• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.03a
• /
• pp.40-52
• /
• 1998

Among the non-traditional machining methods, Abrasive waterjet machining process shows big promise in drilling difficult-to-machine materials due to its numerous advantages such as absence of heat affect zone and thermal distortion. Acoustic emission signal technique is used to understand about material removal mechanisms during abrasive waterjet drilling process. More information about the drilling process is derived through frequency decomposition of auto regressive moving average modeling representing acoustic emission signals.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2003.11a
• /
• pp.384-387
• /
• 2003

The object of the present work is the analysis of head/disk interaction during start/stop and constant speed operation using acoustic emission (AE). The frequency spectrum analysis is performed using the AE signal obtained during the head/disk interaction. The FFT (Fast Fourier Transform) analysis of the AE signals is used to understand the interaction between the AE signal and the state of contact.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5A
• /
• pp.917-925
• /
• 2006

Experimental tests were performed to estimate velocities of the acoustic signals through prestressed concrete beam and source locations using acoustic emission (AE) techniques. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made at 18 locations. The velocities of AE signals are estimated using the time differences of arrival times and the distances between the source locations and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000 m/sec and the velocity decreased with the increase of the distance from source locations to AE sensors due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the errors of source locations are decreased when the velocities of each AE sensor are used rather than the average velocity.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.2
• /
• pp.125-131
• /
• 2002

we analyzed acoustic emission signals obtained from three kinds of brittle materials under compression load by Vickers hardness tester. The results obtained can be summarized as follows; The signal in each material could be divided into three signal based on the properties of load. All specimens were not detected acoustic emission signals in stage II which was load constant region., and were detected in stage I and stage III. Glass was detected high amplitude signals in stage III. $Al_2O_3\;and\;Al_2O_3/Sic$ were detected high amplitude signals in stage I.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.1035-1042
• /
• 1988

The acoustic emission(AE) signal is monitored in milling operation in order to investigate the relationship between the progressive tool wear and the AE signals. A signal processing technique so called time domain averaging(TDA) is presented for the elimination of the influences of the noise imbedded in the periodic signals. The relationship between the progressive tool wear and the AE signals is investigated by varying the cutting speed, feed, depth of cut and the number of insert. From the measured data, it is observed that the averaged level of the AE signal increases at first with the increase of flank wear to a certain critical value, and then stays almost constant or fluctuates with further increase of the flank wear.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.3
• /
• pp.198-204
• /
• 2003

A basic experiment was performed to control tile plant growth using acoustic emission technique considering the environmental conditions for plant. At a dry soil condition, the signals due to the cavitation from xylem of angiosperm and gymnosperm were mainly detected. The strong signal from xylem and the weak signal from plasmodesmata and casparian strip were detected at the same time after distilled water was provided. Two signals after providing tile acid and distilled water were contrary to each other. The wind, number of leaf, music, temperature and humidity affected the acoustic emission count from plants but the frequency ranges of the detected signals were the same.

• Journal of the Korean Society for Precision Engineering
• /
• v.7 no.3
• /
• pp.75-82
• /
• 1990

Automatic monitoring of the cutting conditions is one of the most improtant technologies in machining. In this study, the feasibility in applying acoustic emission(AE) signals for the in-process detection of endmill wear and fracture has been investigated by performing experimental test on the NC vertical milling machine with SM45C for specimen. As the results of detecting and analyzing AE signals on various cutting conditions, the followings have confirmed. (1) The RMS value of acoustic emission is related sensitively to the cutting velocity, but is not affected largely by feed rate. (2) The burst type AE signals of high level have been observed when removing chips distorderly and discontinuously. (3) When the RMS value grows up rapidly due to the increase of wear the endmill are generally broken or fractured, but when the endmills fracture at the conditions of smooth chip-flow or built-up-edge(BUE) occurred frequently, the rapid change of the RMS arenot found. And it is expected that this technigue will be quite useful for in-process sensing of tool wear and fracture.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.17 no.4
• /
• pp.42-47
• /
• 2009

Recently, the wide range of the composite materials is used for the making airplanes, trains and automobiles body for the lightweight. Despite having complex structures, composite materials usually have well defined mechanical characteristics. However, composite materials are difficult to understand the fracture mechanism clearly by simple mechanical test. Nondestructive evaluation (NDE) combined with mechanical testing can play a more important role and especially Acoustic Emission Testing (AET) would become known to be a useful tool to assess damage and fracture behavior of composites. In this study The experiment was performed to acquire the acoustic emission signal during tensile test using unidirectional CFRP specimen and the data was analyzed the acoustic emission parameters with the waveform.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.06a
• /
• pp.437-438
• /
• 2008

• Computers and Concrete
• /
• v.18 no.2
• /
• pp.267-278
• /
• 2016

In order to observe the internal damage of concrete in real time, we introduced acoustic emission nondestructive detecting technology into a series of fracture tests; the test results revealed the whole process that concrete undergoes when it sustains damage that leads to failure, according to the change rules of the acoustic emission parameters. The results showed that both the initiation and unstable loads can be accurately determined using the abrupt change of the acoustic emission rate curves and the turning point of the acoustic emission parameters' accumulative curves. The whole process, from damage to failure, includes five phases, beginning with damage, such as cracking, a stable crack growth process, a critical unstable stage, and unstable propagation. The brittle fracture characteristics of concrete change when steel bars are joined, because the steel bars and the concrete structure bond, which causes an increase in the acoustic emission signals within the fracture process of the reinforced concrete. The unstable propagation stage is also extended. Our research results provide a valid methodology and technical explanations, which can help researchers to monitor the cracking process of concrete structures, in real time, during actual projects.