• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.385-393
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• 1999

An open loop vibrational control for an underactuated mechanical system with amplitude and frequently modulation is investigated. Since there is no direct external input to an unactuated joint, the dynamic coupling between the actuated and unactuated joints is utilized for controlling the unactuated joint. Feedback linearization has been performed to incorporate fully the known nonlinearities of the underactuated system considered. The actuated joints are firstly positioned to their desired locations, and the periodic oscillatory inputs are applied to the actuated joints to move the remaining unactuated joints to their target positions. The amplitudes and frequencies of the vibrations introduced are determined through averaging analysis. A systematic way of obtaining an averaged system for the underactuated system via a coordinate transformation is developed. A control design example of 2R planer manipulator with a free joint with no brake is provided.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.53-58
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• 1994

Beam-column joints of the skeleton structure can be classified as geometrical D-region, where the assumption of Bernoulli is not applicable. For the detailing of D-region in concrete structure, "Strut-and-Tie' Model is a very powerful tool, which has been widely used by practical engineers. This paper shows how the methodology of Strut-and-Tie Model can be applied for the various cases of beam-column joints. We can find this mechanical model does not give only an appropriate answer to the given problem but also a better insight to the structral behavior of beam-column joints.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.705-710
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• 2002

Welding is used not only during the shipbuilding, but also during the repairing of ships. While repairing of ships, it is inevitable to weld new materials with degraded materials. In this case, it is predicted that the strength of both the sections is not identical each other. In this study, the respective welded joints in terms of mechanical properties such as microstructure, mechanical strength and fatigue crack propagation, with the component obtained from the barge used for a long-term period, were analyzed. It was found that the material degradation had a significant effect on the welded joints. The fatigue crack propagation in welded sections showed a big difference. The rate of fatigue crack growth of degraded material for both heat affected zone and parent metal was faster than that of new material. By contrast, The result within identical materials showed that the heat-affected zone was slower than that of parent metal

• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.75-82
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• 2002

Welding is used not only for the shipbuilding, but also for the repairing of ships. While repairing of ships, it is inevitable to weld new materials with degraded materials. In this case, it is predicted that the strength of both the sections is not identical each other. In this study, the respective welded joints in terms of mechanical properties such as microstructure, mechanical strength and fatigue crack propagation, with the component obtained from the barge used for a long-term period, were analyzed. It was found that the material degradation had a significant effect on the welded joints. The fatigue crack propagation in welded sections showed a big difference. The rate of fatigue crack growth of degraded material for both heat affected zone and parent metal was faster than that of new material. By contrast, the result from identical materials showed that the rate of fatigue crack growth of the heat-affected zone was slower than that of parent metal.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2022-2031
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• 2000

Since the surface roughness of adherends affects much the strength of adhesivelybonded joints, the effect of surface roughness on the fatigue life of adhesively bonded tubular single lap joints was investigated analytically and experimentally by fatigue torsion test. The stiffness of the interfacial layer between adherends and adhesive was modeled as a normal statistical distribution function of surface roughness of adherends. From the investigation, it was found that the optimum surface roughness of adherends for the fatigue strength of tubular single lap joints was dependent on bondthickness and applied load.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2174-2183
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• 2000

In this paper, the evaluation method of interfacial fracture toughness to apply the fracture toughness was investigated in adhesively bonded joints of AI/Ced./A1. Four types of adhesively bonded double-cantilever beam(DCB) joints with the interface crack were prepared for the test of interfacial fracture toughness. The experiments to measure the interfacial fracture toughness were performed under the various mixed-mode conditions. The critical energy release rate, Gc, was obtained by the experimental measurement of compliances. From the experimental results, the interfacial fracture toughness for the mixed-mode specimens is well characterized by the energy release rate, and the method of strength evaluation by the interfacial fracture toughness was discussed in adhesively bonded joints.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.313-318
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• 2012

Application of composite structures on naval ships strongly depends on the mechanical strength and collapse behavior of the T-joints of the whole structure. Because of the weight advantages over single skin composite and bolt fastening joining, three types of T-joints using both honeycomb sandwich composite and adhesive bonding were suggested to determine the effect of T-joint configuration. It was found that joining with a urethane foam block and overlaminates using the secondary co-bonding technique improves T-joint strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.95-98
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• 1992

In large panel structures, the design of joints which interconnect panels, is important deciding the load-bearing capacity of structures. Being various factors in the design of joints, it is difficult to develop a the critical system for the structural analysis of large concrete panel structures. Therefore there is a tendency to depend on the experiment. The purpose of this paper is to investigate the strength and the mechanical behavior of vertical joints in large concrete panel structures.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.151-154
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• 1997

An open loop vibrational control of underactuated mechanical systems with amplitude and frequency modulations is investigated. The underactuated systems considered in the paper are assumed to have free joints with no brake. The active joints are positioned first by a linearizing control, and then periodic oscillatory inputs are applied to them to move the remaining free joints to their desired states. A systematic way of obtaining averaged systems for the underactuated systems with oscillatory vibrations is developed. A complete solution to the open loop control strategy in terms of determining amplitudes and frequencies for general system is still under investigation. However, a specific control design for 2R manipulator which is obtained the averaging system is demonstrated.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.355-367
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• 2015

This paper deals with a new designed joint system for single-layer spatial structures. As the stability of these structures is greatly influenced by the joint behaviour, the aim of this paper is the characterization of the joint response in bending through Finite Element Method (FEM) analysis using ABAQUS. The behaviour of the joints studied here was influenced by many geometrical factors, such as bolts and plate sizes, distance between bolts and end-plate thickness. The study comprised five models of joints with different values of those parameters. The numerical results were compared to the results of previous experimental tests and the agreement was good enough. The differences between the numerical and experimental initial stiffness are attributed to the simplifications introduced when modelling the bolt threads as well as the presence of residual stresses in the test specimens.