scholarly journals On the Reference Length and Mode Mixity for a Bimaterial Interface

2007 ◽  
Vol 129 (4) ◽  
pp. 580-587 ◽  
Author(s):  
A. Agrawal ◽  
A. M. Karlsson
Keyword(s):  
Interfacial Fracture ◽  
Bimaterial Interface ◽  
Mode Mixity ◽  
Characteristic Mode ◽  
Linear Elastic ◽  
System A ◽  
Reference Length ◽  
Point Bend ◽  
Arbitrary Location ◽  
Bimaterial System

We investigate properties that govern interfacial fracture within the framework of linear elastic fracture mechanics, including interfacial fracture toughness, mode mixity, and the associated reference length. The reference length describes the arbitrary location where the mode mixity is evaluated, ahead of the crack tip, in a bimaterial system. A method for establishing a reference length that is fixed for a given bimaterial system is proposed. This is referred to as the “characteristic reference length,” with the associated “characteristic mode mixity.” The proposed method is illustrated with an experimental investigation, utilizing a four-point bend test of a bimaterial system.

Adhesion and interfacial fracture in drug-eluting stents

2010 ◽  
Vol 25 (4) ◽  
pp. 641-647 ◽  
Author(s):  
Juan Meng ◽  
Argjenta Orana ◽  
Ting Tan ◽  
Kurt Wolf ◽  
Nima Rahbar ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Interfacial Fracture ◽  
Drug Eluting Stent ◽  
Mode Mixity ◽  
Parylene C ◽  
Energy Release Rates ◽  
Drug Eluting ◽  
Model Drug ◽  
Experimental And Theoretical Studies ◽  
Initial Cracks

This paper presents experimental and theoretical studies of the adhesion between the drug-eluting layer and a Parylene C primer layer in coatings present on a model drug-eluting stent. To quantify adhesion, Brazil nut sandwich specimens were prepared mimicking the layers of this coating. These samples were stressed to fracture, and the resulting initial cracks at the Parylene C/drug interface were used to measure the dependence of interfacial fracture energy of mode mixity. The mating fracture surfaces were then analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The interfacial energy release rates were obtained over a wide variety of mode mixities. Adhesion and fracture mechanics models were then used to estimate the mode mixity dependency of interfacial fracture toughness. Fracture toughness was found to be larger under higher mode mixity than that under lower mixity and the analytical model showed close agreement with experimental results.

scholarly journals Prediction of Experimental Electromagnetic Coupling to a UAV Model Using Characteristic Mode Analysis

2021 ◽  
Author(s):  
Mohamed Hamdalla ◽  
Benjamin Bissen ◽  
James D. Hunter ◽  
Liu Yuanzhuo ◽  
Victor Khilkevich ◽  
...  
Keyword(s):  
Experimental Measurement ◽  
Experimental Approach ◽  
Electromagnetic Coupling ◽  
Mode Analysis ◽  
Angle Of Incidence ◽  
Characteristic Mode ◽  
System A ◽  
Wide Range ◽  
Aerial Vehicle ◽  
Excitation Conditions

<p>In this work, we study the current coupled to a simplified Unmanned Aerial Vehicle (UAV) model using a dual computational and experimental approach. The surrogate structure reduced the computational burden and facilitated the experimental measurement of the coupled currents. For a practical system, a wide range of simulations and measurements must be performed to analyze the induced current variations with respect to the incident excitation properties such as the frequency, angle of incidence, and polarization. To simplify this analysis, Characteristic Mode Analysis (CMA) was used to compute the eigen-currents of the UAV model and predict where and under which RF excitation conditions, the coupled current is maximized. We verified these predictions using direct experimental measurement of the coupled currents. The presented simulations and measurements show the usefulness of CMA for studying electromagnetic coupling to practical systems. </p>

scholarly journals Prediction of Experimental Electromagnetic Coupling to a UAV Model Using Characteristic Mode Analysis

2021 ◽  
Author(s):  
Mohamed Hamdalla ◽  
Benjamin Bissen ◽  
James D. Hunter ◽  
Liu Yuanzhuo ◽  
Victor Khilkevich ◽  
...  
Keyword(s):  
Experimental Measurement ◽  
Experimental Approach ◽  
Electromagnetic Coupling ◽  
Mode Analysis ◽  
Angle Of Incidence ◽  
Characteristic Mode ◽  
System A ◽  
Wide Range ◽  
Aerial Vehicle ◽  
Excitation Conditions

<p>In this work, we study the current coupled to a simplified Unmanned Aerial Vehicle (UAV) model using a dual computational and experimental approach. The surrogate structure reduced the computational burden and facilitated the experimental measurement of the coupled currents. For a practical system, a wide range of simulations and measurements must be performed to analyze the induced current variations with respect to the incident excitation properties such as the frequency, angle of incidence, and polarization. To simplify this analysis, Characteristic Mode Analysis (CMA) was used to compute the eigen-currents of the UAV model and predict where and under which RF excitation conditions, the coupled current is maximized. We verified these predictions using direct experimental measurement of the coupled currents. The presented simulations and measurements show the usefulness of CMA for studying electromagnetic coupling to practical systems. </p>

Superlayer Test for Interfacial Fracture Toughness Measurements

2004 ◽  
Author(s):  
Jiantao Zheng ◽  
Suresh K. Sitaraman
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Interfacial Fracture ◽  
Critical Energy ◽  
Interfacial Fracture Toughness ◽  
Mode Mixity ◽  
Critical Energy Release Rate ◽  
Component Reliability ◽  
Interfacial Delamination ◽  
Interface Delamination

Knowledge of the mode-mixity (?) dependent interfacial fracture toughness (Γ) is needed to predict the interface delamination and the component reliability of thin-film structures. Mode-mixity, ?, is a measure of the relative shearing to tensile opening of the interface crack near the tip. Typically, Γ increases as ? increases, such that the delamination is less likely when the loading on the interface is shear-dominated. The measurement of mode-mixity dependent Γ has been a challenge for thin film interfaces. The single-strip superlayer test, developed by the authors, eliminates the shortcomings of current testing methods. This test employs a stress-engineered superlayer to drive the interfacial delamination between the thin-film and the substrate. An innovative aspect of the proposed test is to introduce a release layer of varying width between the interested interfaces to control the amount of energy available for delamination propagation. By designing a decreasing area of the release layer, it is possible to arrest the interfacial delamination at a given location, and the interfacial fracture toughness or critical energy release rate can be found at the location where the delamination ceases to propagate. Design, preparation, and execution of the test are presented. Results are shown for Ti/Si interfaces of different mode mixities.

Effect of Mode-Mixity and Porosity on Interfacial Fracture of Low-k Dielectrics

2004 ◽  
Vol 812 ◽  
Author(s):  
Caroline C. Merrill ◽  
Paul S. Ho
Keyword(s):  
Shear Stress ◽  
Crack Propagation ◽  
Interfacial Adhesion ◽  
Pure Shear ◽  
Interfacial Fracture ◽  
Mode Ii ◽  
Mode Mixity ◽  
Pure Tension ◽  
Low K

AbstractIn this study, we developed a system allowing interfacial adhesion measurements as a function of mode-mixity, from pure tension to pure shear. Results show that the debonding energy increases, by a factor of 3 to 10, as the amount of shear stress increases, approaching mode II conditions. For low k dielectrics, the debonding energy was found to decrease with increasing porosity and increase with increasing plasticity. The crack propagation is also dependent on mode-mixity.

Validation of Linear Elastic Fracture Mechanics in Predicting the Fracture Toughness of Polyethylene Pipe Materials

2015 ◽  
Author(s):  
Tarek M. A. A. El-Bagory ◽  
Hossam E. M. Sallam ◽  
Maher Y. A. Younan
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Linear Elastic Fracture Mechanics ◽  
Operating Conditions ◽  
Specimen Thickness ◽  
Crosshead Speed ◽  
Linear Elastic ◽  
Piping Systems ◽  
Elastic Fracture ◽  
Point Bend

The main purpose of the present paper is to compare between the fracture toughness based on linear elastic fracture mechanics (GIC), and that based on nonlinear fracture mechanics (JIC). The material of the investigated pipe is a high-density polyethylene (HDPE), which is commonly used in natural gas piping systems. The welds at the pipe junction are produced by butt-fusion (BF), welding. Curved three-point bend (CTPB), fracture specimens are used. The crosshead speed ranged from 5 to 500 mm/min and specimen thickness ranged from 9 to 45mm for both welded and unwelded specimens at room temperature Ta, equal 23°C. The study reveals that the crosshead speed has a significant effect on the fracture toughness of both welded and unwelded specimens. The results of GIC for different specimen thickness and crosshead speed found previously by the authors [1] have been compared with JIC under the same operating conditions [2]. The comparison between welded and unwelded specimens revealed that in the welded specimens there is a marginal difference between fracture toughness measured using linear elastic fracture mechanics LEFM and elastic plastic fracture mechanics EPFM, for both crosshead speeds.

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