A numerical study on the rate sensitivity of cellular metals

Abstract

a b s t r a c tMetallic foams have non-linear deformation behavior, which make them attractive in many applications. Many experimental researches on the dynamic behavior and rate sensitivity of cellular metals have been reported in the literature, but they contain conflicting, and sometimes confusing, conclusions on the strain-rate and inertia effect of cellular metals. In this paper, the dynamic crushing behavior of 2D Voronoi honeycomb is studied by finite element method. The influences of inertia, strain hardening and strain-rate hardening of metal matrix on the deformation mode and plateau stress of the honeycomb are investigated. Three deformation modes are found in different velocity ranges. According to the numerical results, it is found that the plateau stress increases significantly with the increase of impact velocity due to non-uniform deformation induced by inertia. The strain-hardening effect is slight in our numerical tests and the rate effect of the honeycomb is obviously weaker than that of the cell wall material.

High resolution simulations of energy absorption in dynamically loaded cellular structures

“…One notable feature of this class of materials is the enhance-ment of crushing strength observed under dynamic loading due to inertial effects, as seen by Reid and Peng [16] in wood, Tan et al [17] in aluminium foams and Xue and Hutchinson [18] and Wu and Jiang [19] in metallic honeycombs. This phenomenon has also been the subject of a numerical study by Liu et al [20], the conclusions of which identify a critical velocity above which inertial effects become significant.…”

Stress Distribution in Graded Cellular Materials Under Dynamic Compression

“…The force balance should be satisfied in the loading direction at the macro scale because the inertia effect can be ignored under quasi-static situation (Liu et al, 2009). Figure 4 shows that stress balance is almost satisfied at any three nominal strains for the equally distributed stress along the homogeneous honeycomb specimen at the impact velocity of 1 m/s.…”

“…In the Quasi-static mode, the deformation shear bands occur randomly (Zheng et al, 2005;Liu et al, 2009). The force balance should be satisfied in the loading direction at the macro scale because the inertia effect can be ignored under quasi-static situation (Liu et al, 2009).…”

“…Three deformation modes have been observed in irregular honeycombs under dynamic compression (Zheng et al, 2005;Liu et al, 2009), i.e., Quasi-static Mode, Transitional Mode and Shock Mode. In this study, the cross-sectional stress calculation method provides a way to understand the stress distribution along the specimen and how the stress wave propagates.…”

“…Several shock models and mass-spring models have been proposed to understand the shock wave propagation in cellular materials under dynamic impact, such as the R-PP-L (rate-independent, rigid-perfectly plastic-locking) model (Reid and Peng, 1997), the mass-spring model (Li and Meng, 2002), the E-PP-R (elastic-perfectly plastic-rigid) model (Lopatnikov et al, 2003), the power law densification model and the D-R-PH (dynamic, rigidplastic hardening) shock model . Because the assurance of the repeatability of samples and the measurement of local stress and strain states have not been well solved by experimental techniques, finite element (FE) method has been applied to simulate the dynamic crushing of cellular materials, such as regular/irregular honeycombs (Ruan et al, 2003;Zheng et al, 2005;Liu et al, 2009;Zou et al, 2009;Hu and Yu, 2013) and open-/closed-cell foams Zheng et al, 2014;Sun et al, 2016). The typical features of stress enhancement and deformation localization can be appropriately represented.…”