• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.42-47
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• 2014

In this paper, fatigue life analysis of each structure was performed through theoretical analysis method at design stage in order to verify the success or failure of the store's acoustic noise durability according to the Method 515.5 standard of MIL-STD-810F. In addition, experimental analysis was carried out through the ground and flight test by manufacturing the measuring store, and verification of the sound durability was completed through the flight test after manufacture of the actual store. Furthermore, the commercial FEM code through the PSD calculation method applying measured SPL enables verify the durability of new store components development for the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1313-1316
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• 2006

Demands of high volume dry vacuum pumps on the domestic semiconductor and LCD industries are rapidly increasing as the size of wafers and LCD is increasing. This study introduces a new experimental setup for testing the reliability of vacuum pumps. The test system was designed to measure the acoustic pressure and mechanical vibration levels simultaneously. It is shown that the test system enables the analysis and evaluation of the performance of dry pumps under the different gas-load conditions. Detailed experimental result are shown to enable us to examine the characteristics and performance of dry pumps.

• Proceedings of the Safety Management and Science Conference
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• 2008.04a
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• pp.185-196
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• 2008

The objective of this study is to evaluate the mechanical behaviors and structural integrity of the weldment of high strength steel by using an acoustic emission (AE) techniques. Simple tension and AE tests were conducted against the 3 kind of welding test specimens. In order to analysis the effectiveness of weldability, joinability and structural integrity, we used K-means clustering method as a unsupervised learning pattern recognition algorithm for obtained multivariate AE main data sets, such as AE counts, energy, amplitude, hits, risetime, duration, counts to peak and rms signals. Through the experimental results, the effectiveness of the proposed method is discussed.

• Journal of the Korea Safety Management & Science
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• v.10 no.4
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• pp.127-134
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• 2008

The objective of this study is to evaluate the mechanical behaviors and structural integrity of the weldment of high strength steel by using an acoustic emission (AE) techniques. Monotonic simple tension and AE tests were conducted against the 3 kinds of welded specimen. In order to analysis the effectiveness of weldability, joinability and structural integrity, we used K-means clustering method as a unsupervised learning pattern recognition algorithm for obtained multi-variate AE main data sets, such as AE counts, energy, amplitude, hits, risetime, duration, counts to peak and rms signals. Through the experimental results, the effectiveness of the proposed method is discussed.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.1
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• pp.24-33
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• 2004

Recently, ship acoustics takes more important role in acoustic stealth and classification of underwater targets. In this paper, a theoretical concept is proposed for M＆S-based test and evaluation of ship acoustics. The concept is based on two different approaches: on Top-Down method which emphasizes the survivability of the ship and on Bottom-Up method which considers acoustic characteristics of the ship-equipments. In order to improve the effectiveness of M＆S-based T＆E for ship acoustics, it is recommended in this paper to compromise the two approaches as adequate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.317-322
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• 2004

In this paper, It was describe the processes of development of HiFi speaker system. Woofer and tweeter were fabricated by unskilled students and their 1.5 parameters were identified by known mass method. Based on T-S parameters port enclosure was designed and built by means of software. Acoustic radiation phenomena of port enclosure were simulated and compared to test result. Acoustic pressure difference between lower frequency and higher frequency was flattened by adopting optimal crossover network. Finally, built HiFi speaker system was showed good sound quality and sound pressure and electrical impedance was well agreed with test results each other.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.205.1-205.1
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• 2011

This study concerns a low head and kaplan turbine efficiency measurement using the acoustic scintillation flow meter(ASFM). The ASFM is one of absolute discharge measurement methods because it measures velocity-area of discharge with couples of transducers. This study shows that the highest efficiency of turbine is 87.7% and the efficiency is 85.8% in the rated output(600kW). The test result is reliable because the efficiency trend from this test is similar to the result of index test conducted in 1986. In this paper, the principle, measurement methods, application and test procedures of the test are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.747-750
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• 2004

After launching, spacecraft is exposed to extreme environments. So spacecraft should be tested after design/manufacture to verify whether components can be operated functionally. Acceleration transferred from launch vehicle to spacecraft produces quasi-static load, sine vibration and random vibration. Random vibration is also induced by acoustic vibrations transferred by surface of spacecraft. And shock vibration is produced when spacecraft is separated from launch vehicle. To verify operation of spacecraft under these launch environments, separation shock test, sine vibration test, acoustic vibration test and random vibration test should be performed. This paper describes these launch environment test requirements.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.603-608
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• 2001

A certain amount of MBS rubber was added to improve toughness of PVC which has a strong tendency of being brittle, producing a mixture, PVC/MBS, from which test specimens were prepared. PVC has strong chemical resistance, oil resistance, frame retardancy and high mechanical strength. Also, it is relatively inexpensive to produce, but shows weakness to impact and difficult for processing. MBS, a typical toughening agent for PVC is generally known, when added in a small amount, to improve impact resistance and to minimize difficulties during the processing of the PVC without adversely affecting the positive aspects of the PVC. In this investigation, attempts were made to observe and determine the variations in elastic and damping constants of the PVC depending on the amounts of MBS added to the mixture, PVC/MBS, and also on the thicknesses of the specimens. An acoustic resonance technique was used for the tests in this investigation. It serves as a method to characterize properties of materials set in vibrational motions, which is initiated by low level stresses generated by externally supplied acoustic energy. Substantial variations were observed in the test results with the addition of the MBS to the PVC. Generally, the magnitudes of elastic constants decrease while the damping capacity improves when MBS rubber was added.

• The Journal of the Acoustical Society of Korea
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• v.24 no.3E
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• pp.90-98
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• 2005

Enhanced approach using computational and experimental method is proposed and performed to describe very well the behavior of loudspeaker than conventional method. Proposed procedure is composed of four parts. First, Thiele-Small parameters for test loudspeaker are identified by an electrical impedance method like as a delta mass method. Second part includes the processes to measure physical properties. Physical data like masses and thicknesses of loudspeaker's components are measured by an electrical precision scale and a digital vernier caliper. Third, the identified Thiele-Small parameters are proposed to be used as load boundary conditions for vibration analysis instead of electromagnetic circuit analysis to get a driving force upon bobbin part. Also, these parameters and physical data are used to modify physical properties required for computation to accommodate simulated sound pressure level with measured one for loudspeaker enclosure system. These data like as Young's modulus and thickness for a diaphragm are required for vibration analysis of loudspeaker but not measured accurately. Finally, it was investigated that simulated sound pressure level with full acoustic modeling including an acoustic port for test loudspeaker agreed with experimental result very well in the midrange frequency band(from 100 Hz to 2,000 Hz). In addition, several design parametric study is performed to grasp acoustical behaviors of loudspeaker system due to variations of diaphragm thicknesses and shapes of dust cap.