Kaiser Effect Of Acoustic Emission Research Articles

Research on Kaiser effect of acoustic emission in concrete subjected to bending after freeze-thaw

For hydraulic concrete structures in cold coastal areas, the frost resistance of concrete is critical. To determine the range of force applied to concrete during freeze-thaw cycling. In this study, the force on concrete during freeze-thaw cycling were investigated by performing a three-point bending test on concrete after freeze-thaw cycling and also monitoring the damage process of concrete using acoustic emission(AE). Firstly, based on the variation of AE parameters during concrete damage, the range of Kaiser effect points appearing during three-point bending loading was determined. Secondly, the G-P algorithm was used to calculate the correlated fractal dimension of AE. The results of the study showed that the mass and relative dynamic elastic modulus(RDEM) of concrete decreased linearly with the increase in the number of freeze-thaw cycles. The Kaiser effect of increased AE ringing counts and cumulative energy, and decreased correlated fractal dimension, was observed in the freeze-thawed concrete specimens during loading as the load increased. By comparing the two methods, it was found that the difference between the Kaiser effect points determined by the AE parameter method and the correlated fractal dimension method ranged from 0% to 14%. And the ratios between the force corresponding to the Kaiser effect points and the peak force are less than 0.8.

Study on in situ stress testing method based on Kaiser effect of acoustic emission and COMSOL simulation

Study on in situ stress testing method based on Kaiser effect of acoustic emission and COMSOL simulation

Damage analysis of a SiCf/SiC ceramic matrix composite under stepwise fatigue loading with acoustic emission

Continuous fiber-reinforced ceramic matrix composites (CMCs) exhibit different damage mechanisms at multiple scales under cyclic loading. In this paper, the tension-tension fatigue behavior of a plain woven SiCf/SiC CMC was investigated, and damage accumulation and evolution process were studied in detail via acoustic emission (AE) method. With the increase of cycles, the material exhibits obvious hysteresis behavior affected by interfacial slip and wear mechanisms. Most of the fibers with radial fracture characteristic have relatively high strength, showing excellent toughening property. In the stepwise cyclic loading process, the Kaiser effect of AE determines the initiation of AE activities at each initial loading moment, which shows obvious nonlinear damage accumulation behavior of the material. High-energy events are related to significant matrix cracking and fiber fracture, and the evolution process of material damage initiation and propagation is monitored in real time.

Investigation on Acoustic Emission Kaiser Effect and Frequency Spectrum Characteristics of Rock Joints Subjected to Multilevel Cyclic Shear Loads

Rock joints have obvious acoustic emission (AE) Kaiser effect and Felicity effect under multilevel cyclic shear conditions. The TFD-20H/50J rock shear apparatus was used to carry out cyclic loading and unloading joint shear tests, and the acoustic emission parameters and frequency spectrum characteristics of the whole shearing process were analyzed. The results show that, under the cyclic loading, the shear stress-displacement curve forms several cyclic hysteresis loops, and the number of loops increases with the increase of normal stress. With the cycles increase, the shear damage gradually increases, and the Felicity ratio gradually decreases. The Felicity ratio at the final shear failure moment is about 0.94~0.99. The ratio of the RA value (rise time/amplitude) and the average frequency value (RA-AF) is used to classify the cracking mode of the joint sample. There are two AE crack signal types (tensile type and shear type) during shear damage. The peak frequency is displayed as high, medium, and low three frequency bands, which are distributed in the range of 0~35 kHz, 35~122 kHz, and 122~300 kHz, respectively. Both low-frequency and high-frequency signals account for less than 10%, and medium-frequency signals account for more than 90%. The research of the AE monitoring signals of multilevel shear behaviors can help understand the shear-friction mechanisms of rock joints.

A novel in situ stress measurement method based on acoustic emission Kaiser effect: a theoretical and experimental study.

Measurement of in situ stress is critical to understand the deformation and destruction of the underground space surrounding rock, and dynamic disaster of the coal mine. At present, with the increasing depth of mining, in situ stress parameters are more and more important for coal mine. In this paper, a novel method for in situ stress measurement with Kaiser effect was studied and applied in the Baijiao coal mine. First, we presented a comprehensive analysis method for the identification of Kaiser effect point. Then, a calculation method for in situ stress measurement based on the Kaiser effect on acoustic emissions was suggested. After that, the in situ stress test of Baijiao coal mine is taken as the research object, an experiment using acoustic emissions monitoring during uniaxial compression testing was performed to investigate the mechanical properties and acoustic emissions characteristics. Finally, in situ stress of the study area was calculated using the novel calculation method above and calculation results were verified using stress relief method and hydraulic fracturing method. The results showed that the calculation results obtained using the proposed method were valid and credible. Therefore, the calculation method for in situ stress measurement and the proposed comprehensive analysis method using the Kaiser point could be applied for in situ stress testing using the Kaiser effect method.

Study of Damage and Acoustic Emission Properties of Rocks under Uniaxial Cyclic Load-Unload

In order to study the damage and sptial spatial and temporal distribution of acoustic emission of rocks under uniaxial cyclic load-unload, test of rocks with various kinds of heterogeneity under uniaxial cyclic load-unload disturbance was conducted using numerical simulation software RFPA2D.Figure destruction and acoustic emission - load curve of rocks were obtained from the test.The results show that destroy of the rock was produced from tensile stress concentration area surrounding the hole. as the load increases,crack developmented to the edge of the rock.when homogeneity of rock was low, crack development with irregularity due to defects of rocks. with the increasing homogeneity of rock, damage evolution mode under uniaxial cyclic load-unload disturbance transition from ductile to brittle.damage evolvement process can be responsed by acoustic emission. with the increasing homogeneity of rock. The maximum number of acoustic emission Continuously improve and exhibit unexpected. Kaiser effect of acoustic emission under cyclic loading is significantly This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. .

Application of the Kaiser effect of acoustic emission to measure vertical stress in an underground mine

Application of the Kaiser effect of acoustic emission to measure vertical stress in an underground mine

Using Acoustic Emission to Quantify Damage in High-Performance Fiber-Reinforced Cement Composites under Cyclically Compressive Loading

High performance fiber-reinforced cement composites (HPFRCCs) show multiple cracks and a limited damage tolerance capability due to the debonding of the fibers of the cement matrix. For practical applications, it is necessary to investigate the fractural behavior of HPFRCCs to understand the mechanism of the microbehavior of a cement matrix containing reinforcing fibers. We have investigated the acoustic emission (AE) signals in HPFRCCs under monotonic and cyclic uniaxial compressive loads. Four types of specimen were tested. The experimental parameters studied were: the type of fiber (polyethylene or polyvinyl alcohol), the hybrid type (with steel cord), and the loading pattern. The data shows that the progress of the damage in HPFRCCs in the compressive mode is characteristic of the type of hybrid fiber and its volume fraction. From the AE data, the second and third compressive load cycles resulted in a successive decrease in the amplitude compared to the first compressive load cycle. In addition, an AE Kaiser effect was observed in HPFRCCs specimens up to 80% of their ultimate strength. These observations suggest that the AE Kaiser effect has potential for use as a new tool to monitor the loading history of HPFRCCs.

Role of Acoustic Emission for Solving Rock Engineering Problems in Indonesian Underground Mining

In situ stress measurement is not well accepted yet in Indonesia due to the unavailability of technology, high costs and because it is impractical in remote regions. Alternatively, the Kaiser effect of acoustic emission (AE) can be used as a method for determining the stress-state at depth, without creating induced stress and is practical in remote areas. This paper is focused on the development of the AE test. The research has started to study the phenomenon of stress memory in a rock sample, the factors influencing the phenomenon, and finally, to determine the in situ stresses around underground excavations by applying the AE method. It is expected that knowledge in gaining the most important input parameters for maintaining the stability of underground excavations can be well understood and be reliably conducted at a reasonable cost.

AE기법에 의한 압축력을 받는 고인성 섬유보강 시멘트 복합체의 손상 평가

고인성 섬유보강 시멘트 복합체는 시멘트 매트릭스 내 보강된 섬유의 계면부착응력에 의해 다수의 미세균열분산 및 손상저항성능을 갖게 되나, 이를 구조물에 적용하기 위해서는, 고인성 섬유보강 시멘트 복합체의 파괴거동을 규명함과 동시에 보강섬유에 따른 시멘트 매트릭스의 마이크로 파괴메커니즘에 대한 이해가 요구된다. 이 연구에서는 단조 및 반복가력시 고인성 섬유보강 시멘트 복합체의 파괴특성 및 음향방출신호특성을 규명하기 위하여 총 4 시리즈의 시험체가 사용되었으며, 주요 실험변수는 섬유의 종류(PE, PVA, SC), 혼입률, 하이브리드 타입, 가력방법(단조, 반복) 이다. 실험결과, 고인성 섬유보강 시멘트 복합체의 압축거동에 따른 손상진전은 섬유의 혼입률 및 하이브리드에 따라 상이하게 나타났다. 또한 음향방출신호로부터, 각 하중단계의 2, 3번째 사이클에서의 진폭 감소 특성이 나타났으며, 이는 각 사이클별 변형률 증가와의 관련성을 보여 이를 이용한 강도 예측이 가능할 것으로 판단된다. 또한 최대강도의 80%까지 펠리시티 효과 및 카이저 효과가 나타났으며, 하이브리드 섬유 혼입시 매크로 균열 제어로 인해 손상의 복원 및 분산능력이 뛰어난 것으로 나타났다.

음향방출 기법을 이용한 섬유보강 시멘트 복합체의 정량적 손상평가

Dept. of Civil System Engineering, Konyang University, Chungnam 320-711, KoreaABSTRACT Fiber is an important ingredient in fiber-reinforced cement composite (FRCC) which can control fracture of cementcomposite by bridging action. In compliance with the action of the fiber and the aggregate size, it also showed a different failure mech-anism. For practical application, it is needed to investigate the fracture behavior of the FRCC and to understand the micro-mechanismof cement matrix with reinforcing fiber. In order to evaluate a characteristics of fracture process in the FRCC, acoustic emission (AE)technique was used for the analysis and evaluation of FRCC damage by acoustic emission under flexural and cyclic compressive load-ings. The AE signals were monitored by AMSY4 AE instrument during the entire loading period. The specimens are reinforced with0, 1.0, 1.5 and 2.0% (by volume) Polyvinyl alcohol (PVA) fiber. The test results showed that the damage progress of the FRCC wascharacteristic for the fiber replacement ratio. As a result of analyzing the felicity ratio (FR) values, it is shown that this values can beused for evaluating the degree of FRCC damage. On the whole the felicity ratio values of FRCC are shown between 0.4 and 1.1. And,the AE kaiser effect was shown in the all FRCC specimen. In addition, the damage behavior and the microscopic fracture process ofthe FRCC are evaluated using the AE parameters, such as calm ratio, b-value and felicity ratio. The purpose of this reserch was toadvance the state of knowledge regarding the applicability of acoustic emission as an evaluation method for FRCC.Keywords : fiber-reinforced cement composite, bridging action, Kaiser effect, calm ratio, b-value

Numerical simulation on the acoustic emission activities of concrete

Acoustic emission (AE) is a very important tool to study the cracking process and to evaluate the integrity of structures. The numerical simulation on AE activities is helpful for us to explain the AE data observed during the AE test of concrete and to therefore clarify the associated failure mechanism. Based on the knowledge that the AE events of concrete under external loading are closely related to its internal damage, it becomes possible for us to simulate these AE activities of concrete at meso-level with a numerical tool. In this paper, a numerical model is used to simulate the AE activities of mortar and concrete beams under three-point bending. Based on numerical simulation, the load–displacement curves and corresponding AE activities of mortar and concrete specimens are obtained and are calibrated against the corresponding experimental results. Subsequently, this numerical model is utilized to simulate the AE activities of mortar specimen when it is subjected to cyclic loading, and the Kaiser effect of AE is reproduced.

Time-sensitivity of the Kaiser effect of acoustic emission in limestone and its application to measurements of in-situ stress

Measuring in-situ stress by using the Kaiser effect in rocks has such advantages as time-efficiency, low cost and little limitation, but the precision of the method is dependent on rock properties and delay time of the measurement. In this paper, experiments on the Kaiser effect in limestones were performed, and it was found that the limestones had good ability to retain a memory of their recent stress history and high time-sensitivity. The longer the experiment was delayed from the extraction of the stone, the larger the Felicity ratio was. As the Felicity ratio approached 1, significant Kaiser effect was observed. In-situ stress should be determined by the limestone measurements when the delay time was 40–120 days. Finally, the in-situ stress in a limestone formation could be successfully measured in practice.

AE BEHAVIOR OF SMART STRESS MEMORY PATCH AFTER VARIABLE AMPLITUDE LOADING

Recently, the structural health monitoring becomes increasingly great important to assure the ease and safety of our life, and it is required significantly to develop non-destructive evaluation for structures such as bridges and tunnels. Some sacrificed specimens have been developed to evaluate the fatigue damage of structures such as fatigue cycles and residual lifetime, but it can be applied only when the stress history is known beforehand. These fatigue sensors need no cable and can be used at low cost in contrast to strain gage. In previous study, a smart stress memory patch was developed as a new fatigue sensor. The patch can measure simultaneously the maximum stress, stress amplitude and the number of fatigue cycles by crack length measurement and Kaiser effect of Acoustic Emission (AE). The crack growth behavior under constant amplitude (CA) loading has been investigated, and AE behavior also has been evaluated only after CA loading. However, AE characteristics after variable amplitude (VA) loading in service are extremely important. Moreover, it is very important to control AE behavior of the smart patch in order to evaluate the applied stress using Kaiser effect. In this study, fatigue test with single overload was investigated to evaluate its influence. Moreover, effect of crack length and heat treatment on AE behavior was also investigated. Finally, AE behavior of the patch was evaluated after fatigue CA loading with overload or VA loading with log-normal distribution and overload.

Theoretical and experimental analysis on the mechanism of the Kaiser effect of acoustic emission in brittle rocks

The Kaiser effect is formally described as the absence of detectable acoustic emission (AE) events until the load imposed on the material exceeds the previous applied level and is usually used to estimate geostress. By focusing on the heterogeneity of rock material, the mechanism of the Kaiser effect under cyclic loading is analyzed based on statistic damage mechanics. Two groups of granite specimens have been cyclically loaded with two different loading paths to verify the theoretical results. The heterogeneity of rock is the real reason that causes irrecoverable damage on the Kaiser effect of acoustic emission in cyclic loading. The Kaiser effect reflects the damaged state in rocks rather than the previous stress imposed on it. Applications for using the Kaiser effect to estimate geostress were discussed here. It is shown that the commonly used uniaxial loading method for estimating geostress is not in accordance with the theoretical and experimental results. The analysis is of importance to use the Kaiser effect correctly for estimating geostress or in other fields.

Experimental Verification and Theoretical Analysis on Felicity Effect of Acoustic Emission in Concrete

The experiment of acoustic emission (AE) on concrete specimens under uniaxial cyclic loading was conducted. The Kaiser effect of acoustic emission in concrete and the Felicity effect, which manifest the memorizing ability to the maximum previous stress level of Kaiser effect, were validated by the experiment. The mechanism of Felicity effect was analyzed based on the theory of statistical damage mechanics and a tentative AE factor constitutive model of brittle material under uniaxial cyclic loading was suggested. The curve of constitutive model is in good coincidence with the curve from the experiment. The experimental results showed that the Felicity effect became clearer along with the increasing of stress level. Each loading cycle would cause new damage inside the material, and the response of material to the new loading cycle is different from the previous cycle.

Crack Growth Characteristics of Pure Copper for Smart Stress Memory Patch

A new sensing method called “smart stress memory patch”, which could estimate the maximum stress, the stress amplitude and the fatigue cyclic number simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length of this patch, was developed. In this study, the crack growth characteristics of this patch was evaluated. Pure copper was used for this patch because its good corrosion resistance, stable crack propagation and so on. Two kinds of samples which were rolled and electrodeposited copper were prepared to investigate the effect of microstructure on crack growth behavior. Fatigue test was performed under constant stress amplitude to evaluate the crack growth behavior using the relationship between stress intensity factor range and crack propagation rate. The scattering in fatigue crack growth was also investigated to obtain the relationship between crack length and the fatigue cyclic number including two-sided 95% confidence interval. The effect of thickness and grain size on the scattering was discussed. Finally, good crack growth behavior was obtained and the fatigue cyclic number could be estimated by this patch.

Development of Smart Stress Memory Sensor Using AE Kaiser Effect

Reliability of structures is an important task to ensure the ease and safety of our life, and further development of non-destructive evaluation for structures such as bridges and tunnels is required. Some fatigue sensors that consist of sacrificed specimen have been developed to evaluate the fatigue damage of structures such as fatigue cyclic number and residual lifetime. However, these fatigue sensors can be used only when the applied stress amplitude is known. We tried to develop a new smart stress memory patch that measured both maximum stress and number of fatigue cycles simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length. In this study, the characteristics of the smart patch was evaluated. Pure copper was used for this sensor because its good corrosion resistance, stable crack propagation and detectability of AE near yield point. Fatigue test was performed under the constant stress amplitude to evaluate the crack propagation behavior using the relationship between stress intensity factor and crack propagation rate. The obtained curve between crack length and number of fatigue cycles by these crack propagation behavior was in good agreement with experimental results. AE measurement after some fatigue tests was performed and AE was detected at the applied fatigue stress. These results demonstrated that number of fatigue cycles and the maximum stress could be measured by this fatigue sensor.

W03I Development of stress memory patch(International Workshop on "New Frontiers of Smart Materials and Structural Systems")

A new sensing method called "smart stress memory patch", which could estimate the maximum stress, the stress amplitude and the fatigue cyclic number simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length of this patch, was developed. In this study, the crack growth characteristic of this patch was evaluated. Pure copper was used for this patch because its good corrosion resistance, stable crack propagation and so on. Two kinds of samples which were rolled and electrodeposited copper were prepared to investigate the effect of microstructure on crack growth behavior. Fatigue test was performed under constant stress amplitude to evaluate the crack growth behavior using the relationship between stress intensity factor range and crack propagation rate. The scattering in fatigue crack growth was also investigated to obtain the relationship between crack length and the fatigue cyclic number including two-sided 95% confidence interval. The effect of thickness and grain size on the scattering was discussed. Finally, good crack growth behavior was obtained and the fatigue cyclic number could be estimated by this patch.

A new method of determining geostresses by the acoustic emission Kaiser effect

A new method of determining geostresses by the acoustic emission Kaiser effect