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.

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.

Delayed Fracture of the Piezoelectric Ceramics Under Electric Fields in Three-Point Bending

2007 ◽  
Author(s):  
Fumio Narita ◽  
Yasuhide Shindo ◽  
Mitsuru Hirama
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Electric Fields ◽  
Lead Zirconate Titanate ◽  
Release Rate ◽  
Open Crack ◽  
Element Analysis ◽  
Delayed Fracture ◽  
Pzt Ceramics ◽  
Dc Electric Fields

This paper investigates experimentally and analytically the delayed fracture in lead zirconate titanate (PZT) ceramics under electromechanical loading. Delayed fracture tests were conducted on single-edge precracked-beam specimens, and time-to-failure and fracture load under different DC electric fields were obtained. Possible mechanisms for delayed fracture were also discussed by scanning electron microscope (SEM) examination of the fracture surface of the PZT ceramics. Further, a nonlinear finite element analysis was employed to calculate the energy release rate for the permeable, impermeable and open crack models, and the effects of applied DC electric fields and localized polarization switching on the energy release rate are examined.

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 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.

scholarly journals Shear and foundation effects on crack root rotation and mode-mixity in moment- and force-loaded single cantilever beam sandwich specimen

2018 ◽  
Vol 52 (18) ◽  
pp. 2537-2547 ◽  
Author(s):  
Vishnu Saseendran ◽  
Leif A Carlsson ◽  
Christian Berggreen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Energy Release Rate ◽  
Energy Release ◽  
Cantilever Beam ◽  
Release Rate ◽  
Beam Specimen ◽  
Mode Mixity ◽  
Element Analysis ◽  
Fracture Specimens

Foundation effects play a crucial role in sandwich fracture specimens with a soft core. Accurate estimation of deformation characteristics at the crack front is vital in understanding compliance, energy release rate and mode-mixity in fracture test specimens. Beam on elastic foundation analysis of moment- and force-loaded single cantilever beam sandwich fracture specimens is presented here. In addition, finite element analysis of the single cantilever beam specimen is conducted to determine displacements, rotations, energy release rate and mode-mixity. Based on finite element analysis, a foundation modulus is proposed that closely agrees with the numerical compliance and energy release rate results for all cases considered. An analytical expression for crack root rotation of the loaded upper face sheet provides consistent results for both loading configurations. For the force-loaded single cantilever beam specimen (in contrast to the moment-loaded case), it was found that the crack length normalized energy release rate and the mode-mixity phase angle increase strongly as the crack length decreases, a result of increased dominance of shear loading.

scholarly journals Mode II fracture behavior of parallel strand bamboo measured by 3-point end-notched flexure tests

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 3219-3227
Author(s):  
Zhen-wen Zhang ◽  
Jia-liang Zhang ◽  
Yu-shun Li ◽  
Riu Liu
Keyword(s):  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Fracture Process ◽  
Fracture Behavior ◽  
Critical Energy ◽  
Mode Ii ◽  
Critical Energy Release Rate ◽  
Propagation Length

Parallel strand bamboo (PSB) is a new type of bio-composite. In the present study, three-point bend end-notched flexure (3ENF) tests of PSB were conducted to analyze the fracture behavior including fracture process, resistant curves, and critical energy release rate in the longitudinal (L) system. The results show that transverse-longitudinal (TL) and thickness-longitudinal (ZL) specimens had the same fracture process including the stages of fracture process zone (FPZ) development and opening crack propagation but different mode II critical energy release rate (GIIc), and they indicate that the fiber bridging had a significant influence. The fracture processes suggest the PSB specimens of which the initial crack length was 0.5 times the half span had a stable crack propagating process, and the crack propagation length was wide enough to evaluate GIIc, which was 5.02 N∙mm-1 of TL specimens and 2.71 N∙mm-1 of ZL specimens. Besides, there was no obvious influence of span/depth ratio on the fracture resistance of both ZL and TL specimens when the ratio was larger than 15.

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