• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.2
• /
• pp.424-435
• /
• 1991

To develop the photoelastic experiment method for the orthotropic material under pure torsional moment is the main objective of this research. In the development of photoelastic experiment for orthotropic material under pure torsional moment, the important problems and their solutions are the same as following. In the model material for photoelastic experiment, it was found that C.F.E.C.(Copper Fiber Epoxy Composite) can be used as the model material of photoelastic experiment for orthotropic material. In the stress freezing cycle, it was assured that stress freezing cycle for epoxy can be used as the stress freezing cycle of the photoelastic experiment for orthotropic material. In the slicing method, it was found that the negative oblique slicing method can be effectively used as slicing method in 3-dimensional photoelastic experiment. In the measuring method of stress fringe values and physical properties in the high temperature, it was found that stress fringe values can be directly measured by experiment and physical properties can be directly or indirectly by equation between stress fringe values and physical properties developed by author. In the stress analysis method of orthotropic material under pure torsional moment by photoelastic experiment, it will be studied in the second paper.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.228-233
• /
• 2008

The reflection type photoelastic experiment can be used more effectively than the transparent type photoelastic experiment in industrial fields. However, the reflection type photoelastic experiment for orthotropic material has not been studied. Therefore, the reflection type photoelastic experimental hybrid method for the fracture mechanics of orthotropic material was developed in this research. Comparing the results obtained from this method with those from the hybrid method for isotropic material about the same isotropic specimen, the validity of this method was verified. And then, the reflection type photoelastic experiment for orthotropic material was applied to the orthotropic plates with a central crack of the various inclined angle. Using this hybrid method for the orthotropic material, it is able to obtain stress intensity factors and separate stress components at the vicinity of the crack-tip in orthotropic plates from only the isochromatic fringe patterns of isotropic coating material.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.11
• /
• pp.1799-1806
• /
• 2004

The static photoelastic experiment was applied to orthotropic materials. And then the specimens used in photoelastic experiment were fractured under static load. The static photoelastic experimental hybrid method for orthotropic material was introduced and its validity had been assured. Crack propagation criterion used the stress components, which are considered the higher order terms, obtained from the static photoelastic experimental hybrid method was introduced and it was applied to the minimum strain energy density criterion, the maximum tangential stress criterion and mode mixity. Comparing the actual initial angle of crack propagation with the theoretical initial angle of crack propagation obtained from the above failure criterions, the validities of the above two criterions are assured and the optimal distance (${\gamma}$) from the crack-tip is 0.01mm in order to get the initial angle of crack propagation of orthotropic material(C.F.E.C.).

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.8
• /
• pp.1273-1280
• /
• 2003

In this paper, transparent dynamic photoelastic experimental hybrid method for propagating cracks in orthotropic material was developed. Using transparent dynamic photoelastic experimental hybrid method, we can obtain stress intensity factor and separate the stress components from only isochromatic fringe patterns without using isoclinics. When crack is propagated with constant velocity, the contours of stress components in the vicinity of crack tip in orthotropic material are similar to those of isotropic material or orthotropic material with stationary crack under the static load. Dynamic stress intensity factors are decreased as crack growths. It was certified that the dynamic photoelastic experimental hybrid method was very useful for the analysis of the dynamic fracture mechanics.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.8-18
• /
• 1988

In the composite structures or the concrete structures, to analyze stress concentration factor, stress distributions and fracture mechanics of them under forces by photoelastic experiment, it is natural that to develope photoelastic model material for them is surely necessary. Thus, the orthotropic photoelastic model material for the transparent type photoelastic device was developed in the paper, it is called Copper Fiber Epoxy Composite and abbreviated as E.F.E.C. It was found that C.F.E.C. developed in this paper was satisfied with the properties of photoelastic model material that the photoelastic model material should have and that C.F.E.C. had completely properties of composite material. It is thought that C.F.E.C. can be applied to both medical engineering for modeling biological tissue and to the aerospace industry as orthotropic photoelastic material.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.1
• /
• pp.23-36
• /
• 1990

The various composite materials have been developed with the development of high strength material and the increasement of composite material usage. Therefore many researchers have studied about the stress analysis and the fracture mechanics for composite materials through the experiment or the theory. Among the experimental methods, the photoelastic experiments have been used for the stress analysis of the isotropic structures or the anisotropic structures. To analyze the stresses in the orthotropic material with photoelastic experiment, the basic physical properties ( $E_{L}$, $E_{T}$, $G_{LT}$ , .nu.$_{LT}$ ) and the basic stress fringe values ( $f_{L}$, $f_{T}$, $f_{LT}$ )are needed, therefore the relationships between the basic physical properties and the stress fringe values were derived in this paper. When the stress fringe value is very large, it was assured by the experiment that the relationships are established both in the room temperature and in the high temperature (T = 130.deg. C). Therefore the basic physical properties can be obtained from the relationships by measuring stress fringe values instead of measuring the basic physical properties.rties.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.292-297
• /
• 2000

In this research, the dynamic photoelastic experimental hybrid method for bimaterial is introduced. Dynamic biaxial loading device is developed, its strain rate is 31.637 s-1 and its maximum impact load is 20 ton. Manufactured methods for model of the dynamic photoelastic experiment for bimaterial are suggested. They are bonding method(bonding material: AW106, PC-1) and molding method. In the bonding method, residual stress is not occurred in the manufactured bimaterial. Crack is propagated along the interface or sometimes deviated from the interface. While in the molding method, residual stress is occurred in the manufactured bimaterial. Crack is always deviated from the interface and propagated in the epoxy region(softer materila). In order to propagate with constant velocity along the interface of bimaterial with arbitrary stiffer material, edge crack should be located along the interface of the acute angle side of the softer material in the bimaterial.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.102-107
• /
• 2001

Interfacial cracks between an isotropic and orthotropic material, subjected to static far field tensile loading are analyzed using the technique of photoelasticity. The fracture parameters are extracted from the full-field isochromatic data and the same are compared with that obtained using boundary collocation method. Dynamic Photoelasticity combined with high-speed digital photography is employed for capturing the isochromatics in the case of propagating interfacial cracks. The normalized stress intensity factors for static crack is greater when $\alpha=90^{\circ}C$ (fibers perpendicular to the interface) than when $\alpha=0^{\circ}C$ (fiber parallel to the interface) and those when $\alpha=90^{\circ}C$ are similar to ones of isotropic material. The dynamic stress intensity factors for interfacial propagating crack are greater when $\alpha=0^{\circ}C$ than $\alpha=90^{\circ}C$. The relationship between complex dynamic stress intensity factor $|K_D|$ and crack speed C is similar to that for isotropic homogeneous materials, the rate of increase of energy release rate G or $|K_D|$ with crack speed is not as drastic as that reported for homogeneous materials.