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Y. Luo et al.
50.1 Introduction
In the process of electrolytic aluminum production, the cathode carbon block suffers
from the erosion of molten salt at high temperature and the electrochemical action
in the process of electrolysis. The original microcrack expand under the action of
molten salt erosion and mechanical stress, which will lead to the deformation, uplift
and even fracture of the cathode carbon block, all of which will seriously shorten the
life of the electrolytic cell [1, 2]. At present, the damage detection of cathode carbon
block mainly base on physical indicators such as abnormal cathode voltage drop
and temperature. However it is hard to infer the internal crack evolution process and
damage degree of cathode carbon block, while acoustic emission (AE) is a promising
technique showing great potential for real-time monitoring and condition evaluation
of engineering materials and structures [3]. AE is the class of phenomenon whereby
transient elastic waves originate from sudden energy release within material caused
by crack, dislocation, friction, etc. Moreover, AE parameters are closely related to
the crack evolution and fracture mode of materials (tensile fracture, shear fracture
and their coupling fracture), such as ringing counts, amplitude, energy, frequency
and RA-AF value, etc. [4–6]. Therefore, AE technology can be used to monitor the
elastic wave signals generated by the cathode carbon block under the state of stress,
which can obtain the degree of damage and crack growth of the carbon block, so
as to provide experimental basis for online monitoring and failure prediction of the
cathode carbon block in the service process.
Recently, the AE method has been utilized to monitor the microscopic and macroscopic crack initiation in various materials during deformation by many scholars.
Yuyama et al. [4] used AE technology to monitor the fracture process of reinforced
concrete columns subjected to simulated seismic lateral loads under different coaxial
loads. Shiotani et al. [7] conducted fracture tests of bending and shear loads on rock
materials, studied the variation of AE parameters with rock fracture process, and
proposed the classification criterion of fracture state based on AE parameters, with
good practical application effect. Soulioti et al. [8] showed that AE technology could
be used to identify fracture patterns by a four-point bending experiment on steel fiber
reinforced concrete beams. Additionally, as shear cracking follows tensile cracking,
crack classification using suitable AE descriptors can assist the evaluation of the
severity of the damage condition. Aggelis et al. [9] studied the propagation of elastic
wave pulses in microstructure materials and used AE parameters to characterize
the fracture properties of materials, such as RA (rise time/amplitude)-AF (average
frequency) values. Villalobos [10] applied AE technology to monitor the drying
process of bamboo, and pointed out that different avalanche degrees had different
characteristics of AE parameters. Ioka et al. [11] studied the behavior of AE for
four types of graphite to confirm the sources of AE events caused by tensile and
compressive loading. Ekinaga [12] used AE method to monitor the initiation of
macroscopic and microscopic cracks under three-point bending and studied the AE
signal characteristics generated at each loading stage. Yonga et al. [13] studied the
damage mechanisms of carbon fiber reinforced silicon carbide (C/SiC) composites
Y. Luo et al.
50.1 Introduction
In the process of electrolytic aluminum production, the cathode carbon block suffers
from the erosion of molten salt at high temperature and the electrochemical action
in the process of electrolysis. The original microcrack expand under the action of
molten salt erosion and mechanical stress, which will lead to the deformation, uplift
and even fracture of the cathode carbon block, all of which will seriously shorten the
life of the electrolytic cell [1, 2]. At present, the damage detection of cathode carbon
block mainly base on physical indicators such as abnormal cathode voltage drop
and temperature. However it is hard to infer the internal crack evolution process and
damage degree of cathode carbon block, while acoustic emission (AE) is a promising
technique showing great potential for real-time monitoring and condition evaluation
of engineering materials and structures [3]. AE is the class of phenomenon whereby
transient elastic waves originate from sudden energy release within material caused
by crack, dislocation, friction, etc. Moreover, AE parameters are closely related to
the crack evolution and fracture mode of materials (tensile fracture, shear fracture
and their coupling fracture), such as ringing counts, amplitude, energy, frequency
and RA-AF value, etc. [4–6]. Therefore, AE technology can be used to monitor the
elastic wave signals generated by the cathode carbon block under the state of stress,
which can obtain the degree of damage and crack growth of the carbon block, so
as to provide experimental basis for online monitoring and failure prediction of the
cathode carbon block in the service process.
Recently, the AE method has been utilized to monitor the microscopic and macroscopic crack initiation in various materials during deformation by many scholars.
Yuyama et al. [4] used AE technology to monitor the fracture process of reinforced
concrete columns subjected to simulated seismic lateral loads under different coaxial
loads. Shiotani et al. [7] conducted fracture tests of bending and shear loads on rock
materials, studied the variation of AE parameters with rock fracture process, and
proposed the classification criterion of fracture state based on AE parameters, with
good practical application effect. Soulioti et al. [8] showed that AE technology could
be used to identify fracture patterns by a four-point bending experiment on steel fiber
reinforced concrete beams. Additionally, as shear cracking follows tensile cracking,
crack classification using suitable AE descriptors can assist the evaluation of the
severity of the damage condition. Aggelis et al. [9] studied the propagation of elastic
wave pulses in microstructure materials and used AE parameters to characterize
the fracture properties of materials, such as RA (rise time/amplitude)-AF (average
frequency) values. Villalobos [10] applied AE technology to monitor the drying
process of bamboo, and pointed out that different avalanche degrees had different
characteristics of AE parameters. Ioka et al. [11] studied the behavior of AE for
four types of graphite to confirm the sources of AE events caused by tensile and
compressive loading. Ekinaga [12] used AE method to monitor the initiation of
macroscopic and microscopic cracks under three-point bending and studied the AE
signal characteristics generated at each loading stage. Yonga et al. [13] studied the
damage mechanisms of carbon fiber reinforced silicon carbide (C/SiC) composites