• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.10
• /
• pp.84-91
• /
• 2008

Due to the complexity of the engineering problems, it is difficult to obtain directly the stress field around the crack tip by theoretical derivation. In the paper, the hybrid method is employed to calculate full-field stress around the crack tip in uni-axially leaded finite width tensile plate, using the displacement data of given points calculated by finite element method as input data. The method uses complex variable formulations involving conformal mappings and analytical continuity. In order to accurately compare calculated fringes with experimental ones, both actual and reconstructed photoelastic fringe patterns are two times multiplied and sharpened by digital image processing. Reconstructed fringes by hybrid method are quite comparable to actual fringes. The experimental results indicate that Mode I stress intensity factor analyzed by the hybrid method are accurate within a few percent compared with ones obtained by empirical equation and finite element analysis.

• The Korea Journal of Herbology
• /
• v.38 no.2
• /
• pp.1-7
• /
• 2023

Objectives : From this study, we sight to identify Anti-stress effect of Chenwangbosim-Dan (Tianwangbuxin-Dan) Extract∘Fermented Rice Extract (GABA : gamma-aminobutyric acid 30%) Complex Methods : In order to measure the degree of functional evaluation of tension relief due to stress, it was evaluated whether the psychological indicators VAS(Visual Analog Scale) and POMS(Profile Of Mood State) were improved. Which is generally used for stress measurement and has a high frequency of clinical use. All clinical trial subjects were required to take the drug once a day at 9 ± 30 min in the morning for 2 weeks. Results : After intake, the group that Chenwangbosim-Dan(Tianwangbuxin-Dan) Extract∘Fermented Rice Extract (GABA : gamma-aminobutyric acid 30%) Complex had a statistically significant improvement effect compared to before intake due to an improved 30.81% of the VAS scores. The POMS-T score improved 54.13%, the POMS-V score improved 117.5% and the POMS-F score improved 59%, which had a statistically significant effect compared to Placebo group (p<0.001). There is a significant difference between two group, so even considering the placebo effect, the anti stress effect was confirmed in the Chenwangbosim-Dan (Tianwangbuxin-Dan) Extract∘Fermented Rice Extract (GABA : gamma-aminobutyric acid 30%) Complex intake group. Conclusions : The above results showed that the Chenwangbosim-Dan(Tianwangbuxin-Dan) Extract∘Fermented Rice Extract (GABA : gamma-aminobutyric acid 30%) Complex had an anti-stress effect. Therefore, it is expected to be developed as a safe and comfortable mental care health functional food that can reduce the risk of drug abuse.

• Journal of Mechanical Science and Technology
• /
• v.15 no.2
• /
• pp.172-179
• /
• 2001

The effects of the interface and two holes located near the crack path in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system. The dynamic stress field around the dynamically propagating interface crack tip in the three point bending specimens under a dynamic load applied by a hammer dropped from 0.6m high without initial velocity are recorded. The complex stress intensity factors for the dynamically propagating interface crack are extracted by using a overdeterministic least square method. Theoretical dynamic interface isochromatic fringe loops generated by using the numerically determined complex stress intensity factors are compared with the experimental results. Furthermore, the influence of the hole to the dynamic interface crack velocities has been investigated experimentally.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.12
• /
• pp.2165-2171
• /
• 1997

The analysis model is the infinite power law creep material containing the rigid inclusion with crack shape. The present analysis is performed using the complex pseudo-stress function method. The strain rate intensity factor is developed as new fracture mechanics parameter which represents the stress and strain rate distribution near a crack tip in power law creep material. The strain rate intensity factor is developed in terms of Kolosoff stress functions.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.4
• /
• pp.1186-1193
• /
• 1996

The analytic solution of the stress field at creep crack in the presence of grain boundary caviation is to be obtained by solving the governing equation which was derived through the previous paper. The complex integral technique is used to slove the singular integral equation. under the help of the information about stress behaviors at the ends of integral region know by numerical solution. The resultant stress disstribution obtained shows the relaxed crack-tip singularity of $r^{1/2+\theta}$ due to the intervention of cavitation effect, otherwise, it should assumed to be $r^{1/2}$ singularity of linear elastic fracture mechanics with no cavitation.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.7
• /
• pp.208-216
• /
• 2003

In this paper, a two-dimensional electroelastic analysis is performed on a piezoelectric material with an open crack. The approach of Lekhnitskii's complex potential functions is used in the derivation and Bueckner's weight function theory is extended to piezoelectric materials. The stress intensity factors and the electric displacement intensity factor are calculated by the weight function theory.

• Tribology and Lubricants
• /
• v.37 no.2
• /
• pp.48-53
• /
• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.11a
• /
• pp.379-380
• /
• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.319-320
• /
• 2009

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.5 s.176
• /
• pp.1103-1114
• /
• 2000

Recent attempt to enhance the safety against collision reshaped the simple shell structures into the integrated complex shell structures. Moreover, due to various regulations continuously tightened for environment protection, weight reduction of automobiles becomes an increasingly important issue. Auto parts lightening is mainly accomplished by more reasonable design, adoption of lighter materials and miniaturization of the auto bodies. Focusing on the locally enhanced design approach among the above three ways, we here attempt to develop a patching optimization method, and also to determine the thicknesses of an integrated shell structure, both bringing a specified amount of stress relaxation. We first select a cross member as a patching optimization model. Based on the finite element stress calculations, we relieve the stress of cross member by patching in two ways-nonuniform thickness patching and optimized uniform thickness patching, the latter of which is more effective in a practical point of view for the preset amount of stress relaxation. Selecting a box type subframe as another finite element analysis model, we then determine the thickness of each part by axiomatic design approach for a preset amount of stress relaxation. The patching methodology and the axiomatic approach adopted in this work can be applied to the other complex shell structures such as center member and lower control arm.