• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.55-62
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• 2013

An analytical procedure to determine a proper profile of the spring rail that generates intended contact pressure distribution in the flat wiper blade is introduced. The flat wiper blade is one piece blade and subjected to pressing force at a center point. In this type of blade, contact pressure distribution in the tip of rubber strip is determined by the pressing force, the initial profile of the blade before contact and bending stiffness of the blade. Experimentally obtained bending stiffness of the blade assembly is almost identical to that of the spring rail. Principle of reciprocity has been used to define the initial profile of spring rail from the deformed profile that is assumed to be identical to the windshield glass profile. The procedure has been verified experimentally by measuring the contact pressure of the blade assembled with the spring rail designed by the procedure proposed here. Measured contact pressure distributions of the blades show good agreements with intended distributions over the entire blade span. Consequently, it can be concluded that proposed procedure has relatively good accuracy in developing the spring rail for flat blade having a specific contact pressure distribution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.736-741
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• 2017

This paper examines the design for improving the wiper system of rotorcraft. During rotorcraft operation, the wiping performance and excessive clearance can decrease. The wiper system consists of a wiper arm assembly, motor, convertor and flex drive. If there is a problem with the wiper system, the operation ability decreases because the operation is restricted in a rainy environment. There are two main causes of the problem of the wiper system: the lifting forces acting on the wiper arm in aircraft flight and the excessive gap of the components. To remedy these two problems, the wiper arm was improved. The improvements included increased contact pressure on the wiper arm (spring tension), improved gear clearance, and material and shape changes. Durability test, aircraft ground test and flight test were carried out to verify the improved shape, and it was confirmed that the wiping performance and clearance problems were solved. Currently, the rotorcraft is operated without problem by applying the improved shape, and this design improvement process will be a useful reference for future rotorcraft development.

• Journal of KSNVE
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• v.9 no.4
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• pp.841-848
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• 1999

In the quality assurance check process of DC motor systems, even though the overall sound pressure level is acceptable, there is an incident that subjective evaluation leads to failure in product quality due to annoying noise. This kind of problem may be originated from the manufacturing or assembly process. In this paper, the transient spectral analysis, or the time-frequency analysis is applied to the noise quality problem. For the case study, the cause of annoying noise in the wind shield wiper motor is experimentally analyzed in detail. It is concluded that the defect in the shaft causes the impact noise which is not detectable by steady spectral analysis. Also demonstrated is how the time-frequency analysis is effectively applied to the annoying noise identification of the rotor-gear system.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.894-903
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• 2018

In the case of helicopters, the development of parts technology is rapidly changing, and the complexity is rapidly increasing. Particularly, the surge of various electric and electronic systems is recognized as a problem that is directly related to the safety of the helicopter. Due to these problems, there is a growing interest in reliability evaluation in the face of the problem of confirming and certifying the reliability of parts in the development stage. In this paper, the analysis of the failure mechanism of the wiper system was carried out, and the priority and importance of each failure mode were checked by using the results, and major stress factors were derived and the corresponding acceleration model was selected. Also, the accelerated lifetime test time was calculated according to the life test time, acceleration status and acceleration level of the steady state by using the selected acceleration model and characteristic values.