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.

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.

scholarly journals Prediction of delamination strength at interface between thin film and substrate by cohesive zone model

2006 ◽  
Vol 28 (4) ◽  
pp. 252-262 ◽  
Author(s):  
Do Van Truong ◽  
Hiroyuku Hirakata ◽  
Takayuki Katamura
Keyword(s):  
Thin Film ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Electronic Device ◽  
Stress Singularity ◽  
Zone Model ◽  
Cohesive Law ◽  
Gold Thin Film ◽  
Different Shapes ◽  
Interface Edge

An electronic device consists of multi-layered submicron-thick films, and delamination often takes place at an interface edge because of the stress singularity near the edge. Since the stress singularity at an interface edge depends on the edge shape, the fracture mechanics concept cannot be used to compare the delamination strength between the components with different shapes. This paper aims to predict the delamination strength at the interface edge with arbitrary shape using a cohesive zone model. Two different experiments are conducted for a gold thin film on a silicon substrate to calibrate the cohesive law. The validity of the approach is then discussed.

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 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.

Verification of a Cohesive Zone Model for Ductile Fracture

1996 ◽  
Vol 118 (2) ◽  
pp. 192-200 ◽  
Author(s):  
Huang Yuan ◽  
Guoyu Lin ◽  
Alfred Cornec
Keyword(s):  
Ductile Fracture ◽  
Crack Growth ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Normal Modes ◽  
Stable Crack Growth ◽  
Small Region ◽  
Zone Model ◽  
Cohesive Law ◽  
Ductile Crack Growth

In the present paper, ductile crack growth in an aluminium alloy is numerically simulated using a cohesive zone model under both plane stress and plane strain conditions for two different fracture types, shear and normal modes. The cohesive law for ductile fracture consists of two parts—a specific material’s separation traction and energy. Both are assumed to be constant during ductile fracture (stable crack growth). In order to verify the assumed cohesive law to be suitable for ductile fracture processes, experimental records are used as control curves for the numerical simulations. For a constant separation traction, determined experimentally from tension test data, the corresponding cohesive energy was determined by finite element calculations. It is confirmed that the cohesive zone model can be used to characterize a single ductile fracture mode and is roughly independent of stable crack extention. Both the cohesive traction and the cohesive fracture energy should be material specific parameters. The extension of the cohesive zone is restricted to a very small region near the crack tip and is in the order of the physical fracture process. Based on the present observations, the cohesive zone model is a promising criterion to characterize ductile fracture.

scholarly journals The optimal shape of elastomer mushroom-like fibers for high and robust adhesion

2014 ◽  
Vol 5 ◽  
pp. 630-638 ◽  
Author(s):  
Burak Aksak ◽  
Korhan Sahin ◽  
Metin Sitti
Keyword(s):  
Crack Initiation ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Zone Model ◽  
Adhesion Mechanism ◽  
Fiber Arrays ◽  
Tip Radius ◽  
Fibrillar Adhesives ◽  
Fiber Radius ◽  
Significant Effort

Over the last decade, significant effort has been put into mimicking the ability of the gecko lizard to strongly and reversibly cling to surfaces, by using synthetic structures. Among these structures, mushroom-like elastomer fiber arrays have demonstrated promising performance on smooth surfaces matching the adhesive strengths obtained with the natural gecko foot-pads. It is possible to improve the already impressive adhesive performance of mushroom-like fibers provided that the underlying adhesion mechanism is understood. Here, the adhesion mechanism of bio-inspired mushroom-like fibers is investigated by implementing the Dugdale–Barenblatt cohesive zone model into finite elements simulations. It is found that the magnitude of pull-off stress depends on the edge angle θ and the ratio of the tip radius to the stalk radius β of the mushroom-like fiber. Pull-off stress is also found to depend on a dimensionless parameter χ, the ratio of the fiber radius to a length-scale related to the dominance of adhesive stress. As an estimate, the optimal parameters are found to be β = 1.1 and θ = 45°. Further, the location of crack initiation is found to depend on χ for given β and θ. An analytical model for pull-off stress, which depends on the location of crack initiation as well as on θ and β, is proposed and found to agree with the simulation results. Results obtained in this work provide a geometrical guideline for designing robust bio-inspired dry fibrillar adhesives.

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