scholarly journals A Stretch/Bend Method for In Situ Measurement of the Delamination Toughness of Coatings and Films Attached to Substrates

2010 ◽  
Vol 78 (1) ◽  
Author(s):  
M. Y. He ◽  
J. W. Hutchinson ◽  
A. G. Evans
Keyword(s):  
Residual Stress ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Beam Theory ◽  
Companion Paper ◽  
In Situ Measurement ◽  
Delamination Toughness ◽  
Slender Beams

A stretch/bend method for the in situ measurement of the delamination toughness of coatings attached to substrates is described. A beam theory analysis is presented that illustrates the main features of the test. The analysis is general and allows for the presence of residual stress. It reveals that the test produces stable extension of delaminations, rendering it suitable for multiple measurements in a single test. It also provides scaling relations and enables estimates of the loads needed to extend delaminations. Finite element calculations reveal that the beam theory solutions are accurate for slender beams, but overestimate the energy release rate for stubbier configurations and short delaminations. The substantial influence of residual stress on the energy release rate and phase angle is highly dependent on parameters such as the thickness and modulus ratio for the two layers. Its effect must be included to obtain viable measurements of toughness. In a companion paper, the method has been applied to a columnar thermal barrier coating deposited onto a Ni-based super-alloy.

Fracture Properties of Surface Modification Layers Via a Modified Bi-Layer Beam Model

2018 ◽  
Vol 35 (4) ◽  
pp. 499-511
Author(s):  
H. T. Liu ◽  
M. H. Zhao ◽  
J. W. Zhang
Keyword(s):  
Residual Stress ◽  
Surface Modification ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Fracture Process ◽  
Beam Model ◽  
Element Analysis ◽  
Fracture Properties ◽  
Proposed Model

ABSTRACTA modified bi-layer beam model is proposed to study the fracture-dominated scratch process of the brittle material with surface modification layer considering residual stress. The nonlinear analytical solution of the energy release rate is derived considering the graded distribution of the elastic modulus and residual stress. Finite element analysis is also conducted. Both analytical and numerical results show that the graded distribution of the material properties and residual stress plays an important role in the fracture process. Based on the inverse analysis, the proposed model could provide a convenient way to determine the energy release rate of materials possessing a surface modification layer.

Ductile Tearing Prediction in Welds Considering Hydrogen Embrittlement

2013 ◽  
Author(s):  
Vincent Robin ◽  
Philippe Gilles ◽  
Philippe Mourgue ◽  
David Tchoukien
Keyword(s):  
Residual Stress ◽  
Hydrogen Embrittlement ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Crack Front ◽  
Hydrogen Diffusion ◽  
Critical Energy ◽  
Critical Energy Release Rate ◽  
Welding Operation

Some flaws may appear in metal components, in the weld region, and more especially in the case of electron beam girth weld in the slope area of the process (start and stop of the welding operation). These initial flaws can growth with delay even without any external loads. Indeed close to the junction, the material undergoes the combination of high tensile residual stresses due to welding operation and the presence of hydrogen brought by manufacturing process. Hydrogen assisted cracking is then suspected to explain the origin of crack growth through hydrogen embrittlement of the base metal. To understand by numerical modeling, at least qualitatively, the scenario of appearance of such cracks and their evolution, without any external load or under pressure load, the proposed approach consists first in simulating the welding process and its consequences on residual stress distribution and hydrogen concentrations [1]. The hydrogen diffusion computation is pursued after the welding operation simulation in order to highlight the most critical moment at which macroscopic defects may appear. Then, a macroscopic defect is created in the so determined critical zone, the stability of which is studied by estimating the energy release rate at the crack front and by comparing these values with experimental data such as the critical energy release rate at initiation and the tearing resistance curves which may depend on the hydrogen content. So, it is numerically possible to propagate the defect in the time, considering hydrogen diffusion and residual stress rebalancing, by successive crack front definition performed as the crack tip region exceeds the critical energy release rate [14]. Finally, the evolution of the defect is estimated in the same way under pressure test loading conditions. Results and discussions are presented to propose an engineering approach for the design assessment of such specific weld junctions with a low and hydrogen dependant toughness.

scholarly journals Analytical Energy Release Rate of Interfacial Crack in Composite Laminates

2019 ◽  
Vol 37 (1) ◽  
pp. 137-142
Author(s):  
Weiling Zheng ◽  
Longxi Zheng
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Composite Laminates ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Beam Theory ◽  
Three Point Bending ◽  
The Right

In order to study whether the interfacial crack will grow or not in the composite laminates, the energy release rate of a crack in three-point bending model was obtained by using the Timoshenko beam theory and local generalized forces. The results of energy release rate were validated by the finite element results. The results indicate that the energy release rate of left crack tip is equal to that of the right crack tip when the crack before the crack goes cross the loading point; after the crack goes cross the loading point, the energy release rate of the left crack tip increases and then decreases gradually, while the energy release rate of right crack tip decreases first and increases later; the energy release rate of left crack tip is equal to that of the right crack tip again when the crack is symmetric with the loading point.

Effect of ultraviolet cure on the interfacial toughness and structure of SiOC thin film on Si substrate

2010 ◽  
Vol 25 (10) ◽  
pp. 1910-1916 ◽  
Author(s):  
M. Takeda ◽  
N. Matoba ◽  
K. Matsuda ◽  
H. Seki ◽  
K. Inoue ◽  
...  
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Mechanical Energy ◽  
Uv Curing ◽  
Si Substrate ◽  
Force Microscopy ◽  
Interfacial Delamination ◽  
Atomic Force ◽  
Delamination Toughness

An experimental study on the adhesion of thin films was conducted for the ultraviolet (UV)-cured SiOC films on Si substrate by examining the mechanical energy balance during the indentation process combined with atomic force microscopy observation. The effect of UV cure on the interfacial delamination toughness and the structure of the SiOC films are discussed. The energy release rate of the SiOC film/Si substrate interfacial delamination increases with the increases in the time of UV curing, indicating that the indentation method is efficient to examine the adhesion of coating. As the UV curing time increases, the film thickness and the Si–CH3 bond structure decrease, whereas the SiO2 network structure develops and the mechanical properties of the film are improved. Furthermore, the energy release rate of SiOC film/Si interfacial delamination is well correlated in a proportional manner to the Young's modulus of the film.

Analysis of Potential Energy Release Rate of Composite Laminate Based on Timoshenko Beam Theory

2007 ◽  
Vol 334-335 ◽  
pp. 513-516
Author(s):  
Kyohei Kondo
Keyword(s):  
Potential Energy ◽  
Energy Release Rate ◽  
Energy Release ◽  
Timoshenko Beam ◽  
Release Rate ◽  
Double Cantilever Beam ◽  
Beam Theory ◽  
Timoshenko Beam Theory ◽  
Beam Specimen ◽  
Cracked Beam

The Timoshenko beam theory is used to model each part of cracked beam and to calculate the potential energy release rate. Calculations are given for the double cantilever beam specimen, which is simulated as two separate beams connected elastically along the uncracked interface.

A Quantitative Analysis of the Residual Stress and Grain Size Gradient Effects on the Energy Release Rate of a Coating-Substrate System

2011 ◽  
Vol 228-229 ◽  
pp. 356-362
Author(s):  
Ban Quan Yang ◽  
Fa Xin Li
Keyword(s):  
Residual Stress ◽  
Grain Size ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Critical Energy ◽  
Beam Model ◽  
Critical Energy Release Rate ◽  
Gradient Effects ◽  
Size Gradient

The surface heat treatment can lead to the residual stress and inhomogenous effects in coating-substrate system. Based on the well-known Hall-Petch relationship between the coating yield strength and its grain size, the inhomogenous effect can be extended to the grain size gradient effect. In this work, a mechanical model of a coating-substrate specimen is developed to quantify the residual stress and grain size gradient effects on the energy release rate of the coating on its substrate. Using a Micro-Composite-Double-Cantilever Beam Model (MCDCBM), the analytic solutions can be derived, and they can be used to characterize the fracture toughness of the inhomogenous coatings on substrates in terms of the critical energy release rate. Finally, a numerical example is presented to show how the critical energy release rate is obtained.

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