Novel Chiral Structure With Tailored Mechanical Response Exploiting Elastic Instabilities

This paper presents a structural concept that exploits elastic instabilities in novel periodic lattice structures for shape adaptation purposes. The nonlinear behaviour resulting from the occurrence of local buckling is utilised to achieve significant variations in the global structural response of the lattice. For the proposed structural concept, a unit cell is identified and utilised to investigate the mechanical characteristics for the load cases of uniaxial compression, shear, and rotation, conducting nonlinear finite element simulations. The results of the unit cell characterization are compared to the mechanical response of lattice structures under equivalent loading and convergence is achieved for all considered load cases. This paper therefore introduces a novel design concept to achieve selective compliance, especially beneficial for shape adaptation of wing structures.

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Tuning of Static and Dynamic Mechanical Response of LPBFed AlSi10Mg Lattice Structures through heat Treatments

Advanced Engineering Materials ◽

10.1002/adem.202100418 ◽

2021 ◽

Author(s):

Jacopo Fiocchi ◽

Chiara Bregoli ◽

Giulio Gerosa ◽

Ausonio Tuissi ◽

Carlo Alberto Biffi

Keyword(s):

Mechanical Response ◽

Heat Treatments ◽

Lattice Structures ◽

Dynamic Mechanical

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Shape transformers for phononic band gaps tuning in two-dimensional Bloch-periodic lattice structures

European Journal of Mechanics - A/Solids ◽

10.1016/j.euromechsol.2021.104278 ◽

2021 ◽

Vol 89 ◽

pp. 104278 ◽

Cited By ~ 1

Author(s):

Victor E.L. Gasparetto ◽

Mostafa S.A. ElSayed

Keyword(s):

Band Gaps ◽

Periodic Lattice ◽

Lattice Structures ◽

Two Dimensional ◽

Phononic Band Gaps

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Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-021-00251-1 ◽

2021 ◽

Vol 21 (3) ◽

Author(s):

S. Talebi ◽

R. Hedayati ◽

M. Sadighi

Keyword(s):

Surface Area ◽

Dynamic Behavior ◽

Energy Absorption ◽

Peak Stress ◽

Absorption Capacity ◽

Unit Cell ◽

Lattice Structures ◽

Energy Absorption Capacity ◽

Closed Cell ◽

Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

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Mechanical Response of Different Lattice Structures Fabricated Using the CLIP Technology

Volume 2: Advanced Manufacturing ◽

10.1115/imece2016-65907 ◽

2016 ◽

Author(s):

Anil Saigal ◽

John R. Tumbleston ◽

Hendric Vogel

Keyword(s):

Additive Manufacturing ◽

Mechanical Response ◽

Elastic Response ◽

Lattice Structures ◽

Rhombic Dodecahedron ◽

Structured Materials ◽

Specific Strength ◽

Strain Behavior ◽

End Use ◽

Continuous Liquid Interface Production

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 mechanical behavior of octahedral, octet, vertex centroid, dode, diamond, rhombi octahedron, rhombic dodecahedron and solid lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, plastic strain hardening to a peak in strength, followed by a drop in flow stress to a plateau region and finally rapid hardening associated with contact of the deformed struts with each other as part of densification. It was found that the elastic modulus and strength of the various lattice structured materials are proportional to each other. In addition, it was found that the octahedral, octet and diamond lattice structures are amongst the most efficient based on the measured specific stiffness and specific strength.

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

Volume 1A: 36th Computers and Information in Engineering Conference ◽

10.1115/detc2016-60012 ◽

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.

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A Proof of Concept Study of the Mechanical Behavior of Lattice Structures Used to Design a Shoulder Hemi-Prosthesis

Journal of Engineering and Science in Medical Diagnostics and Therapy ◽

10.1115/1.4051419 ◽

2021 ◽

Author(s):

Marinela Peto ◽

Oscar Aguilar-Rosas ◽

Erick Erick Ramirez-Cedillo ◽

Moises Jimenez ◽

Adriana Hernandez ◽

...

Keyword(s):

Mechanical Behavior ◽

Mechanical Response ◽

Mechanical Performance ◽

Cell Attachment ◽

Lattice Structure ◽

Material Model ◽

Patient Specific ◽

Hexagonal Prism ◽

Lattice Structures ◽

Proof Of Concept

Abstract Lattice structures offer great benefits when employed in medical implants for cell attachment and growth (osseointegration), minimization of stress shielding phenomena, and weight reduction. This study is focused on a proof of concept for developing a generic shoulder hemi-prosthesis, from a patient-specific case of a 46 years old male with a tumor on the upper part of his humerus. A personalized biomodel was designed and a lattice structure was integrated in its middle portion, to lighten weight without affecting humerus’ mechanical response. To select the most appropriate lattice structure, three different configurations were initially tested: Tetrahedral Vertex Centroid (TVC), Hexagonal Prism Vertex Centroid (HPVC), and Cubic Diamond (CD). They were fabricated in resin by digital light processing and its mechanical behavior was studied via compression testing and finite element modeling (FEM). The selected structure according to the results was the HPVC, which was integrated in a digital twin of the biomodel to validate its mechanical performance through FEM but substituting the bone material model with a biocompatible titanium alloy (Ti6Al4V) suitable for prostheses fabrication. Results of the simulation showed acceptable levels of Von Mises stresses (325 MPa max.), below the elastic limit of the titanium alloys, and a better response (52 MPa max.) in a model with equivalent elastic properties, with stress performance in the same order of magnitude than the showed in bone’s material model.

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Computational Investigation of Flow Over Geometry Compliant Lattice Structures

Volume 7: Fluids Engineering ◽

10.1115/imece2018-87846 ◽

2018 ◽

Author(s):

James J. Tinsley ◽

Gregory J. Vernon ◽

Kelly O. Homan

Keyword(s):

Heat Transfer ◽

Additive Manufacturing ◽

Integral Geometry ◽

Single Unit ◽

Unit Cell ◽

Lattice Structures ◽

Computational Investigation ◽

Enhance Heat Transfer ◽

Arbitrary Flow ◽

The U.S

With the increasing prevalence of additive manufacturing, geometries that would not have been possible to manufacture just a few years ago are becoming a reality. One example is the ability to create pipes with integral, geometry compliant lattice structures. These compliant lattice structures offer the potential to greatly enhance heat transfer in arbitrary flow passages. This preliminary paper will focus on the development of an isothermal simulation model in OpenFOAM, to model the nature of the flow for a single unit cell, a unit cell screen, and a series of unit cell screens. Honeywell FM&T is a contractor of the U.S. Government under Contract No. DE-NA0002839.

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Microstructural and Mechanical Response of NiTi Lattice 3D Structure Produced by Selective Laser Melting

Metals ◽

10.3390/met10060814 ◽

2020 ◽

Vol 10 (6) ◽

pp. 814 ◽

Cited By ~ 3

Author(s):

Carlo Alberto Biffi ◽

Paola Bassani ◽

Jacopo Fiocchi ◽

Ausonio Tuissi

Keyword(s):

Martensitic Transformation ◽

Selective Laser Melting ◽

Mechanical Response ◽

Electron Backscatter Diffraction ◽

Bulk Material ◽

Niti Alloy ◽

3D Structure ◽

Lattice Structures ◽

Laser Melting ◽

Scanning Calorimetry

Nowadays, additive manufacturing (AM) permits to realize complex metallic structural parts, and the use of NiTi alloy, known as Nitinol, allows the integration of specific functions to the AM products. One of the most promising designs for AM is concerning the use of lattice structures that show lightweight, higher than bulk material deformability, improved damping properties, high exchange surface. Moreover, lattice structures can be realized with struts, having dimensions below 1 mm—this is very attractive for the realization of Nitinol components for biomedical devices. In this light, the present work regarded the experimental characterization of lattice structures, produced by selective laser melting (SLM), by using Ni-rich NiTi alloy. Differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD), and compression testing were carried out for analyzing microstructure, martensitic transformation (MT) evolution, and superelasticity response of the SLMed lattice samples. The lattice microstructures were compared with those of the SLMed bulk material for highlighting differences. Localized martensite was detected in the nodes zones, where the rapid solidification tends to accumulate solidification stresses. An increase of martensitic transformation temperatures was also observed in lattice NiTi.

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