• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.66-74
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• 2003

In non-contact underwater explosion shock test of a real naval ship, measurement of shock loadings and responses should require onboard system to be able to safely trigger an explosive and to simultaneously and successfully measure scores of shock signals in the deteriorated environment. For this purpose, we have developed a shock-hardened measurement system resistible to 170g peak acceleration having 4 msec duration by resiliently mounting general purpose measurement instruments in racks. The system can simultaneously measure and record 200 signals to evaluate shock leadings and responses of the test ship by triggering an explosive and measurement instruments at the same time. We prove the performance of the developed system by introducing the signal acquisition results from of a real ship underwater shock test, firstly performed in Korea.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.5
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• pp.503-510
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• 2021

This paper presents a system that measures the acceleration of the shock caused by the explosion of the precursor warhead for the tandem projectile. The proposed system, which is implemented based on the MIL-STD-810G, Method 517.1, consists of a miniaturized shock measurement device, a cable, accelerometers, and a trigger circuit. The shock measurement device has a size of ¢102 × 171 mm and cable has a length of 3 m. The operational confirmation test is conducted by implementing the measurement system. The Analysis of shock data(accelerometer output data) is carried out using Shock Response Spectrum(SRS), pseudo velocity and plot of acceleration time transient. Through measurement analysis, one can predict the damage of electronics in projectile when precursor warhead is exploded.

• Journal of the Korean Society of Visualization
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• v.13 no.3
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• pp.29-34
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• 2015

The interaction between a normal shock wave and a boundary layer along a wall surface in internal compressible flows causes a very complicated flow. This interaction region containing shock train and mixing region is called as pseudo-shock waves. Pseudo-shock waves in the divergent part of a rectangular nozzle have been investigated by using large-eddy simulation (LES). LES studies have been done for the complex flow phenomena of three-dimensional pseudo-shock waves. The LES results have been validated against experimental wall-pressure measurements. The LES results are in good agreement with experimental results. Pseudo-shock length and corner separation have been studied in three-dimensional LES model. Comparison of centerline pressure measurement and 3D visualization measurement has been discussed for the corner separation position. It has been concluded that the pseudo-shock length should be measured by using 3D visualization measurement.

• Journal of Aerospace System Engineering
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• v.10 no.2
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• pp.34-40
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• 2016

A satellite is exposed to various impact environment until orbit entry. It is particularly undergoing the biggest impact by pyro shock, which is generated when the launch vehicle stages are separated or the satellite is separated from the launch vehicle. In this paper, due to the fact that the pyro shock is prerequisite for performing the test and verification on the ground, we developed an air-gun type shock tester for NEXTSat-1 shock test at the KAIST SaTReC along with the development of program introduced by LabVIEW software. The program operated in shock tester is consist of data measurement and analysis with the convenient implementation of user interface and its easy modification of the code.

• Structural Engineering and Mechanics
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• v.28 no.3
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• pp.335-352
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• 2008

Continuous operation of test and measurement is a new operating technique in the petroleum exploitation, which combines perforation with test and measurement effectively. In order to measure the original pressure of stratum layer exactly and prevent testing instrument from being impaired or damaged, a suitable shock absorber is urgently necessary to research. Based on the attempt on the FEM analysis and experiment research, a new shock absorber is designed and discussed in this paper. 3D finite element model is established and simulated accurately by LS-DYNA, the effect and the dynamic character of the shock absorber impact by half sinusoidal pulse force under the main lobe frequency are discussed both on theoretics and experiment. It is shown that the new designed shock absorber system has good capability of shock absorption for the impact load.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.589-597
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• 2017

This study aims to verify experimentally the specifications of the data acquisition system required for the precise measurement of signals in an underwater explosion (UNDEX) experiment. The three data acquisition systems with different specifications are applied to compare their precision relatively on maximum shock pressures from UNDEX. In addition, a method of assessing the acquired signals is suggested by introducing the concept of measurement uncertainty. The underwater explosion experiments are repeated five times under same conditions, and assessment is conducted on maximum quantities acquired from underwater pressure sensors. It is confirmed that the concept of measurement uncertainty is very useful method in accrediting the measurement results of UNDEX experiments.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.98-104
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• 2009

A solid kick motor is used for propulsion system of KSLV-I 2nd stage. During combustion of the kick motor, vibration and shock could be generated. And it could be transferred to the vehicle equipment bay through the kick motor body. If vibration and shock transferred to the vehicle equipment bay are considerable, electrical equipments could be disordered. Therefore we need to verify influence of vibration and shock caused by combustion of the kick motor. In this research, we measured vibration of the kick motor on the ground firing test. Based on this measurement data, we analyzed random vibration and shock response spectrum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.7
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• pp.489-495
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• 2020

An accelerometer-based system was designed and constructed for drag measurement in a shock tunnel. Drag coefficient of a conical model was measured under a Mach 6 flow condition. A simple and intuitive calibration method was presented to compensate for the friction force of the drag measurement system, and the results of the measurement were compared with computational fluid dynamics in which the simple conical model was analyzed. The influence of drag measurement interference by supports of various shapes was identified and the design was presented to minimize. The drag coefficient measurement using the modified support showed that the error of the drag coefficient by the support was decreased.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.588-593
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• 2012

Nowadays, various forms of electro-optical rifle scope have been developed and used in order to enhance the accuracy of small arms. However, firing shock acceleration has characteristics of pyroshock having a big acceleration value with very short duration time, which the electro-optical scopes should be designed to sustain. In this paper, the firing shock acceleration, which is transmitted to the electro-optical scope, was measured and SRS (Shock Response Spectrum) analysis was performed by using the measured firing shock acceleration. Furthermore, a shock test condition using a drop-table shock tester, which can simulate the actual firing shock acceleration, was devised. The devised shock test condition will be utilized to test the electro-optical scope itself before attaching it to the small arms.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.43-47
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• 2000

Two modes of shock waves, a compression shock wave and a thermal shock wave, propagating in He II have been investigated. The shock waves are at a time generated by the impingement of a gasdynamic shock wave onto a He II free surface in the newly developed superfluid shock tube facility. Superconductive temperature sensors, piezo-type pressure transducers and visualization photograph were used for the measurement of them and the phenomena induced by them were investigated in detail. It is found that the compression by a compression shock wave in He II causes temperature drop because He II has negative thermal expansion coefficient. the thermal shock wave is found to be of a single triangular waveform with a limited shock strength. The waveform is similar to that generated by stepwise strong heating from an electrical heater for relatively long heating time. In the experiments at the temperatures near the lambda temperature, no thermal shock wave is sometimes detected in shock compressed He II. It can be understood that shock compression makes He Ii convert to He I in which no thermal shock wave is excited.