scholarly journals Modelling of crack initiation in adhesively bonded Joint

2012 ◽  
Vol 3 (3) ◽  
pp. 221-227
Author(s):  
H. Al Ali ◽  
M.A. Wahab
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Damage Mechanics ◽  
Cohesive Zone Model ◽  
Stress Singularity ◽  
Strain Energy Release ◽  
Continuum Damage Mechanics ◽  
Zone Model ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joint

 In this paper, a review of some techniques proposed in the literature for modelling crackinitiation in adhesively bonded joints is presented. The techniques reviewed are: a) the singular intensityfactor, b) the inherent flaw size, c) Cohesive-zone model (CZM) and d) Continuum Damage Mechanics(CDM). The singular intensity factor characterizes the stress singularity at the corner point and can beused as a failure criterion to predict crack initiation. The inherent flaw method technique assumes that asmall crack having a fraction of millimetres is initiated at the singular point in order to develop a fracturemechanics criterion for crack initiation. The strain energy release rate for an un-cracked specimen is usedto determine the size of the inherent flaw. The cohesive zone model (CZM) technique is based ondefining parameters from fracture mechanics test specimens and using them to model failure of the joints.Continuum Damage Mechanics makes use of thermodynamics principles in order to derive a damageevolution law. In this damage evolution law the damage variable (D) is expressed as a function of numberof cycles, applied stress range and triaxiality function. Furthermore, the possibility of using the eXtendedFinite Element Method (XFEM) to predict crack initiation is elaborated.

Simulation of Crack Initiation at the Interface Edge Between Sub-Micron Thick Films Under Creep by Cohesive Zone Model

2008 ◽  
Author(s):  
Do Van Truong
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Damage Mechanics ◽  
Cohesive Zone Model ◽  
Thick Films ◽  
Stress Singularity ◽  
Zone Model ◽  
Cohesive Law ◽  
Micro Cantilever ◽  
Interface Edge

Delamination between sub-micron thick films is initiated at an interface edge due to creep deformation, and leads to the malfunction of microelectronic devices. In this study, the cohesive zone model approach with a cohesive law based on damage mechanics was developed to simulate crack initiation process at an interface edge between film layers under creep. Delamination experiments using a micro-cantilever bend specimen with a Sn/Si interface were conducted. The parameters charactering the cohesive law were calibrated by fitting displacement-time curves obtained by experiments and simulations. In addition, the order of the stress singularity, which increases with time and has a significant jump in its value at the crack initiation, was investigated.

A Crack Close to and Perpendicular to an Interface: Resolution of Anomalous Behavior With a Cohesive Zone

2019 ◽  
Vol 86 (3) ◽  
Author(s):  
George G. Adams
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Applied Pressure ◽  
Stress Singularity ◽  
Crack Tip ◽  
Anomalous Behavior ◽  
Work Of Adhesion ◽  
Bimaterial Interface ◽  
Zone Model ◽  
Finite Distance

In this investigation, we consider a crack close to and perpendicular to a bimaterial interface. If the crack tip is at the interface then, depending on material properties, the order of the stress singularity will be equal to, less than, or greater than one-half. However, if the crack tip is located any finite distance away from the interface the stress field is square-root singular. Thus, as the crack tip approaches the interface, the stress intensity factor approaches zero (for cases corresponding to a singularity of order less than one-half) or infinity (for a singularity of order greater than one-half). The implication of this behavior is that for a finite applied pressure the crack will either never reach the interface or will reach the interface with vanishing small applied pressure. In this investigation, a cohesive zone model is used in order to model the crack behavior. It is found that the aforementioned anomalous behavior for the crack without a cohesive zone disappears and that the critical value of the applied pressure for the crack to reach the interface is finite and depends on the maximum stress of the cohesive zone model, as well as on the work of adhesion and the Dundurs' parameters.

scholarly journals A Numerical and Experimental Study of Adhesively-Bonded Polyethylene Pipelines

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1531 ◽  
Author(s):  
Guilpin ◽  
Franciere ◽  
Barton ◽  
Blacklock ◽  
Birkett
Keyword(s):  
Cohesive Zone ◽  
Adhesive Bonding ◽  
Structural Integrity ◽  
Cohesive Zone Model ◽  
Low Cost ◽  
Element Model ◽  
Zone Model ◽  
Adhesively Bonded ◽  
Lap Shear ◽  
Lap Shear Test

Adhesive bonding of polyethylene gas pipelines is receiving increasing attention as a replacement for traditional electrofusion welding due to its potential to produce rapid and low-cost joints with structural integrity and pressure tight sealing. In this paper a mode-dependent cohesive zone model for the simulation of adhesively bonded medium density polyethylene (MDPE) pipeline joints is directly determined by following three consecutive steps. Firstly, the bulk stress–strain response of the MDPE adherend was obtained via tensile testing to provide a multi-linear numerical approximation to simulate the plastic deformation of the material. Secondly, the mechanical responses of double cantilever beam and end-notched flexure test specimens were utilised for the direct extraction of the energy release rate and cohesive strength of the adhesive in failure mode I and II. Finally, these material properties were used as inputs to develop a finite element model using a cohesive zone model with triangular shape traction separation law. The developed model was successfully validated against experimental tensile lap-shear test results and was able to accurately predict the strength of adhesively-bonded MPDE pipeline joints with a maximum variation of <3%.

scholarly journals A parametric study of crack propagation in paintings caused by temperature and relative humidity cycles based on irreversible cohesive zone model

2020 ◽  
Author(s):  
Mohammad Yaghoub Abdollahzadeh Jamalabadi
Keyword(s):  
Relative Humidity ◽  
Crack Initiation ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Initial Crack ◽  
Zone Model ◽  
Initiation Time ◽  
One Dimensional ◽  
Linear Elastic ◽  
Effects Of Temperature

Abstract The current paper aims to use an irreversible cohesive zone model to investigate the effects of temperature and relative humidity cycles on multilayer thin-film paintings crack pattern. The homogenous one-dimensional paint layers composed of alkyd and acrylic gesso over a canvas foundation (support) with known constant thicknesses are considered as the mechanical model of painting. Experimental data used for mathematical modeling of canvas as a linear elastic material and paint as a viscoelastic material with the Prony series. Fatigue damage parameters such as crack initiation time and maximum loads are calculated by an irreversible cohesive zone model used to control the interface separation. With the increase of the painting thickness and/or the initial crack length, the value of the maximum force increases. Moreover, by increasing the relative humidity (RH) and the temperature difference at loading by one cycle per day, the values of initiation time of delamination decrease. It is shown that the thickness of painting layers is the most important parameter in crack initiation times and crack growth rate in historical paintings in museums and conservation settings.

scholarly journals Numerical Representation of Multiple Premature Failures in Steel-Plated RC Beams

2017 ◽  
Vol 14 (04) ◽  
pp. 1750035 ◽  
Author(s):  
Mohammad Arsalan Khan ◽  
Jamal El-Rimawi ◽  
Vadim V. Silberschmidt
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Failure Modes ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
Numerical Representation ◽  
Rc Beams ◽  
Premature Failure ◽  
Different Types ◽  
Complete Failure

Realizing the importance of widely used technique of plating for flexural retrofitting of reinforced concrete (RC) beams and its drawbacks due to premature failure(s), present work concentrates in developing a finite element tool model capable of successfully capturing multiple premature failure modes and their corresponding behaviors. The model is simple but focused; the capability and accuracy of the results have been validated through test literature, particularly focusing on the load capacities of beams at progressive stages of failure modes; which is from crack initiation through to complete failure, such as the load of crack initiation, first crack and complete failure. Acceptable accuracy is shown in terms of crack type(s), crack patterns, sequence, location and direction of propagation through the innovative use of cohesive zone model (CZM). The model clearly explains that debonding and peeling, although originating from a same location for most cases, are extensions of different types of cracks.

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