Stress Wave Propagation and Energy Absorption Properties of Heterogeneous Lattice Materials under Impact Load

A heterogeneous lattice material composed of different cells is proposed to improve the energy absorption capacity. The heterogeneous structure is formed by setting layers of body-centered XY rods (BCCxy) cells as the reinforcement in the body-centered cubic (GBCC) uniform lattice material. The heterogeneous lattice samples are designed and processed by additive manufacturing technology. The stress wave propagation and energy absorption properties of heterogeneous lattice materials under impact load are analyzed by finite element simulation (FES) and Hopkinson pressure bar (SHPB) experiments. The results show that, compared with the GBCC uniform lattice material, the spreading velocity of the stress of the (GBCC)3(BCCxy)2 heterogeneous lattice material is reduced by 18.1%, the impact time is prolonged 27.9%, the stress peak of the transmitted bar is reduced by 34.8%, and the strain energy peak is reduced by 29.7%. It indicates that the heterogeneous lattice materials are able to reduce the spreading velocity of stress and improve the energy absorption capacity. In addition, the number of layers of reinforcement is an important factor affecting the stress wave propagation and energy absorption properties.

A Survey of Modeling and Optimization Methods for Multi-Scale Heterogeneous Lattice Structures

This paper aims to provide a comprehensive review of the state-of-the-art modeling and optimization methods for multi-scale heterogeneous lattice structures (MSHLS) to further facilitate the more design freedom. In this survey, a design process including optimization and modeling for MSHLS is proposed. Material composition and multi-scale geometric modeling methods for representation of material and geometry information are separately discussed. Moreover, the optimization methods including multi-scale and multi-material optimization design methods, as well as the simulation methods suitable for MSHLS are, respectively, reviewed. Finally, the relationship, advantages, and disadvantages of MSHLS modeling and optimization methods are summarized with discussion and comparison, which provides a guidance to further take advantage of MSHLS to improve the performance and multifunctional purpose of production for software developers and researchers concerning the design approaches and strategies currently available.

VOLUMETRIC CELLS: A FRAMEWORK FOR A BIO-INSPIRED GEOMETRIC MODELLING METHOD TO SUPPORT HETEROGENEOUS LATTICE STRUCTURES

Current geometrical modelling approaches are unable to handle complex geometrical objects such as heterogeneous lattice structures. In this work, a framework for a novel bio-inspired geometric modelling method is proposed. The method can potentially support geometric modelling of heterogeneous lattice structures. The method utilises discretisation algorithms that are based on cell division processes encountered in nature. The method is verified on two 2D use-cases.

Transition waves for lattice Fisher-KPP equations with time and space dependence

This paper is concerned with the existence results for generalized transition waves of space periodic and time heterogeneous lattice Fisher-KPP equations. By constructing appropriate subsolutions and supersolutions, we show that there is a critical wave speed such that a transition wave solution exists as soon as the least mean of wave speed is above this critical speed. Moreover, the critical speed we construct is proved to be minimal in some particular cases, such as space-time periodic or space independent.

Intermolecular coupling and fluxional behavior of hydrogen in phase IV

We performed Raman and infrared (IR) spectroscopy measurements of hydrogen at 295 K up to 280 GPa at an IR synchrotron facility of the Shanghai Synchrotron Radiation Facility (SSRF). To reach the highest pressure, hydrogen was loaded into toroidal diamond anvils with 30-μm central culet. The intermolecular coupling has been determined by concomitant measurements of the IR and Raman vibron modes. In phase IV, we find that the intermolecular coupling is much stronger in the graphenelike layer (G layer) of elongated molecules compared to the Br2-like layer (B layer) of shortened molecules and it increases with pressure much faster in the G layer compared to the B layer. These heterogeneous lattice dynamical properties are unique features of highly fluxional hydrogen phase IV.

Additive Manufacturing of Heterogeneous Lattice Structures: An Experimental Exploration

Abstract3D printed heterogeneous lattice structures are beam-and-node based structures characterised by a variable geometry. This variability is obtained starting from a periodic structure and modifying the relative density of the unit cells or by combining unit cells having different shapes. While several consolidated design approaches are described to implement the first approach, there are still computational issues to be addressed to combine different cells properly. In this paper, we describe a preliminary experimental study focused on exploring the design issues to be addressed as well as the advantages that this second type of heterogeneous structures could provide. The Three-Point-Bending test was used to compare the behaviour of different types of heterogeneous structures printed using the Fused Deposition Modeling (FDM) technology. Results demonstrated that the possibility of combining multiple unit cells represents a valid strategy for performing a more effective tuning of the material distribution within the design space. However, further studies are necessary to explore the behaviour of these structures and develop guidelines for helping designers in exploiting their potential.