Dynamic behavior of CrMnFeCoNi high-entropy alloy in impact tension

Density-Graded Cellular Solids: Mechanics, Fabrication, and Applications

In-plane dynamic crushing of a novel honeycomb with functionally graded fractal self-similarity

Effects of cell size vs. cell-wall thickness gradients on compressive behavior of additively manufactured foams

Density gradation has been analytically and experimentally proven to enhance the load-bearing and energy absorption efficiency of cellular solids. This paper focuses on the analytical optimization (by virtual experiments) of polymeric honeycomb structures made from thermoplastic polyurethane to achieve density-graded structures with combined desired mechanical properties. The global stress-strain curves of single-density honeycomb structures are used as input to an analytical model that enables the characterization of the constitutive response of density-graded hexagonal honeycombs with discrete and continuous gradations and for various gradients. The stress-strain outputs are used to calculate the specific energy absorption, efficiency, and ideality metrics for all density-graded structures. The analytical results are shown to be in good agreement with previous experimental measurements. Our findings suggest that the choice of an optimal gradient depends on the specific application and design criteria. For example, graded structures wherein low density layers are dominant are shown to outperform high density uniform honeycombs in terms of specific energy absorption capacity while possessing higher strength compared with low density uniform structures.

Optimization of energy absorption performance of polymer honeycombs by density gradation

Crashworthiness design of graded cellular materials: An asymptotic solution considering loading rate sensitivity

On the penetration of semi-infinite concrete targets by ogival-nosed projectiles at different velocities

The optimization of foam-filled crash boxes is desired to enhance the energy-absorbing capacity of frontal crash management systems and improve vehicle crash safety. A novel foam-filled crash box with partial filling and combined trigger design is proposed based on a double tubular structure. Compression and impact simulations were performed to analyze the energy absorption capacity, initial peak force, deformation modes, and protection capability of the original and improved crash boxes. It is shown that the partial filling design can reduce 67% of the foam used and increase the specific energy absorption compared with the full-filling design. The triggers and the crash-box length together determine the stability of the subsequent deformation after initial buckling. An improved optimization design strategy for the foam-filled crash box is proposed by considering the material utilization and the deformation stability of the frontal system. The design strategy is validated by compression and trolley impact tests. Therefore, the optimization design method of the crash box, considering the joint action of key indicators, is appropriate and convenient for the crashworthiness design of crash boxes. 

Crashworthiness design and impact tests of aluminum foam-filled crash boxes

During a side impact accident of an automobile, the automobile threshold plays an important role in maintaining the living space of passengers, and thus the crashworthiness design of thresholds may...

Crashworthiness design of car threshold based on aluminium foam sandwich structure

Surface roughness involved in elastic adhesion of solids may lead to an unstable loading process, which makes experimental characterization and theoretical modeling full of challenge. The full self-consistent model (FSCM) is the most accurate adhesion contact model in the continuum framework, but the strongly nonlinear coupling relationship between surface gap and interaction is very difficult to solve even with high-precision numerical calculation. In this paper, several techniques including the arc-length control method, the Riemann–Stieltjes integral, the adaptive mesh and the Newton–Raphson iterative method were employed in a new solving program to overcome the difficulty of numerical calculation. This calculation method has high efficiency and precision, and it gives a full force–displacement curve containing all possible stable and unstable equilibrium states. The full force–displacement curves for the adhesive contact of wavy surfaces are zigzag and some additional oscillations or minor roundabouts are observed, which have not been detected in the extended JKR and Maugis–Dugdale models. With the increase of surface roughness, the pull-off force first increases and then decreases, because the adhesion mode transforms from the simple contact mode to the multiple one. It is found that the pressure oscillation induced by waviness leads to interface strengthening for small roughness, and the limitation of the theoretical strength and the development of interface cavitation result in interface weakening for large roughness. Compared to the FSCM, the JKR theory significantly overestimates the pull-off forces for large surface roughness. The extended Maugis–Dugdale model is also invalid for large roughness, and if the step cohesive stress is determined by applying a condition of the identical pull-off force at the rigid limit, it can work well for small roughness.

Yongliang Zhang

Papers

Crashworthiness design of graded cellular materials: An asymptotic solution considering loading rate sensitivity

On the penetration of semi-infinite concrete targets by ogival-nosed projectiles at different velocities

Crashworthiness design and impact tests of aluminum foam-filled crash boxes

Crashworthiness design of car threshold based on aluminium foam sandwich structure

Adhesion of elastic wavy surfaces: Interface strengthening/weakening and mode transition mechanisms