Influence of mesoscale properties on the mechanisms of plastic strain accommodation in plane strain dynamic deformation of concentric Ni-Al laminates

Abstract

The paper presents results on the mechanisms of plastic strain accommodation of Ni-Al laminates composed of concentrically aligned thin foils processed at different conditions undergoing a high strain radial collapse in thick walled cylinder experiments. Numerical simulations were conducted to examine the influence of mesoscale parameters (layer size, defects in mesostructure, and ductility) on the mechanisms of large plastic strain accommodation (high amplitude cooperative buckling; high frequency, low amplitude buckling; and kinking) at high strain rates in pure shear (plane strain) conditions. These mechanisms are dramatically different than observed in solid ductile and brittle homogeneous materials where a pattern of shear bands is the major mode of strain accommodation. It was observed that the layer thickness and ductility greatly influenced the dominant mode of plastic strain accommodation. The number of apices was related to the layer thickness. The presence of defects mainly had a localized area of influence. Numerical simulations showed good qualitative agreement with the experiments and provided the ability to simulate additional mesoscale and material dependencies: the role of friction/bonding, relative layer sizes, and sample thickness.

Shear band patterning and post-critical behavior in AISI 4340 steel with different microstructure

“…The explosive driver was a gelled nitromethane (96% nitromethane, 4% PMMA) diluted 5% by mass with glass microballoons. The same driver was used in [15] and [16] and allowed for the fine tuning of the explosive loading.…”

“…This post-critical behavior is important in many applications, it being responsible for the material's ability to dissipate the mechanical energy due to viscoplastic deformation. The explosively-driven method was proposed by Nesterenko et al [4,[10][11][12][13][14][15][16] to investigate spontaneous shear instability, patterns of shear bands in solid and granular materials, and buckling of laminates (inert and reactive). It also was used by other researchers [17,18] and later modifications of this method using electromagnetic drive [19][20][21][22][23], Hopkinson bar [24], and gas gun [25].…”

Shear localization in 4340 steel with different microstructure using thick wall cylinder method

“…Explosively-driven Thick Walled Cylinder experiments were conducted using the approach described in [18,19]. This method allows reproducible high strain and strain-rate conditions.…”

Cavity collapse in highly heterogeneous granular mixtures with different grain size and porosity

“…Instead, experimental results and numerical simulations have demonstrated that cooperative buckling is the preferential mechanism of flow instability in the collapse of cavities in concentric laminate materials. 26,27 A few mechanisms operate in the cavity collapse in corrugated laminates. 28 It is possible to conclude that the dynamic pore collapse even for initially axially symmetric macrocavities for all materials is unstable at some strains.…”