• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.694-701
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• 2013

The gear-reduction units of Korean high-speed trains consist of a motor reduction unit, an axle gear box reduction unit, and a tripod joint shaft. A reduction gear unit is a gearbox used to reduce the rotational speed of the input shaft to a slower rotational speed on the output shaft. This reduction in output speed helps to increase torque. Defective reduction gear units in high-speed trains are caused by damage to the gear or by gear fatigue. To diagnose potential problems, it is important to know the vibration characteristics of the reduction gear units. In this study, we analyzed the vibration characteristics of reduction gears under various conditions. The test setup included a full-scale test rig to evaluate reduction gear under both normal and extreme operating conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.544-544
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• 2014

Energy harvesting technology, which scavenges electric power from ambient, otherwise wasted, energy sources, has been explored to develop self-powered wireless sensors and possibly eliminate the battery replacement cost for wireless sensors. Among ambient energy sources, vibration energy can be converted into electric power through a piezoelectric energy harvester. For the last decade, although tremendous advances have been made in design methodology to maximize harvestable electric power under a given vibration condition, the research in reliability assessment to ensure durability has been stagnant due to the complicated nature of the multiple failure modes of a piezoelectric energy harvester, such as the interfacial delamination, fatigue failure, and dynamic fracture. Therefore, this study presents the first-ever system reliability analysis for multiple failure modes of a piezoelectric energy harvester using the Generalized Complementary Intersection Method (GCIM), while accounts for the energy conversion performance. The GCIM enables to decompose the probabilities of high-order joint failure events into probabilities of complementary intersection events. The electromechanically-coupled analytical model is implemented based on the Kirchhoff plate theory to analyze its output performances of a piezoelectric energy harvester. Since a durable as well as efficient design of a piezoelectric energy harvester is significantly important in sustainably utilizing self-powered electronics, we believe that technical development on system reliability analysis will have an immediate and major impact on piezoelectric energy harvesting technology.

• Journal of Convergence for Information Technology
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• v.11 no.3
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• pp.250-260
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• 2021

The purpose of this study is to investigate muscle function and symmetry index during whole body vibration exercise using lower extremity training posture for throwing athletes. For throwing athletes in their 20s(6 males, 4 females, age: 24.60±0.92years, height: 177.90±7.40cm, weight: 92.90±22.97kg), lower extremity training postures with squat, carphrase, and lunge movements. Whole body vibration exercise training was performed using. Tensiomyography(TMG) variables Time Delay(Td), Time Contraction(Tc), Time Sustain(Ts) Time Relaxation(Tr), and Displacement Maximumal(Dm) in the lower extremity joint muscles(biceps femoris(BF), gastrocnemius lateral(GL), gastrocnemius medial(GM), rectus femoris(RF), tibialis anterior(TA), lateral vastus(LV), medial latissimus(ML)), were measured to compare and analyze muscle activity, muscle fatigue, and left-right symmetry. The results of the study are left RF, VL, right VM (p<.05) in Td, VM (p<.05) in Tc, GM in Ts (p<.05), left RF in Tr, and right TA (p<. 05) showed a change. Therefore, it has been proven that various whole-body vibration training is an effective exercise with changes in muscle contraction, and stability of the core is secured by symmetry of the left and right muscles. For this reason, the whole body vibration exercise will have a positive effect on rehabilitation training, and it is believed that it will be able to improve performance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.363-373
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• 1995

In this study, a FE model tuning method using experimental modal data was suggested after examining all the published conventional methods. The idea of this method is introducing scale factors to maintain both the structural connectivity and the consistency in the corrected stiffness matrix which makes it always possible to interpret the stiffness elements with the corresponding physical configuration of the targeting structure. The scale factors are determined to minimize the objective function of eigen-properties. The proposed method was tested to determine the joint stiffness of a T shaped beam. The test results were also compared with the tuned stiffness obtained from a probed commercial package (SYSTUNE) and found that this method is very accurate and compatible.

• Earthquakes and Structures
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• v.23 no.6
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• pp.535-547
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• 2022

Handball sport, as its name postulates, is a team sport which highly physical workout. During a handball play, several ball impacts are applied on the hands resulting vibration in the forearm, upper arm, shoulders and in general in whole body. Hand has important role in the handball's game. So, understanding about the dynamics and some issues that improve the stability of the hand is important in the sport engineering field. Ulna and radius are two parallel bones in lower arm of human hand which their ends are located in elbow and wrist joint. The type of the joint provides the capability of rotation of the lower arm. These two bones with their ends conditions in the joints constructs a 4-link frame. The ulna is slightly thinner than radius. So, understanding about hand kinematics in handball's game is an important thing in the engineering field. So, in the current work with the aid of a multi-physics simulation, dynamic stability analysis of the ulna and radius bones will be presented in detail.

• The Journal of the Convergence on Culture Technology
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• v.8 no.4
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• pp.407-413
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• 2022

In this study, the empirical formula for evaluating cable tension based on long-term measurement for about 3 years according to temperature change was proposed by proving the correlation between the expansion joint displacement of the upper road bridge and the cable tension of the lower railway bridge. The tension prediction results using the empirical formula for tension evaluation each cables proposed in this study were found to be in good agreement with the cable tension using the vibration method within 3%. Therefore, it was analyzed that it could be applied together with the vibration method that was an experimental technique, to predict and evaluate the cable tension in serviced railway steel composite bridge. As a result of applying the estimated temperature calculated by the empirical formula for expansion proposed in this study to the empirical formula, it was analyzed that a high level of reliability could be secured when compared with the vibration method. Therefore, it is judged that the empirical formula for cable tension evaluation reflecting the estimated temperature proposed in this study can be used to predict the tension of cables according to climate change in the future and establish a maintenance plan.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.93-100
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• 1993

With increasing technology, requirement to car noise and related dynamics are getting competitive keypoint. Unfortunately, vibro - acoustic behavior of a car is nowadays only possible after development of prototypes. But, obviously, in the Area of Research, many of Industrials, Universities and research centers try to codevelop the design tools to predict the vibro-acoustic behaviors. At this stage, it is more realistic to represent the existing technologies in order for the engineer to get their own know-how to design and to Integrate existing techniques, to setup their test facility, and to develope some tools with which they can successfully predict noise levels of car in the design phase. Moreover, most of the theories which will be represented in this paper can be used in the design phase. At any way, finding the cause of trouble shooting is more urgent than the design of a car to the test engineer. In this paper, transfer path analysis, noise source identification, and the key test method of modal analysis is introduced. Later, if I get the opportunity to present in KSNVE, the approach method of modal analysis is introduced. Later, if I get the opportunity to present in KSNVE, the approach method of finding characteristics of joint and welding part will be introduced. Most parts of this paper was quoted from the papers of LMS.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.642-651
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• 2009

The history of excavator design is not long enough which still causes most of the design considerations to be focused on static analysis or simple functional improvement based on static analysis. However, the real forces experiencing on each component of excavator are highly transient and impulsive. Therefore, the prediction and the evaluation of the movement of the excavator by dynamic load in the early design stage through the dynamic transient analysis of the excavator and ensuring of design technique plays an importance role to reduce development-cost, shorten product-deliver, decrease vehicle-weight and optimize the system design. In this paper, Commercial software DADS and ANSYS help to develop the track model of the crawler type excavator, and to evaluate the performance and the dynamic characteristics of excavator with various simulations. For that reason, the track of crawler type excavator is modelled with DADS Track Vehicle Superelement, and the reaction forces on the track rollers were predicted through the driving simulation. Also, the upper frame and cabin vibration characteristics, at the low RPM idle state, were evaluated with engine rigid body modelling. And flexibility body effects were considered to determine the more accurate joint reaction forces and accelerations under the upper frame swing motion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.645-651
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• 2019

This study examined the correlation between the forward head posture (FHP), temporomandibular joint disorder (TMD), and temporomandibular joint quantitative somatosensory sensation. This study examined the correlation between the temporomandibular joint function and somatosensory sensation according to the change in FHP after the intervention on the head posture in 62 subjects (22.15 ± 2.56 years) Biofeedback training was administered to the FHP, which was performed 12 times for a total of four weeks. To assess the FHP, the craneovertebral angle (CVA) was examined. The temporomandibular joint (TMJ) function was measured by the Therapeutic Range of Motion Scale and the left and right lateral deviation, and the sensation of vibration threshold was measured to confirm the change in somatic sensation. Multiple regression analysis was performed to confirm the influence of each variable and Pearson's correlation analysis was performed to assess the correlation. Changes in the temporal joint function (p<.001) and somatic sensation (p<.001) were correlated significantly with the changes in CVA. These results show that there is a significant correlation between the frontal head position, TMJ function, and somatosensory sensation. These results provide a new paradigm for the treatment of jaw joints for patients suffering from TMD and provide a basis for the future treatment of the temporomandibular joint.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.61-69
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• 2011

The noise and vibration which are occurred by equipment and rail under the train are directly delivered to passenger and effect on comfort. For this reason, Floating floor structure has been applied to Rolling Sotck for minimizing the noise and vibration. And in respect of Floating floor, the strength is an important design element. Because the train has many heavy equipments and accommodates lots of passenger. At the early design stage of Floating floor, different joint type and thickness of plywood, etc. were applied and some problem happened. To solve the problems and apply to the future projects, the standard model of Floating floor structure was required. To find optimum design and standard model for Floating floor structure of Rolling Stock, the applied Floating floor models were analysed by CAE (computer-aided engineering).