Numerical Analysis of Concrete Fracture under Shock Wave Loading
Tóm tắt
Concrete is known for its low tensile
strength. The difference between its compressive and tensile
strengths can reach a factor of 15–20. Therefore, it is
important to predict the behavior of concrete structures under
various operating conditions and unexpected loads. This paper
reports the numerical results on the fracture behavior of a
high-strength concrete target struck by an ogival-nosed
projectile. The problem of impact interaction is numerically
solved by the finite element method in a three-dimensional
formulation within a phenomenological framework of solid
mechanics. Numerical modeling is carried out using an original
EFES 2.0 software, which allows a straightforward
parallelization of the numerical algorithm. Fracture of concrete
is described by the Johnson–Holmquist model that includes the
strain rate dependence of the compressive and tensile strengths
of concrete. The computational algorithm takes into account the
formation of discontinuities in the material and the
fragmentation of bodies with the formation of new contact and
free surfaces. The behavior of the projectile material is
described by an elastoplastic medium. The limiting value of the
plastic strain intensity is taken as a local fracture criterion
for the projectile material. For the computational experiment,
the target was divided into 19 × 106 finite elements
(tetrahedrons). A detailed numerical analysis was performed to
study the stress and strain dynamics of the concrete target and
the effect of shock-wave processes on its fracture. It was found
that the decisive role in the fracture of the target, with the
considered kinematic and geometric interaction parameters, is
played by wave processes. Target fracture occurs in unloading
waves generated on its free surfaces. As a result, three
fracture zones are formed in the target in front of the
penetrating projectile. The first zone is formed near the front
surface of the target. The second one is a spall fracture on the
rear surface. The third fracture zone is formed in the central
part of the target due to the interference of unloading waves
propagating from its lateral surface. These fracture zones merge
with time, and the target shows almost no resistance to the
projectile penetration.
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