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arXiv 1306.1120cond-mat.mtrl-scicond-mat.soft
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高剪切速率下物料粉碎的本构模型

Constitutive Model for Material Comminuting at High Shear Rate

Zdenek P. Bazant, Ferhun C. Caner

摘要:

脆性或准脆性固体的高速冲击的建模受到阻碍的本构模型捕捉到的材料粉碎成非常细的颗粒的影响的不可用性。目前的目标是开发这样一个模型,可用于有限元程序。在非常高的应变率下的粉碎可以耗散撞击导弹的大部分动能。由粉碎耗散的能量的空间导数给出抵抗穿透的力,该力叠加在从有限元程序中的静态本构模型获得的节点力上。本理论的灵感部分来自Grady的模型粉碎由于爆炸内空心球,部分类比湍流。在高速湍流中,通过粘性剪切应力耗散能量的微涡旋(涡流)的形成来增强能量耗散率。类似地,这里假设受限固体快速变形时的能量耗散通过释放与形成颗粒的高速剪切应变相关的运动的动能而得到增强。为了简单起见,这些颗粒在最大剪切速率平面中的形状被认为是正六边形。自由能量密度的释放速率被最小化,所述自由能量密度由该能量和成形颗粒之间的界面的断裂能的总和组成。颗粒尺寸被假定为根据舒曼幂律分布。得出的结论是,最小粒度与剪切应变速率的(2/3)次方成反比,动能释放与剪切应变速率的(2/3)次方成正比,动态粉碎产生的表观材料粘度与剪切应变速率的(1/3)次方成反比。

英文摘要:

The modeling of high velocity impact into brittle or quasibrittle solids is hampered by the unavailability of a constitutive model capturing the effects of material comminution into very fine particles. The present objective is to develop such a model, usable in finite element programs. The comminution at very high strain rates can dissipate a large portion of the kinetic energy of an impacting missile. The spatial derivative of the energy dissipated by comminution gives a force resisting the penetration, which is superposed on the nodal forces obtained from the static constitutive model in a finite element program. The present theory is inspired partly by Grady's model for comminution due to explosion inside a hollow sphere, and partly by analogy with turbulence. In high velocity turbulent flow, the energy dissipation rate is enhanced by the formation of micro-vortices (eddies) which dissipate energy by viscous shear stress. Similarly, here it is assumed that the energy dissipation at fast deformation of a confined solid gets enhanced by the release of kinetic energy of the motion associated with a high-rate shear strain of forming particles. For simplicity, the shape of these particles in the plane of maximum shear rate is considered to be regular hexagons. The rate of release of free energy density consisting of the sum of this energy and the fracture energy of the interface between the forming particle is minimized. The particle sizes are assumed to be distributed according to Schuhmann's power law. It is concluded that the minimum particle size is inversely proportional to the (2/3)-power of the shear strain rate, that the kinetic energy release is to proportional to the (2/3)-power, and that the dynamic comminution creates an apparent material viscosity inversely proportional to the (1/3)-power of the shear strain rate.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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