar topology and shape characteristics. Based on the simulation results, the unit cell design guidelines are developed to provide recommendations to engineers on improving shear flexure of MPCM during the design process.

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.

scholarly journals Four Questions in Cellular Material Design

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1060 ◽  
Author(s):  
Dhruv Bhate
Keyword(s):  
Paradigm Shift ◽  
State Of The Art ◽  
Material Design ◽  
Cellular Materials ◽  
Cellular Material ◽  
Optimal Parameters ◽  
Systematic Methodology ◽  
Design Software ◽  
Design Freedom ◽  
Key Questions

The design of cellular materials has recently undergone a paradigm shift, enabled by developments in Additive Manufacturing and design software. No longer do cellular materials have to be limited to traditional shapes such as honeycomb panels or stochastic foams. With this increase in design freedom comes a significant increase in optionality, which can be overwhelming to the designer. This paper aims to provide a framework for thinking about the four key questions in cellular material design: how to select a unit cell, how to vary cell size spatially, what the optimal parameters are, and finally, how best to integrate a cellular material within the structure at large. These questions are posed with the intent of stimulating further research that can address them individually, as well as integrate them in a systematic methodology for cellular material design. Different state-of-the-art solution approaches are also presented in order to provoke further investigation by the reader.

scholarly journals Unit Cell Analysis of the Superelastic Behavior of Open-Cell Tetrakaidecahedral Shape Memory Alloy Foam under Quasi-Static Loading

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Guillaume Maîtrejean ◽  
Patrick Terriault ◽  
Diego Devís Capilla ◽  
Vladimir Brailovski
Keyword(s):  
Shape Memory ◽  
Static Loading ◽  
Industrial Applications ◽  
Unit Cell ◽  
Cell Analysis ◽  
Solid Materials ◽  
Cellular Solid ◽  
Numerical Effort ◽  
Superelastic Behavior ◽  
Method Approach

Cellular solid materials and, more specifically, foams are increasingly common in many industrial applications due to their attractive characteristics. The tetrakaidecahedral foam microstructure, which can be observed in many types of foams, is studied in the present work in association with shape memory alloys (SMA) material. SMA foams are of particular interest as they associate both the shape memory effect and the superelasticity with the characteristics of foam. A Unit Cell Finite Element Method approach is used, an approach that allows accurate predicting of the macroscale response of the foam with a highly reduced numerical effort. The tetrakaidecahedral foam’s responses, both in the elastic and in the superelastic stages, are then extracted and compared with results from the literature. The tetrakaidecahedral geometry is found to be of particular interest when associated with SMA as it takes more advantage of the superelastic property of the material than foams with randomly distributed porosity.

scholarly journals Blast Alleviation of Sacrificial Cladding with Graded and Uniform Cellular Materials

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5616
Author(s):  
Yuanyuan Ding ◽  
Yuxuan Zheng ◽  
Zhijun Zheng ◽  
Yonggang Wang ◽  
Siyuan He ◽  
...  
Keyword(s):  
Blast Loading ◽  
Critical Length ◽  
Cellular Materials ◽  
Good Choice ◽  
Cellular Material ◽  
Optimal Length ◽  
Blast Design ◽  
Blast Response ◽  
Shock Models ◽  
Shock Fronts

Graded cellular material is a superb sandwich candidate for blast alleviation, but it has a disadvantage for the anti-blast design of sacrificial cladding, i.e., the supporting stress for the graded cellular material cannot maintain a constant level. Thus, a density graded-uniform cellular sacrificial cladding was developed, and its anti-blast response was investigated theoretically and numerically. One-dimensional nonlinear plastic shock models were proposed to analyze wave propagation in density graded-uniform cellular claddings under blast loading. There are two shock fronts in a positively graded-uniform cladding; while there are three shock fronts in a negatively graded-uniform cladding. Response features of density graded-uniform claddings were analyzed, and then a comparison with the cladding based on the uniform cellular material was carried out. Results showed that the cladding with uniform cellular materials is a good choice for the optimal mass design, while the density graded-uniform cladding is more advantageous from the perspective of the critical length design indicator. A partition diagram for the optimal length of sacrificial claddings under a defined blast loading was proposed for engineering design. Finally, cell-based finite element models were applied to verify the anti-blast response results of density graded-uniform claddings.

A Study of the Multi-Stability in a Non-Rigid Stacked Miura-Origami Cellular Mechanism

2021 ◽  
Author(s):  
Jiayue Tao ◽  
Suyi Li
Keyword(s):  
Building Blocks ◽  
Cellular Mechanism ◽  
Unit Cell ◽  
Torsional Stiffness ◽  
Engineering Systems ◽  
Stable States ◽  
Cellular Solid ◽  
Nonlinear Mechanical ◽  
Material Systems ◽  
Stable Structures

Abstract Multi-stable structures have gathered extensive interest because they can provide a broad spectrum of adaptive functions for many engineering systems. Especially, origami sheets with a translational periodicity can be stacked and assembled to form a multi-stable cellular solid, which has emerged as a promising platform to design functional structures. This paper investigates the multi-stability characteristics of a non-rigid stacked Miura-origami mechanism consisting of Miura-ori sheets and accordion-shaped connecting sheets, focusing on the elemental unit cell. A nonlinear mechanical model based on the barhinge approach is established to quantitatively study the unit cell’s multi-stability with intentionally relaxed rigid-folding conditions. Results show that only two stable states are achievable in the unit cell with enforced rigid-folding kinematics. However, if one relaxes the rigid-folding conditions and allows the facet to deform (i.e. non-rigid folding), four stable states are reachable in the unit cell if the crease torsional stiffness of the connecting sheets becomes sufficiently larger than that of the Miura-ori sheets, or the stress-free folding angle deviates away from 0°. A close examination of the potential energy composition of the non-rigid unit cell provides a detailed principle underpinning the multi-stability. By showing the benefits of exploiting facet compliance, this study can become the building blocks for origami-based structures and material systems with a wider variety of novel functionalities.

Effects of the unit cell topology on the compression properties of porous Co-Cr scaffolds fabricated via selective laser melting

2017 ◽  
Vol 23 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Changjun Han ◽  
Chunze Yan ◽  
Shifeng Wen ◽  
Tian Xu ◽  
Shuai Li ◽  
...  
Keyword(s):  
Cell Size ◽  
Selective Laser Melting ◽  
Unit Cell ◽  
Porous Scaffolds ◽  
Compression Tests ◽  
Laser Melting ◽  
Content Type ◽  
Compression Properties ◽  
Fe Simulations ◽  
Cell Topology

Purpose Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit cell topology is a significant factor that determines the mechanical property of porous scaffolds. Therefore, the purpose of this paper is to evaluate the effects of unit cell topology on the compression properties of porous Cobalt–chromium (Co-Cr) scaffolds fabricated by SLM using finite element (FE) and experimental measurement methods. Design/methodology/approach The Co-Cr alloy porous scaffolds constructed in four different topologies, i.e. cubic close packed (CCP), face-centered cubic (FCC), body-centered cubic (BCC) and spherical hollow cubic (SHC), were designed and fabricated via SLM process. FE simulations and compression tests were performed to evaluate the effects of unit cell topology on the compression properties of SLM-processed porous scaffolds. Findings The Mises stress predicted by FE simulations showed that different unit cell topologies resulted in distinct stress distributions on the bearing struts of scaffolds, whereas the unit cell size directly determined the stress value. Comparisons on the stress results for four topologies showed that the FCC unit cell has the minimum stress concentration due to its inclined bearing struts and horizontal arms. Simulations and experiments both indicated that the compression modulus and strengths of FCC, BCC, SHC, CCP scaffolds with the same cell size presented in a descending order. These distinct compression behaviors were correlated with the corresponding mechanics response on bearing struts. Two failure mechanisms, cracking and collapse, were found through the results of compression tests, and the influence of topological designs on the failure was analyzed and discussed. Finally, the cell initial response of the SLM-processed Co-Cr scaffold was tested through the in vitro cell culture experiment. Originality/value A focus and concern on the compression properties of SLM-processed porous scaffolds was presented from a new perspective of unit cell topology. It provides some new knowledge to the structure optimization of porous scaffolds for load-bearing bone implants.

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