• Journal of the Society of Naval Architects of Korea
• /
• v.28 no.1
• /
• pp.108-116
• /
• 1991

In the non-linear behavior of many materials, there is difference between the monotonic behavior by static load and the cyclic behavior by cyclic load. In particular, the short fatigue cracks to propagate in elasto-plastic stress concentrations(notches), are governed significantly by the cyclic behavior of materials. Accordingly, it is needed to investigate and compare the monotonic and cyclic behavior of materials. In the pressent study, the stress-strain relations of materials by monotonic and cyclic load tests were examined for 2 kinds of steels(SS41, HT80) and 5 kinds of Al-alloys(A5083-O, A6N01-T5, A7N01-T4, A7016-T6, A7178-T6). And the constants for mechanical properties of the materials were determined by experimental results, Moreover, when a notch was subjected to cyclic load, the effect of cyclic hardening property of materials on the variation of stress-strain amplitude in the notch tip was discussed by the application of Neuber's rule and experiments for a center notched plate.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.37 no.4
• /
• pp.233-241
• /
• 2024

In this study, finite element analyses of coated steel pipes were conducted to research the development of sensing-based monitoring smart pipes. The coated steel pipes underwent a chemical coating pretreatment process that used modified polyethylene on both the inside and outside surfaces. Furthermore, the steel pipes were designed to minimize damage during the expansion process by incorporating connecting parts. To evaluate structural performance under various loads, four loading conditions were established: static structural analysis by earth pressure, fatigue life evaluation by vehicle load, and resistance to water leakage under both tensile and compressive loads. The analysis estimated a higher fatigue life for the developed steel pipe, compared with that of a steel pipe using ready-made epoxy coatings and joints. In addition, an average maximum displacement reduction of 56.1% and a maximum stress reduction of 61.2% were confirmed under identical conditions and diameters, thereby verifying the safety of the connecting parts of the developed coated steel pipe. Furthermore, the results of stress distribution contour analyses revealed superior water leakage resistance at the fastening parts, compared with the centers of the pipes.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2004.05a
• /
• pp.408-413
• /
• 2004

High speed planning boats also have been required more and more the rational strength analysis and evaluation for the optimal structural design in respect of the structural lightness according to the high speed trend. Even though the suggestion of the simple type equation for the equivalent dynamic pressure is reasonable to design the scantling of ship structure conveniently, many research activities for more reasonable improvement of the simple design pressure, have been continued to suggest the more accurate equivalent static description of tire structural response such as the deflection and stress of hull structure. In this research, we focus on the aluminum bottom stiffened plate structure in which structural scantling is mainly depend on the local loads such as dynamic or impact pressure without other load effects and structural response for the simple dynamic equivalent pressure was investigated through the structural analysis. In order to investigate the structural response of the bottom stiffened plate structure subjected to the dynamic equivalent design pressure, linear and nonlinear structural analysis of the bottom stiffened plate structure of 4.3 ton aluminum planning boat was performed based on the equivalent static applied loads which were derived from the KR regulation and representative one among various dynamic equivalent pressure equations. From above analysis results, we found that the response such as deflection and stress of plate member was similar with the response results of one plate member model with fixed boundary, which was published previous paper and in case of KR design loading, all response of stiffened plate structure were within elastic limit. Through the nonlinear analysis, nearly elastic behavior including the slight geometrical nonlinear response was dominant but plastic local zone was appeared at $85\%$ limit load. Therefore, we can say that through tire linear and nonlinear analysis, this stiffened plate member has no structural strength problem based on the yield criteria in case within $60\%$ limit load except the other strength point of view such as the fatigue and buckling problem.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.12
• /
• pp.5860-5866
• /
• 2012

BOLD technique in functional MRI has to apply multiple stimulations. However as the stimulation time increases failure rates rise. In this study we are proposing proper number of stimulations through our experiments. Ten normal people underwent functional MRI hand motor sanning and the paradigms were designed from first to seventh stimulation. Under Philips Intera Achieva 3.0T MR system and Invivo cop's Eloquence equipment, activation periods and rest periods were repeated ten times each, using BOLD EPI technique. Primary hand motor area stimulation and number of clusters, activation rates and number of activated clusters in and outside the region of interest were compared to each other. Number of clusters in region of interest was lower than others at second stimulation and became static from third stimulation. The stimulated ratios were elevated as the number of stimulations were increased but it was not proportional. Number of clusters outside the ROI became static from the third stimulation and started increasing from sixth stimulation. As results, given the activation ratios of ROI and out side the ROI, three times stimulation was the most appropriate because it does not affect accuracy, also decreasing the fatigue of patients by with the decreased scanning time.

• Composites Research
• /
• v.28 no.4
• /
• pp.219-225
• /
• 2015

Air spoiler, which can reduce the drag during operation, can be considered as a possible means to reduce carbon dioxide emission and to increase fuel efficiency. In this study, a composite air spoiler was designed and tested by static and repeated loads. The Green Water Pressure of 0.1 MPa a ship experiences during operation was perpendicularly applied to the air spoiler. Air spoiler was manufactured with sandwich panel which has glass fabric face and balsa core. Multiple sandwich panels were assembled to steel frame by bolt joint. The joint was designed to have bearing failure and examined by static and fatigue tests. Tests showed that the designed joint has enough margin of safety to endure joint failure. The developed sandwich panel to air spoiler is planned to be applied to a large scale commercial ship.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2004.05a
• /
• pp.337-341
• /
• 2004

Engineering ceramics have superior heat resistance, corrosion resistance, and wear resistance. Consequently, these art significant candidates for hot-section structural components of heat engine and the inner containment of nuclear fusion reactor. Besides, some of them have the ability to heal cracks and great benefit can be anticipated with great benefit the structural engineering field. Especially, law fracture toughness of ceramics supplement with self-healing ability. In the present study, we have been noticed some practically important points for the healing behavior of silicon nitride, alumina, mullite with SiC particle and whisker. The presence of silicon carbide (SiC) in ceramic compound is very important for crack-healing behavior. However, self-healing of SiC has not been investigated well in detail yet. In this study, commercial SiC was selected as sample, which can be anticipated in the excellent crack healing ability. The specimens were produced three-point bending specimen with a critical semi-circular crack of which size that is about $50-700{\mu}m$. Three-point bending test and static fatigue test were performed cracked and healed SiC specimens. A monotonic bending load was applied to cracked specimens by three-point loading at different temperature. The purpose of this paper is to report Strength Properties and Elastic Waves Characteristics of Silicon Carbide with Crack Healing Ability.

• Journal of Biomedical Engineering Research
• /
• v.33 no.2
• /
• pp.89-97
• /
• 2012

The purpose of this study is to develop the guideline of the physicochemical and mechanical properties evaluation for silicone gel filled breast implants. First of all, the use and development status for silicone gel filled breast implants were investigated, and then, standard and criteria about performance evaluation established by the international organizations such as ASTM, FDA guidance and ISO were examined. To evaluate the mechanical properties, data research and testing for breaking strength, elongation, tensile set, joint intensity, silicone gel cohesion, weight loss from heating, static rupture resistance, impact resistance test, fatigue test, and gel bleed were performed. On the other hand, to evaluate the physicochemical properties, volatile matter, extent of cross linking, heavy metals, and extractable were analyzed. In this study, results for general function, mechanical properties and physicochemical properties were examined and reviewed for the accordance with international standard, and objective and standardized guideline was provided.

• Structural Engineering and Mechanics
• /
• v.63 no.6
• /
• pp.735-742
• /
• 2017

Steel cables as the most important components are widely used in the certain types of structures such as cable-supported bridges, but the long-span structures may result in an increase in fatigue under high stress and corrosion of steel cables. The traditional steel cable is becoming a more evident hindrance. Fiber Reinforced Polymer (FRP) cables with lightweight, high-strength are widely used in civil engineering, but there is little research in vibrational characteristics of FRP cables, especially on the damping characteristic. This article studied the two methods to evaluate dynamical damping characteristic of basalt FRP(BFRP) and glass FRP(GFRP) cables. First, the vibration tests of the B/G FRP cables with different diameter and different cable force were executed. Second, the cables forces were calculated using dynamic strain, static strain and dynamic acceleration respectively, which were further compared with the measured force. Third, experimental modal damping of each cables was calculated by the half power point method, and was compared with the calculation by Rayleigh damping theory and energy dissipation damping theory. The results indicate that (1) The experimental damping of FRP cables decreases with the increase of cable force, and the trend of experimental damping changes is roughly similar with the theoretical damping. (2) The distribution of modal damping calculated by Rayleigh damping theory is closer to the experimental results, and the damping performance of GFRP cables is better than BFRP cables.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.1
• /
• pp.117-125
• /
• 2014

The temperature distribution of steady state rolling tires with detailed tread blocks is numerically predicted using the three dimensional full patterned tire model. A three dimensional periodic patterned tire model is constructed by copying 1-sector mesh in the circumferential direction. Using the static tire contact analysis, the strain cycles during one revolution are approximated with the strains at Guassian points of the elements which are sector-wise repeated within the same circular ring of elements, by neglecting the tire rolling effect. Based upon the multi-axial fatigue theory, the maximum principal strain is used to represent the combined effect of six strain components on the hysteretic loss. In the following, the deformation due to the inflation and vertical load is calculated using ABAQUS. Then heat generation rate in each element is calculated using an in-house code. Lastly, temperature distribution is calculated using ABAQUS again. Through the numerical experiments, the validity of the proposed prediction method is examined by comparing with the experiment and the temperature distribution of a patterned tire model is compared with those of the main-grooved simple tire model.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.3
• /
• pp.148-156
• /
• 2013

Since the demand for new military vehicle to fulfill the necessary conditions such as multi-purpose, high-mobility, and survivability has raised continuously from the army, the prototype of a Korean light tactical vehicle was developed to meet these requirements using our own technology. In particular, the new tactical vehicle was equipped with a double wishbone independent suspension to improve ride and handling and maximize off-road driving performance. In this paper, a comprehensive virtual durability process to evaluate the service life of the prototype is presented. A reliability of the trimmed body model based on CATIA data was verified by comparison result between mode analysis and modal test. The dynamic model was constructed using ADAMS/Car, and then the weight distribution and lateral slope driving performance of it were compared with the results of static weight and lateral slope tests. The validity of the VTL(Virtual Test Lab) was checked with test results from the 3-inch spaced impact road. The durability performances of trimmed body and suspension components were evaluated through MSM(Modal Superposition Method) fatigue analysis. It is shown that the virtual durability process could be a helpful tool to find out the weak areas and improve their structures in developing new military vehicle.