Structural Design of a Double-Layer Grid Using the Continuum Method

Addressing the urgent need for lightweight and functionally integrated structures in aerospace, transportation, and other fields, this paper focuses on the systematic design and performance optimization of additive manufacturing-based lattice structures. To overcome the core challenge of the disconnect between theoretical models and manufacturing practice in lattice structure design, this study constructs a comprehensive research system encompassing theoretical modeling, process adaptation, performance optimization, and experimental verification. First, the equivalent mechanical properties of lattice structures are explored in depth, and process adaptability design criteria for additive manufacturing are established to address manufacturability issues. Then, a multi-objective optimization method is used to synergistically improve the static and dynamic mechanical properties and energy absorption characteristics of the lattice structures. Finally, experimental prototypes are prepared by carefully selecting additive manufacturing process parameters, and systematic mechanical performance tests are conducted to verify the accuracy of the numerical model and the effectiveness of the optimized design. The research results not only demonstrate the enormous potential of additively manufactured lattice structures in terms of lightweighting and multifunctional load-bearing capacity but also provide a closed-loop methodology covering design, manufacturing, and performance evaluation for their engineering applications, possessing significant theoretical and engineering reference value.

Cellular structures consist of foams, honeycombs, and lattices. Lattices have many outstanding properties over foams and honeycombs, such as lightweight, high strength, absorbing energy, and reducing vibration, which has been extensively studied and concerned. Because of excellent properties, lattice structures have been widely used in aviation, bio-engineering, automation, and other industrial fields. In particular, the application of additive manufacturing (AM) technology used for fabricating lattice structures has pushed the development of designing lattice structures to a new stage and made a breakthrough progress. By searching a large number of research literature, the primary work of this paper reviews the lattice structures. First, based on the introductions about lattices of literature, the definition and classification of lattice structures are concluded. Lattice structures are divided into two general categories in this paper: uniform and non-uniform. Second, the performance and application of lattice structures are introduced in detail. In addition, the fabricating methods of lattice structures, i.e., traditional processing and additive manufacturing, are evaluated. Third, for uniform lattice structures, the main concern during design is to develop highly functional unit cells, which in this paper is summarized as three different methods, i.e., geometric unit cell based, mathematical algorithm generated, and topology optimization. Forth, non-uniform lattice structures are reviewed from two aspects of gradient and topology optimization. These methods include Voronoi-tessellation, size gradient method (SGM), size matching and scaling (SMS), and homogenization, optimization, and construction (HOC). Finally, the future development of lattice structures is prospected from different aspects.

Effects of design and manufacturing deviations on compressive properties of glass sponge lattice structures manufactured by selective laser melting

Design, mechanical properties and optimization of lattice structures with hollow prismatic struts

A parameterization modeling method based on finite element mesh to create complex large-scale lattice structures for AM is presented, and a corresponding approach for size optimization of lattice structures is also developed. In the modeling method, meshing technique is employed to obtain the meshes and nodes of lattice structures for a given geometry. Then, a parametric description of lattice unit cells based on the element type, element nodes and their connecting relationships is developed. Once the unit cell design is selected, the initial lattice structure can be assembled by the unit cells in each finite element. Furthermore, modification of lattice structures can be operated by moving mesh nodes and changing cross-sectional areas of bars. The graded and non-uniform lattice structures can be constructed easily based on the proposed modeling method. Moreover, a size optimization algorithm based on moving iso-surface threshold (MIST) method is proposed to optimize lattice structures for enhancing the mechanical performance. To demonstrate the effectiveness of the proposed method, numerical examples and experimental testing are presented, and experimental testing shows 11% improved stiffness of the optimized non-uniform lattice structure than uniform one.

PurposeMethods to optimize lattice structure design, such as ground structure optimization, have been shown to be useful when generating efficient design concepts with complex truss-like cellular structures. Unfortunately, designs suggested by lattice structure optimization methods are often infeasible because the obtained cross-sectional parameter values cannot be fabricated by additive manufacturing (AM) processes, and it is often very difficult to transform a design proposal into one that can be additively designed. This paper aims to propose an improved, two-phase lattice structure optimization framework that considers manufacturing constraints for the AM process.Design/methodology/approachThe proposed framework uses a conventional ground structure optimization method in the first phase. In the second phase, the results from the ground structure optimization are modified according to the pre-determined manufacturing constraints using a second optimization procedure. To decrease the computational cost of the optimization process, an efficient gradient-based optimization algorithm, namely, the method of feasible directions (MFDs), is integrated into this framework. The developed framework is applied to three different design examples. The efficacy of the framework is compared to that of existing lattice structure optimization methods.FindingsThe proposed optimization framework provided designs more efficiently and with better performance than the existing optimization methods.Practical implicationsThe proposed framework can be used effectively for optimizing complex lattice-based structures.Originality/valueAn improved optimization framework that efficiently considers the AM constraints was reported for the design of lattice-based structures.

Multi-scale and multi-material topology optimization of gradient lattice structures using surrogate models

Additive manufacturing technologies enable the fabrication of parts characterized by shape complexity and therefore allow the design of optimized components based on minimal material usage and weight. In the literature two approaches are available to reach this goal: adoption of lattice structures and topology optimization. In a recent work a Computer-Aided method for generative design and optimization of regular lattice structures was proposed. The method was investigated in few configurations of a cantilever beam, considering six different cell types and two load conditions. In order to strengthen the method, in this paper a number of test cases have been carried out. Results explain the behavior of the method during the iterations, and the effects of the load and of the cell dimension. Moreover, a visual comparison between the proposed method and the results achieved by topology optimization is shown.

Lattice structure is a type of cellular structures which is made of interconnected struts. It attracts a great research interest, since it can achieve different desired properties for a broad spectrum of applications. To generate the geometric model of lattice structures with multiscale complexities is not an easy task for most existing conventional CAD software, especially when the number of cells or struts is very large. To solve this issue, an innovative hybrid geometric modeling method is proposed in this paper. This proposed method can be divided into three steps. They are lattice frame generation, construction of geometric functions, and voxelization. A detailed description of the algorithms and data structures used in each stage are provided in this paper. Several case studies are given at the end of this paper to illustrate the effectiveness and efficiency of the proposed method. In general, by integrating the advantages of several different geometric modeling methods, the proposed method not only provides an efficient and flexible way for designers to generate different types of lattice structures for desired properties, but also offers an interface between the geometric and simulation model of lattice structures. It further removes the barrier in the design and optimization of lattice structures with multiscale complexities.

In the current work, a fail-safe optimization of lattice structures is carried out. For the optimization, unit cells are not homogenized, but their members are modeled as beam elements. This allows applying a commonly used engineering approach for obtaining a fail-safe design. It consist of removing one beam element at a time and optimizing the remaining structure. At the end, the maximum beam radii are used for the final design. This approach is computationally extremely expensive for lattice structures, as it requires one optimization per removed beam. In our contribution, we show that the design obtained from this approach actually does not fulfill the desired fail-safe behavior. We therefore apply an alternative approach in which the fail-safe requirement is an optimization constraint. This is still computationally demanding and therefore, criteria are discussion for reducing the number of beam elements to be considered for the fail-safe requirement within the optimization.

In today’s world, reducing fuel consumption is one of the most important goals for the automotive industry. For this reason, weight reduction is one of the main topics in this research and for various companies. In this research, topology optimization was conducted on a suspension arm as a means of ensuring balance in automobiles. Subsequently, the model, formed by topology optimization was filled with a lattice structure and re-optimized by size optimization to obtain optimum dimensions for the model. These operations are described as lattice structure optimization. Additive manufacturing (3D printer) is necessary to produce complex models (after topology and lattice structure optimization). A static analysis of the new models was conducted by using the finite element method, and the results were compared with those of the initial design of the model. As a result of the comparison, positive results were obtained, and it was shown that topology optimization and lattice structural optimization could be used in the design of vehicle elements. According to the results obtained from lattice structure optimization, design structure can be formed more reliably than via topology optimization. In addition, both configurations and layouts of the cellular structures have a special effect on the overall performance of the lattice structure.

In today’s world, reducing fuel consumption is one of the most important goals for the automotive industry. For this reason, weight reduction is one of the main topics in this research and for various companies. In this research, topology optimization was conducted on a suspension arm as a means of ensuring balance in automobiles. Subsequently, the model, formed by topology optimization was filled with a lattice structure and re-optimized by size optimization to obtain optimum dimensions for the model. These operations are described as lattice structure optimization. Additive manufacturing (3D printer) is necessary to produce complex models (after topology and lattice structure optimization). A static analysis of the new models was conducted by using the finite element method, and the results were compared with those of the initial design of the model. As a result of the comparison, positive results were obtained, and it was shown that topology optimization and lattice structural optimization could be used in the design of vehicle elements. According to the results obtained from lattice structure optimization, design structure can be formed more reliably than via topology optimization. In addition, both configurations and layouts of the cellular structures have a special effect on the overall performance of the lattice structure.

Topology optimization (TO) is a mathematical method that optimizes the material layout in a pre-defined design domain. Its theoretical background is widely known for macro-, meso-, and microscale levels of a structure. The macroscale TO is now available in the majority of commercial TO software, while only a few software packages offer a mesoscale TO with the design and optimization of lattice structures. However, they still lack a practical simultaneous macro–mesoscale TO. It is not clear to the designers how they can combine and apply TO at different levels. In this paper, a two-scale TO is conducted using the homogenization theory at both the macro- and mesoscale structural levels. In this way, the benefits of the existence and optimization of mesoscale structures were researched. For this reason, as a case study, a commercial example of the known jet engine bracket from General Electric (GE bracket) was used. Different optimization workflows were implemented in order to develop alternative design concepts of the same mass. The design concepts were compared with respect to their weight, strength, and simulation time for the given load cases. In addition, the lightest design concept among them was identified.

Topological design optimization of lattice structures to maximize shear stiffness

This paper presents a novel multiscale explicit topology optimisation approach for concurrently optimizing the structure at the macro level and the bio-mimicking porous infillings at the micro level. Solid bar components with cross-section control at the macro level and sphere components at the micro level are constructed as the minimal control units to replace the manipulation of material distribution at each grid. The overlapping, moving and morphing of bar components provide the ability to generate flexible structural shapes at the macro level. Using the inspiration of the turtle shell (carapace), the sphere components are designed to move, overlap, and resize inside the bar to sufficiently mimic both the regular and irregular porous features. Classical beam designs, lattice structure designs and unit cell designs are illustrated as numerical examples to demonstrate the functionalities and correctness of the proposed method. As a result, the stochastic pores distribution and porosity control can be validated. The abilities of optimising lattice structure at truss-level and single unit cell level are demonstrated. Moreover, the samples are fabricated by selective laser melting (SLM) technology and then scanned with the X-ray micro-computed tomography (micro-CT) technique to further examine the manufacturability.