• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1026-1029
• /
• 1993

Inherent speed-torque performance of Switched Reluctance Motor is similar to that of series wound DC motor. Thus, the speed of the motor is extremely regulated according to load torque. For the purpose of controlling the speed and torque of SRM it is necessary to change the applied DC link voltage or the switch-ON and switch-OFF angles which control the phase current of the motor. This paper describes speed-torque characteristics of an integral horse power Switched Reluctance Motor by adjusting the switch-ON and switch-OFF angles. Speed at rated load torque can be regulated by adjusting the switching angles and the control scheme is applied to 2kW, 3 phase, 6/4 SRM.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.2
• /
• pp.8-16
• /
• 2000

The thread load distribution as applied to large stud bolts for steam turbines is investigated using the finite element method. The stress concentration in tapered threads is studied with varying prestress and taper angle. Based upon the thread load distribution, the optimal taper angles to reduce the stress concentration are determined for various prestresses. The presented finite element model is validated by comparing results of the calculated thread load with analytic ones. The optimal taper angles obtained from this research can be used in designing tapered threads of large stud bolts for steam turbines.

• Steel and Composite Structures
• /
• v.19 no.6
• /
• pp.1333-1354
• /
• 2015

A higher order analytical solution for static analysis of a truncated conical composite sandwich panel subjected to different loading conditions was presented in this paper which was based on a new improved higher order sandwich panel theory. Bending analysis of sandwich structures with flexible cores subjected to concentrated load, uniform distributed load on a patch, harmonic and uniform distributed loads on the top and/or bottom face sheet of the sandwich structure was also investigated. For the first time, bending analysis of truncated conical composite sandwich panels with flexible cores was performed. The governing equations were derived by principle of minimum potential energy. The first order shear deformation theory was used for the composite face sheets and for the core while assuming a polynomial description of the displacement fields. Also, the in-plane hoop stresses of the core were considered. In order to assure accuracy of the present formulations, convergence of the results was examined. Effects of types of boundary conditions, types of applied loads, conical angles and fiber angles on bending analysis of truncated conical composite sandwich panels were studied. As, there is no research on higher order bending analysis of conical sandwich panels with flexible cores, the results were validated by ABAQUS FE code. The present approach can be linked with the standard optimization programs and it can be used in the iteration process of the structural optimization. The proposed approach facilitates investigation of the effect of physical and geometrical parameters on the bending response of sandwich composite structures.

• Journal of the Korean Society of Safety
• /
• v.37 no.5
• /
• pp.1-6
• /
• 2022

In this study, to confirm the effects of the mixed load of normal and shear forces acting on a fixing bolt, fatigue design criteria were developed by varying the loading angle and conducting tensile and fatigue tests. After evaluating and comparing the test results under different loading angles, the evaluation criteria were selected. These evaluation criteria were then applied to develop the design criteria. An Arcan fixture was designed and manufactured to simultaneously apply a mixed load of normal and shear forces to the fixing bolt of a turntable, and a fatigue test was conducted. S-N diagrams for various loading angles were obtained, and a 1% P-S-N diagram of failure probability was determined using statistical processing techniques. Our results show that failures of the fixing bolt can be prevented using these diagrams as a basis for developing fatigue design criteria.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.5 no.1 s.16
• /
• pp.69-76
• /
• 2005

The pull-out capacity of expansion anchor(heavy duty anchor and wedge anchor) was studied experimentally in this paper. Loading conditions included tension, shear, and combined tension and shear. The heavy duty anchor and wedge anchor were manufactured in domestic and installed In plain concrete. The failure mode of steel and concrete were studied carefully for the analytical formula of the anchorage design and the experimental data were compared with different models for the interaction of tension and shear capacities. Based on the research, the following conclusion may be drawn : The interaction of forces is well-described by an elliptical interaction relationship.

• Tribology and Lubricants
• /
• v.20 no.2
• /
• pp.51-57
• /
• 2004

Micro/nano adhesion and friction properties of mixed self-assembled monolayer (SAM) with different chain length for MEMS application were experimentally studied. Many kinds of SAM having different spacer chains(C6, C10 and C18) and their mixtures (1:1) were deposited onto Si-wafer, where the deposited SAM resulted in the hydrophobic nature. The adhesion and friction properties between tip and SAM surfaces under nano scale applied load were measured using an atomic force microscope (AFM) and under micro scale applied load were measured using ball-on-flat type micro-tribotester. Surface roughness and water contact angles were measured with SPM (scanning probe microscope) and contact anglemeter. Results showed that water contact angles of mixed SAMs were similar to those of pure SAMs. The morphology of coating surface was roughened as mixing of SAM. Nano adhesion and nano friction decreased as increasing of the spacer chain length and mixing of SAM. Micro friction was decreased as increasing of the spacer chain length, but micro friction of mixed SAM showed the value between pure SAMs. Nano adhesion and friction mechanism of mixed SAM was proposed in a view of stiffness of spacer chain modified chemically and topographically.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2003.11a
• /
• pp.56-63
• /
• 2003

Micro/nano adhesion and friction properties of mixed self-assembled monolayer (SAM) with different chain length for MEMS application were experimentally studied. Many kinds of SAM having different spacer chains(C6, C10 and C18) and their mixtures (1:1) were deposited onto Si-wafer, where the deposited SAM resulted in the hydrophobic nature. The adhesion and friction properties between tip and SAM surfaces under nano scale applied load were measured using an atomic force microscope (AFM) and micro scale applied load were measured using ball-on-flat type micro-tribotester. Surface roughness and water wetting angles were measured with SPM (scanning probe microscope) and contact anglemeter. Results showed that wetting angles of mixed SAMs showed the similar value of pure SAMs. The coating surface morphology was increased as mixing of SAM. Nano adhesion and nano friction decreased as increasing of the spacer chain length and mixing of SAM. Micro friction was decreased as increasing of the spacer chain, but micro friction of mixed SAM showed the value between pure SAMs. Nano adhesion and friction mechanism of mixed SAM was proposed in a view of stiffness of spacer chain modified chemically and topographically.

• Journal of the Korean Society of Mechanical Technology
• /
• v.20 no.6
• /
• pp.894-900
• /
• 2018

Among the soft ground improvement methods, PBD is the most common construction method because it is cheap and construction is fast. However, if the ground is rigid, additional work is required. In this study, the structural safety, natural vibration, and safety angle of the steel vertical tower structure were evaluated in the development of the PBD composite perforator which can be combined with drilling work and PBD construction. Structural safety was assessed when the wind load of 20 m/s was simultaneously applied to the PBD construction load of 20 tons, the perforating operation of 25 tons, and the wind speed of 50 m/s was applied only to the wind load. The natural frequencies were evaluated up to the sixth mode, and the safety angle was evaluated for static and dynamic safety angles.

• Tribology and Lubricants
• /
• v.24 no.5
• /
• pp.228-233
• /
• 2008

In this study, the methodology for determination of shoulder height in the internal shape design of ball bearing using 3D contact analysis is proposed. The static analysis of a ball bearing was performed to calculate the distribution of applied contact load and angles among the rolling elements. From each rolling element loads and the contact geometry between ball and inner/outer raceway, 3D contact analyses using influence function are conducted. These methodology is applied to HDD ball bearing. A critical axial load and a critical shoulder height which are not affected by edge are calculated. The proposed methodology may be applied to other rolling element bearing for the purpose of reducing the material cost and improving the efficiency of the bearing design process.

• Tribology and Lubricants
• /
• v.21 no.3
• /
• pp.107-113
• /
• 2005

Micro/nano adhesion and friction properties of self-assembled monolayers (SAMs) with different head- and end-group were experimentally studied according to the coating methods. Various kinds of SAM having different spacer chains (C10 and C18), head-group and end-group were deposited onto Si-wafer by dipping and chemical vapour deposition (CVD) methods under atmospheric pressure, where the deposited SAM resulted in the hydrophobic nature. The adhesion and friction properties between tip and SAM surfaces under nano scale applied load were measured using an atomic force microscope (AFM) and also those under micro scale applied load were measured using a ball-on-flat type micro-tribotester. Surface roughness and water contact angles were measured with SPM (scanning probe microscope) and contact anglemeter respectively. Results showed that water contact angles of SAMs with the end-group of fluorine show higher relatively than those of hydrogen. SAMs with the end-group of fluorine show lower nano-adhesion but higher micro/nanofriction than those with hydrogen. Water contact angles of SAMs coated by CVD method show high values compared to those by dipping method. SAMs coated by CVD method show the increase of nano-adhesion but the decrease of nano-friction. Nano-adhesion and friction mechanism of SAMs with different end-group was proposed in a view of size of fluorocarbon molecule.