• Geomechanics and Engineering
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• v.33 no.4
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• pp.393-400
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• 2023

Displacements near crack and stress intensity factor (SIF) are key parameters to solve rock failure issue when using fracture mechanics. In order to study the horizontal displacement and stress intensity factor of the mode I fracture, a series of three-point bending tests of granite specimens with central notch were carried out. The evolution of horizontal displacements of precast notch and crack tip opening displacements (CTOD) were analyzed based on the digital image correlation (DIC) method. Stress intensity factors for three-point bending beams with arbitrary span-to-width ratios(S/W) were calculated by using the WU-Carlsson analytical weight function for edge-crack finite width plate and the analytical solution of un-cracked stress by Filon. The present study provides a high efficient and accurate method for fracture mechanics analysis of the three-point bending granite beams.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.282-286
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• 2001

In this study, CT specimens were prepared from spring steel(SUP9) processed shot peening which was room temperature, low temperature and high temperature experiment. And we got the following characteristics from fatigue crack growth test carried out in the environment of room, low temperature and high temperature at $25^{\circ}C$,$-30^{\circ}C$,$-50^{\circ}C$,$-70^{\circ}C$ and $-100^{\circ}C$ in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range $\Delta K_{th}$ in the early stage of fatigue crack growth (Region I ) and stress intensity factor range $\Delta K$ in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.106-111
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• 2003

This study made an experiment On fatigue crack propagation da/dn, stress intensity factor range ${\Delta}K$ respectively in room temperature and in low temperature. And we got the following characteristics from fatigue crack growth test carried Out in the environment of room temperature and law temperature at $25^{\circ}C$, $-60^{\circ}C$, $-80^{\circ}C$, and $-100^{\circ}C$ in the range of stress ratio of 0.3 by means of opening made displacement. The threshold stress intensity factor range ${\Delta}Kth$ in the early stage of fatigue crack growth (Mode I) and stress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Made II) was decreased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at law temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Computers and Concrete
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• v.19 no.5
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• pp.509-514
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• 2017

Concrete retaining walls are the most common types of geotechnical structures for controlling instable slopes resulting from lateral pressure. In analytical stability, calculation of the concrete retaining walls is regarded as a rigid mass when its safety is required. When cracks in these structures are created, the stability may be enforced and causes to defeat. Therefore, identification, creation and propagation of cracks are among the important steps in control of lacks and stabilization. Using the numerical methods for simulation of crack propagation in concrete retaining walls bodies are among the new aspects of geotechnical analysis. Among the considered analytical methods in geotechnical appraisal, the boundary element method (BEM) for simulation of crack propagation in concrete retaining walls is very convenient. Considered concrete retaining wall of this paper is Pars Power Plant structured in south side in Assalouyeh, SW of Iran. This wall's type is RW6 with 11 m height and 440 m length and endurance of refinery construction lateral forces. To evaluate displacement and stress distributions (${\sigma}_{1,max}/{\sigma}_{3,min}$), the surrounding, especially in tip and its opening crack BEM, is considered an appropriate method. By considering the result of this study, with accurate simulation of crack propagation, it is possible to determine the final status of progressive failure in concrete retaining walls and anticipate the suitable stabilization method.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.65-70
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• 2001

In this study, CT specimens were prepared from spring steel(SUP9) processed shot peening which was room temperature, low temperature and high temperature experiment. And we got the following characteristics from fatigue crack growth test carried out in the environment of room, low temperature and high temperature at $25^{\circ}C$, -3$0^{\circ}C$, -5$0^{\circ}C$, -7$0^{\circ}C$, -10$0^{\circ}C$ and 5$0^{\circ}C$, 10$0^{\circ}C$ , 15$0^{\circ}C$, 18$0^{\circ}C$ and in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range $\DeltaK_{th}$ in the early stage of fatigue crack growth (Region I ) and stress intensity factor range ΔK in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.535-541
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• 2018

In this study, wedge splitting tests were performed to evaluate fracture behavior of particle reinforced composite materials. Crack resistance was evaluated by using CTOD (crack tip opening displacement) and crack tip opening angle (CTOA). The particle reinforced composites were tested under various temperature ($-60^{\circ}C{\sim}50^{\circ}C$) and load speed (5~500mm/min). Also, digital image correlation method (DIC) was used to analyze the strain field at crack tip. Test results showed that the fracture energy increased with decreasing temperature and crack resistance increased with increasing load velocity.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.167-172
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• 2002

In this study, CT specimens were prepared from spring steel(SUP9) processed shot peening which was room temperature, high temperature experiment. And ire got the following characteristics from fatigue crack growth test carried out in the environment of room, and high temperature at $25^{\circ}C,\;100^{\circ}C,\;150^{\circ}C$ and $180^{\circ}C$ in the range of stress ratio of 0.3 by means of opening mode displacement. The threshold stress intensity factor range ${\Delta}Kth$ in the early stage of fatigue crack growth (Region I) and stress intensity (actor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1886-1895
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• 1999

The delamination behavior of multidirectional carbon-fiber/epoxy composite laminates under 10NA intermediate and high rates of test, up to rate of about 11.4m s has been investigated using the double cantilever beam specimens. The mode I loading under rates above l.0m/s showed considerable dynamic effects on the load-time curves and thus higher values of the average crack velocity than that expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Based on the assumption of constant flexural modulus, values of $G_{IC}$ at the crack initiation and arrest were decreased with an increase of the test rate up to 5.7m/s, but the maximum $G_{IC}$ was increased at 11.4m/s.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.15-22
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• 2003

The fatigue crack growth model is derived and the retardation model is proposed. The fatigue crack growth model considers the residual plastic stretch on the crack surface which results from the plastic deformation at the tip of fatigue crack. The fatigue crack growth rate is calculated by using the cumulative fatigue damage and plastic strain energy in the material elements at the crack tip. This model gives the crack growth rate in reasonable agreement with test data for aluminum alloy AL6061-T651 and 17-4PH casting steel. The fatigue crack growth retardation model is based on the residual plastic stretch produced from a tensile overload which reduced the plastic strain range of the following load cycles. A strip-yield model of a crack tip plasticity is used for the calculation of a plastic zone size. The proposed retardation model characterized the observed features and delayed retardation of the fatigue crack growth under tensile overload.

• Computational Structural Engineering : An International Journal
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• v.1 no.2
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• pp.117-130
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• 2001

Investigations of low-rice unbounded reinforced concrete shear walls with or without openings are performed with comparison of analytical and experimental results. Theoretical analysis is based on nonlinear finite element algorithm, which incorporates concrete failure criterion and nonlinear constitutive relationships. Studios focus on the effects of height-to-length ratio of shear walls, opening ratio, horizontal and vertical reinforcement radios, and diagonal reinforcement. Analytical solutions conform well with experimental results. Equations for cracking, yielding and ultimate loads with corresponding lateral displacements are derived by regression using analytical results and experimental data. Also, failure modes of low-rise unbounded shear walls are theoretically investigated. An explanation of change in failure mode is ascertained by comparing analytical results and ACI code equations. Shear-flexural failure can be obtained with additional flexural reinforcement to increase a wall's capacity. This concept leads to a design method of reducing flexural reinforcement in low-rise bounded solid shear wall's. Avoidance of shear failure as well as less reinforcement congestion leer these walls is expected.