• Journal of the Korean Society for Precision Engineering
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• v.13 no.6
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• pp.136-144
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• 1996

We developed a part of stroke sensing cylinder for position control of automatic excavator and its measurement system. In this paper, for development of stroke sensing cylinder, we consist of 2-axis control instrument system with Hall sensor. A performance of piston rod with magnetic scales is evaluated by the developed measurement system. Furthermore, the position control for good performance of instrument system is achieved by a sliding mode control which is a new method diminishing the chattering in that control by setting 2-dead band along the swtching line. The unknown parameters for sliding mode control are estimated by the signal compression method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1044-1047
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• 1996

This paper presents durability characteristics of electrorheological(ER) fluids which undergo a reversible phase change depending upon the imposition of electric fields. The field-dependent Bingham properties are subjected to be altered from long time use of the ER fluid. The level of the changed properties depends upon employed device and test conditions. A piston-rod system which has same mechanism as ER dampers is adopted in this study and tested by increasing operation cycle up to 1 million. Bingham properties of initial and us ER fluids are tested and compared. In addition, these ER fluids are applied to ER damper in order to evaluate damping force performance.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.961-966
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• 2004

The cylinder without seal has a piston with air bearing which is partly cylindrical and conical shape. The description of system geometry is deviation by the flow rate equation. Then pressure distribution and bearing force equations are derived. Several non-dimensional parameters are suggested. The relationship among bearing force, leakage flow and geometry of the bearing is investigated by simulation. And determination method for optimal design of sealless cylinder is given. A prototype of sealless cylinder which had rod bearing with four pockets, five pockets, and six pockets was built respectively. As a result of leakage flow test, it is evaluation to air bearing in sealless cylinder.

• Plant Journal
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• v.6 no.4
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• pp.63-71
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• 2010

The best way to prevent the corrosion of piston rod is a selection of quality of the material and method of construction which minimize the porosity. The high velocity oxy fuel(HVOF) method, which generates lower porosity than existing plasma spray, was applied to ceramic laminated bond layer. Porosity percentage fell to bellow 2%, lower than that of plasma spray at 7%. Coating material of ceramic-coated main layer was selected as the $Cr_2O_3$ affiliation material, which is more dense than $Al_2O_3$ affiliation. To fill up the pores formed after the coating process, we sealed the bond layer and main layer. Sealing process was performed twice, once after the coating and once after the grinding. Upon the anti-corrosion test on the sealed sample and on the non-sealed sample, it is confirmed that the sealed sample was not corroded for 1,000 hours while the non-sealed sample was corroded within 48 hours.

• Tribology and Lubricants
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• v.4 no.2
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• pp.28-35
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• 1988

A general and efficient algorithm is proposed for the analysis of the frictionless elastic contact problems. It utilizes a simplex-type algorithm with a modified entry rule and incoporates finite element method to obtain flexibility matrices. The algorithmic solution is compared with the Hertzian solution for the contact problem between two cylinders to prove its accuracy and the contact problem between pin and piston rod is solved and compared with the numerical results of Frankavilla and Zienkiewicz to demonstrate the generality and effectiveness of the suggested algorithm. The contact problem between mating involute gear teeth at the worst load position is considered. The computed contact stress is smaller than the result of Hertz's theory applied to the contact between two kinematically equivalent discs and the contact area is larger than that of Hertz's theory.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.196-201
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• 1997

In point of noise and vibration, it is easy to occur a noise and vibration, because the reciprocal compressor is composed of crank shaft, rod piston and etc. Therefore, it is important to understand the mechanism of reciprocal compressor. In this study, we measured the sound pressure level of compressor. There are two dominent frequencies. The first of one results from the suction part. In suction process, the suction valve flutteres, and it produces the noise of the first frequency. The other results from the structural vibration of the shell resonated by discharge pipe. Thus, to reduce the noise of compressor, it will be most efficiency to redesign muffler for the first frequency and discharge pipe for the second frequency.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.133-137
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• 2003

The shock absorber for vehicles is the important component to absorb the shock in driving. These essential components, piton and piston rod, must be made of S25C, S45C and SCM440 generally depending on kind of vehicles, precisely machined and assembled by the bolt. And it has been difficult to weld this sort of dissimilar materials. They could be unstable in the quality by the conventional arc welding. And also they have a lot of technical problems in manufacturing. But by the friction welding technique, it will be able to be made without such problems. These factors above necessitate nowadays the domestic development of the shock absorber by friction welding and a new approach of study on real-time quality evaluation by AE techniques.

• Structural Engineering and Mechanics
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• v.46 no.5
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• pp.673-693
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• 2013

This paper presents a systematic design and training procedure for the feed-forward back-propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

• Journal of Power System Engineering
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• v.6 no.2
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• pp.48-53
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• 2002

Plunger (piston rod) materials are used in high-pressure condition. So STD11 is the essential material to build this plunger. However, it costs more to make a plunger by using only STD11 than using the welding of STD11 to SCM440 and other dissimilar material. And it has been difficult to weld this sort of dissimilar materials. They could be unstable in the quality by the conventional arc welding. And also they have a lot of technical problems in manufacturing. But, by the friction welding technique, it will be able to be made without such problems. And then, on account of such reasons, we need a new approach of study on real-time quality evaluation by acoustic emission (AE) techniques as well as a domestic development of the plunger by friction welding. So that, the purpose of this study for such developments is the development of a plunger by optimizing of friction welding with more reliability and more applicability. Then, this study aimed not only to develop the optimization of friction welding of dissimilar plunger steels of STD11 to SCM440, but also to develop the application technique of the acoustic emission to accomplish an in-process real-time quality evaluation during friction welding of the plunger materials by the AE technique.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.478-485
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• 2003

Today, although there have been high technical developments of a compressor in the respect of its capacity, it has been so hard to develop in the respect of vibration and noise because mechanical structure of it has originally numerous vibration and noise. However, if we can grasp the point of systematic phenomena of vibration and noise through the understanding of dynamic characteristics in mechanical equipment, it may be possible to consider countermeasures. In this study about a reciprocal compressor, the part of its machinery is modeled as rigid body, and the part of its spring is modeled as flexible body, and then they are analyzed by DADS. Each rigid body and spring are connected with joint torque of a motor is applied to shaft, and pressure is applied to a piston so that a compressor can be revolved. Based on this modeling, influence of a compressor's vibration is analyzed through changes of offset, connecting rod and crank radius In the case of weight balance, it I produced after re-design, and then changes of vibration of a compressor's inside are checked through experiments. These analysis data may help set measures of reducing vibration of a reciprocal compressor.