Strain Rate Dependent Microplane Constitutive Model for Comminution of Concrete under Projectile Impact
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TLDR
In this paper, a crack band model with a random tetrahedral mesh is used to predict the crater shapes and exit velocities of projectiles penetrating concrete walls as closely as the previous models.Abstract:
The pulverization, fracturing and crushing of materials, briefly called comminution, creates numerous cracks which dissipate a large amount of kinetic energy during projectile impact. At high shear strain rates (10/s − 10/s), this causes an apparent large increase of strength, called ‘dynamic overstress’. This long debated phenomenon has recently been explained by the theory of release of local kinetic energy of shear strain rate in finite size particles that are about to form. The theory yields the particle size and the additional kinetic energy density that must be dissipated in finite element codes. In previous research, it was dissipated by additional viscosity, in a model partly analogous to turbulence theory. Here it is dissipated by scaling up the material strength. Microplane model M7 is used and its stress-strain boundaries are scaled up by theoretically derived factors proportional to the −4/3 power of the effective deviatoric strain rate and to its time derivative. The crack band model with a random tetrahedral mesh is used and all the artificial damping is eliminated from the finite element program. The scaled model M7 is seen to predict the crater shapes and exit velocities of projectiles penetrating concrete walls as closely as the previous models. The choice of the finite strain threshold for element deletion, which can have a big effect, is also studied. It is proposed to use the highest threshold above which a further increase has a negligible effect.read more
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Journal ArticleDOI
Crack band theory for fracture of concrete
Zdeněk P. Bažant,Byung H. Oh +1 more
TL;DR: In this article, a fracture theory for a heterogenous aggregate material which exhibits a gradual strain-softening due to microcracking and contains aggregate pieces that are not necessarily small compared to structural dimensions is developed.
Journal ArticleDOI
Computational modelling of impact damage in brittle materials
G. T. Camacho,Michael Ortiz +1 more
TL;DR: In this paper, a Lagrangian finite element method of fracture and fragmentation in brittle materials is developed, where a cohesive-law fracture model is used to propagate multiple cracks along arbitrary paths.
Dynamic Fracture Mechanics
TL;DR: In this article, basic elastodynamic solutions for a stationary crack and asymptotic fields near a moving crack tip are presented. But they do not consider the elasticity and rate effects during crack growth.
Book
Dynamic Fracture Mechanics
L. B. Freund,John W. Hutchinson +1 more
TL;DR: In this article, basic elastodynamic solutions for a stationary crack and asymptotic fields near a moving crack tip are presented. But they do not consider the elasticity and rate effects during crack growth.
Journal ArticleDOI
Fragmentation of shell cases.
TL;DR: An expression is given for the length of the average fragment, which is shown to depend on the radius and velocity of the case at the moment of break-up, and on the mechanical properties of the metal.
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