• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.114-118
• /
• 1996

Evaluation of cutting condition is one of the most important aspect to improve productivity and quality. In this study, the wear and cutting characteristics(cutting force, acoustic emission signal and surface roughness) of ceramic cutting tool for hardened die material(SKD11) were investigated by experiment. Flank wear on relief face of tool was occurred more dominant than crater wear on rake face. Experiments were performed under the various cutting condition.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.678-682
• /
• 1996

Acoustic emission(AE) is monitored during end milling with a sensor attached to the cutting fluid discharge nozzle. Cutting forces are also measured and compared with the AE signals to examine the reliability of the AE signals. It is demonstrated that the AE signals provide reliable informations about the cutting processes and tool states. Moreover, edge chipping and fracture of tools can be successfully detected using both the AE signals and cutting forces.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.90-94
• /
• 1996

Thermal problems of creep-feed grinding are more serious than regular grinding. So grinding fluid supply in creep-feed grinding is very important. Grinding fluid supply quantity is not linear with effectiveness because grinding wheel is porosity material and the grinding area is solid contact area. In this paper, by using AE signal, optimal quantity of fluid supply was determined. And surface characteristics of wet creep-feed grinding were analized.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.56-60
• /
• 1996

An experimental study on the grinding temperature and Acoustic Emission(AE) signals due to the different shapes of wheel was conducted. The grinding characteristics by slotted shapes of wheel changed by width and helical angle, were compared with those by general one. Lower grinding temperature was obtained for 30$^{\circ}$ helical angle with 10mm width, Root Mean Square(RMS) values of AE signals were higher for slotted wheel rather than general one.

• Journal of Welding and Joining
• /
• v.28 no.5
• /
• pp.10-14
• /
• 2010

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.6
• /
• pp.87-94
• /
• 2007

Reuse of recycled aggregate from demolished concrete structure is beneficial and necessary from the viewpoint of environmental preservation and effective utilization of resources. The most important mechanical properties of recycled aggregate concrete (RAC) are the compressive strength, the tensile and the flexural strengths, the bond strength and the elastic modulus of such concrete. In particular, the stress-strain relation and fracture process of RAC in compression is especially important in theoretical and numerical analysis as well as engineering design of RAC structures. In this paper, to clarify the characteristics of fracture process in RAC, acoustic emission(AE) method is applied to detect micro-cracking in concrete under compression. From AE parameters, it is found that cracking and fracture behaviors in recycled aggregate concrete fairly differ from that of normal and recycled sand concrete.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.4
• /
• pp.276-284
• /
• 2000

The acoustic emission (AE) behavior of reinforced concrete beams tested under flexural loading was investigated to characterize and identify the source of damage. This research was aimed at identifying the characteristic AE response associated with micro-crack development, localized crack propagation, corrosion, and debonding of the reinforcing steel. Concrete beams were prepared to isolate the damage mechanisms by using plain, notched-plain, reinforced, and corroded-reinforced specimens. The beams were tested using four-point cyclic step-loading. The AE response was analyzed to obtain key parameters such as the time history of AE events, the total number and rate of AE events, and the characteristic features of the waveform. Initial analysis of the AE signal has shown that a clear difference in the AE response is observed depending on the source of the damage. The Felicity ratio exhibited a correlation with the overall damage level, while the number of AE events during unloading can be an effective criterion to estimate the level of corrosion distress in reinforced concrete structures. Consequently, AE measurement characterization appears to provide a promising approach for estimating the level of deterioration in reinforced concrete structure.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.13 no.4
• /
• pp.113-120
• /
• 2004

The object of this study is to investigate the effect of compounded welding through the AE(Acoustic Emission) characteristics for weld HAZ(Heat Affected Zone) under the static tensile test. This study was carried out an SWS 490A, high tension steel for electric shield metal arc welding(SMAW), $CO_2$ gas arc welding and TIG welding. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. The accumulated AE event curve of HAZ definitely have the point of inflection subject to tensile test. The results of the tensile test of HAZ come out electric shield arc welding ＞$CO_2$ gas arc welding＞TIG welding in case of single welding, but generally the tensile test of HAZ come out electric shield arc welding＞ TIG welding ＞ $CO_2$ gas arc welding. These history plots give us useful and powerful information to analyze the results of material evaluation testing.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.18 no.4
• /
• pp.59-66
• /
• 2010

Aerospace structures need high stability and long life because many personal injuries can result from an accident and securing structural integrity for various external environments is more important than any other thing. So first of all we must prove the destruction properties for operating environment, have prediction technology about damage evolution and life, and develop an economical non-destructive technology capable of detecting structure damage. Acoustic emission (AE) have no need of artificial environment like ultrasonic inspection or radio fluoroscopy to emit a certain energy, is a testing technique using seismic signal resulting from interior changes of solids, and enables to observe if any fault is appeared and it grows seriously or not while running. In this study we suggest the method of structural integrity evaluation for aerospace structures through the acoustic emission technique, for which a model plane was manufactured and an actual operation test was conducted.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2000.04a
• /
• pp.51-56
• /
• 2000

Demand for new nondestructive evaluations is growing to detect tensile crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we analysed acoustic emission signals obtained in tensile test of high strength fire resistance steel for frame structure with time frequency analysis methods. The results obtained are summaries as follows ; In the T and TN specimen consisting of ferrite and pearlite grains, most of acoustic emission events were produced near yield point, mainly due to the dislocation activities during the deformation. However, B specimen under $600^{\circ}C$ - 10min had a two peak which was attribute to the presence of martensite phase. The first peak is before yield point the second is after yield point. The sources of second acoustic emission peak were the debonding of martensite-martensite interface and the micro-cracking of brittle martensite phase. In $600^{\circ}C$-30min to $700^{\circ}C$-60min specimens, many signals were observed from area before yield point and counts were decreased after yield point.