Cohesive Crack Model for Geomaterials: Stability Analysis and Rate Effect

1994 ◽  
Vol 47 (6S) ◽  
pp. S91-S96 ◽  
Author(s):  
Zdeneˇk P. Bazˇant ◽  
Yuan-Neng Li
Keyword(s):  
Stability Analysis ◽  
Stability Problem ◽  
Good Description ◽  
Maximum Load ◽  
Cohesive Crack ◽  
Crack Model ◽  
Cohesive Crack Model ◽  
Opening Displacement ◽  
Cohesive Stress ◽  
Quasibrittle Materials

The cohesive (or ficticious) crack model, characterized by softening stress-displacement relations, provides a good description of fracture of quasibrittle materials such as conrete, rock, or tough ceramics. The cohesive crack model is formulated in terms of compliance influence functions and the failure is analyzed as a stability problem. The size effect is determined by means of an eigenvalue problem. In this problem, the structure size for which a given relative crack length yields the maximum load is the eigenvalue. The model is further generalized to time dependence. The opening displacement is considered as a function of the cohesive stress and the opening rate of the crack. Finally, applications to rock and concrete are discussed.

scholarly journals A Particle-Based Cohesive Crack Model for Brittle Fracture Problems

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3573
Author(s):  
Hu Chen ◽  
Y. X. Zhang ◽  
Linpei Zhu ◽  
Fei Xiong ◽  
Jing Liu ◽  
...  
Keyword(s):  
Fracture Process ◽  
Cohesive Crack ◽  
Contact Model ◽  
Experimental Result ◽  
Crack Model ◽  
Mixed Mode Fracture ◽  
Cohesive Crack Model ◽  
Zone Method ◽  
The Impact ◽  
Linear Softening

Numerical simulations of the fracture process are challenging, and the discrete element (DE) method is an effective means to model fracture problems. The DE model comprises the DE connective model and DE contact model, where the former is used for the representation of isotropic solids before cracks initiate, while the latter is employed to represent particulate materials after cracks propagate. In this paper, a DE particle-based cohesive crack model is developed to model the mixed-mode fracture process of brittle materials, aiming to simulate the material transition from a solid phase to a particulate phase. Because of the particle characteristics of the DE connective model, the cohesive crack model is constructed at inter-particle bonds in the connective stage of the model at a microscale. A potential formulation is adopted by the cohesive zone method, and a linear softening relation is employed by the traction–separation law upon fracture initiation. This particle-based cohesive crack model bridges the microscopic gap between the connective model and the contact model and, thus, is suitable to describe the material separation process from solids to particulates. The proposed model is validated by a number of standard fracture tests, and numerical results are found to be in good agreement with the analytical solutions. A notched concrete beam subjected to an impact loading is modeled, and the impact force obtained from the numerical modeling agrees better with the experimental result than that obtained from the finite element method.

State-of-the-Art Review on Concrete Softening Curve

2010 ◽  
Vol 168-170 ◽  
pp. 669-673
Author(s):  
Zhi Fang Zhao ◽  
Zhi Gang Zhao ◽  
Xiao Jie Feng ◽  
Ming Li
Keyword(s):  
Constitutive Law ◽  
Cohesive Crack ◽  
Crack Model ◽  
Cohesive Crack Model ◽  
Direct Tension ◽  
Tension Softening ◽  
Nonlinear Form ◽  
Determination Methods ◽  
Relationship Of ◽  
Inverse Analysis Method

The cohesive crack model is widely employed to the fracture analysis of concrete for mode I crack. The tension softening relationship is a very important constitutive law in the cohesive crack model. The determination methods of tension softening relationship of concrete are introduced in this paper which are direct tension methods, J-integral method and inverse analysis method. Meanwhile, those simplified softening curves including linear form and nonlinear form are summarized.

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