• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.8
• /
• pp.965-970
• /
• 2010

Bolts and nuts are widely used to fasten mechanical parts together in machines and structures. The primary role of a nut is to maintain the axial force of a bolt. In this paper, a new type of a lock nut that uses a spring is studied. To have a spring within a nut, a cocking process to narrow the top of the nut is adopted, but cracking occurred in the process. In this study, strain of an initial model is measured using the finite element analysis program, MSC/Marc. The occurrence of the crack was studied by comparing the maximum observed strain of a model with the maximum strain indicated by an accurate stress-strain diagram of 1020 steel. Then, the structure of the lock nut was optimized by response surface analysis to prevent cracking. The prototype of the lock nut was manufactured on the basis of the optimization result, and cracking did not occur.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.34 no.6
• /
• pp.393-401
• /
• 2021

In this paper, we proposed a numerical model based on moment-curvature, to evaluate the resistance of reinforced concrete (RC) members subjected to blast loading. To consider the direct shear failure mode, we introduced a dimensionless spring element based on the empirical direct shear stress-slip relation. Based on the dynamic increase factor equations for materials, new dynamic increase factor equations were constructed in terms of the curvature rate for the section which could be directly applied to the moment-curvature relation. Additionally, equivalent bending stiffness was introduced in the plastic hinge region to consider the effect of bond-slip. To verify the validity of the proposed model, a comparative study was conducted against the experimental results, and the superiority of this numerical model was confirmed through comparison with the analytical results of the single-degree of freedom model. Pressure-impulse (P-I) diagrams were produced to evaluate the resistance of members against bending failure and direct shear failure, and additional parametric studies were conducted.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1530-1535
• /
• 2003

The automatic load transfer switch (ALTS) typically automatically transfers electrical loads from a normal electrical power source to an emergency electrical power source upon reduction or loss of normal power source voltage. It can also automatically re-transfer the load to the normal power source when the normal voltage has been restored within acceptable limits. The transfer operation of ALTS is accomplished by a spring-driven linkage mechanism. In this paper we build a dynamic model of driving mechanism for ALTS using ADAMS and checked the characteristics of the transfer operation. Finally we performed a detailed design of the driving mechanism through results of analysis and confirmed it to satisfy design requirements.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.5
• /
• pp.47-56
• /
• 2003

In this paper, the cyclic soil behavior model. which can accommodate the cyclic hardening, was developed by modifying the original parallel IWAN model. In order to consider the irrecoverable plastic strain of soil. the cyclic threshold strain, above which the backbone curve deviates from the original curve, was defined and the accumulated strain was determined by summation of the strains above the cyclic threshold in the stress-strain curve with applying Masing rule on unloading and reloading curves. The isotropic hardening elements are attached to the original parallel IWAN model and the slip stresses in the isotropic hardening elements are shown to increase according to the hardening functions. The hardening functions have a single parameter to account for the cyclic hardening and are defined by the symmetric limit cyclic loading test in forms of accumulated shear strain. The model development procedures are included in this paper and the verifications of developed model are discussed in the companion paper.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.7
• /
• pp.827-833
• /
• 2011

In this study, a simulation model to estimate the current-collection performance of a high-speed train was developed by using a commercial finite element analysis software, SAMCEF. A three-dimensional springDdamperDmass model of a pantograph was created, and its reliability was validated by comparing the receptance of the model to that of the actual pantograph. The wave propagation speed of the catenary model was compared with the analytical wave propagation speed of the catenary system presented in the UIC 799 OR standard. The length of the droppers was controlled, and the pre-sag of the contact wire due to gravity was considered. The catenary and the pantograph were connected by using a contact element, and the contact force variation when the pantograph was moved at velocities of 300 km/h and 370 km/h was obtained. The average, standard deviation, maximum, and minimum values of the contact force were analyzed, and the effectiveness of the developed simulation model was examined.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.3
• /
• pp.252-259
• /
• 2008

The deep-sea mining system is generally composed of surface vessel, lifting system, buffer, flexible pipe and miner. The mining system can be regarded as a large-scale system in which each subsystem is interconnected to other ones. In order to control a large-scale system, decentralized control approaches have been proposed recently. In this paper, as a basic study on application of decentralized control, firstly, the mining system was modeled in a simplified way. Lifting system and buffer were regarded as a spherical pendulum and the flexible pipe was taken as a two-dimensional linear spring connection. Based on the simplified model dynamics, the mining system can be decentralized two subsystems, the one consisting of surface vessel, lifting system and buffer, and the other, the miner. Next, this paper proposed the design of controller for each decentralized subsystem by regarding the interacting terms as disturbances. The controllers kept the constant distance between two subsystems during the miner was moving on the specified track. Finally, the efficiency of proposed controller was proven through the numerical simulation of the derived model.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.2
• /
• pp.91-96
• /
• 2010

The combination of a bolt and nut is the element most widely used for connecting machines and structures. When a load is repetitively applied in the direction right angle to the bolt axis after the bolt and nut is fastened, the nut gradually becomes loose. To solve this problem, in this study, a new type of the loose-proof nut, called a lock nut, is developed. The lock nut is equipped with a spring, and the spring increases the axial force of the bolt. Then, the connection force between the bolt and nut is also augmented. Three dimensional finite element models for the bolt and spring are generated, and the change of the axial force of the bolt while the bolt is being inserted into the spring is analyzed using MSC/Marc, a commercial finite element program. Finally, the optimum shape of the spring is found according to the response surface analysis methodology. The optimization result is verified by comparing the variation of the axial force of the bolt when the bolt is inserted to the initial and optimized spring.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.502-502
• /
• 2007

A catenary system should be designed to have an uniform elasticity over a span in order to maintain the lowest possible loss of contact between a pantograph and a contact wire. A elasticity uniformity of a catenary can be regarded as a important design factor used for predicting the current collection performance for a catenary. There are a couple of formulas to calculate the degree of elasticity uniformity of a catenary according to the literature survey. The effectiveness of these formulas is reviewed by performing catenary elasticity and loss of contact analysis for various different configurations of catenary systems using a beam element based FEM program. The results reveals that these formulas are not suitable to predict the current collection performance for a catenary. Therefore, a new formula based on the standard deviation of the elasticity over a span is proposed in this study. The analysis results show that the new formula for an elasticity uniformity of a catenary is very effective in predicting the current collection performance for a catenary.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.7
• /
• pp.837-842
• /
• 2010

The wiper system of a vehicle is important because it wipes the windshield, thereby enabling drivers to see through the windshield even under conditions of rain and snow. The blade is the key component of the wiper system because it wipes the windshield. When wiper-arm spring causes the blade to be pressed on the windshield optimum performance of wiping can be achieved when appropriate contact pressure is maintained. In this study, a dynamic analysis of the wiper system is carried out. A three-dimensional finite-element model of the wiper system is generated using SAMCEF, a commercial structural dynamic analysis program. The distribution of the contact pressure of the blade in its dynamic state is calculated. The simulation result is compared to the experiment result. Using the results of this study, the contact pressure of the blade can be estimated.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.5
• /
• pp.315-323
• /
• 2015

Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.