2023 Vol. 43, No. 12
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2023, 43(12): 122201.
doi: 10.11883/bzycj-2023-0153
Abstract:
To study the response law of a metal target plate under the simultaneous initiation of two charges and to construct a calculation model for the deformation and deflection of the target plate under the action of dual explosion source shock waves, the dynamic response of the metal plate under the action of double explosion sources was studied through dimensional analysis. Based on the numerical simulation calculation results using the finite element software, the influence of the charge quality, charge spacing, and vertical distance from the charge to the target plate of the double explosion source on the maximum deflection of the 45 steel target plate was summarized. The results show that the maximum deflection of the target plate increases linearly with the charge mass, decreases linearly with the charge spacing and decreases exponentially with the vertical distance from the charge to the target plate. The functional relationship between different parameters and the maximum deformation deflection of the target plate was fitted. This study can to some extent achieve rapid calculation of the explosion effect of charges with different distributions.
To study the response law of a metal target plate under the simultaneous initiation of two charges and to construct a calculation model for the deformation and deflection of the target plate under the action of dual explosion source shock waves, the dynamic response of the metal plate under the action of double explosion sources was studied through dimensional analysis. Based on the numerical simulation calculation results using the finite element software, the influence of the charge quality, charge spacing, and vertical distance from the charge to the target plate of the double explosion source on the maximum deflection of the 45 steel target plate was summarized. The results show that the maximum deflection of the target plate increases linearly with the charge mass, decreases linearly with the charge spacing and decreases exponentially with the vertical distance from the charge to the target plate. The functional relationship between different parameters and the maximum deformation deflection of the target plate was fitted. This study can to some extent achieve rapid calculation of the explosion effect of charges with different distributions.
2023, 43(12): 123101.
doi: 10.11883/bzycj-2023-0022
Abstract:
A split Hopkinson pressure bar (SHPB) device was used to study the dynamic mechanical properties and deformation and failure characteristics of the rock mass combined with different sandwich materials, using sandstone and granite as the soft and hard rock matrix. The discrete lattice spring method (DLSM) was used to further investigate the crack propagation, the reaction and transmission at the interlayer interface and the energy distribution characteristics of rock mass combined with different interlayer materials. The results show that the growth factor of rock mass dynamic strength increases with the increase of rock mass dynamic compressive strength, showing an obvious dynamic compressive strength dependence. The rock mass combined with different interlayer materials has a obvious nonlinear section in the initial loading stage, and the closed pores and cracks in the sandstone of non-interlayer rock have the longest nonlinear section in the initial stress stage. With the increase of the strength of interlayer material, the obstacle ability of interlayer to crack propagation and development of rock mass gradually becomes weak, and the energy consumption of rock mass crack and failure is gradually reduced. The failure of the intercalated rock mass starts at the cementation surface of the intercalated rock mass. With the increase of the strength of the intercalated material, the failure of the soft rock near the cementation surface is gradually intensified, while the hard rock has no obvious failure. The rock mass with interlayer has a good clipping effect. With the decrease of the strength of interlayer material, the peak stress value of both ends gradually increases and decreases, whilst the energy absorption density of the interlayer rock mass increases in a short time, and the stability becomes worse, so it is easy to be destroyed.
A split Hopkinson pressure bar (SHPB) device was used to study the dynamic mechanical properties and deformation and failure characteristics of the rock mass combined with different sandwich materials, using sandstone and granite as the soft and hard rock matrix. The discrete lattice spring method (DLSM) was used to further investigate the crack propagation, the reaction and transmission at the interlayer interface and the energy distribution characteristics of rock mass combined with different interlayer materials. The results show that the growth factor of rock mass dynamic strength increases with the increase of rock mass dynamic compressive strength, showing an obvious dynamic compressive strength dependence. The rock mass combined with different interlayer materials has a obvious nonlinear section in the initial loading stage, and the closed pores and cracks in the sandstone of non-interlayer rock have the longest nonlinear section in the initial stress stage. With the increase of the strength of interlayer material, the obstacle ability of interlayer to crack propagation and development of rock mass gradually becomes weak, and the energy consumption of rock mass crack and failure is gradually reduced. The failure of the intercalated rock mass starts at the cementation surface of the intercalated rock mass. With the increase of the strength of the intercalated material, the failure of the soft rock near the cementation surface is gradually intensified, while the hard rock has no obvious failure. The rock mass with interlayer has a good clipping effect. With the decrease of the strength of interlayer material, the peak stress value of both ends gradually increases and decreases, whilst the energy absorption density of the interlayer rock mass increases in a short time, and the stability becomes worse, so it is easy to be destroyed.
2023, 43(12): 123102.
doi: 10.11883/bzycj-2023-0223
Abstract:
To reveal the influence law of graphite ore with different bedding angles under impact load, impact experiments on graphite ore samples with different bedding angles (0°, 45° and 90°) were conducted by using a 50 mm diameter split Hopkinson pressure bar (SHPB) device, with the combined use of high-speed photography and electron microscopy scan. The dynamic mechanical properties and impact failure modes were investigated during the dynamic fracture process. The results show that most of the minerals in graphite ore are arranged in an allotriomorphic granular orientation within an irregular contact boundary. There is a high content of muscovite and quartz, associated with graphite and enriched along the bedding planes. The bedding angles have a deterioration effect on samples, and the 45° bedding angle has the strongest deterioration effect. The energy dissipation characteristics show a U-shaped trend with the increase of bedding angle, similar to the strength characteristics. At the same strain rate, the average particle size of the broken samples is strongly correlated with the energy dissipation density. The average particle size of 0° bedding angle is the smallest, with the largest energy dissipation density. On the contrary, the average particle size is the largest when the bedding angle is 45°, with the smallest energy dissipation density. When graphite flakes are subjected to external forces, they will not only break from the inside but also be torn by associated minerals. The destruction form can be summarized as the evolution of tensile failure-shear failure-tensile splitting failure. The relevant characteristic results obtained from the experiments show that the damage degree of the graphite flakes is mainly controlled by the magnitude and direction of the impact load. Tensile failure can reduce the internal fracture of graphite flakes, and a low strain rate can reduce the production of rock powder. Therefore, the destructive effect of blasting impact load on graphite flakes can be reduced by adjusting the propagation direction of the shock wave, reducing the peak stress, and increasing the failure area of ore tensile stress.
To reveal the influence law of graphite ore with different bedding angles under impact load, impact experiments on graphite ore samples with different bedding angles (0°, 45° and 90°) were conducted by using a 50 mm diameter split Hopkinson pressure bar (SHPB) device, with the combined use of high-speed photography and electron microscopy scan. The dynamic mechanical properties and impact failure modes were investigated during the dynamic fracture process. The results show that most of the minerals in graphite ore are arranged in an allotriomorphic granular orientation within an irregular contact boundary. There is a high content of muscovite and quartz, associated with graphite and enriched along the bedding planes. The bedding angles have a deterioration effect on samples, and the 45° bedding angle has the strongest deterioration effect. The energy dissipation characteristics show a U-shaped trend with the increase of bedding angle, similar to the strength characteristics. At the same strain rate, the average particle size of the broken samples is strongly correlated with the energy dissipation density. The average particle size of 0° bedding angle is the smallest, with the largest energy dissipation density. On the contrary, the average particle size is the largest when the bedding angle is 45°, with the smallest energy dissipation density. When graphite flakes are subjected to external forces, they will not only break from the inside but also be torn by associated minerals. The destruction form can be summarized as the evolution of tensile failure-shear failure-tensile splitting failure. The relevant characteristic results obtained from the experiments show that the damage degree of the graphite flakes is mainly controlled by the magnitude and direction of the impact load. Tensile failure can reduce the internal fracture of graphite flakes, and a low strain rate can reduce the production of rock powder. Therefore, the destructive effect of blasting impact load on graphite flakes can be reduced by adjusting the propagation direction of the shock wave, reducing the peak stress, and increasing the failure area of ore tensile stress.
2023, 43(12): 123301.
doi: 10.11883.bzycj-2023-0130
Abstract:
The impact resistance of T300 carbon fiber blades was studied through experiments and numerical simulations. The deformation damage pattern and the effect of the number of fiber layers on the impact resistance of the blade are studied. The impact experiment was conducted on the carbon fiber blades of different layers. Based on the macro-level continuum damage mechanics theory and the Hashin failure criterion, a vectorized user-material subroutine was written for the carbon fiber material, and the smooth particle hydrodynamics algorithm was used to simulate the gelatin projectiles. Numerical simulations of bird impact on the composite blades with different layers were carried out in ABAQUS/Explicit. The blade deformation process, bird flow state, and impact duration time of the experiments agree well with the numerical results. In the initial impact stage, the blade specimens have large deformations, and the deformation modes of the three carbon fiber blades with different layers are similar to each other. However, in the impact attenuation and constant flow stages, the deflection and fracture of different layers of carbon fiber blades are quite different. The damage mode of the 6-layer carbon fiber blade is complete fractures at the blade root and top, the damage mode of the 8-layer carbon fiber blade is root fracture, and there is no obvious macroscopic visible damage in the 10-layer carbon fiber blade. Under the gelatin projectile impact loading, the blade deformation mode is mainly coupled with the bending and torsional deformation process, and the bending deformation dominates the damage and failure process. Experimental results show that the damage pattern of carbon fiber blades is mainly classified as (1) edge damage at the root, (2) complete fracture at the root, and (3) complete fracture at the root and top edge. The impact resistance of carbon fiber is greatly influenced by the number of layers. The mechanism analysis of gelatin projectile impact on carbon fiber blades through experiments and numerical simulations can provide a reference for the engineering design and application of carbon fiber blades.
The impact resistance of T300 carbon fiber blades was studied through experiments and numerical simulations. The deformation damage pattern and the effect of the number of fiber layers on the impact resistance of the blade are studied. The impact experiment was conducted on the carbon fiber blades of different layers. Based on the macro-level continuum damage mechanics theory and the Hashin failure criterion, a vectorized user-material subroutine was written for the carbon fiber material, and the smooth particle hydrodynamics algorithm was used to simulate the gelatin projectiles. Numerical simulations of bird impact on the composite blades with different layers were carried out in ABAQUS/Explicit. The blade deformation process, bird flow state, and impact duration time of the experiments agree well with the numerical results. In the initial impact stage, the blade specimens have large deformations, and the deformation modes of the three carbon fiber blades with different layers are similar to each other. However, in the impact attenuation and constant flow stages, the deflection and fracture of different layers of carbon fiber blades are quite different. The damage mode of the 6-layer carbon fiber blade is complete fractures at the blade root and top, the damage mode of the 8-layer carbon fiber blade is root fracture, and there is no obvious macroscopic visible damage in the 10-layer carbon fiber blade. Under the gelatin projectile impact loading, the blade deformation mode is mainly coupled with the bending and torsional deformation process, and the bending deformation dominates the damage and failure process. Experimental results show that the damage pattern of carbon fiber blades is mainly classified as (1) edge damage at the root, (2) complete fracture at the root, and (3) complete fracture at the root and top edge. The impact resistance of carbon fiber is greatly influenced by the number of layers. The mechanism analysis of gelatin projectile impact on carbon fiber blades through experiments and numerical simulations can provide a reference for the engineering design and application of carbon fiber blades.
2023, 43(12): 123901.
doi: 10.11883/bzycj-2023-0113
Abstract:
In frigid regions, the construction of sluice pier structures within river systems is confronted with considerable challenges arising from the presence of severe ice loads and ice-induced vibrations. The collision process between ice and sluice piers is further complicated due to the intricate hydrodynamic effects exerted by water. The arbitrary Lagrangian-Eulerian (ALE) fluid-structure interaction (FSI) method is employed in this research to meticulously account for the fluid forces acting upon both the ice and sluice pier surfaces. A comprehensive coupled model encompassing the interactions among water, ice, and sluice piers is established to thoroughly investigate the mechanical characteristics associated with ice-sluice pier collisions under highly unpredictable conditions. Corresponding ice-concrete collision tests are meticulously designed and conducted, revealing an exemplary concurrence between the simulated impact forces and the values obtained from experimental observations. Upon analyzing the fluid-structure interaction and hydrodynamic effects, the present study demonstrates that the water-ice-sluice pier coupled model adeptly captures the fluid characteristics inherent to water. During the approach of an ice mass towards a sluice pier, the initial hydrodynamic effects initiated by the water medium effectively augment the kinetic energy possessed by the ice. As the ice forcefully interacts with the sluice pier, the water medium swiftly generates a transient high-pressure field, thereby establishing a phenomenon colloquially referred to as the water cushion effect. This effect is manifested by absorbing a portion of the ice’s kinetic energy, effectively dampening its movement. Distinctive scenarios characterized by varying ice volumes and compression strengths elucidate that the ice forces exerted upon the sluice pier structure directly correlate with the magnitude of the ice volume, while the influence of ice compression strength on said forces is relatively negligible. The consequential damages inflicted upon the ice and the response exhibited by the sluice pier structure primarily manifest within the contact area at the moment of collision. Consequently, the collisions between ice and the sluice pier structure induce vibrations that are uniquely attributed to ice-related factors. The volume of ice significantly influences the acceleration of sluice pier vibrations. Furthermore, under the condition of maintaining a consistent ice volumes, an increase in compression strength yields only marginal discrepancies in vibration amplitude. This finding convincingly substantiates the critical role played by ice volume as the paramount parameter governing ice-sluice pier collisions.
In frigid regions, the construction of sluice pier structures within river systems is confronted with considerable challenges arising from the presence of severe ice loads and ice-induced vibrations. The collision process between ice and sluice piers is further complicated due to the intricate hydrodynamic effects exerted by water. The arbitrary Lagrangian-Eulerian (ALE) fluid-structure interaction (FSI) method is employed in this research to meticulously account for the fluid forces acting upon both the ice and sluice pier surfaces. A comprehensive coupled model encompassing the interactions among water, ice, and sluice piers is established to thoroughly investigate the mechanical characteristics associated with ice-sluice pier collisions under highly unpredictable conditions. Corresponding ice-concrete collision tests are meticulously designed and conducted, revealing an exemplary concurrence between the simulated impact forces and the values obtained from experimental observations. Upon analyzing the fluid-structure interaction and hydrodynamic effects, the present study demonstrates that the water-ice-sluice pier coupled model adeptly captures the fluid characteristics inherent to water. During the approach of an ice mass towards a sluice pier, the initial hydrodynamic effects initiated by the water medium effectively augment the kinetic energy possessed by the ice. As the ice forcefully interacts with the sluice pier, the water medium swiftly generates a transient high-pressure field, thereby establishing a phenomenon colloquially referred to as the water cushion effect. This effect is manifested by absorbing a portion of the ice’s kinetic energy, effectively dampening its movement. Distinctive scenarios characterized by varying ice volumes and compression strengths elucidate that the ice forces exerted upon the sluice pier structure directly correlate with the magnitude of the ice volume, while the influence of ice compression strength on said forces is relatively negligible. The consequential damages inflicted upon the ice and the response exhibited by the sluice pier structure primarily manifest within the contact area at the moment of collision. Consequently, the collisions between ice and the sluice pier structure induce vibrations that are uniquely attributed to ice-related factors. The volume of ice significantly influences the acceleration of sluice pier vibrations. Furthermore, under the condition of maintaining a consistent ice volumes, an increase in compression strength yields only marginal discrepancies in vibration amplitude. This finding convincingly substantiates the critical role played by ice volume as the paramount parameter governing ice-sluice pier collisions.
2023, 43(12): 123902.
doi: 10.11883/bzycj-2023-0227
Abstract:
In order to study the evolution law of the temperature field of carbon dioxide blasting jet, an infrared thermal imaging test system of carbon dioxide blasting was constructed, which enabled the space development and temperature evolution of the carbon dioxide blasting jet being analyzed through carbon dioxide blasting experiment. This paper will first introduce the principle of carbon dioxide blasting technology and the structure of carbon dioxide blasting device, and expound the physical properties of carbon dioxide. Through the operation of Span-Wagner equation of state, the relationship between temperature and pressure of carbon dioxide is revealed, and then the temperature-pressure relationship curve is drawn. Secondly, the evolution cloud map of jet temperature field is analyzed, showing that before the overtemperature phenomenon, the temperature gradient of the jet is the highest in the outer ring, slightly lower in the inner ring, and the lowest in the core region. While overtemperature occurs, the temperature gradient of the carbon dioxide jet is the lowest in the outer ring, slightly higher in the inner ring, and the highest in the core region. Therefore, the ambient temperature around the jet decreases first and then increases during the carbon dioxide explosion. Finally, the temperature-time curve of the jet is studied. One the one hand, the higher the initial discharge pressure, the higher the peak temperature of the carbon dioxide blasting jet, and the longer the time required to reach the peak temperature, with the highest temperature in the test reaching 133.7 ℃. While the lower the initial energy release pressure, the lower the temperature valley value, the shorter the time required to reach the temperature valley value, with the lowest temperature in the test being −3.4 ℃. On the other hand, the peak of jet temperature basically appears in the initial stage of blasting energy discharge, and then the temperature rises slightly, followed by the temperature drop to the valley value. The main stage of jet heating is in the pipe, and the study shows that the temperature of carbon dioxide blasting jet generally presents a trend of first rising followed by decreasing.
In order to study the evolution law of the temperature field of carbon dioxide blasting jet, an infrared thermal imaging test system of carbon dioxide blasting was constructed, which enabled the space development and temperature evolution of the carbon dioxide blasting jet being analyzed through carbon dioxide blasting experiment. This paper will first introduce the principle of carbon dioxide blasting technology and the structure of carbon dioxide blasting device, and expound the physical properties of carbon dioxide. Through the operation of Span-Wagner equation of state, the relationship between temperature and pressure of carbon dioxide is revealed, and then the temperature-pressure relationship curve is drawn. Secondly, the evolution cloud map of jet temperature field is analyzed, showing that before the overtemperature phenomenon, the temperature gradient of the jet is the highest in the outer ring, slightly lower in the inner ring, and the lowest in the core region. While overtemperature occurs, the temperature gradient of the carbon dioxide jet is the lowest in the outer ring, slightly higher in the inner ring, and the highest in the core region. Therefore, the ambient temperature around the jet decreases first and then increases during the carbon dioxide explosion. Finally, the temperature-time curve of the jet is studied. One the one hand, the higher the initial discharge pressure, the higher the peak temperature of the carbon dioxide blasting jet, and the longer the time required to reach the peak temperature, with the highest temperature in the test reaching 133.7 ℃. While the lower the initial energy release pressure, the lower the temperature valley value, the shorter the time required to reach the temperature valley value, with the lowest temperature in the test being −3.4 ℃. On the other hand, the peak of jet temperature basically appears in the initial stage of blasting energy discharge, and then the temperature rises slightly, followed by the temperature drop to the valley value. The main stage of jet heating is in the pipe, and the study shows that the temperature of carbon dioxide blasting jet generally presents a trend of first rising followed by decreasing.
2023, 43(12): 124101.
doi: 10.11883/bzycj-2023-0129
Abstract:
Based on the classical one-dimensional stress wave theory and the assumption of force equilibrium of the specimen, a new method for separating left-going and right-going stress waves on the standard Hopkinson pressure bar set-up is proposed. It can solve the problem of left-going and right-going stress wave signal overlapping in a standard Hopkinson pressure bar used for a long-duration experiment effectively and with simplicity. By introducing virtual strain measuring points at the specimen end of the incident bar and the free end of the transmission bar, the separation problem of stress waves in each bar which using only one strain gage is transformed into the two-point wave separation problem and then the separation of the left and right traveling stress waves is conveniently accomplished. In principle, this new method allows unlimited duration of test data analysis thus the overall experimental process can be analyzed. It thereby significantly enhances the test ability of the standard Hopkinson pressure bar. New experimental data processing formulas based on the left-going and right-going stress wave signals are presented. They are actually the generalizations of the classical data processing formulas. These new formula are equivalent to the classical formulas when the wave separation processing is unnecessary. Full model simulations of the split Hopkinson pressure bar experiment were carried out on the ABAQUS/Explicit finite element simulation platform. The simulated strain signals at the test positions then are processed in the way of virtual experiment under various experimental conditions. Based on this, the effectiveness and errors are verified or evaluated. The simulation result shows that this new stress wave separation method can give a good data processing result. Some experiments were carried out on a standard Hopkinson pressure bar apparatus with a 1-m-length incident bar and a 1-m-length transmission bar. The new wave separation technique and data process formulas were used. For the 2014 aluminum alloy test, the specimen stress and deformation progresses was clearly captured for the first and second loading process. For the aluminum foam test, a quasi-direct impact technique was used to achieve long-time continuous loading on the specimen and the experiment result was complete, clean and satisfactory.
Based on the classical one-dimensional stress wave theory and the assumption of force equilibrium of the specimen, a new method for separating left-going and right-going stress waves on the standard Hopkinson pressure bar set-up is proposed. It can solve the problem of left-going and right-going stress wave signal overlapping in a standard Hopkinson pressure bar used for a long-duration experiment effectively and with simplicity. By introducing virtual strain measuring points at the specimen end of the incident bar and the free end of the transmission bar, the separation problem of stress waves in each bar which using only one strain gage is transformed into the two-point wave separation problem and then the separation of the left and right traveling stress waves is conveniently accomplished. In principle, this new method allows unlimited duration of test data analysis thus the overall experimental process can be analyzed. It thereby significantly enhances the test ability of the standard Hopkinson pressure bar. New experimental data processing formulas based on the left-going and right-going stress wave signals are presented. They are actually the generalizations of the classical data processing formulas. These new formula are equivalent to the classical formulas when the wave separation processing is unnecessary. Full model simulations of the split Hopkinson pressure bar experiment were carried out on the ABAQUS/Explicit finite element simulation platform. The simulated strain signals at the test positions then are processed in the way of virtual experiment under various experimental conditions. Based on this, the effectiveness and errors are verified or evaluated. The simulation result shows that this new stress wave separation method can give a good data processing result. Some experiments were carried out on a standard Hopkinson pressure bar apparatus with a 1-m-length incident bar and a 1-m-length transmission bar. The new wave separation technique and data process formulas were used. For the 2014 aluminum alloy test, the specimen stress and deformation progresses was clearly captured for the first and second loading process. For the aluminum foam test, a quasi-direct impact technique was used to achieve long-time continuous loading on the specimen and the experiment result was complete, clean and satisfactory.
2023, 43(12): 125101.
doi: 10.11883/bzycj-2023-0025
Abstract:
To investigate the influence of damage characteristics, dynamic response, and failure mechanism on reinforced concrete (RC) square columns under multi-point simultaneous initiation, a series of experiments were conducted on RC square columns subjected to synchronous contact explosive loading using single, double, and four-point charges. Furthermore, LS-DYNA was used to analyze the damage characteristics and stress evolution process based on the experimental results obtained from the explosive loading. The analysis results indicate that the damage effect of RC square columns relies on both the number of detonation points and the placement position, given the same total mass of explosives. Multi-point simultaneous initiation causes superior damage to RC square columns with both crushed and punched damage, as compared to single-point explosions. Additionally, the degree of damage and acceleration response of the RC square columns is the highest at the condition of four-point charges on adjacent sides. The effectiveness of enhancing the damaging effect on RC square columns is directly correlated with the increase in the number of detonation points. The RC square column initially enters a high-stress state throughout the entire section, and in the condition of four-point charges placed on all four sides, there are four corners where the concrete stress is concentrated, leading to enhanced damage effects. During single-point initiation, the stress inside the concrete at the measuring point decreases as the distance from the center of the explosion increases. However, during multi-point initiation, when multiple explosion stress waves are combined within the cross-section of the RC square column, the stress at the central concrete significantly increases. Taking into account the spatial coupling and superposition of stress waves, the concrete's peak stress at the center of the RC square column section increased significantly under the explosive conditions of four-point charges on adjacent sides. Specifically, the peak stress reached 37.3 MPa, with stress increases of 3.82 times, 1.21 times, and 0.67 times compared to the other three explosion conditions. The increase in stress coupling is the primary factor contributing to the extensive damage observed in the RC square column.
To investigate the influence of damage characteristics, dynamic response, and failure mechanism on reinforced concrete (RC) square columns under multi-point simultaneous initiation, a series of experiments were conducted on RC square columns subjected to synchronous contact explosive loading using single, double, and four-point charges. Furthermore, LS-DYNA was used to analyze the damage characteristics and stress evolution process based on the experimental results obtained from the explosive loading. The analysis results indicate that the damage effect of RC square columns relies on both the number of detonation points and the placement position, given the same total mass of explosives. Multi-point simultaneous initiation causes superior damage to RC square columns with both crushed and punched damage, as compared to single-point explosions. Additionally, the degree of damage and acceleration response of the RC square columns is the highest at the condition of four-point charges on adjacent sides. The effectiveness of enhancing the damaging effect on RC square columns is directly correlated with the increase in the number of detonation points. The RC square column initially enters a high-stress state throughout the entire section, and in the condition of four-point charges placed on all four sides, there are four corners where the concrete stress is concentrated, leading to enhanced damage effects. During single-point initiation, the stress inside the concrete at the measuring point decreases as the distance from the center of the explosion increases. However, during multi-point initiation, when multiple explosion stress waves are combined within the cross-section of the RC square column, the stress at the central concrete significantly increases. Taking into account the spatial coupling and superposition of stress waves, the concrete's peak stress at the center of the RC square column section increased significantly under the explosive conditions of four-point charges on adjacent sides. Specifically, the peak stress reached 37.3 MPa, with stress increases of 3.82 times, 1.21 times, and 0.67 times compared to the other three explosion conditions. The increase in stress coupling is the primary factor contributing to the extensive damage observed in the RC square column.
2023, 43(12): 125102.
doi: 10.11883/bzycj-2023-0033
Abstract:
In order to study the anti-explosion protection performance of porous polymers on underwater concrete structures, underwater explosion experiments were carried out on reinforced concrete slabs with a polymer protective layer, and an ordinary reinforced concrete slab was set as a comparing subject. A fully coupled model of underwater explosion of reinforced concrete slab with polymer protective layer was established by the AUTODYN finite element program, while the reliability of the proposed model was verified by the comparison of the calculatied results with experimental ones. Thus, the propagation characteristics of explosion load in water and the damage results of the structure can be better simulated by this model. In addition, the effect of the front steel plate on the enhancement of the protection performance of the polymer layer was further analyzed by numerical simulation. The front steel plate can evenly exert the pressure generated by the explosion load on the inner core layer, so that the polymer layer can display a better energy-absorbing effect. Taking the mid-span residual displacement of the reinforced concrete slab as an index, the influences of the amount of detonating charge and the layer thickness ratio of the composite structure on the underwater protection effect of the polymer layer are analyzed parametrically. The results show that the damage degree of the concrete structure under underwater explosion can be reduced by the polymer protective layer; arranging the steel thin plate on the outside of the polymer layer can improve the energy-absorbing effect of the polymer layer and provide better protection to the reinforced concrete slab; and the protection effect is the best when the ratio of the polymer layer to the front steel plate layer thickness is 20. The research results can provide a reference for the subsequent studies and application of polymer materials in the protection of underwater engineering structures.
In order to study the anti-explosion protection performance of porous polymers on underwater concrete structures, underwater explosion experiments were carried out on reinforced concrete slabs with a polymer protective layer, and an ordinary reinforced concrete slab was set as a comparing subject. A fully coupled model of underwater explosion of reinforced concrete slab with polymer protective layer was established by the AUTODYN finite element program, while the reliability of the proposed model was verified by the comparison of the calculatied results with experimental ones. Thus, the propagation characteristics of explosion load in water and the damage results of the structure can be better simulated by this model. In addition, the effect of the front steel plate on the enhancement of the protection performance of the polymer layer was further analyzed by numerical simulation. The front steel plate can evenly exert the pressure generated by the explosion load on the inner core layer, so that the polymer layer can display a better energy-absorbing effect. Taking the mid-span residual displacement of the reinforced concrete slab as an index, the influences of the amount of detonating charge and the layer thickness ratio of the composite structure on the underwater protection effect of the polymer layer are analyzed parametrically. The results show that the damage degree of the concrete structure under underwater explosion can be reduced by the polymer protective layer; arranging the steel thin plate on the outside of the polymer layer can improve the energy-absorbing effect of the polymer layer and provide better protection to the reinforced concrete slab; and the protection effect is the best when the ratio of the polymer layer to the front steel plate layer thickness is 20. The research results can provide a reference for the subsequent studies and application of polymer materials in the protection of underwater engineering structures.
2023, 43(12): 125103.
doi: 10.11883/bzycj-2023-0160
Abstract:
To establish the p-I (pressure-impulse) diagram for flexural damage assessment of ultra-high performance concrete (UHPC) panels under blast loadings, cross-sectional analysis using the strip method was performed to establish the moment curvature relationship for simply supported one-way UHPC panels. This process involved considering the tensile/compressive softening of UHPC through the utilization of material constitutive models with softening properties and describing the strain rate effect of UHPC and reinforcement with the dynamic increase factor (DIF) that varies according to different strip layers. Subsequently, the nonlinear resistance function considering the effect of plastic hinge was developed, based on the moment curvature relationship and a simplified half-span symmetric beam model. Then, an equivalent single degree of freedom (ESDOF) theoretical model, adopting the nonlinear resistance function, was established and employed to predict the deflection-time histories of UHPC panels under explosions. The reliability of the above theoretical model was verified by comparing the predicted results with the deflection time histories of test UHPC panels in six shots of explosion tests. Additionally, the superiority of the proposed ESDOF model was proved by comparing with the corresponding calculation results obtained from the recommended methods using bilinear ideal elastic-plastic resistance functions based on the UFC 3-340-02 and FHWA codes. Furthermore, based on the verified ESDOF model, p-I diagrams for evaluating the flexural damage level of UHPC panels were established and parametric analysis was carried out. The results indicate that increasing the concrete strength grade, yield strength of reinforcement, tensile reinforcement ratio, and panel thickness, while reducing the clear span, are beneficial for the blast-resistant performance of UHPC panels. Finally, empirical formulae for p-I diagrams, taking into consideration the abovementioned influencing factors, were proposed and verified for assessing the flexural damage of UHPC panels. These formulae can serve as a valuable reference for evaluating blast-induced damage in UHPC panels.
To establish the p-I (pressure-impulse) diagram for flexural damage assessment of ultra-high performance concrete (UHPC) panels under blast loadings, cross-sectional analysis using the strip method was performed to establish the moment curvature relationship for simply supported one-way UHPC panels. This process involved considering the tensile/compressive softening of UHPC through the utilization of material constitutive models with softening properties and describing the strain rate effect of UHPC and reinforcement with the dynamic increase factor (DIF) that varies according to different strip layers. Subsequently, the nonlinear resistance function considering the effect of plastic hinge was developed, based on the moment curvature relationship and a simplified half-span symmetric beam model. Then, an equivalent single degree of freedom (ESDOF) theoretical model, adopting the nonlinear resistance function, was established and employed to predict the deflection-time histories of UHPC panels under explosions. The reliability of the above theoretical model was verified by comparing the predicted results with the deflection time histories of test UHPC panels in six shots of explosion tests. Additionally, the superiority of the proposed ESDOF model was proved by comparing with the corresponding calculation results obtained from the recommended methods using bilinear ideal elastic-plastic resistance functions based on the UFC 3-340-02 and FHWA codes. Furthermore, based on the verified ESDOF model, p-I diagrams for evaluating the flexural damage level of UHPC panels were established and parametric analysis was carried out. The results indicate that increasing the concrete strength grade, yield strength of reinforcement, tensile reinforcement ratio, and panel thickness, while reducing the clear span, are beneficial for the blast-resistant performance of UHPC panels. Finally, empirical formulae for p-I diagrams, taking into consideration the abovementioned influencing factors, were proposed and verified for assessing the flexural damage of UHPC panels. These formulae can serve as a valuable reference for evaluating blast-induced damage in UHPC panels.
2023, 43(12): 125401.
doi: 10.11883/bzycj-2023-0058
Abstract:
To reveal the explosion suppression mechanism of micron/nano polymethyl methacrylate (PMMA) dusts, the synchronous thermal analyzer and the 20-L explosion test device were used to test the pyrolysis oxidation characteristics and the explosion overpressure evolution characteristics of micro/nano PMMA dust under the intervention of NaHCO3. Coats-Redfern method was used to calculate the kinetic parameters for the rapid pyrolysis of 30 μm and 100 nm PMMA and micro/nano mixtures, and the correlation between pressure characteristics and thermochemical kinetics during suppression of micro/nano PMMA dust explosion was analyzed, and then the suppression mechanism of dust explosion based on thermochemical kinetics was discussed by establishing the physical model of suppression mechanism of NaHCO3 on micro/nano PMMA dust explosions. The results show that the pyrolysis oxidation processes of 30 μm and 100 nm PMMA dusts are suppressed by NaHCO3, and the apparent activation energy and pre-exponential factor are increased. The maximum explosion pressure and the maximum explosion pressure rise rate of both micro- and nano-PMMA dusts are decreased obviously. In the pyrolysis stage of the mixture system, the suppression effect of NaHCO3 is mainly dominated by physical suppression, including the cooling effect of both pyrolysis reaction and products as well as the dilution effect on the concentration of combustible reactant. In the oxidation stage of the mixture system, the suppression effect of NaHCO3 is mainly dominated by chemical suppression. The free radicals are absorbed by the active groups NaOH, forming the Na↔NaOH suppression cycle. And for explosion suppressant, the smaller the particle size and the larger the adding mass ratio, the greater the apparent activation energy E of explosion mixture system, and the more significant the suppression effect. It is worth noting that compared with the maximum explosion pressure, the sensitivity of explosion pressure rise rate to the E increment of explosion mixture system is great, and nano-PMMA dust is more sensitive to the E increment of explosion mixture system than micro-PMMA dust, and the corresponding suppression effect of NaHCO3 on nano-PMMA dust is more significant.
To reveal the explosion suppression mechanism of micron/nano polymethyl methacrylate (PMMA) dusts, the synchronous thermal analyzer and the 20-L explosion test device were used to test the pyrolysis oxidation characteristics and the explosion overpressure evolution characteristics of micro/nano PMMA dust under the intervention of NaHCO3. Coats-Redfern method was used to calculate the kinetic parameters for the rapid pyrolysis of 30 μm and 100 nm PMMA and micro/nano mixtures, and the correlation between pressure characteristics and thermochemical kinetics during suppression of micro/nano PMMA dust explosion was analyzed, and then the suppression mechanism of dust explosion based on thermochemical kinetics was discussed by establishing the physical model of suppression mechanism of NaHCO3 on micro/nano PMMA dust explosions. The results show that the pyrolysis oxidation processes of 30 μm and 100 nm PMMA dusts are suppressed by NaHCO3, and the apparent activation energy and pre-exponential factor are increased. The maximum explosion pressure and the maximum explosion pressure rise rate of both micro- and nano-PMMA dusts are decreased obviously. In the pyrolysis stage of the mixture system, the suppression effect of NaHCO3 is mainly dominated by physical suppression, including the cooling effect of both pyrolysis reaction and products as well as the dilution effect on the concentration of combustible reactant. In the oxidation stage of the mixture system, the suppression effect of NaHCO3 is mainly dominated by chemical suppression. The free radicals are absorbed by the active groups NaOH, forming the Na↔NaOH suppression cycle. And for explosion suppressant, the smaller the particle size and the larger the adding mass ratio, the greater the apparent activation energy E of explosion mixture system, and the more significant the suppression effect. It is worth noting that compared with the maximum explosion pressure, the sensitivity of explosion pressure rise rate to the E increment of explosion mixture system is great, and nano-PMMA dust is more sensitive to the E increment of explosion mixture system than micro-PMMA dust, and the corresponding suppression effect of NaHCO3 on nano-PMMA dust is more significant.
2023, 43(12): 125402.
doi: 10.11883/bzycj-2023-0057
Abstract:
Ten batches of liquefied petroleum gas (LPG) tank explosion tests under fires were conducted to investigate the overpressure load characteristics and blast wave propagation of LPG tank boiling liquid expansion vapor explosion (BLEVE) in unconfined space. Five different LPG tanks were considered in the tests with the variations of filters, LPG mass and tank shape. The explosion process and overpressure load of BLEVE were recorded by high-speed camera and overpressure sensors. The effects of filters, LPG mass, tank shape on the overpressure loads of BLEVEs were revealed and discussed. The empirical models of BLEVE overpressure loads are reviewed and the predictions of the simplified models are compared with the data of multi-scale BLEVE tests. The limitation and suggestion of the simplified empirical models are proposed. It is found that the existence of filters during explosion tests brings about the secondary gas cloud explosion of LPG tank BLEVE and the effect of secondary vapor cloud explosion on overpressure loads of BLEVE in unconfined space is limited due to the specific testing conditions. Typically, the overpressure loads of BLEVE have two positive phases and one negative phase, which is significantly different from the loads of TNT and gas explosions. The peak value of BLEVE overpressure loads decreases with the increase of distance and the decrease of LPG mass. Among the existed empirical models, the Brode model is the most conservative in predicting the BLEVE overpressure loads and the Planas model can predict the large scale BLEVE reasonably. The Birk model shows good predictions for large, medium and small scale tests, while the results are prone to danger. With the increase of scaled distance, the peak value of BLEVE overpressure loads decays exponentially. Moreover, the performance of the Baker-Tang blast curve method is better than that of the TNT equivalent method in the prediction of BLEVE loads.
Ten batches of liquefied petroleum gas (LPG) tank explosion tests under fires were conducted to investigate the overpressure load characteristics and blast wave propagation of LPG tank boiling liquid expansion vapor explosion (BLEVE) in unconfined space. Five different LPG tanks were considered in the tests with the variations of filters, LPG mass and tank shape. The explosion process and overpressure load of BLEVE were recorded by high-speed camera and overpressure sensors. The effects of filters, LPG mass, tank shape on the overpressure loads of BLEVEs were revealed and discussed. The empirical models of BLEVE overpressure loads are reviewed and the predictions of the simplified models are compared with the data of multi-scale BLEVE tests. The limitation and suggestion of the simplified empirical models are proposed. It is found that the existence of filters during explosion tests brings about the secondary gas cloud explosion of LPG tank BLEVE and the effect of secondary vapor cloud explosion on overpressure loads of BLEVE in unconfined space is limited due to the specific testing conditions. Typically, the overpressure loads of BLEVE have two positive phases and one negative phase, which is significantly different from the loads of TNT and gas explosions. The peak value of BLEVE overpressure loads decreases with the increase of distance and the decrease of LPG mass. Among the existed empirical models, the Brode model is the most conservative in predicting the BLEVE overpressure loads and the Planas model can predict the large scale BLEVE reasonably. The Birk model shows good predictions for large, medium and small scale tests, while the results are prone to danger. With the increase of scaled distance, the peak value of BLEVE overpressure loads decays exponentially. Moreover, the performance of the Baker-Tang blast curve method is better than that of the TNT equivalent method in the prediction of BLEVE loads.
2023, 43(12): 125403.
doi: 10.11883/bzycj-2023-0224
Abstract:
In the future, the use of bioethanol for hydrogen production in integrated hydrogen production and hydrogenation stations, along with its transportation through natural gas pipelines, will become the mainstream approach. However, the mixture of fuels poses risks related to storage and pipeline transportation, and in the presence of an ignition source, it can lead to explosive accidents. Therefore, studying the explosion characteristics of hydrogen-methane-ethanol mixture fuels is of paramount importance. In this study, the explosion characteristics of hydrogen-methane-ethanol mixtures were investigated using a 1.94 L constant-volume combustion bomb. Experiments were conducted under various initial conditions, including an initial temperature of 400 K, different initial pressures (0.1, 0.2, 0.4 MPa), and equivalence ratios (0.8−1.4). Mixtures with ethanol volume fractions of 20%, 50%, and 80% were examined. Detailed data analysis involved parameters such as explosion pressure, pressure rise rate, explosion index, and explosion time. These parameters were used to assess the intensity of combustible material explosions. Additionally, fundamental combustion characteristics were explored, including laminar burning velocity, sensitivity, and reaction pathways of the fuel. The results revealed that with an increase in initial pressure, the explosion pressure peak, maximum pressure rise rate, explosion index, and explosion time of the premixed fuel significantly increased. An increase in ethanol content lowered the maximum pressure rise rate and explosion index but raised the explosion pressure and time. Regardless of initial pressure and ethanol content, the fuel consistently reached its peak explosion pressure, maximum pressure rise rate, explosion index, and minimum explosion time within an equivalence ratio range of 1.2−1.3. Moreover, sensitivity analysis indicated that at high pressures and low ethanol ratios, more H and OH radicals were produced during the fuel reaction process. From the reaction pathway diagram, it is evident that the radical quantity decreases with an increase in ethanol content, explaining the increased explosion index at high pressure and low ethanol ratios. Overall, the obtained explosion index remains below 20 MPa∙m/s in most operating conditions, signifying that the fuel operates at a relatively safe level.
In the future, the use of bioethanol for hydrogen production in integrated hydrogen production and hydrogenation stations, along with its transportation through natural gas pipelines, will become the mainstream approach. However, the mixture of fuels poses risks related to storage and pipeline transportation, and in the presence of an ignition source, it can lead to explosive accidents. Therefore, studying the explosion characteristics of hydrogen-methane-ethanol mixture fuels is of paramount importance. In this study, the explosion characteristics of hydrogen-methane-ethanol mixtures were investigated using a 1.94 L constant-volume combustion bomb. Experiments were conducted under various initial conditions, including an initial temperature of 400 K, different initial pressures (0.1, 0.2, 0.4 MPa), and equivalence ratios (0.8−1.4). Mixtures with ethanol volume fractions of 20%, 50%, and 80% were examined. Detailed data analysis involved parameters such as explosion pressure, pressure rise rate, explosion index, and explosion time. These parameters were used to assess the intensity of combustible material explosions. Additionally, fundamental combustion characteristics were explored, including laminar burning velocity, sensitivity, and reaction pathways of the fuel. The results revealed that with an increase in initial pressure, the explosion pressure peak, maximum pressure rise rate, explosion index, and explosion time of the premixed fuel significantly increased. An increase in ethanol content lowered the maximum pressure rise rate and explosion index but raised the explosion pressure and time. Regardless of initial pressure and ethanol content, the fuel consistently reached its peak explosion pressure, maximum pressure rise rate, explosion index, and minimum explosion time within an equivalence ratio range of 1.2−1.3. Moreover, sensitivity analysis indicated that at high pressures and low ethanol ratios, more H and OH radicals were produced during the fuel reaction process. From the reaction pathway diagram, it is evident that the radical quantity decreases with an increase in ethanol content, explaining the increased explosion index at high pressure and low ethanol ratios. Overall, the obtained explosion index remains below 20 MPa∙m/s in most operating conditions, signifying that the fuel operates at a relatively safe level.
