Dynamic crushing of uniform and density graded cellular structures based on the circle arc model

Abstract

A new circle-arc model was established to present the cellular structure. Dynamic response of models with density gradients under constant velocities is investigated by employing Ls-dyna 971. Compared with the uniform models, the quasi-static plateau stress of different layers seems a significant parameter correlated with the deformation mode except for inertia effect when the density gradient is introduced. The impact velocity becomes much more vital on the deformation of the unit cell than the density gradient. The stress at both the impact and stationary sides is investigated in details. Furthermore, the stress-strain curve is compared with the modified shock wave theory. The density gradient does have some remarkable influence on the energy absorption capability, and a certain density gradient is not always beneficial to the energy absorption. Irrespective of the impact velocity, there seems always a critical strain where the energy absorbed by all these specimens could approximate to nearly the same value. So the critical strain-velocity curve is plotted and gives the beneficial area for energy absorption pertinent to density gradients and impact velocity.

Dynamic response of functionally graded cellular materials based on the Voronoi model

“…This phenomenon could also be found in our previous work in Ref. [26] by constructing the local strain field. So the stress of 0.02 β = at stationary side is close to the quasi-static crushing stress of the weakest layer and will increase sharply when the wave front reaches the stationary side.…”

“…Zhang et al [26] established a circle-arc model and investigated the response of the regular graded cellular material. Results showed that introducing density functional gradation in hexagonal honeycombs brought about new deformation patterns due to changes in material distribution and preferential cell wall collapse of the weaker members [27].…”

“…In comparison with the V-shape collapse observed in the graded honeycomb and circle-arc models [25,26], there is only there is just the I-shape collapse for the negative graded models, so the transforming velocity of this case was not taken into consideration.…”

“…[26], which may be due to the different response of the graded Voronoi structure compared with the uniform circle-arc model.…”

Stress Distribution in Graded Cellular Materials Under Dynamic Compression

“…Their results show that the elastic modulus and yield strength of cellular structures increase with the increasing of density. Dynamic behaviors of Voronoi model (Zhang et al, 2016) and circle-arc model (Zhang et al, 2015) with density gradient subjected to constant velocity impact were simulated and analyzed and three deformation modes were observed to be velocitydependent. Numerical simulations were carried out to verify the predictions of the theoretical analysis of the propagation of stress waves in cellular solids with non-uniform density to deepen the understanding of their dynamic compaction due to impact loading (Karagiozova and Alves, 2015).…”