Interfaces and fatigue Damage in a Ti-15–3/SCS-6 [0/90]2s Composite

1996 ◽  
Vol 458 ◽  
Author(s):  
W. O. Soboyejo ◽  
B. Rabeeh ◽  
Y. Li ◽  
S. Rokhlin
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Damage ◽  
Interfacial Strength ◽  
Fatigue Tests ◽  
Crack Bridging ◽  
Strength Variation ◽  
Mechanics Model ◽  
Initiation And Propagation ◽  
Push Out

AbstractThe key role of interfaces in the initiation and propagation of fatigue damage is elucidated for a model eight ply [0/90]2s Ti-15V-3Cr-3Al-3Sn (Ti-15–3) composite reinforced with SiC (SCS-6) fibers. Interfacial strengths obtained from fiber push-out tests are used in the quantification of shielding due to crack bridging. Composite fatigue tests are predicted using an idealized fracture mechanics model. The possible effects of interfacial strength variation on the predicted fatigue lives are also elucidated.

Interfacial Versus Cohesive Failure on Polymer-Metal Interfaces in Electronic Packaging—Effects of Interface Roughness

2002 ◽  
Vol 124 (2) ◽  
pp. 127-134 ◽  
Author(s):  
Qizhou Yao ◽  
Jianmin Qu
Keyword(s):  
Surface Roughness ◽  
Fracture Mechanics ◽  
Electronic Packaging ◽  
Interfacial Adhesion ◽  
Interfacial Strength ◽  
Interface Roughness ◽  
Cohesive Failure ◽  
Mechanics Model ◽  
Polymer Metal ◽  
Metal Interfaces

Debonding of polymer-metal interfaces often involves both interfacial and cohesive failure. Since the cohesive strength of polymers is usually much greater than the polymer-metal interfacial strength, cohesive failure near the interface is usually desired for enhancing the interfacial adhesion. Roughened surfaces generally produce more cohesive failure; therefore, they are used commonly in practice to obtain better adhesion. This paper develops a fracture mechanics model that can be used to quantitatively predict the amount of cohesive failure once the surface roughness data are given. An epoxy/Al interface was investigated using this fracture mechanics model. The predicted amount of cohesive failure as a function of surface roughness compares very well with the experimentally measured values. It is believed that this model can be extended to other polymer–metal interfaces. Contributed by the Electronic and Photonic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received by the EPPD.

Interfacial Versus Cohesive Failure on Underfill-Aluminum Interface: Effects of Interface Roughness

2000 ◽  
Author(s):  
Qizhou Yao ◽  
Jianmin Qu
Keyword(s):  
Surface Roughness ◽  
Fracture Mechanics ◽  
Interfacial Adhesion ◽  
Flip Chip ◽  
Interfacial Strength ◽  
Interface Roughness ◽  
Cohesive Failure ◽  
Mechanics Model ◽  
Polymer Metal ◽  
Metal Interfaces

Abstract This paper is concerned with the interfacial adhesion and failure of underfill materials in flip-chip packages. Debonding of polymer-metal interfaces often involves both interfacial and cohesive failure. Since the cohesive strength of polymers is usually much greater than the polymer-metal interfacial strength, cohesive failure near the interface is usually desired to enhance the interfacial adhesion. Roughened surfaces generally produce more cohesive failure, therefore, are used commonly in practice to obtain better adhesion. In this paper a fracture mechanics model is developed that can be used to quantitatively predict the amount of cohesive failure once the surface roughness data are given. An epoxy/Al interface was investigated using this fracture mechanics model. The predicted amount of cohesive failure as a function of surface roughness compares very well with the experimentally measured values. It is believed that this model can be extended to other polymer – metal interfaces.

scholarly journals On the Degree of Irreversibility of Friction in Sheared Soft Adhesive Contacts

2020 ◽  
Vol 68 (3) ◽  
Author(s):  
M. Ciavarella ◽  
A. Papangelo
Keyword(s):  
Fracture Mechanics ◽  
Shear Stresses ◽  
Large Set ◽  
Tangential Load ◽  
Mechanics Model ◽  
Constant Shear Stress ◽  
Similar Materials ◽  
Adhesive Contacts ◽  
Brittle Fracture Mechanics

Abstract A number of authors have experimentally assessed the influence of friction on adhesive contacts, and generally the contact area has been found to decrease due to tangential shear stresses at the interface. The decrease is however generally much smaller than that predicted already by the Savkoor and Briggs 1977 classical theory using “brittle” fracture mechanics mixed mode model extending the JKR (Griffith like) solution to the contact problem. The Savkoor and Briggs theory has two strong assumptions, namely that (i) shear tractions are also singular at the interface, whereas they have been found to follow a rather constant distribution, and that (ii) no dissipation occurs in the contact. While assumption (ii) has been extensively discussed in the Literature the role of assumption (i) remained unclear. We show that assuming entirely reversible slip at the interface with a constant shear stress fracture mechanics model leads to results almost indistinguishable from the Savkoor and Briggs model (and further in disagreement with experiments), hence it is assumption (ii) that critically affects the results. We analyze a large set of experimental data from Literature and show that the degree of irreversibility of friction can vary by orders of magnitude, despite similar materials and geometries, depending on the velocity at which the tangential load is applied.

Managing Compressor Rotor Rim Fatigue Damage

2017 ◽  
Author(s):  
John R. Scheibel ◽  
Robert P. Dewey ◽  
Jay Richardson ◽  
Huawei Shi ◽  
Swami Swaminathan
Keyword(s):  
Stress Intensity ◽  
Fatigue Damage ◽  
Field Measurements ◽  
Crack Size ◽  
Fatigue Tests ◽  
Root Cause ◽  
Remaining Service Life ◽  
Compressor Rotor ◽  
Initiation And Propagation ◽  
Transient Thermal

Described within this paper are the results derived from an investigation into the root cause of cracks which are prematurely forming within the aft end rotor rim attachments of large combustion turbine compressors. The overall objective for this program was to use these results to develop a means for projecting the remaining service life of similarly affected rotors based on non-destructive measurements which identified the degree of fatigue damage sustained in the critical disc rim fillets. Projected rotor retirement was identified by systematically calculating the change in stress intensity for a crack as it propagated from a corner of the attachment fillet through the disc rim. Risk of catastrophic failure was identified when the stress intensity along the front of a given crack size and depth exceeded the fracture toughness of the rotor material, risking failure. Estimates of both crack initiation and propagation relied on properties derived from fatigue tests of specimens obtained from a retired rotor and stress results from a transient thermal analysis of the stages. When compared, projections of crack growth correlated well against field measurements of damaged rims.

An Study of Influence of Imperfections on the Delamination of Diamond-Like Carbon Films

2002 ◽  
Vol 719 ◽  
Author(s):  
Myoung-Woon Moon ◽  
Kyang-Ryel Lee ◽  
Jin-Won Chung ◽  
Kyu Hwan Oh
Keyword(s):  
Cross Sections ◽  
Focused Ion Beam ◽  
Imaging System ◽  
Ion Beam ◽  
Carbon Films ◽  
Diamond Like Carbon ◽  
Glass Substrates ◽  
Atomic Force ◽  
Initiation And Propagation

AbstractThe role of imperfections on the initiation and propagation of interface delaminations in compressed thin films has been analyzed using experiments with diamond-like carbon (DLC) films deposited onto glass substrates. The surface topologies and interface separations have been characterized by using the Atomic Force Microscope (AFM) and the Focused Ion Beam (FIB) imaging system. The lengths and amplitudes of numerous imperfections have been measured by AFM and the interface separations characterized on cross sections made with the FIB. Chemical analysis of several sites, performed using Auger Electron Spectroscopy (AES), has revealed the origin of the imperfections. The incidence of buckles has been correlated with the imperfection length.

A novel model of Z-pin insertion in prepreg based on fracture mechanics

2021 ◽  
pp. 095440542110144
Author(s):  
Guobiao Ji ◽  
Liang Cheng ◽  
Shaohua Fei ◽  
Jiangxiong Li ◽  
Yinglin Ke
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Analytical Model ◽  
Model Parameters ◽  
Force Model ◽  
Fe Model ◽  
Cohesive Elements ◽  
Fe Method ◽  
Insertion Force ◽  
Mechanics Model

Through-thickness reinforcement is a promising solution to the problem of delamination susceptibility in laminated composites. Modeling Z-pin–prepreg interaction is essential for accurate robotics-assisted Z-pin insertion. In this paper, a novel Z-pin insertion force model combining the classical cohesive finite element (FE) method with a dynamic analytical fracture mechanics model is proposed. The velocity-dependent cohesive elements, in which the fracture toughness is provided by the analytical model, are implemented in Z-pin insertion FE model to predict the crack initiation and propagation. Then Z-pin insertion experiments are performed on prepreg sample with metallic Z-pins at different velocities to identify the analytical model parameters and validate the simulation predictions offered by the model. Dynamics of Z-pin interaction with inhomogeneous prepreg is described and the effects of insertion velocity on prepreg contact force are studied. Results show that the force model agrees well with experiments and the fracture toughness rises with the increasing Z-pin insertion velocity.

A fracture mechanics model to predict the rate sensitivity of mode I fracture of concrete

1987 ◽  
Vol 17 (2) ◽  
pp. 249-262 ◽  
Author(s):  
Reji John ◽  
Surendra P. Shah ◽  
Yeou-Shang Jeng
Keyword(s):  
Fracture Mechanics ◽  
Rate Sensitivity ◽  
Mode I ◽  
Mode I Fracture ◽  
Mechanics Model

Effective Modeling of Fatigue Crack Growth in Pipelines

2012 ◽  
Author(s):  
Steven J. Polasik ◽  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Models ◽  
Critical Parameters ◽  
Operating Pressure ◽  
Mechanics Model ◽  
Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

scholarly journals Fatigue Damage of Al/SiC Composites - Macroscopic and Microscopic Analysis

2015 ◽  
Vol 60 (1) ◽  
pp. 101-105 ◽  
Author(s):  
A. Rutecka ◽  
Z.L. Kowalewski ◽  
K. Makowska ◽  
K. Pietrzak ◽  
L. Dietrich
Keyword(s):  
Fatigue Damage ◽  
Microscopic Analysis ◽  
Inelastic Strain ◽  
Damage Parameter ◽  
Fatigue Tests ◽  
Cyclic Plasticity ◽  
Damage Mechanisms ◽  
Before And After ◽  
Fatigue Damage Parameter ◽  
Sic Composites

Abstract The results of comparative examinations of mechanical behaviour during fatigue loads and microstructure assessment before and after fatigue tests were presented. Composites of aluminium matrix and SiC reinforcement manufactured using the KoBo method were investigated. The combinations of two kinds of fatigue damage mechanisms were observed. The first one governed by cyclic plasticity and related to inelastic strain amplitude changes and the second one expressed in a form of ratcheting based on changes in mean inelastic strain. The higher SiC content the less influence of the fatigue damage mechanisms on material behaviour was observed. Attempts have been made to evaluate an appropriate fatigue damage parameter. However, it still needs further improvements.

A Comparison of Fracture Mechanics and S–N Curve Approaches in Designing Drill Pipe

1992 ◽  
Vol 114 (3) ◽  
pp. 205-211 ◽  
Author(s):  
A. Ertas ◽  
G. Mustafa ◽  
O. Cuvalci
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Damage ◽  
Drill Pipe ◽  
Ball Joint ◽  
Marine Riser ◽  
Deep Drilling ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Total Damage ◽  
Dynamic Fatigue

It is well known that the upper ball joint in a marine riser, in deep drilling, can cause fatigue damage in the drill pipe passing through it. A study of fracture mechanics and S–N curve approaches has been undertaken to determine the dynamic fatigue damage in the drill pipe. Miner’s rule is utilized in both methods to determine the total damage. The results of both methods are compared.

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