• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1863-1870
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• 2000

When an impact stress is applied on the external boundary of double cantilever beam of orthotropic material which crack length is greater than specimen hight and anistropic ratio is very high, dyna mic energy release rate is derived, and the relationship between dynamic energy release rate and crack propagating velocity is studied. Dynamic energy release rate to static energy release rate is decreased with increasment of crack propagating velocity. The relationships between dynamic energy release rate and vertical strain have a similar pattern with those between static energy release rate and vertical strain. When normalized time(Cstla) is greater than or equal to 2, dynamic energy release rate approaches to a constant value.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2792-2799
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• 1996

It was shown in the previous study that the numerically derived elastic work factor for CLS specimen was independent of fiber direction for a unidirectional case. Also, it was proposed the elastic work factor could be used to determine energy release rate from a single test record. In the present study, elastic work factor was derived from a simple beam theory to investigate its dependence on material property and geometric condition. Also, the elastic work factor of CLS specimen was applied experimentally to determine critical energy release rate in order to prove its validity determining critical energy release rate from a single specimen. For this purpose, critical energy release rate determined using the elastic work factor was compared with that determined by the compliance method. The results showed that while elastic work factor is affected by $t_2/t_1$ and $L_2/L_1$ it is independent of fiber angle for a unidirectional case. It was also found that critical energy release rates determined by both methods are comparable each other, thus elastic work factor approach can be used to determine energy release rate from a single test specimen.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.04a
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• pp.1-6
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• 2001

In this paper, edge delaminations in cracked composite plates are analytically investigated. A theoretical model based upon a sub-laminate approach is used to determine the strain energy release rate, $G^{ed}$, in [$\pm$$\theta_m$/$90_n$]$_s$ carbon/epoxy laminates loaded in tension. The analysis provides closed-form expressions for the reduced stiffness due to edge delamination and matrix cracking and the total energy release rate. The parameters controlling the laminate behaviour are identified. It is shown that the available energy for edge delamination is increased notably due to transverse ply cracking. Also thermal stresses increase substantially the strain energy release rate and this effect is magnified by the presence of matrix cracking. Prediction for the edge delamination onset strain is presented and compared with experimental data. The analysis could be applied to ceramic matrix composite laminates where similar mechanisms develop, but further experimental evidence is required.

• Coupled systems mechanics
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• v.12 no.1
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• pp.69-81
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• 2023

This paper considers a delamination analysis of a statically undetermined inhomogeneous beam structure of rectangular section with viscoelastic behavior under torsion. The beam is built in at its two ends. The beam has two longitudinal inhomogeneous layers with a delamination crack between them. A notch is made in the upper crack arm. The external torsion moment applied on the beam is a function of time. Under these conditions, the beam has one degree of indeterminacy. In order to derive the strain energy release rate, first, the static indeterminacy is resolved. Then the strain energy release rate is obtained by analyzing the balance of the energy with considering the viscoelastic behavior. The strain energy release rate is found also by analyzing the compliance of the beam for checkup. Solution of the strain energy release rate in a beam without a notch in the upper crack arm is derived too. In this case, the beam has two degrees of static indeterminacy (the torsion moment in the upper crack arm is treated as an additional internal redundant unknown). A parametric investigation of the strain energy release rate is carried-out.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.97-107
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• 1995

Global postbuckling analysis is accomplished for one-dimensional and two-dimensional delaminations. A new finite element model, which can be used to model the global postbuckling analysis of one-dimensional and two-dimensional delaminations, is presented. In order to calculate the strain energy release rate, geometrically nonlinear analysis is accomplished, and the incremental crack closure technique is introduced. To check the effectiveness of the finite element models and the incremental crack closure technique, the simplified closed-form sloution for a through-the-width delamination with plane strain condition is derived and compared with the finite element result. The finite element results show good agreement with the closed-foul1 solutions. The present method was extended to calculate the strain energy release rate for two-dimensional delamination. For a symmetric circular delamination, the strain energy release rate shows great variation along the delamination front. and the delamination growth appears to occur perpendicular to the loading direction.

• Coupled systems mechanics
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• v.11 no.3
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• pp.217-231
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• 2022

The present paper is concerned with a delamination analysis of a multilayered frame structure that exhibits non-linear creep behavior. A solution to the strain energy release rate is obtained by considering the time-dependent complementary strain energy in the frame. The mechanical behavior of the frame is treated by using a non-linear stress-strain-time relationship. The time-dependent solution to the strain energy release rate obtained in the present paper holds for a multilayered frame made of arbitrary number of adhesively bonded layers of different thicknesses and material properties. Besides, the dealamination is located arbitrary along the thickness. The solution to the strain energy release rate is verifiedby applying the J-integral approach. A parametric study of the strain energy release rate is carried-out. Two three-layered frame configurations are analyzed in order to evaluate the influence of the delamination crack location along the thickness on the strain energy release rate. The strain energy release is analyzed also for the case when a notch is cut-out in the inner delamination crack arm. The results obtained are compared with these for a frame without a notch.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2172-2180
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• 1993

Under general loadings, including body forces, crack-face tractions and thermal loading, the energy release rate equation for a two-dimensional cracked body is presented. Defining the virtual crack extension as the variation of the geometry, the equation is directly derived by a shape design sensitivity of the potential energy. Although the form of the derived energy release rate equation is different from other researchers's results, the three example show that the former is exactly the same as the latter. However, the final integral equation do not involve the derivative of the displacement on the crack surface and crack tip region, thereby improving the numerical accuracy in the computation of the energy relase rate. Moreover, as it was derived from the governing equation including non-linear elasticity without special assumptions, the energy release rate of a elasto-plastic fracture can be obtained and any numerical stress analysis method can be applied.

• Advances in materials Research
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• v.12 no.1
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• pp.15-29
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• 2023

In this paper, fracture analysis of a continuously inhomogeneous arch structure with two longitudinal cracks is developed in terms of the time-dependent strain energy release rate. The arch under consideration exhibits non-linear creep behavior. The cross-section of the arch is a rectangle. The material is continuously inhomogeneous along the thickness of the cross-section. The arch is loaded by two bending moments applied at its end sections. The mechanical behavior of the material is described by using a non-linear stress-strain-time relationship. The two longitudinal cracks are located symmetrically with respect to the mid-span of the arch. Due to the symmetry, only half of the arch is considered. Time-dependent solutions to strain energy release rate are obtained by analyzing the balance of the energy. For verification, time-dependent solutions to the strain energy release rate are derived also by considering the time-dependent complementary strain energy. The evolution of the strain energy release rate with the time is analyzed. The effects of material inhomogeneity, locations of the two cracks along the thickness of the arch and the magnitude of the external loading on the time-dependent strain energy release rate are evaluated.

• Geomechanics and Engineering
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• v.14 no.5
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• pp.439-451
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• 2018

The stress path characteristics of surrounding rock in the formation of gob were analysed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analysing the instability of deep gob was established based on the mechanism of stress relief in deep mining. The energy evolution law was investigated by introducing the local energy release rate index (LERR), and the energy criterion of instability of surrounding rock was established based on the cusp catastrophe theory. The results showed that the evolution equation of the local energy release energy of the surrounding rock was quartic function with one unknown and the release rate increased gradually during the mining. The calculation results showed that the gob was stable. The LERR per unit volume of the bottom structure was relatively smaller, which mean the stability was better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meet the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release, transfer and dissipation which provided an important reference for the study of the stability of deep mined out area.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1486-1496
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• 2000

The initial flame kernel development and flame propagation in a constant volume combustion chamber is analyzed by the heat release rate and the mass fraction burnt. The combustion pressure is measured with a piezoelectric type pressure sensor. In order to evaluate the effects of ignition system and ignition energy on the flame propagation, four different ignition systems are designed and tested, and the ignition energy is varied by the dwell time. Several different spark plugs are also tested and examined to analysis the effects of electrodes on flame kernel development. The results show that the when the dwell time is increased, and when the spark plug gap is extended, heat release rate and the mass burnt fraction are increased. The materials and shapes of electrodes affect the flame development, because they change the energy transfer efficiency from electrical energy to chemical energy. The diameter of electrodes influences not only the heat release rate but also the mass burnt fraction as well.