Mechanical Properties Of Lattice Structures Research Articles

An investigation into reinforced and functionally graded lattice structures

Lattice structures are regarded as excellent candidates for use in lightweight energy-absorbing applications, such as crash protection. In this paper we investigate the crushing behaviour, mechanical properties and energy absorption of lattices made by an additive manufacturing process. Two types of lattice were examined: body-centred-cubic (BCC) and a reinforced variant called BCC z. The lattices were subject to compressive loads in two orthogonal directions, allowing an assessment of their mechanical anisotropy to be made. We also examined functionally graded versions of these lattices, which featured a density gradient along one direction. The graded structures exhibited distinct crushing behaviour, with a sequential collapse of cellular layers preceding full densification. For the BCC z lattice, the graded structures were able to absorb around 114% more energy per unit volume than their non-graded counterparts before full densification, 1371 ± 9 kJ/m3 versus 640 ± 10 kJ/m3. This highlights the strong potential for functionally graded lattices to be used in energy-absorbing applications. Finally, we determined several of the Gibson–Ashby coefficients relating the mechanical properties of lattice structures to their density; these are crucial in establishing the constitutive models required for effective lattice design. These results improve the current understanding of additively manufactured lattices and will enable the design of sophisticated, functional, lightweight components in the future.

Quantifying effects of material extrusion additive manufacturing process on mechanical properties of lattice structures using as-fabricated voxel modeling

During additive manufacturing processes, part geometry is approximated because the layer by layer deposition procedure can yield stair-step irregularities between layers. Moreover, since finite-sized filaments are deposited in the material extrusion process, air gaps are generated among the filaments. These lead to geometrical errors in additively manufacturing parts and degradation of the parts’ mechanical properties, such as elastic modulus and strength, based on slicing and material deposition strategies. Geometric errors that arise during the manufacturing procedure have a particularly significant impact on fabricated lattice structures, which consist of a network of small struts, because they have large bounding surfaces that must be approximated during fabrication. In addition, since the struts in lattice structures are generally small, voids among filaments affect the structures’ mechanical properties significantly even if they are small. In order to avoid property degradation it is necessary to consider these phenomena during lattice structure design. In this paper, an as-fabricated modeling approach for a material extrusion process is proposed, for use in modeling and assessing the effects of geometric degradation on additively fabricated lattice structures. The approach implements a voxel based modeling technique to consider stair steps and deposition paths at each layer. Using the proposed method, numerical models for evaluating mechanical properties are generated. Estimated mechanical properties using the as-fabricated voxel modeling approach are compared with experimental results. The effects of the stair step and deposition path phenomena on mechanical properties are quantified and demonstrate good correspondence with experiments, particularly for elastic modulus.

Improving the mechanical efficiency of electron beam melted titanium lattice structures by chemical etching

The microstructure and mechanical properties of lattice structures of various relative densities manufactured by Electron Beam Melting were analyzed. Their microstructure was compared to that of bulk parts. Special interest was given to the effect of surface roughness on their elastic behavior. An efficient chemical etching post-treatment was performed on these structures. The elastic mechanical behavior of both as-built and etched structures was analyzed. Compression testing revealed that the important decrease in roughness caused by chemical etching results in an increase in relative stiffness, in comparison with an as-built structure of the same relative density.

Preparation and experimental study on anti-penetration capability of the interlocking lattice sandwich plate filled with ceramic rods and hybrid fillers

For exploring lightweight protective structures, a type of lattice sandwich plate and its preparation method are introduced, and anti-penetration capability is investigated. This lattice sandwich structure includes two metal sheets and multimetal pyramidal lattice trusses, which is prepared based on the three-dimensional interlocking process, parallel ceramic rods, and hybrid fillers mixed with chopped glass fibers and epoxy resins. Mechanical properties of lattice structures with different relative densities are compared. Then, penetration experiments with ball-shaped projectiles on this plate and a contrast structure with no ceramic rods are performed, so that the failure modes, anti-penetration mechanisms, and impact absorption efficiency can be initially explored. The results indicate that this process introduced is suitable for any conductive material, with no requirement of strong plasticity and liquidity; deformation processes of lattice structures with different truss width are similar, and inelastic buckling model can describe the failure mode and compression limit well. Owing to the macrobending deformation of the main metal sheets, severe plastic deformation, and shear reaming of the lattice trusses, smash and failure of ceramic rods and hybrid fillers occur, which bring about much energy absorption. A significant anti-penetration capability of this plate is shown with energy absorption rate being 75% approximately.

Basic Research on Lattice Structures Focused on the Tensile Strength

This scientific survey is about the mechanical properties of lattice structures which are made by Selective Laser Melting. It’s a process based on Additive Manufacturing technologies. This technology allows the manufacturing of complex lattice structures, and further the integration of lattice structures into different applications. Focusing on the integration of these structures, it is necessary to know what kind of effect they have on applications and what positive properties they might support. More and more the industry searches for new supporting technologies and the trend is towards lightweight and material saving possibilities. [1, 2] A survey on this topic is indispensable. The main aim is to analyze different parameters that affect the mechanical properties. First of all the definition of the experimental set-up and the definition of the, to be tested, parameters are necessary. Furthermore the aim is to find several different parameters that have a positive effect on the mechanical properties. Above all the focus is on experimental set-ups that use mechanical tests, beginning with the test on tensile strength in accordance with DIN 50125. Depending on the results an application area could be chosen and assigned.

Mechanical Properties of Ti-6Al-4V Selectively Laser Melted Parts with Body-Centred-Cubic Lattices of Varying cell size

Significant weight savings in parts can be made through the use of additive manufacture (AM), a process which enables the construction of more complex geometries, such as functionally graded lattices, than can be achieved conventionally. The existing framework describing the mechanical properties of lattices places strong emphasis on one property, the relative density of the repeating cells, but there are other properties to consider if lattices are to be used effectively. In this work, we explore the effects of cell size and number of cells, attempting to construct more complete models for the mechanical performance of lattices. This was achieved by examining the modulus and ultimate tensile strength of latticed tensile specimens with a range of unit cell sizes and fixed relative density. Understanding how these mechanical properties depend upon the lattice design variables is crucial for the development of design tools, such as finite element methods, that deliver the best performance from AM latticed parts. We observed significant reductions in modulus and strength with increasing cell size, and these reductions cannot be explained by increasing strut porosity as has previously been suggested. We obtained power law relationships for the mechanical properties of the latticed specimens as a function of cell size, which are similar in form to the existing laws for the relative density dependence. These can be used to predict the properties of latticed column structures comprised of body-centred-cubic (BCC) cells, and may also be adapted for other part geometries. In addition, we propose a novel way to analyse the tensile modulus data, which considers a relative lattice cell size rather than an absolute size. This may lead to more general models for the mechanical properties of lattice structures, applicable to parts of varying size.

Homogenization of 1D and 2D magnetoelastic lattices

This paper investigates the equivalent in-plane mechanical properties of one dimensional (1D) and two dimensional (2D), periodic magneto-elastic lattices. A lumped parameter model describes the lattices using magnetic dipole moments in combination with axial and torsional springs. The homogenization procedure is applied to systems linearized about stable configurations, which are identified by minimizing potential energy. Simple algebraic expressions are derived for the properties of 1D structures. Results for 1D lattices show that a variety of stiffness changes are possible through reconfiguration, and that magnetization can either stiffen or soften a structure. Results for 2D hexagonal and re-entrant lattices show that both reconfigurations and magnetization have drastic effects on the mechanical properties of lattice structures. Lattices can be stiffened or softened and the Poisson’s ratio can be tuned. Furthermore for certain hexagonal lattices the sign of Poisson’s ratio can change by varying the lattice magnetization. In some cases presented, analytical and numerically estimated equivalent properties are validated through numerical simulations that also illustrate the unique characteristics of the investigated configurations.

Mechanical response of TiAl6V4 lattice structures manufactured by selective laser melting in quasistatic and dynamic compression tests

This paper focusses on the investigation of the mechanical properties of lattice structures manufactured by selective laser melting using contour-hatch scan strategy. The motivation for this research is the systematic investigation of the elastic and plastic deformation of TiAl6V4 at different strain rates. To investigate the influence of the strain rate on the mechanical response (e.g., energy absorption) of TiAl6V4 structures, compression tests on TiAl6V4-lattice structures with different strain rates are carried out to determine the mechanical response from the resulting stress-strain curves. Results are compared to the mechanical response of stainless steel lattice structures (316L). It is shown that heat-treated TiAl6V4 specimens have a larger breaking strain and a lower drop of stress after failure initiation. Main finding is that TiAl6V4 lattice structures show brittle behavior and low energy absorption capabilities compared to the ductile behaving 316L lattice structures. For larger strain rates, ultimate tensile strength of TiAl6V4 structures is more than 20% higher compared to lower strain rates due to cold work hardening.

206 マイクロラティス構造の機械特性に及ぼす形状不均一性の影響

206 マイクロラティス構造の機械特性に及ぼす形状不均一性の影響

圧縮荷重を受ける軽量Lattice構造の機械特性の評価 : 第3報,端部の拘束による機械特性への影響

圧縮荷重を受ける軽量Lattice構造の機械特性の評価 : 第3報,端部の拘束による機械特性への影響

圧縮荷重を受ける軽量Lattice構造の機械特性の評価 : 第2報,圧縮負荷方向の違いおよび不完全セルの存在による機械特性への影響

圧縮荷重を受ける軽量Lattice構造の機械特性の評価 : 第2報,圧縮負荷方向の違いおよび不完全セルの存在による機械特性への影響