Determination of crack opening displacement and critical load parameter within a cohesive zone model

2018 ◽  
Vol 31 (2) ◽  
pp. 569-586 ◽  
Author(s):  
Mikhailo F. Selivanov ◽  
Yuri O. Chornoivan ◽  
Oleksandr P. Kononchuk
Keyword(s):  
Critical Load ◽  
Crack Opening Displacement ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Crack Opening ◽  
Load Parameter ◽  
Zone Model ◽  
Opening Displacement

Numerical Investigation of the Damage Behavior of S355 EBW by Cohesive Zone Modeling

2015 ◽  
Vol 1102 ◽  
pp. 149-153 ◽  
Author(s):  
H.Y. Tu ◽  
Ulrich Weber ◽  
Siegfried Schmauder
Keyword(s):  
Tensile Test ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Crack Opening ◽  
Compact Tension ◽  
Initial Crack ◽  
Cohesive Zone Modeling ◽  
Zone Model ◽  
Opening Displacement ◽  
Zone Modeling

In this paper, the cohesive zone model is used to study the fracture behavior of an electron beam welded (EBW) steel joint. Mechanical properties of different weld regions are derived from the tensile test results of flat specimens, which are obtained from the respective weld regions. Based on the tensile test of notched round specimens, the cohesive strength T0can be fixed. With the fixed T0value, the cohesive model is applied to compact tension (C(T)) specimens with the initial crack located at different positions of weldment with different cohesive energy values Γ0. Numerical simulations are compared with the experimental results in the form of force vs. Crack Opening Displacement (COD) curves as well as fracture resistance (JR) curves.

Existence and Convergence Questions in Computational Modelling of Crack Growth in Brittle and Quasi-Brittle Materials

2016 ◽  
Vol 258 ◽  
pp. 157-160 ◽  
Author(s):  
Jiří Vala
Keyword(s):  
Crack Growth ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Computational Modelling ◽  
Brittle Materials ◽  
Zone Model ◽  
Static Tests ◽  
Materials Used ◽  
Proper Analysis

Computational modelling of the crack growth in brittle and quasi-brittle materials used in mechanical, civil, etc. engineering applies the cohesive zone model with various traction separation laws; determination of micro-mechanical parameters comes then from static tests, microscopic observation and numerical calibration. Although most authors refer to ill-possedness and need of artificial regularization in inverse problems (identification of material parameters), some difficulties originate even in nonlinear formulations of direct and sensitivity problems. This paper demonstrates the possibility of proper analysis of the existence of a weak solution and of the convergence of a corresponding numerical algorithm for such model problem, avoiding non-physical assumptions.

Determination of crack-opening displacement by the method of caustics

1974 ◽  
Vol 9 (3) ◽  
pp. 197-205 ◽  
Author(s):  
P S Theocaris
Keyword(s):  
Crack Opening Displacement ◽  
Mechanical Characteristics ◽  
Crack Opening ◽  
Crack Tip ◽  
External Loading ◽  
Small Scale ◽  
Opening Displacement ◽  
Cracked Plates ◽  
Good Agreement

A new experimental technique based on the method of caustics is presented for the measurement of the distance between the lips of a crack near the crack-tip. The two parts of the caustic formed by reflections from the front and rear faces of the specimen lie at a distance from each other. The gap between these parts depends on the total c.o.d. (crack-opening displacement), that is the initial opening and the opening due to loading, as well as on the optical and mechanical characteristics of the material By increasing the external loading of the cracked plate, the gap between the parts of the caustic was changed and this gap measured the instantaneous c.o.d. due to loading. The method was applied to the measurement of small c.o.d.s. due to small-scale loading, with satisfactory results. Therefore it can certainly be used to measure c.o.d.s at large loading steps, up to fracture, because the gap between the parts of the caustic becomes significant and easy to measure. Measurements with cracked plates made of p.m.m.a. (polymethylmethacrylate) and polycarbonate showed that the results obtained are in good agreement with theory. Thus, it has been proved that the method of caustics yields a very sensitive means for measuring c.o.d.s, especially in small-scale deformations, where measurement of c.o.d by conventional methods is inaccurate. A great advantage of the method is that it measures the c.o.d.s at a well defined region, which always remains near to the crack tip.

scholarly journals Size effect in particle debonding: Comparisons between finite fracture mechanics and cohesive zone model

2018 ◽  
Vol 53 (14) ◽  
pp. 1941-1954 ◽  
Author(s):  
Timothée Gentieu ◽  
Julien Jumel ◽  
Anita Catapano ◽  
James Broughton
Keyword(s):  
Fracture Mechanics ◽  
Critical Load ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Interface Strength ◽  
Particle Radius ◽  
Zone Model ◽  
Finite Fracture Mechanics ◽  
Particle Debonding ◽  
The Relationship

The present study aims at describing the debonding phenomenon of a particle embedded in an elastic matrix. Two types of fracture mechanics approaches are developed and compared in this context. The phenomenon is analytically described using a finite fracture mechanics approach, while numerical simulations are performed using a cohesive zone model to describe the decohesion process. Both methods rely on two mechanical parameters: the interface strength, σmax and the fracture energy, Gc, of the interface. Both modelling approaches produce results that show larger particles tend to debond before smaller ones although noticeable differences are observed, especially concerning the relationship between the critical load and the particle radius: in the framework of the FFM, the critical load is inversely proportional to the square root of the particle radius, while when using CZM, the critical load is inversely proportional to the particle radius.

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.

scholarly journals Toughness Calculation of Postfire Normal Concrete

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Qingyang Chen ◽  
Anjing Tang ◽  
Zhoudao Lu
Keyword(s):  
Fracture Toughness ◽  
Critical Load ◽  
Crack Opening Displacement ◽  
Analytical Method ◽  
Crack Opening ◽  
Fracture Model ◽  
Opening Displacement ◽  
Normal Concrete ◽  
Critical Fracture ◽  
Fracture Tests

Fracture tests of postfire normal concrete with ten temperatures up to 600°C are implemented. Residual fracture toughness using analytical method is determined. Two situations are divided at critical load when calculating the cohesive fracture toughness. The initial and critical fracture toughness could be calculated from the complete load-crack opening displacement curves. Finally, the validation of double-Kfracture model to the postfire concrete specimens is proved.

scholarly journals The J-integral for mixed-mode loaded cracks with cohesive zones

2020 ◽  
Vol 227 (1) ◽  
pp. 79-94
Author(s):  
Johannes Scheel ◽  
Alexander Schlosser ◽  
Andreas Ricoeur
Keyword(s):  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Crack Tip ◽  
Constitutive Law ◽  
Zone Model ◽  
J Integral ◽  
Cohesive Law ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

AbstractThe J-integral quantifies the loading of a crack tip, just as the crack tip opening displacement (CTOD) emanating from the cohesive zone model. Both quantities, being based on fundamentally different interpretations of cracks in fracture mechanics of brittle or ductile materials, have been proven to be equivalent in the late 60s of the previous century, however, just for the simple mode-I loading case. The relation of J and CTOD turned out to be uniquely determined by the constitutive law of the cohesive zone in front of the physical crack tip. In this paper, a J-integral vector is derived for a mixed-mode loaded crack based on the cohesive zone approach, accounting for the most general case of a mode-coupled cohesive law. While the $$J_1$$ J 1 -coordinate, as energy release rate of a straight crack extension, is uniquely related to the cohesive potential at the physical crack tip and thus to the CTOD, the $$J_2$$ J 2 -coordinate depends on the solution of the specific boundary value problem in terms of stresses and displacement gradients at the cohesive zone faces. The generalized relation is verified for the Griffith crack, employing solutions of the Dugdale crack based on improved holomorphic functions.

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