Lattice structures 3D modeling and static analysis

Additive manufacturing (AM) is a process in which a three-dimensional object is built from a computer-aided design (CAD) model, usually by successively adding material in a layer-by-layer fashion. AM is different from conventional manufacturing processes (such as machining, casting and forging) where material is removed from a block or injected into a mold to form the product and detailed process planning must be made to determine machining steps to obtain the physical geometries. With AM there are no limits in terms of design, geometrical complexity of the components no longer impedes the process (hollow features, assembly consisting of several components). Obviously some constraints remain (e.g., overhang and build size) but parts can generally be made according to the design that best fulfills their function. Part of best fulfilling a required function is the effective use of all materials, or using as little material as necessary. This is especially true in the automotive and aerospace industry, where saving a seemingly insignificant amount of mass can translate to substantial cost reduction or performance increase. A great demand for functional part manufactured with minimal material exists, lattice structure can help to accomplish this goal. A lattice consists of a pattern repeated regularly in all directions. This pattern is known as a unit cell. Because the unit cell is not solid material, the lattice structure has less mass per volume than the solid part. Lattice structures are usually used in lightweight structure design to minimize material loss and energy consumption in the manufacturing process. The three major factors influencing the properties of lattice structures are the properties of the material, the topology and shape of the cell and the relative density of the cellular structure. Furthermore, today’s applications require lattice structures to contain more and more beams and have smaller and smaller features leading to several difficulties for 3D rendering and manipulating such complex structures. As a result the mesh of these complex structures has become crucial for additive manufacturing. The objective of this discussion is to explore two different unit cells structures and their tensile properties through specific 3D modeling and CAE simulation software. The ultimate goal is to build a workflow to effectively and efficiently replace solid parts with lattice structures and create new parts utilizing them to their full potential. The introduction chapter consists in an overview of the additive manufacturing, lattice structures with some applications and the nTopology software which has been used to perform the analysis. It continues with the presentation of the case study and the preparation of the 3D models to be analysed. For the 3D modeling of the components Siemens NX software has been used, while for the implementation of the lattice structures and the static analysis executions nTopology software has been chosen. An important part of the paper is dedicated to the choice of the design parameters and loads and constraints definition. The thesis proceeds with the best cases definition and the consequent CAE validation, in order to verify the consistency of the obtained results. The final part is dedicated to a different approach, a multi-scale one, and a comparison between the resulting findings. In conclusion, the main results of the proposed analysis are summarised and some future developments are presented in order to improve the efficiency of the workflow.