scholarly journals Influence of Boundary Conditions on the Simulation of a Diamond-Type Lattice Structure: A Preliminary Study

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Patrick Terriault ◽  
Vladimir Brailovski
Keyword(s):  
Boundary Conditions ◽  
Material Properties ◽  
Lattice Structure ◽  
Industrial Applications ◽  
Unit Cell ◽  
Equivalent Material ◽  
Unit Cells ◽  
Type Lattice ◽  
Diamond Type ◽  
Equivalent Material Properties

Emergent additive manufacturing processes allow the use of metallic porous structures in various industrial applications. Because these structures comprise a large number of ordered unit cells, their design using conventional modeling approaches, such as finite elements, becomes a real challenge. A homogenization technique, in which the lattice structure is simulated as a fully dense volume having equivalent material properties, can then be employed. To determine these equivalent material properties, numerical simulations can be performed on a single unit cell of the lattice structure. However, a critical aspect to consider is the boundary conditions applied to the external faces of the unit cell. In the literature, different types of boundary conditions are used, but a comparative study is definitely lacking. In this publication, a diamond-type unit cell is studied in compression by applying different boundary conditions. If the porous structure’s boundaries are free to deform, then the periodic boundary condition is found to be the most representative, but constraint equations must be introduced in the model. If, instead, the porous structure is inserted in a rigid enclosure, it is then better to use frictionless boundary conditions. These preliminary results remain to be validated for other types of unit cells loaded beyond the yield limit of the material.

Study on Homogenization Process of Masonry Using Numerical Simulation Based on Periodic Boundary Conditions

2012 ◽  
Vol 204-208 ◽  
pp. 768-773
Author(s):  
Chun Xia Yang ◽  
Ji Mei Shen ◽  
Wei Jun Yang
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Finite Element Modeling ◽  
Material Properties ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Equivalent Material ◽  
Element Modeling ◽  
Relationship Of ◽  
Equivalent Material Properties

The homogenization technique has been used to derive equivalent material properties of masonry for many years, however, very few studies by most previous researchers concerntrated on the strain state of RVE, which is very important to calculate the equivalent material properties in the finite element modeling. In this paper, periodic boundary conditions is established automatically with the python re-development produce in ABAQUS environment, and is used to simulate the stress-strain relationship of RVE in different load cases based on ABAQUS. Equivalent elastic constants is derived and make a contrast to other researchers. The results indicated that the periodic boundary conditions derived in this article is feasible, and a reference is made for the finite element modeling of RVE.

Determination of Optimal Unit-Cell Size of Homogeneous Conformal Unit-Cell Lattice Structure Using Solid Shape Matching

2016 ◽  
Author(s):  
Mahmoud A. Alzahrani ◽  
Seung-Kyum Choi
Keyword(s):  
Cell Size ◽  
Solid Body ◽  
Strain Energy ◽  
Lattice Structure ◽  
Weight Ratio ◽  
Unit Cell ◽  
Optimal Size ◽  
Lattice Structures ◽  
Unit Cell Size ◽  
Unit Cells

With rapid developments and advances in additive manufacturing technology, lattice structures have gained considerable attention. Lattice structures are capable of providing parts with a high strength to weight ratio. Most work done to reduce computational complexity is concerned with determining the optimal size of each strut within the lattice unit-cells but not with the size of the unit-cell itself. The objective of this paper is to develop a method to determine the optimal unit-cell size for homogenous periodic and conformal lattice structures based on the strain energy of a given structure. The method utilizes solid body finite element analysis (FEA) of a solid counter-part with a similar shape as the desired lattice structure. The displacement vector of the lattice structure is then matched to the solid body FEA displacement results to predict the structure’s strain energy. This process significantly reduces the computational costs of determining the optimal size of the unit cell since it eliminates FEA on the actual lattice structure. Furthermore, the method can provide the measurement of relative performances from different types of unit-cells. The developed examples clearly demonstrate how we can determine the optimal size of the unit-cell based on the strain energy. Moreover, the computational cost efficacy is also clearly demonstrated through comparison with the FEA and the proposed method.

Rapid Modeling and Design Optimization of Multi-Topology Lattice Structure Based on Unit-Cell Library

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Yuan Liu ◽  
Shurong Zhuo ◽  
Yining Xiao ◽  
Guolei Zheng ◽  
Guoying Dong ◽  
...  
Keyword(s):  
Topology Optimization ◽  
Lattice Structure ◽  
Structure Design ◽  
Parametric Modeling ◽  
Unit Cell ◽  
Element Analysis ◽  
Structure Generation ◽  
Cell Library ◽  
Unit Cells ◽  
Property Space

Abstract Lightweight lattice structure generation and topology optimization (TO) are common design methodologies. In order to further improve potential structural stiffness of lattice structures, a method combining the multi-topology lattice structure design based on unit-cell library with topology optimization is proposed to optimize the parts. First, a parametric modeling method to rapidly generate a large number of different types of lattice cells is presented. Then, the unit-cell library and its property space are constructed by calculating the effective mechanical properties via a computational homogenization methodology. Third, the template of compromise Decision Support Problem (cDSP) is applied to generate the optimization formulation. The selective filling function of unit cells and geometric parameter computation algorithm are subsequently given to obtain the optimum lightweight lattice structure with uniformly varying densities across the design space. Lastly, for validation purposes, the effectiveness and robustness of the optimized results are analyzed through finite element analysis (FEA) simulation.

Analysis of Buffering Properties of Honeycomb Material

2012 ◽  
Vol 482-484 ◽  
pp. 1146-1149
Author(s):  
Ming Bo Yang ◽  
Jin Bao Chen ◽  
Fei Deng ◽  
Meng Chen
Keyword(s):  
Theoretical Analysis ◽  
Material Properties ◽  
Orthotropic Material ◽  
Soil Mechanics ◽  
Material Model ◽  
Lunar Soil ◽  
Equivalent Material ◽  
User Material Model ◽  
Honeycomb Material ◽  
Equivalent Material Properties

The buffering properties of honeycomb material are analyzed in the presented work. Theoretical analysis based on energy method is first presented, the buffering process of honeycomb material can be divided into three phases, honeycomb material can be equivalent to orthotropic material and the equivalent material properties are given. Being good at soil mechanics, Abaqus can simulate lunar soil very well. Using a constitutive model for honeycomb material, which is a built-in user material model, the presented work developed a honeycomb material simulation model and verified with a practical example. Now we can analysis the entire landing buffer process in Abaqus, which is a complement to existing analysis processes.

Effective Stress Ratio of Triangular Pattern Perforated Plates

2008 ◽  
Author(s):  
Naoto Kasahara ◽  
Hideki Takasho ◽  
Nobuchika Kawasaki ◽  
Masanori Ando
Keyword(s):  
Effective Stress ◽  
Material Properties ◽  
Constitutive Equations ◽  
Stress Ratio ◽  
Equivalent Material ◽  
Solid Materials ◽  
Perforated Plates ◽  
Non Linear ◽  
Effective Stress Ratio ◽  
Equivalent Material Properties

Tubesheet structures utilized in heat exchangers have complex perforated portions. For realistic design analysis, axisymmetric models with equivalent solid materials of perforated plate are conventionally adopted to simplify perforated area (figure1). Sec.III Appendix A-8000 (ASME 2004) provides elastic equivalent solid materials for flat tubesheets. Plastic properties were studied by Porowski et al. (1974), Gorden et al. (2002) and so on. Elevated temperature design of tubesheets requires plastic and creep properties in addition. The purpose of this study is to develop a general determination method of non-linear equivalent material properties for perforated plates and to confirm their applicability to both flat and spherical tubesheets. Main loadings of tubesheets in fast reactor heat exchanges are inner pressure and thermal stress at transient operations. Under above conditions, average stress of perforated area becomes approximately equi-biaxial. Therefore, average inelastic behaviors of various perforated plates subjected to equi-biaxial field were investigated by inelastic finite element method. Though above investigations, Authors clarified that perforated plates have their own effective stress ratio (ESR). ESR is a function of geometry and is independent from their materials. ESR can determine non-linear equivalent material properties of perforated plates for any kind of constitutive equations of base metals. For simplified inelastic analysis of perforated plates, the brief equations were proposed to determine equivalent plastic and creep material properties for perforated plates. It is considered that physical meaning of ESR is an effective stress ratio between perforated plates and equivalent solid plates. ESR is a function of geometry and is independent from constitutive equations. ESR can determine non-linear equivalent material properties for perforated plates from any kind of constitutive equations of base materials. Assumptions in ESR are von Mises’s equivalent stress-strain relationship and equi-biaxial loadings. Applicability of ESR was investigated through finite element analyses of various flat and spherical tubesheets.

scholarly journals Compressive Properties of Al-Si Alloy Lattice Structures with Three Different Unit Cells Fabricated via Laser Powder Bed Fusion

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2902 ◽  
Author(s):  
Xiaoyang Liu ◽  
Keito Sekizawa ◽  
Asuka Suzuki ◽  
Naoki Takata ◽  
Makoto Kobashi ◽  
...  
Keyword(s):  
Strain Rate ◽  
Lattice Structure ◽  
Unit Cell ◽  
Lattice Structures ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Compressive Properties ◽  
Powder Bed ◽  
Unit Cells ◽  
Indentation Tests

In the present study, in order to elucidate geometrical features dominating deformation behaviors and their associated compressive properties of lattice structures, AlSi10Mg lattice structures with three different unit cells were fabricated by laser powder bed fusion. Compressive properties were examined by compression and indentation tests, micro X-ray computed tomography (CT), together with finite element analysis. The truncated octahedron- unit cell (TO) lattice structures exhibited highest stiffness and plateau stress among the studied lattice structures. The body centered cubic-unit cell (BCC) and TO lattice structures experienced the formation of shear bands with stress drops, while the hexagon-unit cell (Hexa) lattice structure behaved in a continuous deformation and flat plateau region. The Hexa lattice structure densified at a smaller strain than the BCC and TO lattice structures, due to high density of the struts in the compressive direction. Static and high-speed indentation tests revealed that the TO and Hexa exhibited slight strain rate dependence of the compressive strength, whereas the BCC lattice structure showed a large strain rate dependence. Among the lattice structures in the present study, the TO lattice exhibited the highest energy absorption capacity comparable to previously reported titanium alloy lattice structures.

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