Mechanical Properties of Open-Cell Cellular Structures With Rhombic Dodecahedron Cells

2010 ◽  
Author(s):  
Sahab Babaee ◽  
Babak Haghpanah Jahromi ◽  
Amin Ajdari ◽  
Hamid Nayeb-Hashemi ◽  
Ashkan Vaziri
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Single Unit ◽  
Cellular Structure ◽  
Three Dimensional ◽  
Small Deformation ◽  
Unit Cell ◽  
Analytical Models ◽  
Open Cell ◽  
Principal Directions

We present a series of analytical models and finite element results (FE) for special 3-D open cellular foam to determine the effective material properties of a 3D rhombic dedecahedron open-cell cellular structure. The analytical approach is based on minimizing the total energy associated with small deformation of a single unit cell of the cellular structure. The finite element models were developed for both a single unit cell and three dimensional foam structure and used to obtain the mechanical properties in all three principal directions.

Mechanical properties of the three-dimensional compression-twist cellular structure

2019 ◽  
Vol 39 (7-8) ◽  
pp. 260-277
Author(s):  
Wei Zhang ◽  
Xiaoyu Bai ◽  
Bowen Hou ◽  
Yadong Sun ◽  
Xiao Han
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Cellular Structure ◽  
Cell Structure ◽  
Twist Angle ◽  
Three Dimensional ◽  
Thickness Ratio ◽  
Cell Length ◽  
Element Analysis

The cellular structure can exhibit many special mechanical behaviors due to its variable cell shape. A three-dimensional compression-twist cell structure based on the rotation mechanism of two-dimensional chiral cell structure is developed, which has twist deformation under axial compression. The shape of three-dimensional compression-twist cell structure is determined through cell angle, cell length, and thickness ratio. Analytical expressions of effective Young’s modulus, Poisson’s ratio, and twist angle are derived by using beam theory, which have a good agreement with the finite element calculations and the deformation process of the cell is discussed. To work on the effect of geometric parameters of cell on the mechanical properties, a finite element analysis model of compression-twist cell structure is carried out, which shows the process of elastic and plastic deformation under compression. Effects of cell angle, cell length, and thickness ratio are fully discussed, which indicate that cell angle has obvious nonlinear effect on relative twist angle and could stiffen it. Finally, a compression-twist cell structure sample is made through three-dimensional printing, and an in-plane compressive experiment is carried out to prove analytical and finite element analysis results.

Effect of Bone Tumor and Osteoporosis on Mechanical Properties of Bone and Bone Tissue Properties: A Finite Element Study

2007 ◽  
Author(s):  
Vipul P. Gohil ◽  
Paul K. Canavan ◽  
Hamid Nayeb-Hashemi
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Bone Density ◽  
Bone Tissue ◽  
Bone Tumor ◽  
Cellular Structure ◽  
Bone Tumors ◽  
World Health ◽  
Tissue Stiffness ◽  
Tissue Properties

This research is aimed to study the variations in the biomechanical behavior of bone and bone tissues with osteoporosis and bone tumors. Osteoporosis and bone tumors reduce the mechanical strength of bone, which creates a greater risk of fracture. In the United States alone, ten million individuals, eight million of whom are women, are estimated to already have osteoporosis, and almost 34 million more are estimated to have low bone mass (osteopenia) placing them at increased risk for osteoporosis. World Health Organization defines osteopenia, as a bone density between one and two and a half standard deviations (SD) below the bone density of a normal young adult. (Osteoporosis is defined as 2.5 SD or more below that reference point.). Together, osteoporosis and osteopenia are expected to affect an estimated 52 million women and men age 50 and older by 2010, and 61 million by 2020. The current medical cost of osteoporosis total is nearly about $18 billion in the U.S. each year. There is a dearth of literature that addresses the effects of osteoporosis on bone tissue properties. Furthermore, there are few studies published related to the effect of bone tumors such as Adamantinoma of long bones, Aneurysmal bone cyst, Hemangioma and others on overall behavior of bone. To understand the variations in bio-mechanical properties of internal tissues of bone with osteoporosis and bone tumor, a 2D finite element (FE) model of bone is developed using ANSYS 9.0 ® (ANSYS Inc., Canonsburg, PA). Trabecular bone is modeled using hexagonal and voronoi cellular structure. This finite element model is subjected to change in BVF (bone volume fraction) and bone architecture caused by osteoporosis. The bone tumor is modeled as finer multi-cellular structure and the effects of its size, location, and property variation of tumor on overall bone behavior are studied. Results from this analysis and comparative data are used to determine behavior of bone and its tissue over different stage of osteoporosis and bone tumor. Results indicate that both bone tumor and osteoporosis significantly change the mechanical properties of the bone. The results show that osteoporosis increases the bone tissue stiffness significantly as BVF reduces. Bone tissue stiffness is found to increase by 80 percent with nearly 55 percent reduction of BVF. The results and methods developed in this research can be implemented to monitor variation in bio-mechanical properties of bone up to tissue level during medication or to determine type and time for need of external support such as bracing.

SEA model for structural acoustic coupling by means of periodic finite element models of the structural subsystems

2021 ◽  
Vol 263 (1) ◽  
pp. 5301-5309
Author(s):  
Luca Alimonti ◽  
Abderrazak Mejdi ◽  
Andrea Parrinello
Keyword(s):  
Finite Element ◽  
Numerical Approach ◽  
Unit Cell ◽  
Analytical Models ◽  
Finite Element Models ◽  
Fe Model ◽  
Acoustic Coupling ◽  
Representative Unit Cell ◽  
Definition Of ◽  
Acoustic Treatment

Statistical Energy Analysis (SEA) often relies on simplified analytical models to compute the parameters required to build the power balance equations of a coupled vibro-acoustic system. However, the vibro-acoustic of modern structural components, such as thick sandwich composites, ribbed panels, isogrids and metamaterials, is often too complex to be amenable to analytical developments without introducing further approximations. To overcome this limitation, a more general numerical approach is considered. It was shown in previous publications that, under the assumption that the structure is made of repetitions of a representative unit cell, a detailed Finite Element (FE) model of the unit cell can be used within a general and accurate numerical SEA framework. In this work, such framework is extended to account for structural-acoustic coupling. Resonant as well as non-resonant acoustic and structural paths are formulated. The effect of any acoustic treatment applied to coupling areas is considered by means of a Generalized Transfer Matrix (TM) approach. Moreover, the formulation employs a definition of pressure loads based on the wavenumber-frequency spectrum, hence allowing for general sources to be fully represented without simplifications. Validations cases are presented to show the effectiveness and generality of the approach.

Examination of Response of a Skewed Steel Bridge Superstructure During Deck Placement

2003 ◽  
Vol 1845 (1) ◽  
pp. 66-75 ◽  
Author(s):  
Elizabeth K. Norton ◽  
Daniel G. Linzell ◽  
Jeffrey A. Laman
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Analytical Models ◽  
Levels Of Analysis ◽  
Steel Bridge ◽  
Bridge Superstructure ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Skewed Bridge

The response of a 74.45-m (244-ft 0-in.) skewed bridge to the placement of the concrete deck was monitored to compare measured and predicted behavior. This comparison was completed to ( a) determine theoretical deflections and rotations with analytical models for comparison to actual deformations monitored during construction; ( b) compare the results of various levels of analysis to determine the adequacy of the methods; and ( c) examine variations on the concrete placement sequence to determine the most efficient deck placement methods. Two levels of analysis were used to achieve the objectives. Level 1 was a two-dimensional finite element grillage model analyzed with STAAD/Pro. Level 2 was a three-dimensional finite element model analyzed with SAP2000. These studies are discussed and findings are presented.

Process modeling, joint-property characterization and construction of joint connectors for mechanical fastening by self-piercing riveting

2014 ◽  
Vol 10 (4) ◽  
pp. 631-658 ◽  
Author(s):  
Mica Grujicic ◽  
Jennifer Snipes ◽  
S. Ramaswami ◽  
Fadi Abu-Farha
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Large Scale ◽  
Constitutive Relations ◽  
Computational Cost ◽  
Three Dimensional ◽  
Modeling And Simulations ◽  
Content Type ◽  
Material Parameters ◽  
Computational Analyses

Purpose – The purpose of this paper is to propose a computational approach in order to help establish the effect of various self-piercing rivet (SPR) process and material parameters on the quality and the mechanical performance of the resulting SPR joints. Design/methodology/approach – Toward that end, a sequence of three distinct computational analyses is developed. These analyses include: (a) finite-element modeling and simulations of the SPR process; (b) determination of the mechanical properties of the resulting SPR joints through the use of three-dimensional, continuum finite-element-based numerical simulations of various mechanical tests performed on the SPR joints; and (c) determination, parameterization and validation of the constitutive relations for the simplified SPR connectors, using the results obtained in (b) and the available experimental results. The availability of such connectors is mandatory in large-scale computational analyses of whole-vehicle crash or even in simulations of vehicle component manufacturing, e.g. car-body electro-coat paint-baking process. In such simulations, explicit three-dimensional representation of all SPR joints is associated with a prohibitive computational cost. Findings – It is found that the approach developed in the present work can be used, within an engineering optimization procedure, to adjust the SPR process and material parameters (design variables) in order to obtain a desired combination of the SPR-joint mechanical properties (objective function). Originality/value – To the authors’ knowledge, the present work is the first public-domain report of the comprehensive modeling and simulations including: self-piercing process; virtual mechanical testing of the SPR joints; and derivation of the constitutive relations for the SPR connector elements.

Assessment of Corner Failure Depths in the Deep Drawing of 3D Panels Using Simplified 2D Numerical and Analytical Models

2000 ◽  
Vol 123 (2) ◽  
pp. 248-257 ◽  
Author(s):  
Hong Yao ◽  
Jian Cao
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Analytical Models ◽  
Design Stage ◽  
Beam Model ◽  
Preliminary Design ◽  
Powerful Means ◽  
Preliminary Design Stage ◽  
Blank Size

Methodologies of rapidly assessing maximum possible forming heights are needed for three-dimensional 3D sheet metal forming processes at the preliminary design stage. In our previous work, we proposed to use an axisymmetric finite element model with an enlarged tooling and blank size to calculate the corner failure height in a 3D part forming. The amount of enlargement is called center offset, which provides a powerful means using 2D models for the prediction of 3D forming behaviors. In this work, an analytical beam model to calculate the center offset is developed. Starting from the study of a square cup forming, a simple analytical model is proposed and later generalized to problems with corners of an arbitrary geometry. The 2D axisymmetric models incorporated with calculated center offsets were compared to 3D finite element simulations for various cases. Good assessments of failure height were obtained.

Prediction of Mechanical Properties of Microcellular Plastics Using the Variational Asymptotic Method for Unit Cell Homogenization (VAMUCH) Method

2013 ◽  
Author(s):  
Emily Yu ◽  
Lih-Sheng Turng
Keyword(s):  
Mechanical Properties ◽  
Asymptotic Method ◽  
Thermoplastic Polyurethane ◽  
Three Dimensional ◽  
Unit Cell ◽  
Element Analysis ◽  
Microcellular Plastics ◽  
Variational Asymptotic ◽  
Variational Asymptotic Method ◽  
Injection Molded

This work presents the application of the micromechanical variational asymptotic method for unit cell homogenization (VAMUCH) with a three-dimensional unit cell (UC) structure and a coupled, macroscale finite element analysis for analyzing and predicting the effective elastic properties of microcellular injection molded plastics. A series of injection molded plastic samples — which included polylactic acid (PLA), polypropylene (PP), polystyrene (PS), and thermoplastic polyurethane (TPU) — with microcellular foamed structures were produced and their mechanical properties were compared with predicted values. The results showed that for most material samples, the numerical prediction was in fairly good agreement with experimental results, which demonstrates the applicability and reliability of VAMUCH in analyzing the mechanical properties of porous materials. The study also found that material characteristics such as brittleness or ductility could influence the predicted results and that the VAMUCH prediction could be improved when the UC structure was more representative of the real composition.

scholarly journals STEADY STATE FINITE ELEMENT ANALYSIS OF A SINGLE STACK COLD PLATE WITH HEAT LOSSES

2017 ◽  
Vol 19 (1) ◽  
pp. 77-90 ◽  
Author(s):  
G. A. Quadir ◽  
Shiao Lin Bell ◽  
K. N. Seetharamu ◽  
A. Y. Hassan
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Single Unit ◽  
Heat Losses ◽  
Unit Cell ◽  
Bottom Surface ◽  
Cold Plate ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Unit Cells

Steady state analysis of a single stack cold plate used for the cooling of electronic components is carried out using the finite element method. The present methodology takes into account the heat losses from the top and bottom surfaces of the stack. In addition dimensionless parameters are used in the analysis. The analysis is divided into two parts: a single unit cell analysis and the analysis of the assembly of several unit cells. The results from the present analysis of a single unit cell for single stack cold plate without heat losses compare well with those available in the literature. The analyses of the assembly of unit cells with heat losses from the top and bottom surface of the stack show that the single unit cell can be considered to be the representative of the stacks only when there are no heat losses.

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