A Continuum Model for Void Nucleation by Inclusion Debonding

1987 ◽  
Vol 54 (3) ◽  
pp. 525-531 ◽  
Author(s):  
A. Needleman
Keyword(s):  
Cohesive Zone ◽  
Continuum Model ◽  
Cohesive Zone Model ◽  
Characteristic Length ◽  
Void Nucleation ◽  
Finite Geometry ◽  
Zone Model ◽  
Unified Framework ◽  
Full Account ◽  
Spherical Inclusions

A cohesive zone model, taking full account of finite geometry changes, is used to provide a unified framework for describing the process of void nucleation from initial debonding through complete decohesion. A boundary value problem simulating a periodic array of rigid spherical inclusions in an isotropically hardening elastic-viscoplastic matrix is analyzed. Dimensional considerations introduce a characteristic length into the formulation and, depending on the ratio of this characteristic length to the inclusion radius, decohesion occurs either in a “ductile” or “brittle” manner. The effect of the triaxiality of the imposed stress state on nucleation is studied and the numerical results are related to the description of void nucleation within a phenomenological constitutive framework for progressively cavitating solids.

Cohesive Zone-Based Damage Evolution in Periodic Materials Via Finite-Volume Homogenization

2014 ◽  
Vol 81 (10) ◽  
Author(s):  
Wenqiong Tu ◽  
Marek-Jerzy Pindera
Keyword(s):  
Finite Volume ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Displacement Discontinuity ◽  
Zone Model ◽  
Infinite Matrix ◽  
Unified Framework ◽  
Linear Region ◽  
Interfacial Separation ◽  
Periodic Materials

The zeroth-order parametric finite-volume direct averaging micromechanics (FVDAM) theory is further extended in order to model the evolution of damage in periodic heterogeneous materials. Toward this end, displacement discontinuity functions are introduced into the formulation, which may represent cracks or traction-interfacial separation laws within a unified framework. The cohesive zone model (CZM) is then implemented to simulate progressive separation of adjacent phases or subdomains. The new capability is verified in the linear region upon comparison with an exact elasticity solution for an inclusion surrounded by a linear interface of zero thickness in an infinite matrix that obeys the same law as CZM before the onset of degradation. The extended theory's utility is then demonstrated by revisiting the classical fiber/matrix debonding phenomenon observed in SiC/Ti composites, illustrating its ability to accurately capture the mechanics of progressive interfacial degradation.

Analyses of Interfacial Failure

1990 ◽  
Vol 43 (5S) ◽  
pp. S274-S275 ◽  
Author(s):  
A. Needleman
Keyword(s):  
Cohesive Zone ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Interfacial Strength ◽  
Finite Geometry ◽  
Complete Separation ◽  
Type Model ◽  
Interfacial Failure ◽  
Unified Framework ◽  
Full Account

A cohesive zone type model, taking full account of finite geometry changes, is used to provide a unified framework for describing the process of interfacial decohesion from initial debonding through complete separation. Constitutive relations are specified independently for material phases and for the interface. This model permits the prediction of interfacial decohesion without the necessity of introducing some additional failure criterion. Also, since the mechanical response of the interface is specified in terms of both a critical interfacial strength and the work of separation per unit area, dimensional considerations introduce a characteristic length. Various issues associated with the analysis of interfacial failure phenomena within this framework will be discussed.

scholarly journals Ultrasonic Deicing Efficiency Prediction and Validation for a Flat Deicing System

2020 ◽  
Vol 10 (19) ◽  
pp. 6640
Author(s):  
Zhonghua Shi ◽  
Zhenhang Kang ◽  
Qiang Xie ◽  
Yuan Tian ◽  
Yueqing Zhao ◽  
...  
Keyword(s):  
Lead Zirconate Titanate ◽  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Lead Zirconate ◽  
Efficiency Factor ◽  
Zone Model ◽  
Shear Stresses ◽  
Stress Distributions ◽  
Total Energy Density ◽  
Average Shear

An effective deicing system is needed to be designed to conveniently remove ice from the surfaces of structures. In this paper, an ultrasonic deicing system for different configurations was estimated and verified based on finite element simulations. The research focused on deicing efficiency factor (DEF) discussions, prediction, and validations. Firstly, seven different configurations of Lead zirconate titanate (PZT) disk actuators with the same volume but different radius and thickness were adopted to conduct harmonic analysis. The effects of PZT shape on shear stresses and optimal frequencies were obtained. Simultaneously, the average shear stresses at the ice/substrate interface and total energy density needed for deicing were calculated. Then, a coefficient named deicing efficiency factor (DEF) was proposed to estimate deicing efficiency. Based on these results, the optimized configuration and deicing frequency are given. Furthermore, four different icing cases for the optimize configuration were studied to further verify the rationality of DEF. The effects of shear stress distributions on deicing efficiency were also analyzed. At same time, a cohesive zone model (CZM) was introduced to describe interface behavior of the plate and ice layer. Standard-explicit co-simulation was utilized to model the wave propagation and ice layer delamination process. Finally, the deicing experiments were carried out to validate the feasibility and correctness of the deicing system.

scholarly journals An Improved Cohesive Zone Model for Interface Mixed-Mode Fractures of Railway Slab Tracks

2021 ◽  
Vol 11 (1) ◽  
pp. 456
Author(s):  
Yanglong Zhong ◽  
Liang Gao ◽  
Xiaopei Cai ◽  
Bolun An ◽  
Zhihan Zhang ◽  
...  
Keyword(s):  
Interface Crack ◽  
Cohesive Zone ◽  
Mixed Mode ◽  
Cohesive Zone Model ◽  
Complex Loading ◽  
Bending Test ◽  
Mixed Mode Fracture ◽  
Zone Model ◽  
Slab Track ◽  
Interfacial Cracks

The interface crack of a slab track is a fracture of mixed-mode that experiences a complex loading–unloading–reloading process. A reasonable simulation of the interaction between the layers of slab tracks is the key to studying the interface crack. However, the existing models of interface disease of slab track have problems, such as the stress oscillation of the crack tip and self-repairing, which do not simulate the mixed mode of interface cracks accurately. Aiming at these shortcomings, we propose an improved cohesive zone model combined with an unloading/reloading relationship based on the original Park–Paulino–Roesler (PPR) model in this paper. It is shown that the improved model guaranteed the consistency of the cohesive constitutive model and described the mixed-mode fracture better. This conclusion is based on the assessment of work-of-separation and the simulation of the mixed-mode bending test. Through the test of loading, unloading, and reloading, we observed that the improved unloading/reloading relationship effectively eliminated the issue of self-repairing and preserved all essential features. The proposed model provides a tool for the study of interface cracking mechanism of ballastless tracks and theoretical guidance for the monitoring, maintenance, and repair of layer defects, such as interfacial cracks and slab arches.

Cohesive Zone Model for the Interface of Multiwalled Carbon Nanotubes and Copper: Molecular Dynamics Simulation

2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Ibrahim Awad ◽  
Leila Ladani
Keyword(s):  
Carbon Nanotubes ◽  
Normal Stress ◽  
Multiwalled Carbon Nanotubes ◽  
Cohesive Zone ◽  
Large Scale ◽  
Cohesive Zone Model ◽  
Dynamics Simulation ◽  
Zone Model ◽  
Multiwalled Carbon ◽  
Significant Difference

Due to their superior mechanical and electrical properties, multiwalled carbon nanotubes (MWCNTs) have the potential to be used in many nano-/micro-electronic applications, e.g., through silicon vias (TSVs), interconnects, transistors, etc. In particular, use of MWCNT bundles inside annular cylinders of copper (Cu) as TSV is proposed in this study. However, the significant difference in scale makes it difficult to evaluate the interfacial mechanical integrity. Cohesive zone models (CZM) are typically used at large scale to determine the mechanical adherence at the interface. However, at molecular level, no routine technique is available. Molecular dynamic (MD) simulations is used to determine the stresses that are required to separate MWCNTs from a copper slab and generate normal stress–displacement curves for CZM. Only van der Waals (vdW) interaction is considered for MWCNT/Cu interface. A displacement controlled loading was applied in a direction perpendicular to MWCNT's axis in different cases with different number of walls and at different temperatures and CZM is obtained for each case. Furthermore, their effect on the CZM key parameters (normal cohesive strength (σmax) and the corresponding displacement (δn) has been studied. By increasing the number of the walls of the MWCNT, σmax was found to nonlinearly decrease. Displacement at maximum stress, δn, showed a nonlinear decrease as well with increasing the number of walls. Temperature effect on the stress–displacement curves was studied. When temperature was increased beyond 1 K, no relationship was found between the maximum normal stress and temperature. Likewise, the displacement at maximum load did not show any dependency to temperature.

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