2020 Vol. 40, No. 4
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2020, 40(4): 041101.
doi: 10.11883/bzycj-2020-0082
Abstract:
Pulse waves cannot be understood simply as pressure waves (longitudinal waves) propagating in compressible blood fluid, nor as radially expanding-contracting displacement waves (transverse waves) propagating along solid blood vessels, but rather as complex waves with fluid-solid coupling and longitudinal wave-transverse wave coupling beyond ordinary imagination. Starting from a new approach to analyze the coupling constitutive relation, a series model is proposed, providing more information for traditional Chinese medicine (TCM) pulse diagnosis in terms of the “position, rate, shape and potential”. It is shown that the equivalent volumetric compression modulus Ks and the corresponding pulse wave propagation velocity cs of the coupling pulse wave system, mainly depend on two dimensionless parameters: the ratio of the blood modulus to the vessel modulus, Kb(p)/E(p) and the ratio of the diameter to the thickness, D(p)/h0, of thin-walled blood vessels, which may vary from person to person and from different pulse locations for the same person. The influences of them on the cs are quantitatively analyzed, showing that for human body the magnitude of Kb/E is in the order of 103 so that the magnitude of cs is in the order of 100–101 m/s to adapt to the human physio-biochemical reactions. By clinical invasive measurements, it is confirmed that the pulse volume transverse wave and the pulse pressure longitudinal wave are coupled and propagate at the same speed, and it is shown that the pulse wave is actually a “biological wave” with oxygenation and biochemical reactions on the wave front. Furthermore, the relations of the “pulse pressure amplification” with the nonlinear constitutive relation and with the load enhanced reflection at the bifurcation of blood vessels, as well as the Lewis’s hypothesis about the formation of dicrotic wave are discussed.
Pulse waves cannot be understood simply as pressure waves (longitudinal waves) propagating in compressible blood fluid, nor as radially expanding-contracting displacement waves (transverse waves) propagating along solid blood vessels, but rather as complex waves with fluid-solid coupling and longitudinal wave-transverse wave coupling beyond ordinary imagination. Starting from a new approach to analyze the coupling constitutive relation, a series model is proposed, providing more information for traditional Chinese medicine (TCM) pulse diagnosis in terms of the “position, rate, shape and potential”. It is shown that the equivalent volumetric compression modulus Ks and the corresponding pulse wave propagation velocity cs of the coupling pulse wave system, mainly depend on two dimensionless parameters: the ratio of the blood modulus to the vessel modulus, Kb(p)/E(p) and the ratio of the diameter to the thickness, D(p)/h0, of thin-walled blood vessels, which may vary from person to person and from different pulse locations for the same person. The influences of them on the cs are quantitatively analyzed, showing that for human body the magnitude of Kb/E is in the order of 103 so that the magnitude of cs is in the order of 100–101 m/s to adapt to the human physio-biochemical reactions. By clinical invasive measurements, it is confirmed that the pulse volume transverse wave and the pulse pressure longitudinal wave are coupled and propagate at the same speed, and it is shown that the pulse wave is actually a “biological wave” with oxygenation and biochemical reactions on the wave front. Furthermore, the relations of the “pulse pressure amplification” with the nonlinear constitutive relation and with the load enhanced reflection at the bifurcation of blood vessels, as well as the Lewis’s hypothesis about the formation of dicrotic wave are discussed.
2020, 40(4): 042101.
doi: 10.11883/bzycj-2019-0106
Abstract:
After the gas explosion, preventing the propagation of explosion flame can better eliminate the disaster. In this paper, three kinds of nitrogen nozzle arrangement are set to carry out experiments for explosion prevention. The nitrogen pressures used in experiments include 0.1, 0.2, 0.3, 0.4 and 0.5 MPa, Nitrogen is spurted into the pipe after the occurrence of the explosion and immediately shut down after quenching the explosion. The results show that the spurted nitrogen under each pressure can not prevent the explosion with single nitrogen nozzle, which is 20 cm away from the vent. But the average propagation speed of the flame in the whole pipe decreases with the increase of nitrogen pressure. With single nitrogen nozzle, which is 35 cm away from the vent, the spurted nitrogen at pressure 0.5 MPa succeed in explosion prevention, while the explosion can not be prevented at other pressure. When double nozzle is used to spurt nitrogen, the explosion is prevented in the case of pressure 0.3, 0.4 and 0.5 MPa. And the greater the nitrogen pressure, the more forward the flame is blocked. The explosion prevention requires nitrogen to dilute the premixed gas below the combustible limit. Nitrogen volume is the important parameter affecting dilution. With single nitrogen nozzle, the situation of nozzle far from the vent is easier to prevent the explosion than that of nozzle near from the vent. When double nozzles are used, the nitrogen region will enlarge. With double nozzle, lower nitrogen pressure and less nitrogen quantity are required for preventing the explosion as comparing with single nozzle.
After the gas explosion, preventing the propagation of explosion flame can better eliminate the disaster. In this paper, three kinds of nitrogen nozzle arrangement are set to carry out experiments for explosion prevention. The nitrogen pressures used in experiments include 0.1, 0.2, 0.3, 0.4 and 0.5 MPa, Nitrogen is spurted into the pipe after the occurrence of the explosion and immediately shut down after quenching the explosion. The results show that the spurted nitrogen under each pressure can not prevent the explosion with single nitrogen nozzle, which is 20 cm away from the vent. But the average propagation speed of the flame in the whole pipe decreases with the increase of nitrogen pressure. With single nitrogen nozzle, which is 35 cm away from the vent, the spurted nitrogen at pressure 0.5 MPa succeed in explosion prevention, while the explosion can not be prevented at other pressure. When double nozzle is used to spurt nitrogen, the explosion is prevented in the case of pressure 0.3, 0.4 and 0.5 MPa. And the greater the nitrogen pressure, the more forward the flame is blocked. The explosion prevention requires nitrogen to dilute the premixed gas below the combustible limit. Nitrogen volume is the important parameter affecting dilution. With single nitrogen nozzle, the situation of nozzle far from the vent is easier to prevent the explosion than that of nozzle near from the vent. When double nozzles are used, the nitrogen region will enlarge. With double nozzle, lower nitrogen pressure and less nitrogen quantity are required for preventing the explosion as comparing with single nozzle.
2020, 40(4): 042102.
doi: 10.11883/bzycj-2019-0237
Abstract:
Hydrogen-doped fuel has gradually become the focus of research due to its excellent combustion characteristics. In order to further study the detonation characteristics of hydrogen-doped fuel, a cylindrical semi-enclosed tube with the length of 3 000 mm and the diameter of 30 mm was designed. The detonation characteristics of three premixed gases, CH4-2O2, 6CH4-H2-12.5O2 and 3CH4-H2-6.5O2 (hydrogen ratio is 0%, 5.1% and 9.5%, respectively), were studied experimentally under different initial pressures. Smoked foils, ion probes and pressure sensors were used to measure the cell structures, the flame positions and the internal pressures, respectively. The results show that hydrogen-doped methane/oxygen can effectively increase the propagation velocity of detonation waves, and the higher the concentration of hydrogen, the faster the propagation velocity. In addition, hydrogen can reduce the velocity loss at the outlet of the tube and accelerate the coupling of flame and shock wave at lower initial pressures, reduce the cell size and improve detonation sensitivity.
Hydrogen-doped fuel has gradually become the focus of research due to its excellent combustion characteristics. In order to further study the detonation characteristics of hydrogen-doped fuel, a cylindrical semi-enclosed tube with the length of 3 000 mm and the diameter of 30 mm was designed. The detonation characteristics of three premixed gases, CH4-2O2, 6CH4-H2-12.5O2 and 3CH4-H2-6.5O2 (hydrogen ratio is 0%, 5.1% and 9.5%, respectively), were studied experimentally under different initial pressures. Smoked foils, ion probes and pressure sensors were used to measure the cell structures, the flame positions and the internal pressures, respectively. The results show that hydrogen-doped methane/oxygen can effectively increase the propagation velocity of detonation waves, and the higher the concentration of hydrogen, the faster the propagation velocity. In addition, hydrogen can reduce the velocity loss at the outlet of the tube and accelerate the coupling of flame and shock wave at lower initial pressures, reduce the cell size and improve detonation sensitivity.
2020, 40(4): 042201.
doi: 10.11883/bzycj-2019-0268
Abstract:
This work aims at the explosion problem in long-distance gas pipelines. An experimental study on the influence of ultrafine water mist with NaCl on the gas explosion characteristics of pipes with different blocking ratios was carried out in a self-built horizontally transparent duct. Such effects are quantified via the analysis of pressure and flame speed. The results show that the explosion overpressure increases with the increase of the pipeline blocking ratio in such gas explosion of the pipeline that is only under the pressure relief ports with different blocking ratios (0, 0.2, 0.4 and 0.6). Under the action of ultrafine water mist, the blocking ratio varies nonlinear with the time of flame front movement propagation to the end of the pipe. When the blocking rate is 0.2, the average flame velocity is the highest. When the fog flux is 8.4 mL and mass fraction of NaCl in it is 8%, the ultrafine water mist containing NaCl has the best fire and explosion suppression effect as the maximum explosion pressure drops by 59.2%. The ultra-fine mist containing NaCl acts directly on the explosion flame to suppress the explosion.
This work aims at the explosion problem in long-distance gas pipelines. An experimental study on the influence of ultrafine water mist with NaCl on the gas explosion characteristics of pipes with different blocking ratios was carried out in a self-built horizontally transparent duct. Such effects are quantified via the analysis of pressure and flame speed. The results show that the explosion overpressure increases with the increase of the pipeline blocking ratio in such gas explosion of the pipeline that is only under the pressure relief ports with different blocking ratios (0, 0.2, 0.4 and 0.6). Under the action of ultrafine water mist, the blocking ratio varies nonlinear with the time of flame front movement propagation to the end of the pipe. When the blocking rate is 0.2, the average flame velocity is the highest. When the fog flux is 8.4 mL and mass fraction of NaCl in it is 8%, the ultrafine water mist containing NaCl has the best fire and explosion suppression effect as the maximum explosion pressure drops by 59.2%. The ultra-fine mist containing NaCl acts directly on the explosion flame to suppress the explosion.
2020, 40(4): 042301.
doi: 10.11883/bzycj-2019-0239
Abstract:
In order to study the reaction characteristics of reactive materials under explosive loading, two typical reactive materials, namely Al/PTFE and Al/Ni, as well as two inert materials, namely Al2O3/PTFE and Al2O3/PTFE/W, were manufactured by powder compaction. Explosion-driven tests were conducted on the four materials, by combining with the high-speed photography technology, far-infrared thermal imager testing technology and peak overpressure testing technology. The characteristics of explosive fireball, distribution of temperature and peak overpressure of blast shock waves were analyzed for different materials. Furthermore, the chemical energy released from the reactive materials was considered in the empirical calculation model to estimate the peak overpressure of blast shock waves. The influence of the released energy on the blast shock wave was analyzed by the model. The results show that during the explosion driving process, the reactive materials undergo such stages as reaction under strong loading, debris generation and scattering around, impact on steel plates and subsequent reaction. Reactive materials can strengthen the air shock wave produced by explosive explosion, and only part of the chemical reaction occurs at the moment of explosion loading.
In order to study the reaction characteristics of reactive materials under explosive loading, two typical reactive materials, namely Al/PTFE and Al/Ni, as well as two inert materials, namely Al2O3/PTFE and Al2O3/PTFE/W, were manufactured by powder compaction. Explosion-driven tests were conducted on the four materials, by combining with the high-speed photography technology, far-infrared thermal imager testing technology and peak overpressure testing technology. The characteristics of explosive fireball, distribution of temperature and peak overpressure of blast shock waves were analyzed for different materials. Furthermore, the chemical energy released from the reactive materials was considered in the empirical calculation model to estimate the peak overpressure of blast shock waves. The influence of the released energy on the blast shock wave was analyzed by the model. The results show that during the explosion driving process, the reactive materials undergo such stages as reaction under strong loading, debris generation and scattering around, impact on steel plates and subsequent reaction. Reactive materials can strengthen the air shock wave produced by explosive explosion, and only part of the chemical reaction occurs at the moment of explosion loading.
2020, 40(4): 042302.
doi: 10.11883/bzycj-2019-0260
Abstract:
To solve the premature-combustion problem of FAE fuel during the dispersal process by explosive, fire retardant medium with superfine ABC powder as the main component was introduced along with the structural design of central dispersed explosive. High-speed camera and infrared thermal imager were used to study the temperature and flame generated by the dispersed explosive. The experimental results show that the maximum temperature of the dispersed explosive fireball was 1355.4 °C, and the duration of the temperature exceeding 150 °C was 264.8 ms. The flame generated by the dispersed explosive almost completely disappears after the introduction of the flame retardant medium. The maximum temperature of the fireball decreases by more than 90%, and the surface temperature of the fireball does not exceed 100 °C. At the same time, the verification experiment was carried out. The mixture fuel of 1 kg ether and aluminum powder was dispersed by the dispersed explosive filled with flame retardant medium. When the mass ratio of dispersed explosive to fuel was more than 4%, the premature-combustion was restrained successfully. It shows that filling the flame retardant medium can effectively prevent the premature-combustion in the fuel dispersion process.
To solve the premature-combustion problem of FAE fuel during the dispersal process by explosive, fire retardant medium with superfine ABC powder as the main component was introduced along with the structural design of central dispersed explosive. High-speed camera and infrared thermal imager were used to study the temperature and flame generated by the dispersed explosive. The experimental results show that the maximum temperature of the dispersed explosive fireball was 1355.4 °C, and the duration of the temperature exceeding 150 °C was 264.8 ms. The flame generated by the dispersed explosive almost completely disappears after the introduction of the flame retardant medium. The maximum temperature of the fireball decreases by more than 90%, and the surface temperature of the fireball does not exceed 100 °C. At the same time, the verification experiment was carried out. The mixture fuel of 1 kg ether and aluminum powder was dispersed by the dispersed explosive filled with flame retardant medium. When the mass ratio of dispersed explosive to fuel was more than 4%, the premature-combustion was restrained successfully. It shows that filling the flame retardant medium can effectively prevent the premature-combustion in the fuel dispersion process.
2020, 40(4): 043301.
doi: 10.11883/bzycj-2019-0280
Abstract:
In order to improve the crashworthiness of thin-walled tubes, the multi-cell bionic thin-walled tubes based on a shrimp chela structure were designed by the principle of structural bionics. By taking the cell number (2−6) and the impact angle (0°, 10°, 20°, 30°) as experimental factors, the finite element method was used to simulate the crashworthiness of the bionic tubes, the reliability of the results by the simulation test was verified by the drop-weight tests. The results show that the two-cell bionic tube has the best crashworthiness under axial and oblique loads. Under the same working conditions, the reduction of the number of unit cells can reduce the peak loads of the bionic tubes. Under the oblique impact load, the time for the bionic tubes to maintain the stable collapse deformation mode is shortened with the increase of the number of the cells, and the crashworthiness of the bionic tubes decreases with the increase of the number of the cells. The combination of a shrimp cheek structure and an ordinary circular tube effectively improves the crashworthiness of the designed structures. So it can provide a reference for the design of energy-absorbing components in vehicles.
In order to improve the crashworthiness of thin-walled tubes, the multi-cell bionic thin-walled tubes based on a shrimp chela structure were designed by the principle of structural bionics. By taking the cell number (2−6) and the impact angle (0°, 10°, 20°, 30°) as experimental factors, the finite element method was used to simulate the crashworthiness of the bionic tubes, the reliability of the results by the simulation test was verified by the drop-weight tests. The results show that the two-cell bionic tube has the best crashworthiness under axial and oblique loads. Under the same working conditions, the reduction of the number of unit cells can reduce the peak loads of the bionic tubes. Under the oblique impact load, the time for the bionic tubes to maintain the stable collapse deformation mode is shortened with the increase of the number of the cells, and the crashworthiness of the bionic tubes decreases with the increase of the number of the cells. The combination of a shrimp cheek structure and an ordinary circular tube effectively improves the crashworthiness of the designed structures. So it can provide a reference for the design of energy-absorbing components in vehicles.
2020, 40(4): 043302.
doi: 10.11883/bzycj-2019-0207
Abstract:
In order to evaluate the effect of blasting vibration on an adjacent concrete pipeline with bell-and-spigot joints buried in a silty clay layer, four blasting field experiments were conducted by applying the DH5956 dynamic strain testing system and TC-4850 blasting vibration device mounted on the buried pipelines, and the dynamic response characteristics of the concrete pipelines under blasting vibration were studied. The spatial distributions of the dynamic strain and vibration velocity of the pipe bodies and the bell-and-spigot joints were analyzed. Based on the maximum allowable deflection degree of the bell-and-spigot joints in the specification and the criterion of the dynamic tensile stress failure of the concrete, the safety criterion of the blasting vibration velocity for the bell-and-spigot concrete pipelines was proposed. The results show that there is an uncoordinated response between the pipe bodies and bell-and-spigot joints under the action of blasting vibration; the bell-and-spigot joints are the most venerable positions of the pipelines, and the failure of the the bell-and-spigot joints should be noticed when considering the effect of blasting vibration; the blasting vibration velocity control threshold of the the bell-and-spigot concrete pipelines is 5 cm/s, this research can provide a guidance for the pipeline protection in similar construction projects.
In order to evaluate the effect of blasting vibration on an adjacent concrete pipeline with bell-and-spigot joints buried in a silty clay layer, four blasting field experiments were conducted by applying the DH5956 dynamic strain testing system and TC-4850 blasting vibration device mounted on the buried pipelines, and the dynamic response characteristics of the concrete pipelines under blasting vibration were studied. The spatial distributions of the dynamic strain and vibration velocity of the pipe bodies and the bell-and-spigot joints were analyzed. Based on the maximum allowable deflection degree of the bell-and-spigot joints in the specification and the criterion of the dynamic tensile stress failure of the concrete, the safety criterion of the blasting vibration velocity for the bell-and-spigot concrete pipelines was proposed. The results show that there is an uncoordinated response between the pipe bodies and bell-and-spigot joints under the action of blasting vibration; the bell-and-spigot joints are the most venerable positions of the pipelines, and the failure of the the bell-and-spigot joints should be noticed when considering the effect of blasting vibration; the blasting vibration velocity control threshold of the the bell-and-spigot concrete pipelines is 5 cm/s, this research can provide a guidance for the pipeline protection in similar construction projects.
2020, 40(4): 043303.
doi: 10.11883/bzycj-2019-0293
Abstract:
By coupling the implicit static analysis and the explicit dynamic analysis in ABAQUS, a numerical method to simulate the lateral impact process of concrete filled steel tubular (CFST) member in fire is presented. The tests about temperature field, the axial impact under fire and lateral impact at ambient temperature of CFST members are simulated to verify the feasibility of the method, respectively. Based on the proposed method, the finite element analysis (FEA) model of lateral impact of CFST members at different temperatures is developed. The time history curves of mid-span deflection and impact force at different temperatures are compared respectively. The post-extremumequal impact force (Fpe) and energy absorption capacity (μ) are used to quantitatively analyze the lateral impact resistance of the member. Finally, the impact process of the member at 600 °C is analyzed. The results show that the temperature has a significant influence on the lateral impact performance of the member. With the increase of temperature, the mid-span deflection increases and the impact duration is longer. The time history curve of impact force at high temperature is obviously different from that at ambient temperature. And the curve at high temperature can be divided into three stages, including the oscillating phase, the descending phase and the unloading phase. The kinetic energy of the drop hammer is mainly absorbed by the overall bending deformation of the member. The Fpe and μ decrease with the increase of temperature, indicating that the impact resistance of the member decreases. When the temperature of exceeds 400 °C, the impact resistance of the member is seriously lost.
By coupling the implicit static analysis and the explicit dynamic analysis in ABAQUS, a numerical method to simulate the lateral impact process of concrete filled steel tubular (CFST) member in fire is presented. The tests about temperature field, the axial impact under fire and lateral impact at ambient temperature of CFST members are simulated to verify the feasibility of the method, respectively. Based on the proposed method, the finite element analysis (FEA) model of lateral impact of CFST members at different temperatures is developed. The time history curves of mid-span deflection and impact force at different temperatures are compared respectively. The post-extremumequal impact force (Fpe) and energy absorption capacity (μ) are used to quantitatively analyze the lateral impact resistance of the member. Finally, the impact process of the member at 600 °C is analyzed. The results show that the temperature has a significant influence on the lateral impact performance of the member. With the increase of temperature, the mid-span deflection increases and the impact duration is longer. The time history curve of impact force at high temperature is obviously different from that at ambient temperature. And the curve at high temperature can be divided into three stages, including the oscillating phase, the descending phase and the unloading phase. The kinetic energy of the drop hammer is mainly absorbed by the overall bending deformation of the member. The Fpe and μ decrease with the increase of temperature, indicating that the impact resistance of the member decreases. When the temperature of exceeds 400 °C, the impact resistance of the member is seriously lost.
2020, 40(4): 044201.
doi: 10.11883/bzycj-2019-0151
Abstract:
The reinforced concrete (RC) shield building is the first external defense layer of AP1000 structure. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as the blast loading. In this study, the coupled Euler-Lagrange (CEL) method was used to numerically simulate the fluid and structure interaction (FSI) between air and AP1000 RC shield building. The dynamic response analysis of the 20 contact explosion positions of the shield building under explosive loads were carried out, and the damage mass was used to evaluate the damage. The evolution mechanism of pressure and damage mode were discussed. The numerical results clearly show that, under the contact explosive loads, the RC shield building has the local damage near the explosive point. The damage degree at the same height but with different circumferential angle are similar, while those in the same circumferential angle with different height are different. In addition, through analyzing the pressure and damage evolution, the strategy of the different parts of the plant reinforcement was proposed. These results might be helpful to understand the behaviors and characteristics of the AP1000 RC shield building under contact explosion and provide valuable references in design and engineering practice.
The reinforced concrete (RC) shield building is the first external defense layer of AP1000 structure. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as the blast loading. In this study, the coupled Euler-Lagrange (CEL) method was used to numerically simulate the fluid and structure interaction (FSI) between air and AP1000 RC shield building. The dynamic response analysis of the 20 contact explosion positions of the shield building under explosive loads were carried out, and the damage mass was used to evaluate the damage. The evolution mechanism of pressure and damage mode were discussed. The numerical results clearly show that, under the contact explosive loads, the RC shield building has the local damage near the explosive point. The damage degree at the same height but with different circumferential angle are similar, while those in the same circumferential angle with different height are different. In addition, through analyzing the pressure and damage evolution, the strategy of the different parts of the plant reinforcement was proposed. These results might be helpful to understand the behaviors and characteristics of the AP1000 RC shield building under contact explosion and provide valuable references in design and engineering practice.
2020, 40(4): 045101.
doi: 10.11883/bzycj-2019-0126
Abstract:
In order to obtain the suitable structure of the metal diaphragm in the double-pulse engine compartment, this study used the Johnson-Cook material damage model to numerically simulate the pressure-bearing and rupture process of metal diaphragms of different specifications. The results determined the metal diaphragm of a certain specification to meet the design requirements. A set of two-way pressure measuring device was designed to study the pressure-bearing and rupture behaviors of the metal diaphragm. The results show that the metal diaphragm has no structural rupture during one-pulse operation. During the two-pulse operation, the metal diaphragm breaks along the pre-cut and no metal fragments are detached. The pressure-bearing and rupture behavior can meet the working requirements in the engine. The results obtained by numerical simulation are in good agreement with the experiment data, which shows that it is feasible to use the numerical simulation method to study the bearing and cracking of metal diaphragm. Furthermore, simulation study shows that as the diameter increases with the thickness-diameter ratio of the metal diaphragm kept constant, the pressure required for the rupture increases at first and then decreases, and then it increases again.
In order to obtain the suitable structure of the metal diaphragm in the double-pulse engine compartment, this study used the Johnson-Cook material damage model to numerically simulate the pressure-bearing and rupture process of metal diaphragms of different specifications. The results determined the metal diaphragm of a certain specification to meet the design requirements. A set of two-way pressure measuring device was designed to study the pressure-bearing and rupture behaviors of the metal diaphragm. The results show that the metal diaphragm has no structural rupture during one-pulse operation. During the two-pulse operation, the metal diaphragm breaks along the pre-cut and no metal fragments are detached. The pressure-bearing and rupture behavior can meet the working requirements in the engine. The results obtained by numerical simulation are in good agreement with the experiment data, which shows that it is feasible to use the numerical simulation method to study the bearing and cracking of metal diaphragm. Furthermore, simulation study shows that as the diameter increases with the thickness-diameter ratio of the metal diaphragm kept constant, the pressure required for the rupture increases at first and then decreases, and then it increases again.
2020, 40(4): 045201.
doi: 10.11883/bzycj-2019-0092
Abstract:
Accurate removal of signal trend items is of practical importance for improving the accuracy of blasting vibration signal analysis. Here, aiming at the defects of EMD identification, such as mode aliasing and terminal effect, a method based on variational mode decomposition (VMD) to remove signal trend term is proposed. The principle of identifying the trend term of blasting signals by VMD method is described in details, and the simulation experiment was carried out. The results show that the influence of the trend term frequency on the decomposition effect is relatively small. When the trend term frequency is between 1 and 5 Hz, the effect of the frequency on the decomposition effect remains basically the same. The amplitude has a significant influence on the decomposition effect. Furthermore, the amplitude is smaller, the decomposition effect of the VMD method is worse. When the amplitude of the trend term exceeds 1/3 of the maximum amplitude of the original blasting signal, the VMD method has a better decomposition effect. Finally, the VMD method and the EMD method are applied to process the measured blasting vibration signal containing the trend term. Compared with the EMD method, the signals processed by the VMD method are basically consistent and have no terminal effect, and have wider applicability in the field of blasting signal trend item removal.
Accurate removal of signal trend items is of practical importance for improving the accuracy of blasting vibration signal analysis. Here, aiming at the defects of EMD identification, such as mode aliasing and terminal effect, a method based on variational mode decomposition (VMD) to remove signal trend term is proposed. The principle of identifying the trend term of blasting signals by VMD method is described in details, and the simulation experiment was carried out. The results show that the influence of the trend term frequency on the decomposition effect is relatively small. When the trend term frequency is between 1 and 5 Hz, the effect of the frequency on the decomposition effect remains basically the same. The amplitude has a significant influence on the decomposition effect. Furthermore, the amplitude is smaller, the decomposition effect of the VMD method is worse. When the amplitude of the trend term exceeds 1/3 of the maximum amplitude of the original blasting signal, the VMD method has a better decomposition effect. Finally, the VMD method and the EMD method are applied to process the measured blasting vibration signal containing the trend term. Compared with the EMD method, the signals processed by the VMD method are basically consistent and have no terminal effect, and have wider applicability in the field of blasting signal trend item removal.
