Imaging opening-mode fracture in sandstone under three-point bending: A direct identification of the fracture process zone and traction-free crack based on cohesive zone model

2020 ◽  
Vol 136 ◽  
pp. 104516
Author(s):  
Qing Lin ◽  
Siqi Wang ◽  
Peng-Zhi Pan ◽  
Xin Bian ◽  
Yunhu Lu
Keyword(s):  
Cohesive Zone ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Cohesive Zone Model ◽  
Process Zone ◽  
Zone Model ◽  
Direct Identification ◽  
Mode Fracture ◽  
Three Point Bending ◽  
Opening Mode

Analysis of Energy Balance When Using Cohesive Zone Models to Simulate Fracture Processes

2002 ◽  
Vol 124 (4) ◽  
pp. 440-450 ◽  
Author(s):  
C. Shet ◽  
N. Chandra
Keyword(s):  
Cohesive Energy ◽  
Cohesive Zone ◽  
Strain Energy ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Elastic Strain Energy ◽  
Inelastic Strain ◽  
External Work ◽  
Cohesive Zone Models

Cohesive Zone Models (CZMs) are being increasingly used to simulate fracture and fragmentation processes in metallic, polymeric, and ceramic materials and their composites. Instead of an infinitely sharp crack envisaged in fracture mechanics, CZM presupposes the presence of a fracture process zone where the energy is transferred from external work both in the forward and the wake regions of the propagating crack. In this paper, we examine how the external work flows as recoverable elastic strain energy, inelastic strain energy, and cohesive energy, the latter encompassing the work of fracture and other energy consuming mechanisms within the fracture process zone. It is clearly shown that the plastic energy in the material surrounding the crack is not accounted in the cohesive energy. Thus cohesive zone energy encompasses all the inelastic energy e.g., energy required for grainbridging, cavitation, internal sliding, surface energy but excludes any form of inelastic strain energy in the bounding material.

scholarly journals MODELLING OF CRACK PROPAGATION: COMPARISON OF DISCRETE LATTICE SYSTEM AND COHESIVE ZONE MODEL

2020 ◽  
Vol 26 ◽  
pp. 39-44 ◽  
Author(s):  
Karel Mikeš ◽  
Franz Bormann ◽  
Ondřej Rokoš ◽  
Ron H.J. Peerlings
Keyword(s):  
Crack Propagation ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Process Zone ◽  
Crack Opening ◽  
Lattice Models ◽  
Bending Test ◽  
Zone Model ◽  
Realistic Problem ◽  
Micro Structures

Lattice models are often used to analyze materials with discrete micro-structures mainly due to their ability to accurately reflect behaviour of individual fibres or struts and capture macroscopic phenomena such as crack initiation, propagation, or branching. Due to the excessive number of discrete interactions, however, such models are often computationally expensive or even intractable for realistic problem dimensions. Simplifications therefore need to be adopted, which allow for efficient yet accurate modelling of engineering applications. For crack propagation modelling, the underlying discrete microstructure is typically replaced with an effective continuum, whereas the crack is inserted as an infinitely thin cohesive zone with a specific traction-separation law. In this work, the accuracy and efficiency of such an effective cohesive zone model is evaluated against the full lattice representation for an example of crack propagation in a three-point bending test. The variational formulation of both models is provided, and obtained results are compared for brittle and ductile behaviour of the underlying lattice in terms of force-displacement curves, crack opening diagrams, and crack length evolutions. The influence of the thickness of the process zone, which is present in the full lattice model but neglected in the effective cohesive zone model, is studied in detail.

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