Explore the vast range of titles available.

The ongoing need for better protective structures has led to the development of various methods to improve specific energy absorption, including functional grading. This study explores how axial grading affects the energy absorption of simple cubic (SC) and body-centered cubic (BCC) plate lattices, comparing them to their uniform counterparts of the same relative density. Using ABAQUS, a numerical analysis simulates the quasi-static compression of plate lattices made from tough Nylon through material extrusion 3D printing. The results show that severe axial grading can increase the specific energy absorption of BCC plate lattices by up to 32% while grading with less severity reduces it. SC plate lattices show unstable behavior due to the vertical walls buckling and the grading also shows an unstable effect. This study highlights the impact of axial grading on these lattices and provides useful information for designing better protective structures.

Metal-coated lattice structures hold significant promise for customizing mechanical properties in diverse industrial applications, including the mechanical arms of unmanned aerial vehicles. However, their intricate geometries pose computational challenges, resulting in time-intensive and costly numerical evaluations. This study introduces a parameterization-based multiscale method to analyze body-centered cubic lattice structures with metal coatings. We establish the validity and precision of our proposed method with a comparative analysis of numerical results at the Representative Volume Element (RVE) scale and experimental findings, specifically addressing both elastic tensile and bending stiffness. Furthermore, we showcase the method’s accuracy in interpreting the bending stiffness of coated lattice structures using a homogenized material-based solid model, underscoring its effectiveness in predicting the elastic properties of such structures. In exploring the mechanical characterization of coated lattice structures, we unveil positive correlations between elastic tensile stiffness and both coating thickness and strut diameter. Additionally, the metal coating significantly enhances the structural elastic bending stiffness multiple times over. The diverse failure patterns observed in coated lattices under tensile and bending loads primarily stem from varied loading-induced stress states rather than external factors. This work not only mitigates computational challenges but also successfully bridges the gap between mesoscale RVE mechanical properties and those at the global structural scale.

Abstract Buckling failure is the dominant failure mode in strut-based or thin-walled lattice structures, limiting their effectiveness in structural applications requiring high stiffness and strength. This paper investigates a novel buckling-based 3D topology optimization method to generate buckling-resistant strut-based lattice structure for the first time. A MATLAB code for 3D topology optimization, based on buckling objective/constraint, is developed inspired by a 2D code available in literature. A single cell from a simple cubic lattice with square cross-sectional struts, a body-centred cubic lattice with circular struts, and a multi-cell 2 × 2 simple cubic lattice are investigated as reference structures. Through analysing their buckling modes, the buckling-prone members are actively optimized via topology optimization exercise to maximize buckling load factors, whilst constraining the volume fraction and stiffness of the structure. The results demonstrate that topology-optimized designs exhibit higher buckling load factors than the reference structure. Numerical validation of linear buckling analysis using ABAQUS software is also performed. Few parametric studies with varying cell sizes and relative densities are also discussed. This methodology can be easily extended to enhance the buckling resistance of any lattice structure without altering the relative density of the corresponding reference structure. Future directions include numerical post-buckling studies with experimental validation. Graphical Abstract Graphical Abstract

We reduce the upper bound for the bond percolation threshold of the cubic lattice from 0.447 792 to 0.347 297. The bound is obtained by a growth process approach which views the open cluster of a bond percolation model as a dynamic process. A three-dimensional dynamic process on the cubic lattice is constructed and then projected onto a carefully chosen plane to obtain a two-dimensional dynamic process on a triangular lattice. We compare the bond percolation models on the cubic lattice and their projections, and demonstrate that the bond percolation threshold of the cubic lattice is no greater than that of the triangular lattice. Applying the approach to the body-centered cubic lattice yields an upper bound of 0.292 893 for its bond percolation threshold.

A new improved body-centered cubic (BCC) lattice structure is proposed to improve the load capacity by adding a body-centered ball to reduce stress concentrations. The new lattice structure, named as body-centered cubic with balls (BCC-B) lattice structure, is characterized by lightweight, compactness, large load capacity, radiation resistance, and corrosion resistance, which can be widely used for vibration isolation in various areas such as ships, aerospace, nuclear facility, and so on. Theoretical model of BCC-B lattice structure is established. The influences of structure parameters of BCC-B lattice structure are analyzed by both theoretical and numerical methods. Both BCC and BCC-B lattice structure samples are prepared by using Ti-6Al-4V, of which the stiffness, rated load capacity, and yield strength are tested and compared detailly. Compared with the BCC lattice structure, the BCC-B lattice structure shows a 31.58% increase in rated load capacity, a 10.15% decrease in natural frequency, and a 29.53% increase in yield strength. This study might provide some insights for the development of vibration isolators with large load and low stiffness for applications in extreme environmental conditions such as limited space, nuclear radiation, and high temperatures in future.

A method is proposed for solving the inverse problem of reconstructing acoustic wave sources from field measurements on some surface using wavefront reversal in the particle dynamics method. In this method, the studied medium is represented as a set of interacting particles (material points or solid bodies), for which classical equations of motion are written. The paper considers the representation of a medium as a set of particles in a body-centered cubic crystal lattice. The case of a linear dependence of the force of attraction of particles on distance is considered. The advantage of this approach is the ability to take into account wave propagation in arbitrarily inhomogeneous media using a single numerical model. The possibility of visualizing two spherical acoustic wave sources in water behind an obstacle has been demonstrated numerically and experimentally, despite the presence of transverse waves in the considered model of a solid body; their influence is negligible in this case. The method was tested experimentally on a soundproof screen with an aperture simulating a sound-emitting object of complex shape. A wave from a point source of short pulses passes through the aperture. Using a receiving acoustic sensor mounted on a two-dimensional scanner, the spatiotemporal distribution of sound vibrations on the water surface was measured. By processing the data using wavefront reversal in the particle model, the image of the aperture in the soundproof screen was reconstructed.

Intermetallic alloys have traditionally been characterized by their inherent brittleness due to their lack of sufficient slip systems and absence of strain hardening. However, here we developed a single-phase B2 high-entropy intermetallic alloy that is both strong and plastic. Unlike conventional intermetallics, this high-entropy alloy features a highly distorted crystalline lattice with complex chemical order, leading to multiple slip systems and high flow stress. In addition, the alloy exhibits a dynamic hardening mechanism triggered by dislocation gliding that preserves its strength across a wide range of temperatures. As a result, this high-entropy intermetallic circumvents precipitous thermal softening, with extensive plastic flows even at high homologous temperatures, outperforming a variety of both body-centered cubic and B2 alloys. These findings reveal a promising direction for the development of intermetallic alloys with broad engineering applications. Intermetallics are traditionally characterised by their inherent brittleness due to a lack of sufficient slip systems and the absence of strain hardening. Here authors show that a single-phase distorted high entropy B2 intermetallic alloy displays notable strength and plasticity at room temperature, along with stable plastic flow at high homologous temperatures.

Revealing the atomistic mechanisms for the high-temperature mechanical behavior of materials is important for optimizing their properties for service at high-temperatures and their thermomechanical processing. However, due to materials microstructure’s dynamic recovery and the absence of available in situ techniques, the high-temperature deformation behavior and atomistic mechanisms of materials are difficult to evaluate. Here, we report the development of a microelectromechanical systems-based thermomechanical testing apparatus that enables mechanical testing at temperatures reaching 1556 K inside a transmission electron microscope for in situ investigation with atomic-resolution. With this unique technique, we first uncovered that tungsten fractures at 973 K in a ductile manner via a strain-induced multi-step body-centered cubic (BCC)-to-face-centered cubic (FCC) transformation and dislocation activities within the strain-induced FCC phase. Both events reduce the stress concentration at the crack tip and retard crack propagation. Our research provides an approach for timely and atomic-resolved high-temperature mechanical investigation of materials at high-temperatures. High-temperature deformation of materials is challenging to evaluate. Here the authors develop a novel device that allows atomic resolved in situ high temperature mechanical tests inside a transmission electron microscope and reveal ductile fracture of a single crystal tungsten deformed at 973 K.

Additive manufacturing (AM) techniques such as selective laser melting (SLM) enable the fabrication of complex metallic lattice structures. By tuning geometric and topological parameters, these structures can be manufactured to exhibit a range of useful properties, including excellent strength-to-weight ratios and energy absorption capabilities. While the effects of these parameters on various aspects of AM lattice performance have been previously studied, such as the effects of manufacturability, material selection and geometric parameters on the quasi-static performance of AM lattice structures, the effect of topology on the dynamic behaviour of SLM AlSi10Mg lattice structures remains relatively unexplored. Lattice structure specimens with five different topologies were manufactured using SLM AlSi10Mg and tested under quasi-static and dynamic loading conditions. The tested topologies were body-centred cubic with (BCCZ) and without (BCC) z-struts; face-centred cubic with (FCCZ) and without (FCC) z-struts; and body and face-centred cubic with z-struts (FBCCZ). A numerical model was developed to investigate failure modes and collapse mechanisms. Specimens were found to fail by the emergence of diagonal shear planes, and the orientation of which was dependent on topology, due to the uneven concentration of stress in struts across the structure. No significant rate sensitivity was identified for any of the tested topologies in the range of tested strain rates. The FCCZ topology was demonstrated to provide the greatest efficiency in terms of both strength-to-weight and stiffness-to-weight ratios. These results assist in the characterisation of the dynamic behaviour of SLM AlSi10Mg lattice structures and contribute to their further commercialisation.

Power laws are omnipresent and actively studied in many scientific fields, including plasticity of materials. Here, we report the power-law statistics in the second and subsequent pop-in magnitudes during load-controlled nanoindentation testing, whereas the first pop-in is characterized by Gaussian-like statistics with a well-defined average value. The transition from Gaussian-like to power-law is due to the change in the deformation mechanism from dislocation nucleation to dislocation network evolution in the sharp-indenter induced abruptly decaying stress and dislocation density fields. Based on nanoindentation testing on the (100) and (111) surfaces of body-centered cubic (BCC) iron and the (100) surface of face-centered cubic (FCC) copper, the scaling exponents of the power laws were determined to be 5.6, 3.9, and 6.4, respectively. These power-law exponents are much higher than those typically observed in micro-pillar plasticity (1.0–1.8), suggesting that the nanoindentation plasticity belongs to a different universality class than the micro-pillar plasticity. Although power laws are observed during nanoindentation and the power-law exponents are estimated to be approximately 1.5-1.6 for face-centered cubic metals, the origin of the exponent remains unclear. In this paper, we show the power-law statistics in pop-in magnitudes and unveil the nature of the exponent.