Fracture Toughness of Northeast China Larch

Wood, as a green and environment-friendly building material, is widely used in building engineering. Naturally grown, wood has various defects like knots, cracks and inclined grain. Fracture Mechanics is thus an efficient tool to investigate the mechanical behavior of wood and wood-based composite products. According to Linear-elastic Fracture Mechanics (LEFM), fracture toughness can be introduced to measure the resistance to crack propagation. Crack was assumed to occur when the stress intensity factorKreached a critical valueKC.Fracture in wood usually involves not only the Mode I type (open) fracture, but also the Mode II type (shear) fracture. For getting a better understanding of the crack growth phenomenon of Northeast China Larch, it is, therefore, essential to assess theKICandKIIC, which are the critical stress intensity factors for Mode I and Mode II type fracture, respectively. In the current study,KICandKIIC, of Northeast China Larch were determined through tests with compact tension specimens and tests with compact symmetric shear specimens, respectively. In addition, the material properties tests were also performed. All of the specimens were cut from the same batch of Glulam beams. Based on the obtained data from experiments, LEFM was employed to explain the fracture failure in the form of crack propagation. Using Extended Finite Element Method (XFEM), simulation of the crack propagation in Mode I and Mode II was performed incorporating ABAQUS. The crack propagation and the load-displacement curves of numerical simulation were in good agreement with experiments, which validated that the proposed numerical approach is suitable for analysis of crack growth in the specimens. As part of a larger program to investigate the fracture behavior of Glulam beams made of Northeast China Larch, this study provides the material properties and validation of the numerical simulation approach. A series of experiments of full-size curved Glulam beams subject to bending and the corresponding simulations extending the numerical approach of this study to the cases of full-size wood composite members are under development.

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Effect of polypropylene fibers on the mode I, mode II, and mixed-mode fracture toughness and crack propagation in fiber-reinforced concrete

Theoretical and Applied Fracture Mechanics ◽

10.1016/j.tafmec.2020.102723 ◽

2020 ◽

Vol 109 ◽

pp. 102723

Author(s):

Mitra Hatami Jorbat ◽

Mehdi Hosseini ◽

Mahdi Mahdikhani

Keyword(s):

Fracture Toughness ◽

Reinforced Concrete ◽

Crack Propagation ◽

Mixed Mode ◽

Fiber Reinforced Concrete ◽

Mode I ◽

Mode Ii ◽

Mixed Mode Fracture ◽

Polypropylene Fibers ◽

Mode Fracture

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Three-Dimensional Mode Separation to Obtain Stress Intensity Factors

Volume 2: Computer Technology ◽

10.1115/pvp2006-icpvt-11-93249 ◽

2006 ◽

Author(s):

Pei Gu ◽

R. J. Asaro

Keyword(s):

Stress Intensity ◽

Crack Propagation ◽

Stress Intensity Factors ◽

Three Dimensional ◽

Integral Approach ◽

Mode I ◽

Mode Ii ◽

Intensity Factors ◽

Mode Iii ◽

Mode Separation

For mixed-mode loading at a crack tip under small-scale yielding condition, mode I, mode II and mode III stress intensity factors control the crack propagation. This paper discusses three-dimensional mode separation to obtain the three stress intensity factors using the interaction integral approach. The 2D interaction integral approach to obtain mode I and mode II stress intensity factors is derived to 3D arbitrary crack configuration for mode I, mode II and mode III stress intensity factors. The method is implemented in a finite element code using domain integral method and numerical examples show good convergence for the domains around the crack tip. A complete solution for the three stress intensity factors is obtained for a bar with inclined crack face to the cross-section from numerical calculations. The solution for the bar is plotted into curves in terms of a set of non-dimensional parameters for practical engineering purpose. From the solution, mode mixity along the crack front and its implication to the direction of crack propagation is discussed.

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Determination of mode I and mode II fracture toughness of walnut and cherry in TR and RT crack propagation system by the Arcan test

Holzforschung ◽

10.1515/hf-2017-0063 ◽

2017 ◽

Vol 71 (12) ◽

pp. 985-990 ◽

Cited By ~ 4

Author(s):

Koji Murata ◽

Erik Valentine Bachtiar ◽

Peter Niemz

Keyword(s):

Fracture Toughness ◽

Crack Propagation ◽

Release Rate ◽

Strain Energy ◽

Shear Plane ◽

Mode I ◽

Mode Ii ◽

Mode Ii Fracture ◽

Mode Ii Fracture Toughness

AbstractTwo specimen types, each from walnut and cherry wood, were prepared for tangential-radial (TR) and radial-tangential (RT) crack propagation systems at 65% of RH and 20°C before mode I and mode II fracture toughness was determined through Arcan tests. It was found that fracture toughness in mode I is in agreement with literature data. In the mode II test, however, the crack propagated in the direction normal to the shear plane and not parallel to it. The release rate of strain energy in terms of the opening failure in mode II was lower than that in mode I. It can be concluded that it is difficult to determine the fracture toughness of RT or TR propagation in hardwood specimens in mode II.

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Simulation of reinforcement-corrosion-induced crack propagation in concrete by acoustic emission technique and boundary element method analysis

Canadian Journal of Civil Engineering ◽

10.1139/l07-028 ◽

2007 ◽

Vol 34 (10) ◽

pp. 1197-1207 ◽

Cited By ~ 6

Author(s):

A K.M Farid Uddin ◽

M Ohtsu ◽

K M.A Hossain ◽

M Lachemi

Keyword(s):

Acoustic Emission ◽

Stress Intensity ◽

Boundary Element Method ◽

Crack Propagation ◽

Boundary Element ◽

Moment Tensor ◽

Mode I ◽

Mode Ii ◽

Dimensionless Stress ◽

Element Method

Corrosion of reinforcement is one of the major causes of deterioration in reinforced concrete structures. Various crack patterns are nucleated around reinforcement in concrete due to expansion of corrosion products. Crack kinematics of locations, types, and orientations are quantitatively determined by the acoustic emission (AE) – simplified Green’s functions for moment tensor analysis (SiGMA) procedure in association with laboratory tests conducted on concrete specimens simulating corrosion-induced damage. These kinematic outcomes are obtained as three-dimensional (3-D) locations and vectors, and are thus visualized in 3-D by using virtual reality modeling language (VRML). Numerical analysis is conducted by the boundary element method (BEM) based on the concept of linear elastic fracture mechanics (LEFM) to clarify the mechanisms of corrosion-induced crack extension. Relationships between dimensionless stress intensity factors and cracking types are studied by BEM. Contributions of mode I and mode II failures are dependent on the cracking types. It is found that the process of crack propagation due to corrosion of reinforcement in concrete is mostly a mode I fracture with mixed-mode and, in a few cases, mode II fracture.Key words: acoustic emission, moment tensor, corrosion cracking, stress intensity factor.

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Effects of Thickness on Fracture Toughness of Carbon/Polyester Composite

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.471-472.886 ◽

2011 ◽

Vol 471-472 ◽

pp. 886-891

Author(s):

Mohammad Hossein Heydari ◽

Naghdali Choupani

Keyword(s):

Fracture Toughness ◽

Stress Intensity ◽

Stress Intensity Factors ◽

Mixed Mode ◽

Mode I ◽

Mode Ii ◽

Pure Mode ◽

Intensity Factors ◽

Interlaminar Fracture ◽

Polyester Composite

The aim of this paper is to evaluate interlaminar fracture toughness and non dimensional stress intensity factors of woven Carbon-Polyester composite based on numerical and experimental methods. A modified version of Arcan specimen was employed to conduct a mixed-mode fracture test using a special loading device. By changing the loading angle, α, from 0° to 90°, mode-I, mode-II and all mixed-mode data were created. The finite element analysis was performed with Abaqus software. The interaction j-integral was used to separate the mixed mode stress intensity factors and energy release rate at the crack tip under different loading conditions and different thickness of specimens. The results of fracture toughness tests revealed that the interlaminar fracture of composite is strong under the shearing-mode loading but weaker to the opening- mode loading. It can be seen that by increasing the thickness of the composite specimen, non dimensional stress intensity factors for pure mode I (α=0°) and pure mode II (α=90° ) loading conditions were decreased.

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The effect of friction on crack propagation in the dovetail fixings of compressor discs

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/0954406981521132 ◽

1998 ◽

Vol 212 (3) ◽

pp. 171-181 ◽

Cited By ~ 1

Author(s):

R L Burguete ◽

E A Patterson

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Crack Propagation ◽

Coefficient Of Friction ◽

Stress Intensity Factors ◽

Mode I ◽

Mode Ii ◽

Intensity Factors ◽

The Coefficient Of Friction

Stress frozen photoelasticity has been used to model dovetail compressor blade fixings. During loading a known coefficient of friction was applied and the effect of the variation of this parameter on crack initiation and propagation was investigated. Data were recorded from the specimen using an automated computer aided polariscope based on the method of phase stepping. Isochromatic and isoclinic data were collected and used to determine the stress distribution, the stress intensity factor and the crack propagation direction. The method to predict the direction of crack propagation has been improved so that photoelastic data can be used reliably for this purpose. Three values of the coefficient of friction were used for two different dovetail geometries. It was found that the initial values of the mode II stress intensity factors were higher for a lower friction coefficient. An increase in crack length produced a corresponding decrease in the mode I stress intensity factor and a decrease in the mode II value. It was concluded that the coefficient of friction influenced crack growth at all stages of crack growth because it affects the relative levels of the mode I and mode II stress intensity factors. This has an effect on the direction of the maximum principal stress direction and so on the direction of crack propagation.

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Experimental and Numerical Investigation of the Mixed-Mode Delamination of PAN Based Carbon/Epoxy Composite Using Modified Arcan Fixture

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.471-472.880 ◽

2011 ◽

Vol 471-472 ◽

pp. 880-885 ◽

Cited By ~ 1

Author(s):

M. Ziaee ◽

Naghdali Choupani

Keyword(s):

Fracture Toughness ◽

Stress Intensity ◽

Mixed Mode ◽

Sliding Mode ◽

Epoxy Composite ◽

Mode I ◽

Mode Ii ◽

Mixed Mode Fracture ◽

Pure Mode ◽

Element Analysis

The present research examines analytically and experimentally the mode-I and mode-II and mixed mode-Interlaminar fracture toughness of PAN based carbon/epoxy composite. A modified Arcan fixture, well-suited for the study of the behavior of used composite assemblies, was developed in order to focus on the analysis of the fracture behavior of the material. The edge effects are minimized by using an appropriate design of the substrates so that experimental results give reliable data. Also the mode-I and mode-II stress intensity factors were computed for different crack lengths and load orientation angles using finite element analysis. The numerical results show that the modified Arcan specimen is able to provide pure mode-I, pure mode-II and any mixed mode loading conditions. It is shown that the results obtained from the fracture tests are consistent very well with mixed mode fracture theories. Obtained results indicated that fracture toughness and stress intensity factor for sliding mode enhanced up when the loading angle increased. Mechanism of fracture and toughening were examined by using scanning electron microscopy.

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Dynamic Fracture Experiment of Medium with Defects under Impact Loading

Shock and Vibration ◽

10.1155/2021/8860929 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Chenglong Xiao ◽

Renshu Yang ◽

Chenxi Ding ◽

Cheng Chen ◽

Yong Zhao ◽

...

Keyword(s):

Stress Intensity Factor ◽

Stress Intensity ◽

Intensity Factor ◽

Crack Initiation ◽

Crack Propagation ◽

Dynamic Fracture ◽

Mode I ◽

Mode Ii ◽

Obvious Effect ◽

Initiation Stage

Defects have a significant effect on the dynamic fracture characteristics of the medium. In this paper, the dynamic fracture experiment of specimens with bias precracks is designed by utilizing the digital laser dynamic caustics system, and the effect of defect eccentricity on the dynamic fracture behavior is studied. Research shows that crack propagation can be divided into four stages: crack initiation stage, attraction stage, repulsion stage, and specimen fracture stage. The change of defect eccentricity has no obvious effect on the crack propagation behavior in the crack initiation stage and penetration stage but has a significant effect on the attraction stage and specimen fracture stage. In the process of the interaction between defect and crack, mode I stress intensity factor decreases at first and then increases. The decrease of mode I stress intensity factor reduces with the increase of defect eccentricity. The value of mode II stress intensity factor changes from negative to positive. With the increase of defect eccentricity, the symbol of mode II stress intensity factor no longer changes. The fractal dimension and the deflection angle of crack trajectory both decrease with the increase of defect eccentricity. In addition, a numerical simulation of the experiment is conducted by ABAQUS, which provides results that are in good agreement with the experimental results.

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