Acoustic emission measurements and lattice simulations of microfracture events in spruce

Holzforschung ◽  
2010 ◽  
Vol 64 (4) ◽  
Author(s):  
Edwin Nagy ◽  
Eric N. Landis ◽  
William G. Davids
Keyword(s):  
Acoustic Emission ◽  
Fracture Energy ◽  
Energy Release ◽  
Lattice Model ◽  
Failure Modes ◽  
Mechanical Damage ◽  
Peak Strain ◽  
Cumulative Energy ◽  
Ae Energy ◽  
Total Fracture

Abstract A statistical lattice model was developed to investigate the energy associated with damage and failure of wood. The model incorporates several important morphological aspects of wood such as grain direction, early wood percentage and grain geometry. The model was developed to investigate progressive damage under enforced boundary displacements and has been adapted to predict fracture energy related phenomena. In this particular study, notched specimens were loaded in uniaxial tension while monitored by a passive acoustic emission (AE) measurement system. The energy associated with the mechanical damage was measured by the AE instruments and compared with the energy released by ruptured elements in the lattice model. Cumulative energy release was tracked as a function of specimen load and deformation in both model and experiment. A ratio was established between the cumulative AE energy released at the first drop in load and the cumulative fracture energy released when the model load-deformation relationship becomes significantly non-linear. An additional ratio was established between the total fracture energy measured prior to 50% of peak strain and the total fracture energy measured prior to peak strain. The magnitudes of these energy release ratios vary owing to a change in failure modes between the short model and the larger specimens; however, the shape of the AE energy release curve up to failure coincides well with that predicted by the model simulations.

Study on the Effect of Cl- Concentration on the Corrosion Fatigue Damage in a Rolled AZ31B Magnesium Alloy by Acoustic Emission

2007 ◽  
Vol 353-358 ◽  
pp. 327-330 ◽  
Author(s):  
Hua Mao Zhou ◽  
Jian Qiu Wang ◽  
Qi Shan Zang ◽  
En Hou Han
Keyword(s):  
Acoustic Emission ◽  
Magnesium Alloy ◽  
Energy Release ◽  
Fatigue Damage ◽  
Corrosion Fatigue ◽  
Room Temperature ◽  
Fatigue Performance ◽  
Ae Energy ◽  
Magnesium Alloy Az31b ◽  
Wrought Magnesium Alloy

The fatigue performance of one widely used wrought magnesium alloy AZ31B in rolled form was studied using acoustic emission (AE). AE energy release during corrosion fatigue (CF) testing was measured at room temperature. It is found that AE energy release can express corrosion fatigue damage experienced by the material.

Experimental Research on Acoustic Emission of Granite under Uniaxial Compression and Splitting Tensile

2012 ◽  
Vol 232 ◽  
pp. 24-27
Author(s):  
Zong Zhan Li ◽  
Jun Lin Tao ◽  
Yi Li
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Loading Rate ◽  
Testing Machine ◽  
Peak Stress ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Ae Energy

This paper makes the acoustic emission of granite under uniaxial compression and splitting tensile test by electro-hydraulic testing machine and AE .We studied the relationship of uniaxial compressive strength and splitting tensile strength with the loading rate and AE characteristics of granite .The results show that uniaxial compressive strength and peak strain raise with loading rate, the AE energy gradually increases and get maximum in the 30% of the peak stress in the process of uniaxial compression test, and in the splitting tensile AE energy generates in the initial loading and gets maximum when the granite brittle fracture.

scholarly journals Acoustic Emission and Failure Modes for Coal-Rock Structure under Different Loading Rates

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Ning Wang ◽  
Yingqian Xu ◽  
Dengyuan Zhu ◽  
Nan Wang ◽  
Benfu Yu
Keyword(s):  
Acoustic Emission ◽  
Energy Release ◽  
Failure Modes ◽  
Loading Rate ◽  
Failure Process ◽  
Coal Mass ◽  
Transient Growth ◽  
Loading Rates ◽  
Rock Structure ◽  
Coal Rock

Coal bump refers to a sudden catastrophic failure of coal seam and usually causes serious damages to underground mining facilities and staff. Considering the combined coal-rock structure for coal bumps, failure process and acoustic emission (AE) characteristics of combined coal-sandstone samples under different loading rates were studied by uniaxial compression tests, and three basic failure modes and bump proneness for coal-rock structure were obtained. The following conclusions are drawn: (1) when loading rate was relatively low, plastic deformation of coal mass fully developed, while surface cracks of coal mass was not apparent and slip along the transfixion crack occurred in the postpeak stage; (2) with the increase in loading rate, surface tensile cracks developed into splitting cracks at the end of the prepeak stage and throughout the postpeak stage, and brittle failure finally happened due to the release of nonlinear step-shaped energy or one-time strain energy release of upper rock mass, resulting in the damage of internal bearing structure and weakening of bearing capacity; (3) the deformation and failure process of combined samples showed obvious phases, and corresponding AE energy release rate could be divided into periodic linear growth and transient growth, while the cumulative energy of AE events has multiple peak points and transient growth with the increase of loading rate; (4) it was demonstrated that two distinct frequency bands existed in AE events, which were about 50 kHz and 150 kHz, and the distribution of AE events near 50 kHz was larger and stronger, representing the main frequency range of cracks in coal mass. According to the damage characteristics and AE parameters for combined samples, an brittle model for coal-rock structure with mutation characteristics was proposed, and three basic failure modes for the combined structure with the increase of loading rate were progressive shear failure, splitting failure, and structural failure, respectively.

scholarly journals Acoustic emission characteristics of pre-cracked specimens under biaxial compression

2019 ◽  
Vol 16 (6) ◽  
pp. 1164-1177 ◽  
Author(s):  
Xuewei Liu ◽  
Quansheng Liu ◽  
Bin Liu ◽  
Qi Liu
Keyword(s):  
Acoustic Emission ◽  
Energy Release ◽  
Confining Pressure ◽  
B Value ◽  
Biaxial Compression ◽  
Linear Elastic ◽  
Ae Energy ◽  
Unstable Failure ◽  
Release Ratio ◽  
Cracked Specimens

Abstract This paper presents an experimental study in which molded gypsum pre-cracked specimens with two types of flaw (single and X-shaped cross flaws) were tested under biaxial compression. Results show that acoustic emission (AE) energy rate curves can be divided into three different periods during uniaxial compression, which correspond to crack closure, linear elastic and unstable failure stages of specimens. However, only two periods are observed during biaxial compression, which correspond to linear elastic deformation and unstable failure. Furthermore, two proposed AE parameters, namely the AE energy ratio and AE energy release ratio, and a classical AE parameter b-value were used to analyze the influence of biaxial compression loading on AE energy, respectively. With increasing confining pressure, the AE energy release ratio, as well as AE b-value decreases gradually while AE energy ratio increases. Moreover, maximum and average AE energy rate values decrease as confining pressure increases. Data presented herein is useful to study the AE characteristics of pre-cracked specimens under biaxial compression.

scholarly journals Acoustic Emission Characteristics and Damage Evolution of Rock under Different Loading Modes

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3649
Author(s):  
Ersheng Zha ◽  
Ru Zhang ◽  
Zetian Zhang ◽  
Ting Ai ◽  
Li Ren ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fracture Surface ◽  
Tensile Stress ◽  
Energy Release ◽  
Failure Modes ◽  
Failure Process ◽  
Tensile Tests ◽  
Single Fracture ◽  
Loading Modes ◽  
Ae Signals

To study the evolution of acoustic emission (AE) parameters and the differences in the fracturing and failure process of rocks under different loading modes, AE signals of marble were detected during uniaxial compression tests (UCTs), direct tensile tests (DTTs) and indirect tensile tests (ITTs) in this paper. Then, the temporal and spatial evolution of the AE parameters and damage development of rock under different loading modes were analyzed. The results showed that the sequence of total AE events and AE counts under different loading modes was UCT > DTT > ITT. In the DTT and ITT, the energy release of AE signals was concentrated at the peak stress and weakened rapidly afterward, whereas in the UCT, there were still a large number of AE signals accompanied by violent AE energy release during the postpeak stage. The generation mechanism of AE sources in rock and the corresponding failure modes were different under different loading modes. In the UCT, the multiple cleavage fractures were mainly caused by compression-induced fracturing. In the DTT, the single fracture surface was generated by tensile stress, whereas in the ITT, compressive-tensile stress was applied to the fracture surface. In addition, the stress levels at which the b-value and the spatial fractal dimension Ds of AE events decreased dramatically were consistent under the different loading modes, and the sequence was UCT < DTT < ITT. According to the changes in AE parameters during the whole process of rock deformation and failure, the first and second precursor points before failure were defined to distinguish the development of microfracture damage and failure processes in rocks under the different loading modes. The above results have certain significance for future studies on the monitoring of surrounding rock instability and failure prediction.

scholarly journals Research on Acoustic Emission Characteristics and Constitutive Model of Rock Damage Evolution with Different Sizes

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Haijiang Zhang ◽  
Xiaohu Zhang ◽  
Hongbo Zhou
Keyword(s):  
Acoustic Emission ◽  
Constitutive Model ◽  
Scale Effect ◽  
Damage Evolution ◽  
Failure Modes ◽  
Development Stage ◽  
Diameter Ratio ◽  
Emission Characteristics ◽  
Peak Strain ◽  
Evolution Law

In this study, considering the scale effect of rock mass, the influence of different height-to-diameter ratios on rock mechanics and acoustic emission characteristics was studied by using PFC2D software. The damage constitutive model of rock was established, and the damage evolution characteristics of rock with different height-to-diameter ratios were further analyzed. The results showed that, with the increase of height-to-diameter ratio K, the uniaxial compressive strength and peak strain of rock exhibited a gradual decrease; however, the elastic modulus gradually increased. Moreover, rock failure modes exhibited different characteristics under different K values. The scale effect showed little influence on the acoustic emission characteristics in the elastic stage; nonetheless, in the plastic deformation stage and the residual damage stage, with the increase of the rock’s height-to-diameter ratio, the maximum number of impacts of acoustic emission increased, the range of strong strain of acoustic emission decreased, and the maximum time of acoustic emission impacts increased gradually. The height-to-diameter ratio of the rock slightly influenced the zero-damage stage of the rock, but the damage affecting the rock increased slowly and accelerated the development stage. The damage evolution law was found to be similar when the K values varied from 1.0 to 2.0; however, when the K was greater than 2.0, the damage evolution law exhibited the characteristics of slowing down in the acceleration phase.

scholarly journals Acoustic Emission Characteristics and Joint Nonlinear Mechanical Response of Rock Masses under Uniaxial Compression

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 200
Author(s):  
Zhongliang Feng ◽  
Xin Chen ◽  
Yu Fu ◽  
Shaoshuai Qing ◽  
Tongguan Xie
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Failure Modes ◽  
Strain Curve ◽  
Particle Flow Code ◽  
Rock Masses ◽  
Physical Experiments ◽  
Inclination Angles ◽  
Joint Inclination

The joint arrangement in rock masses is the critical factor controlling the stability of rock structures in underground geotechnical engineering. In this study, the influence of the joint inclination angle on the mechanical behavior of jointed rock masses under uniaxial compression was investigated. Physical model laboratory experiments were conducted on jointed specimens with a single pre-existing flaw inclined at 0°, 30°, 45°, 60°, and 90° and on intact specimens. The acoustic emission (AE) signals were monitored during the loading process, which revealed that there is a correlation between the AE characteristics and the failure modes of the jointed specimens with different inclination angles. In addition, particle flow code (PFC) modeling was carried out to reproduce the phenomena observed in the physical experiments. According to the numerical results, the AE phenomenon was basically the same as that observed in the physical experiments. The response of the pre-existing joint mainly involved three stages: (I) the closing of the joint; (II) the strength mobilization of the joint; and (III) the reopening of the joint. Moreover, the response of the pre-existing joint was closely related to the joint’s inclination. As the joint inclination angle increased, the strength mobilization stage of the joint gradually shifted from the pre-peak stage of the stress–strain curve to the post-peak stage. In addition, the instantaneous drop in the average joint system aperture (aave) in the specimens with medium and high inclination angles corresponded to a rapid increase in the form of the pulse of the AE activity during the strength mobilization stage.

Cumulative acoustic emission energy for damage detection in composites reinforced by carbon fibers within low-cycle fatigue regime at various displacement amplitudes and rates

2021 ◽  
pp. 096739112098570
Author(s):  
Mohammad Azadi ◽  
Mohsen Alizadeh ◽  
Seyed Mohammad Jafari ◽  
Amin Farrokhabadi
Keyword(s):  
Acoustic Emission ◽  
Carbon Fibers ◽  
Polymer Matrix Composites ◽  
Low Cycle Fatigue ◽  
Energy Parameter ◽  
Fatigue Tests ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Cycle Fatigue ◽  
Cumulative Energy

In the present article, acoustic emission signals were utilized to predict the damage in polymer matrix composites, reinforced by carbon fibers, in the low-cycle fatigue regime. Displacement-controlled fatigue tests were performed on open-hole samples, under different conditions, at various displacement amplitudes of 5.5, 6.0, 6.5 and 7.0 mm and also under various displacement rates of 25, 50, 100 and 200 mm/min. After acquiring acoustic emission signals during cycles, two characteristic parameters were used, including the energy and the cumulative energy. Obtained results implied that the energy parameter of acoustic emission signals could be used only for the macroscopic damage, occurring at more than 65% of normalized fatigue cycles under different test conditions. However, the cumulative energy could properly predict both microscopic and macroscopic defects, at least two failure types, including matrix cracking at first cycles and the fiber breakage at last cycles. Besides, scanning electron microscopy images proved initially such claims under all loading conditions.

scholarly journals Effect of the Reinforcement Phase on Indentation Resistance and Damage Characterization of Glass/Epoxy Laminates Using Acoustic Emission Monitoring

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
C. Suresh Kumar ◽  
K. Saravanakumar ◽  
P. Prathap ◽  
M. Prince ◽  
G. Bharathiraja ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Glass Fiber ◽  
Research Work ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Cumulative Energy ◽  
Static Indentation ◽  
Felicity Ratio ◽  
Woven Glass Fiber ◽  
Energy Absorbing

The effect of reinforcement phases on indentation resistance and damage behavior of glass/epoxy laminates was investigated in this research work. Woven glass fiber mat and nonwoven chopped glass fiber mat were used as fiber reinforcement phases for fabricating the laminates. Low-velocity impact and quasi-static indentation tests were performed on both laminates to investigate the contact behavior and energy-absorbing capability. Moreover, the acoustic emission (AE) technique was employed to monitor the indentation damage resistance. AE parameters including normalized cumulative counts (NCC), normalized cumulative energy (NCE), rise angle (RA), and felicity ratio (FR) were analyzed. The bidirectional laminates showed premature load drops and drastic changes in the normalized cumulative counts/energy profile in the beginning of loading cycles, indicating the development of macrodamage such as debonding/delamination. AE sentry function results of bidirectional laminates show longer PII function at the earlier stages, associated with minor PIII function and greater PIV function, indicating the continuous degradation and progression of damage. In contrast, the chopped laminates exhibited superior postimpact performance than the bidirectional laminates. The presence of randomly oriented fibres prevents the delamination crack propagation during compression loading, which was attributed with the increased residual compressive strength.

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