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Acoustic Emission Monitoring and Microscopic Investigation of Cracks in ERCuNi Cladding 被引量:1
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作者 S.P.Lu O.Y.Kwon +1 位作者 K.J.Lee T.B.Kim 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2003年第3期201-205,共5页
A corrosion resistant CuNi cladding was deposited on SM45C (equivalent to AISI1045) substrate by DC inverse arc welding. During the welding process, a three channel acoustic emission (AE) monitoring system was applied... A corrosion resistant CuNi cladding was deposited on SM45C (equivalent to AISI1045) substrate by DC inverse arc welding. During the welding process, a three channel acoustic emission (AE) monitoring system was applied to detect the crack signals generating from both the cladding process and after cladding. Characteristics of the welding crack signal and noise signal had been analyzed systematically. Based on the record time of the signal, the solidification crack and delayed crack were distinguished. By two-dimensional AE source location, the crack position was located, and then investigated by scanning electron microscopy (SEM). Results showed that the AE system could detect the welding crack with high sensitivity and the two-dimensional source location could accurately determine the crack position. Microstructures of the cladding and heat affected zone (HAZ) were examined. Dendrites in the cladding and coarse grains in the HAZ were found. 展开更多
关键词 CLADDING acoustic emission monitoring CRACK CuNi alloy
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Acoustic emission monitoring of rockbursts during TBM-excavated headrace tunneling at Jinping Ⅱ hydropower station 被引量:6
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作者 Wuwei Cheng Wenyou Wang +1 位作者 Shiqiang Huang Peng Ma 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2013年第6期486-494,共9页
To better understand the mechanical properties of marble at Jinping II hydropower station, this paper examines the changes of brittle rocks in excavation damaged zones(EDZs) before and after excavation of tunnel with ... To better understand the mechanical properties of marble at Jinping II hydropower station, this paper examines the changes of brittle rocks in excavation damaged zones(EDZs) before and after excavation of tunnel with the tunnel boring machine(TBM). The paper attempts to employ the acoustic emission(AE) to study the AE characteristics and distribution of rockburst before and after TBM-excavated tunnel. It is known that the headrace tunnel #2, excavated by the drill-and-blast(D&B) method, is ahead of the headrace tunnel #3 that is excavated by TBM method. The experimental sub-tunnel #2–1, about 2000 m in depth and 13 m in diameter, between the two tunnels is scheduled. In the experimental sub-tunnel #2–1, a large number of experimental boreholes are arranged, and AE sensors are installed within 10 m apart from the wall of the headrace tunnel #3. By tracking the microseismic signals in rocks, the location, frequency, quantity, scope and intensity of the microseismic signals are basically identifed. It is observed that the AE signals mainly occur within 5 m around the rock wall, basically lasting for one day before tunnel excavation and a week after excavation. Monitoring results indicate that the rockburst signals are closely related to rock stress adjustment. The rock structure has a rapid self-adjustment capacity before and after a certain period of time during tunneling. The variations of rock stresses would last for a long time before reaching a fnal steady state. Based on this, the site-specifc support parameters for the deep tunnels can be accordingly optimized. 展开更多
关键词 acoustic emission(AE) monitoring Tunnel construction Microseismic event Relaxation time Rockbursts
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Study on Acoustic Emission Characteristics of Deformation Damage Process of Zirconia Ceramics
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作者 Qingchuan Fu Yushu Lai 《Journal of Materials Science and Chemical Engineering》 2024年第2期61-72,共12页
Zirconia ceramics have become increasingly widely used in recent years and are favored by relevant enterprises. From the traditional dental field to aerospace, parts manufacturing has been used, but there is limited r... Zirconia ceramics have become increasingly widely used in recent years and are favored by relevant enterprises. From the traditional dental field to aerospace, parts manufacturing has been used, but there is limited research on the deformation and damage process of zirconia ceramics. This article analyzes the acoustic emission characteristics of each stage of ceramic damage from the perspective of acoustic emission, and explores its deformation process characteristics from multiple perspectives such as time domain, frequency, and EWT modal analysis. It is concluded that zirconia ceramics exhibit higher brittleness and acoustic emission strength than alumina ceramics, and when approaching the fracture, it tends to generate lower frequency acoustic emission signals. 展开更多
关键词 Zirconia Ceramics acoustic emission monitoring Crack Damage
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Research on acoustic emission monitoring of pitting corrosion on 304 stainless steel 被引量:3
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作者 ZHANG Zhongzheng GONG Jianming LIANG Hua 《Chinese Journal of Acoustics》 2013年第1期71-78,共8页
In order to study acoustic emission (AE) characteristics of pitting corrosion on 304 stainless steel under higher than normal temperature, pitting corrosion process of 304 stainless steel in 6° ferric chloride ... In order to study acoustic emission (AE) characteristics of pitting corrosion on 304 stainless steel under higher than normal temperature, pitting corrosion process of 304 stainless steel in 6° ferric chloride solution at 70° was monitored by AE technology. Conventional parameter-based approach and signal-based analysis were combined to deal with recorded AE signals, and micrographic observation was performed for further verification. The results showed that AE hit and energy increased gradually with time and reached the peak at certain time, and then declined and maintained a stable condition. Signal waveform was mainly composed of low-frequency (〈 100 kHz) flexural wave with larger amplitude and energy and high-frequency (〉 100 kHz) expansion wave with lower amplitude and energy. The research results have some certain significance for AE monitoring of pitting corrosion on 304 stainless steel under higher than normal temperature. 展开更多
关键词 PIT Research on acoustic emission monitoring of pitting corrosion on 304 stainless steel
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Shear failure behaviors and degradation mechanical model of rockmass under true triaxial multi-level loading and unloading shear tests OA
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作者 Zhi Zheng Ronghua Li +3 位作者 Pengzhi Pan Jinghua Qid Guoshao Su Hong Zheng 《International Journal of Mining Science and Technology》 SCIE EI CAS 2024年第10期1385-1408,共24页
The redistribution of three-dimensional(3D)geostress during underground tunnel excavation can easily induce to shear failure along rockmass structural plane,potentially resulting in engineering disasters.However,the c... The redistribution of three-dimensional(3D)geostress during underground tunnel excavation can easily induce to shear failure along rockmass structural plane,potentially resulting in engineering disasters.However,the current understanding of rockmass shear behavior is mainly based on shear tests under2D stress without lateral stress,the shear fracture under 3D stress is unclear,and the relevant 3D shear fracture theory research is deficient.Therefore,this study conducted true triaxial cyclic loading and unloading shear tests on intact and bedded limestone under different normal stressσnand lateral stressσpto investigate the shear strength,deformation,and failure characteristics.The results indicate that under differentσnandσp,the stress–strain hysteresis loop area gradually increases from nearly zero in the pre-peak stage,becomes most significant in the post-peak stage,and then becomes very small in the residual stage as the number of shear test cycles increases.The shear peak strength and failure surface roughness almost linearly increase with the increase inσn,while they first increase and then gradually decrease asσpincreases,with the maximum increases of 12.9%for strength and 15.1%for roughness.The shear residual strength almost linearly increases withσn,but shows no significant change withσp.Based on the acoustic emission characteristic parameters during the test process,the shear fracture process and microscopic failure mechanism were analyzed.As the shear stressτincreases,the acoustic emission activity,main frequency,and amplitude gradually increase,showing a significant rise during the cycle near the peak strength,while remaining almost unchanged in the residual stage.The true triaxial shear fracture process presents tensile-shear mixture failure characteristics dominated by microscopic tensile failure.Based on the test results,a 3D shear strength criterion considering the lateral stress effect was proposed,and the determination methods and evolution of the shear modulus G,cohesion cjp,friction angleφjp,and dilation angleψjpduring rockmass shear fracture process were studied.Under differentσnandσp,G first rapidly decreases and then tends to stabilize;cjp,φjp,andψjpfirst increase rapidly to the maximum value,then decrease slowly,and finally remain basically unchanged.A 3D shear mechanics model considering the effects of lateral stress and shear parameter degradation was further established,and a corresponding numerical calculation program was developed based on3D discrete element software.The proposed model effectively simulates the shear failure evolution process of rockmass under true triaxial shear test,and is further applied to successfully reveal the failure characteristics of surrounding rocks with structural planes under different combinations of tunnel axis and geostress direction. 展开更多
关键词 True triaxial shear test Lateral stress effect acoustic emission monitoring Shear parameters evolution Shear degradation mechanical model
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