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, Available online , doi: 10.11883/bzycj-2026-0015
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To elucidate the mechanism by which shock and obstacle interactions induce local detonation initiation, an experimental investigation was conducted on flame acceleration of premixed hydrogen–air mixtures in an obstacle-laden tube. Experiments were performed over a range of equivalence ratios from 0.8 to 1.3, spanning both fuel-lean and fuel-rich conditions relative to stoichiometry. Particular emphasis was placed on the interaction between the Mach stem of the leading shock and a single obstacle, and on how this interaction governs the formation of localized hot spots and the subsequent onset of local detonation. At an equivalence ratio of 0.8, initiation was not observed. Under this condition, the reflected shock interacted with the flame front and induced Richtmyer–Meshkov instability, generating pronounced wrinkling of the flame surface. This interaction further densified the pre-existing flame folds and increased the flame surface area, thereby accelerating the flame; however, no local detonation was initiated. In contrast, if the equivalence ratio was within the range from 0.9 to 1.3, successful initiation was observed. Shock reflection in the obstacle vicinity generated localized regions of elevated temperature that acted as hot spots, providing favorable conditions for rapid energy release and the onset of a locally detonative event. However, the locally initiated detonation did not develop into a self-sustained stable detonation. During subsequent diffraction, expansion waves imposed pronounced cooling and attenuation, causing progressive decoupling between the leading shock and the reaction zone, and thereby suppressing further development into a stable detonation wave. Through analysis of the critical initiation characteristics, it is found that increasing either the shock strength or the equivalence ratio increases the critical initiation parameter, and the critical initiation parameter is more sensitive to shock strength than to equivalence ratio. Furthermore, considering the discrepancy between the Thomas critical initiation model and the incident shock wave in the present experiments, the shock reflection zone was divided into sections for calculation. The analysis reveals that, at an equivalence ratio of 1.2, the lower sonic velocity following reflection of the leading shock wave prolongs the time taken for the expansion wave to reach the base of the obstacle, thereby favoring initiation. Conversely, at an equivalence ratio of 0.8, the lower equivalence ratio reduces the reactivity of the mixture, leading to a longer ignition delay time and consequently reducing the likelihood of initiation.
To elucidate the mechanism by which shock and obstacle interactions induce local detonation initiation, an experimental investigation was conducted on flame acceleration of premixed hydrogen–air mixtures in an obstacle-laden tube. Experiments were performed over a range of equivalence ratios from 0.8 to 1.3, spanning both fuel-lean and fuel-rich conditions relative to stoichiometry. Particular emphasis was placed on the interaction between the Mach stem of the leading shock and a single obstacle, and on how this interaction governs the formation of localized hot spots and the subsequent onset of local detonation. At an equivalence ratio of 0.8, initiation was not observed. Under this condition, the reflected shock interacted with the flame front and induced Richtmyer–Meshkov instability, generating pronounced wrinkling of the flame surface. This interaction further densified the pre-existing flame folds and increased the flame surface area, thereby accelerating the flame; however, no local detonation was initiated. In contrast, if the equivalence ratio was within the range from 0.9 to 1.3, successful initiation was observed. Shock reflection in the obstacle vicinity generated localized regions of elevated temperature that acted as hot spots, providing favorable conditions for rapid energy release and the onset of a locally detonative event. However, the locally initiated detonation did not develop into a self-sustained stable detonation. During subsequent diffraction, expansion waves imposed pronounced cooling and attenuation, causing progressive decoupling between the leading shock and the reaction zone, and thereby suppressing further development into a stable detonation wave. Through analysis of the critical initiation characteristics, it is found that increasing either the shock strength or the equivalence ratio increases the critical initiation parameter, and the critical initiation parameter is more sensitive to shock strength than to equivalence ratio. Furthermore, considering the discrepancy between the Thomas critical initiation model and the incident shock wave in the present experiments, the shock reflection zone was divided into sections for calculation. The analysis reveals that, at an equivalence ratio of 1.2, the lower sonic velocity following reflection of the leading shock wave prolongs the time taken for the expansion wave to reach the base of the obstacle, thereby favoring initiation. Conversely, at an equivalence ratio of 0.8, the lower equivalence ratio reduces the reactivity of the mixture, leading to a longer ignition delay time and consequently reducing the likelihood of initiation.
, Available online , doi: 10.11883/bzycj-2026-0021
Abstract:
N-butane is a highly versatile low-molecular-weight alkane that serves not only as a clean and efficient energy carrier but also as a key feedstock in the modern petrochemical industry. However, its inherently high flammability and explosibility pose significant safety challenges during production, storage, transportation, and utilization. To effectively mitigate explosion risks, an integrated multi-view gas/dust/liquid-mist explosion-suppression test apparatus was employed to investigate the explosion behavior of n-butane–air mixtures and the suppression effects of pure N2 and N2/CO2 mixtures. By varying the n-butane concentration, the most explosive concentration was first determined. Subsequently, different concentrations of nitrogen and N2/CO2 mixtures with varying proportions were introduced. As the proportion of CO2 increased, the maximum explosion pressure, maximum pressure rise rate, and explosion index of the n-butane–air mixture progressively decreased, whereas the times required to reach the peak pressure and maximum pressure rise rate were progressively prolonged. Adjustment of the inert-gas composition revealed that the physicochemical synergistic suppression effect of the N2/CO2 mixture was stronger than the purely physical suppression effect of N2 alone. High-speed camera observations of changes in flame velocity and morphology further confirmed the superiority of this synergistic suppression effect. It was therefore concluded that the physicochemical synergistic suppression effect of N2/CO2 is superior to the physical suppression effect of pure N2. Furthermore, the chemical reaction kinetics of premixed n-butane–air mixtures under different conditions were investigated using Chemkin numerical simulation software. The results demonstrate that, as the proportion of CO2 in the inert-gas mixture increases, the sensitivity of explosion pressure gradually decreases and the explosion reaction rate is substantially reduced. Compared with pure N2, CO2 exhibits a stronger synergistic physicochemical inhibitory effect on H and OH radicals during the reaction process. Moreover, it alters the maximum reaction rates (ROPs) of elementary reactions, thereby effectively suppressing the explosion reactions of premixed n-butane gas. These findings provide experimental evidence and theoretical support for technologies aimed at suppressing n-butane explosions.
N-butane is a highly versatile low-molecular-weight alkane that serves not only as a clean and efficient energy carrier but also as a key feedstock in the modern petrochemical industry. However, its inherently high flammability and explosibility pose significant safety challenges during production, storage, transportation, and utilization. To effectively mitigate explosion risks, an integrated multi-view gas/dust/liquid-mist explosion-suppression test apparatus was employed to investigate the explosion behavior of n-butane–air mixtures and the suppression effects of pure N2 and N2/CO2 mixtures. By varying the n-butane concentration, the most explosive concentration was first determined. Subsequently, different concentrations of nitrogen and N2/CO2 mixtures with varying proportions were introduced. As the proportion of CO2 increased, the maximum explosion pressure, maximum pressure rise rate, and explosion index of the n-butane–air mixture progressively decreased, whereas the times required to reach the peak pressure and maximum pressure rise rate were progressively prolonged. Adjustment of the inert-gas composition revealed that the physicochemical synergistic suppression effect of the N2/CO2 mixture was stronger than the purely physical suppression effect of N2 alone. High-speed camera observations of changes in flame velocity and morphology further confirmed the superiority of this synergistic suppression effect. It was therefore concluded that the physicochemical synergistic suppression effect of N2/CO2 is superior to the physical suppression effect of pure N2. Furthermore, the chemical reaction kinetics of premixed n-butane–air mixtures under different conditions were investigated using Chemkin numerical simulation software. The results demonstrate that, as the proportion of CO2 in the inert-gas mixture increases, the sensitivity of explosion pressure gradually decreases and the explosion reaction rate is substantially reduced. Compared with pure N2, CO2 exhibits a stronger synergistic physicochemical inhibitory effect on H and OH radicals during the reaction process. Moreover, it alters the maximum reaction rates (ROPs) of elementary reactions, thereby effectively suppressing the explosion reactions of premixed n-butane gas. These findings provide experimental evidence and theoretical support for technologies aimed at suppressing n-butane explosions.
, Available online , doi: 10.11883/bzycj-2026-0122
Abstract:
Transient pressure fluctuations generated during perforating operations in ultra-deep wells can induce severe axial vibration, stress-wave reflection, local stress amplification, and failure of perforating strings and downhole tools. The objective was to establish a dynamic-analysis framework that represents the complete wellbore-pressure history and clarifies the respective effects of the detonation-pressure peak and the dynamic-underbalance trough on string response and failure risk. A transient pressure-evolution model was first used to reproduce the initial equilibrium, rapid detonation-induced pressure rise, pressure decline, dynamic-underbalance formation, pressure recovery, and final equilibrium stages. The calculated pressure history was then converted into the incremental axial load acting at the lower end of the string. The string below the packer was represented as a one-dimensional elastic rod with a fixed upper boundary. Initial deformation caused by gravity and pre-perforation pressure was separated from the transient incremental displacement to avoid repeated loading. The governing equation incorporated axial elasticity, inertia, and equivalent viscous damping induced by the annular fluid. An explicit finite-difference method was adopted to calculate the displacement, acceleration, axial stress, and stress-wave propagation along the string. Field measurements from Well X1 in the Junggar Basin were used for validation, and an ultra-deep well in the Sichuan Basin was analyzed to evaluate spatial response characteristics and parameter sensitivity. For well X1, the relative error between the predicted and measured peak axial accelerations was 8.62%, confirming that the model reproduced the dominant response during the initial strong-impact stage. The case analysis shows that axial stress waves attenuate during propagation but are reflected and superimposed at the fixed packer boundary, raising the local peak stress to 199.43 MPa and identifying the packer and adjacent connections as critical. When the detonation-pressure peak increased from 75 MPa to 115 MPa, maximum tensile and compressive stresses increased by 17.24% and 44.71%, respectively, and the effective compressive load approached the sinusoidal-buckling threshold. When the dynamic-underbalance trough decreased from 30 MPa to 10 MPa, the maximum tensile and compressive stresses increased by 80.73% and 53.67%, respectively. These results demonstrate that the detonation-pressure peak primarily controls compressive stress and buckling susceptibility, whereas a lower dynamic-underbalance trough primarily amplifies tensile stress and connection-failure risk. The complete pressure history is therefore essential for integrity assessment and operational optimization of perforating strings in ultra-deep wells.
Transient pressure fluctuations generated during perforating operations in ultra-deep wells can induce severe axial vibration, stress-wave reflection, local stress amplification, and failure of perforating strings and downhole tools. The objective was to establish a dynamic-analysis framework that represents the complete wellbore-pressure history and clarifies the respective effects of the detonation-pressure peak and the dynamic-underbalance trough on string response and failure risk. A transient pressure-evolution model was first used to reproduce the initial equilibrium, rapid detonation-induced pressure rise, pressure decline, dynamic-underbalance formation, pressure recovery, and final equilibrium stages. The calculated pressure history was then converted into the incremental axial load acting at the lower end of the string. The string below the packer was represented as a one-dimensional elastic rod with a fixed upper boundary. Initial deformation caused by gravity and pre-perforation pressure was separated from the transient incremental displacement to avoid repeated loading. The governing equation incorporated axial elasticity, inertia, and equivalent viscous damping induced by the annular fluid. An explicit finite-difference method was adopted to calculate the displacement, acceleration, axial stress, and stress-wave propagation along the string. Field measurements from Well X1 in the Junggar Basin were used for validation, and an ultra-deep well in the Sichuan Basin was analyzed to evaluate spatial response characteristics and parameter sensitivity. For well X1, the relative error between the predicted and measured peak axial accelerations was 8.62%, confirming that the model reproduced the dominant response during the initial strong-impact stage. The case analysis shows that axial stress waves attenuate during propagation but are reflected and superimposed at the fixed packer boundary, raising the local peak stress to 199.43 MPa and identifying the packer and adjacent connections as critical. When the detonation-pressure peak increased from 75 MPa to 115 MPa, maximum tensile and compressive stresses increased by 17.24% and 44.71%, respectively, and the effective compressive load approached the sinusoidal-buckling threshold. When the dynamic-underbalance trough decreased from 30 MPa to 10 MPa, the maximum tensile and compressive stresses increased by 80.73% and 53.67%, respectively. These results demonstrate that the detonation-pressure peak primarily controls compressive stress and buckling susceptibility, whereas a lower dynamic-underbalance trough primarily amplifies tensile stress and connection-failure risk. The complete pressure history is therefore essential for integrity assessment and operational optimization of perforating strings in ultra-deep wells.
, Available online , doi: 10.11883/bzycj-2025-0307
Abstract:
To investigate the mechanism of underwater explosion-induced ice breaking in polar low-temperature environments and the influence of different factors on ice layer failure modes, numerical analysis was conducted using LS-DYNA finite element software. The influence of differences in atmospheric and seawater temperatures on the temperature distribution of natural sea ice in low-temperature environments was considered. The dynamic response and failure mechanism of the ice layer under shock-wave loads and bubble motion were analyzed. The factors influencing the ice-breaking effect and the failure modes of the ice layer were investigated. The results show that under typical operating conditions, the dynamic response of ice layers can be chronologically divided into five stages: the stress wave action stage, the initial crack initiation stage, the local bending deformation stage, the overall retreat stage, and the jet penetration stage. Increasing the charge mass can enhance the range of ice fragmentation and crack zones, but the ice breaking efficiency per unit charge shows a decreasing trend. There exists an optimal detonation distance, and due to the different load characteristics of shock waves and bubbles, the optimal detonation distance for the fragmentation zone is greater than that for the crack zone. The ice layer thickness has a nonlinear effect on the ice breaking effectiveness. As the thickness increases, the radius of the fragmentation zone gradually decreases, while the radius of the crack zone dominated by bubble motion increases within a certain range. It is found that the range of the fragmentation zone is minimally affected by temperature gradients, but temperature gradients have a significant impact on the range of the ice layer crack zone, with the radius of the crack zone being 82.3% of that in the equivalent uniform-temperature ice layer. Therefore, when studying ice layers with large thickness and significant temperature differences, the influence of non-uniform temperature distribution must be considered.
To investigate the mechanism of underwater explosion-induced ice breaking in polar low-temperature environments and the influence of different factors on ice layer failure modes, numerical analysis was conducted using LS-DYNA finite element software. The influence of differences in atmospheric and seawater temperatures on the temperature distribution of natural sea ice in low-temperature environments was considered. The dynamic response and failure mechanism of the ice layer under shock-wave loads and bubble motion were analyzed. The factors influencing the ice-breaking effect and the failure modes of the ice layer were investigated. The results show that under typical operating conditions, the dynamic response of ice layers can be chronologically divided into five stages: the stress wave action stage, the initial crack initiation stage, the local bending deformation stage, the overall retreat stage, and the jet penetration stage. Increasing the charge mass can enhance the range of ice fragmentation and crack zones, but the ice breaking efficiency per unit charge shows a decreasing trend. There exists an optimal detonation distance, and due to the different load characteristics of shock waves and bubbles, the optimal detonation distance for the fragmentation zone is greater than that for the crack zone. The ice layer thickness has a nonlinear effect on the ice breaking effectiveness. As the thickness increases, the radius of the fragmentation zone gradually decreases, while the radius of the crack zone dominated by bubble motion increases within a certain range. It is found that the range of the fragmentation zone is minimally affected by temperature gradients, but temperature gradients have a significant impact on the range of the ice layer crack zone, with the radius of the crack zone being 82.3% of that in the equivalent uniform-temperature ice layer. Therefore, when studying ice layers with large thickness and significant temperature differences, the influence of non-uniform temperature distribution must be considered.
, Available online , doi: 10.11883/bzycj-2026-0060
Abstract:
The bubble coupling and morphological evolution characteristics in underwater multipoint explosions have long been a focus of research. Among various research approaches, the centrifuge-based hypergravity underwater explosion experiments have emerged as one of the most effective methods for conducting prototype experiments on large-yield underwater explosions, owing to its simultaneous satisfaction of both the Mach number and the Froude number. This study presents both experimental and numerical investigation into the coupling dynamics of underwater multipoint explosion bubbles under hypergravity conditions. First, two-point underwater explosion experiments were conducted under a hypergravity environment with a acceleration of 100g, and the morphological evolution of dual bubbles was captured with high precision using a high-speed camera. Second, a hypergravity underwater multi-point explosion numerical model, validated against the experimental data, was employed to further investigate the effects of gravitational field on the coupled morphological evolution and characteristic parameters of dual bubbles. The results indicate that under higher gravitational acceleration, the morphological evolution, pulsation, and migration characteristics of underwater explosion bubbles differ significantly from those under normal gravity. This hypergravity environment, as an extreme physical condition, intensifies the pressure gradient and buoyancy effects, leading to unique jetting behaviors. The hypergravity environment increases the vertical pressure gradient in the flow field, enhances the instability on the bubble surfaces, and induces more intense fluid acceleration, thereby leading to higher bubble migration velocities. In addition, the hypergravity field introduces a "spatiotemporal compression effect" on bubble pulsation and alters the buoyancy-inertia force balance of the bubble system, which significantly affects the jetting direction and the interaction intensity between the bubbles, consequently modifying the energy distribution within the dual-bubble system.
The bubble coupling and morphological evolution characteristics in underwater multipoint explosions have long been a focus of research. Among various research approaches, the centrifuge-based hypergravity underwater explosion experiments have emerged as one of the most effective methods for conducting prototype experiments on large-yield underwater explosions, owing to its simultaneous satisfaction of both the Mach number and the Froude number. This study presents both experimental and numerical investigation into the coupling dynamics of underwater multipoint explosion bubbles under hypergravity conditions. First, two-point underwater explosion experiments were conducted under a hypergravity environment with a acceleration of 100g, and the morphological evolution of dual bubbles was captured with high precision using a high-speed camera. Second, a hypergravity underwater multi-point explosion numerical model, validated against the experimental data, was employed to further investigate the effects of gravitational field on the coupled morphological evolution and characteristic parameters of dual bubbles. The results indicate that under higher gravitational acceleration, the morphological evolution, pulsation, and migration characteristics of underwater explosion bubbles differ significantly from those under normal gravity. This hypergravity environment, as an extreme physical condition, intensifies the pressure gradient and buoyancy effects, leading to unique jetting behaviors. The hypergravity environment increases the vertical pressure gradient in the flow field, enhances the instability on the bubble surfaces, and induces more intense fluid acceleration, thereby leading to higher bubble migration velocities. In addition, the hypergravity field introduces a "spatiotemporal compression effect" on bubble pulsation and alters the buoyancy-inertia force balance of the bubble system, which significantly affects the jetting direction and the interaction intensity between the bubbles, consequently modifying the energy distribution within the dual-bubble system.
, Available online , doi: 10.11883/bzycj-2026-0012
Abstract:
Vented deflagrations in ducts with a high length-to-diameter ratio are frequently encountered in hydrogen–ammonia energy systems, yet the pressure evolution and the applicability of engineering venting standards remain insufficiently validated for “large length-to-diameter ratio plus small end vent” configurations. An experimental study was therefore conducted to quantify how end-vent diameter affected the internal and external pressure characteristics of ammonia–hydrogen premixed gas in a long tube, and to improve the prediction accuracy of the NFPA (national fire protection association) standard 68, which standard on explosion protection by deflagration venting. Experiments were carried out in a stainless-steel duct system with a total length of 2 m, one end closed and the other end equipped with an end vent sealed by a thin vent membrane. Three circular vent diameters (120, 80, and 40 mm) were tested, corresponding to venting ratios of 100%, 44.4%, and 11.1%, respectively. Tests were performed under near-ambient initial conditions at a fixed equivalence ratio of 0.8, while the ammonia fraction in the fuel (ammonia plus hydrogen) was varied from 30% to 70%. Gas mixtures were prepared by partial-pressure charging after evacuating the mixing vessel, followed by sufficient standing time to promote homogeneity. A pressure transducer installed near the downstream region recorded the pressure–time history. For each condition, 3–4 repeated runs were conducted; representative traces were selected based on proximity to the mean of characteristic parameters. From each pressure trace, the membrane burst pressure, the internal venting peak pressure, the peak pressure associated with an external secondary explosion, and the duration of the pressure plateau or quasi-plateau were extracted. The maximum reduced explosion pressure was also calculated using NFPA 68 and compared against measurements; a correction correlation was then developed by incorporating the geometric venting ratio and the static activation pressure of the venting device. Under full venting, pressure histories exhibited a typical three-peak structure corresponding to membrane rupture, internal venting peak, and external secondary explosion peak. Increasing the ammonia fraction caused only minor changes in burst pressure but markedly reduced both the internal venting peak and the external secondary-explosion peak, while extending the plateau or quasi-plateau duration; at high ammonia fractions, the external secondary explosion was strongly suppressed. Decreasing the vent diameter intensified pressure oscillations, prolonged the time to membrane rupture, and generally increased both burst pressure and internal venting peak pressure; the external peak showed a vent-size-dependent trend that differed between low- and high- ammonia regimes. NFPA 68 predictions were close to measurements for the largest vent but showed systematic overestimation for medium and small vents; the deviation was governed mainly by vent geometry rather than mixture composition. For the investigated duct (length-to-diameter ratio about 16.7) with end venting, the overestimation reached approximately 4–8 times for the medium vent and about 30–80 times for the small vent. A correction model incorporating geometric venting ratio and static activation pressure reduced the discrepancy substantially, with the corrected-to-measured maximum reduced explosion pressure ratio mostly constrained within about 1–4.3. These findings provide experimentally grounded guidance and a practical correlation for vent design and safety evaluation of end-vented long-duct systems using ammonia–hydrogen premixed fuels.
Vented deflagrations in ducts with a high length-to-diameter ratio are frequently encountered in hydrogen–ammonia energy systems, yet the pressure evolution and the applicability of engineering venting standards remain insufficiently validated for “large length-to-diameter ratio plus small end vent” configurations. An experimental study was therefore conducted to quantify how end-vent diameter affected the internal and external pressure characteristics of ammonia–hydrogen premixed gas in a long tube, and to improve the prediction accuracy of the NFPA (national fire protection association) standard 68, which standard on explosion protection by deflagration venting. Experiments were carried out in a stainless-steel duct system with a total length of 2 m, one end closed and the other end equipped with an end vent sealed by a thin vent membrane. Three circular vent diameters (120, 80, and 40 mm) were tested, corresponding to venting ratios of 100%, 44.4%, and 11.1%, respectively. Tests were performed under near-ambient initial conditions at a fixed equivalence ratio of 0.8, while the ammonia fraction in the fuel (ammonia plus hydrogen) was varied from 30% to 70%. Gas mixtures were prepared by partial-pressure charging after evacuating the mixing vessel, followed by sufficient standing time to promote homogeneity. A pressure transducer installed near the downstream region recorded the pressure–time history. For each condition, 3–4 repeated runs were conducted; representative traces were selected based on proximity to the mean of characteristic parameters. From each pressure trace, the membrane burst pressure, the internal venting peak pressure, the peak pressure associated with an external secondary explosion, and the duration of the pressure plateau or quasi-plateau were extracted. The maximum reduced explosion pressure was also calculated using NFPA 68 and compared against measurements; a correction correlation was then developed by incorporating the geometric venting ratio and the static activation pressure of the venting device. Under full venting, pressure histories exhibited a typical three-peak structure corresponding to membrane rupture, internal venting peak, and external secondary explosion peak. Increasing the ammonia fraction caused only minor changes in burst pressure but markedly reduced both the internal venting peak and the external secondary-explosion peak, while extending the plateau or quasi-plateau duration; at high ammonia fractions, the external secondary explosion was strongly suppressed. Decreasing the vent diameter intensified pressure oscillations, prolonged the time to membrane rupture, and generally increased both burst pressure and internal venting peak pressure; the external peak showed a vent-size-dependent trend that differed between low- and high- ammonia regimes. NFPA 68 predictions were close to measurements for the largest vent but showed systematic overestimation for medium and small vents; the deviation was governed mainly by vent geometry rather than mixture composition. For the investigated duct (length-to-diameter ratio about 16.7) with end venting, the overestimation reached approximately 4–8 times for the medium vent and about 30–80 times for the small vent. A correction model incorporating geometric venting ratio and static activation pressure reduced the discrepancy substantially, with the corrected-to-measured maximum reduced explosion pressure ratio mostly constrained within about 1–4.3. These findings provide experimentally grounded guidance and a practical correlation for vent design and safety evaluation of end-vented long-duct systems using ammonia–hydrogen premixed fuels.
, Available online , doi: 10.11883/bzycj-2025-0309
Abstract:
An uniaxial compression tests were conducted on chicken femoral cortical bone under quasi-static (0.001 s−1) and dynamic (350 and 700 s−1) conditions by using a universal testing machine and a split Hopkinson pressure bar (SHPB). Chicken femoral cortical bone specimens were obtained via cutting and grinding, with high-contrast speckle patterns prepared on them. Images of cortical bone were recorded during the experiment using two cameras, with an acquisition frequency of 5 Hz for the quasi-static test and 150 kHz for the dynamic test. Full-field strain distributions were obtained using digital image correlation (DIC), and fracture micro-morphology was observed via scanning electron microscopy (SEM) to analyze the effect of strain rate on fracture behavior. The experimental results show that the failure stress of cortical bone exhibits a non-monotonic trend with increasing strain rate, with average values of 99.6, 195.5 and 171.3 MPa at 0.001, 350, and 700 s−1, respectively, demonstrating an “increase-then-decrease” tendency. A similar trend was observed for fracture strain. Under quasi-static loading, the macroscopic crack propagation path aligns with the maximum shear strain region, and the fracture surface exhibits typical shear failure characteristics (layered delamination and abundant debris), indicating shear strain as the primary fracture driver. In contrast, under dynamic loading, the macroscopic crack correlates more closely with the maximum tensile strain region, and the fracture surface appears smooth, characteristic of tensile fracture morphology, confirming tensile strain as the dominant mechanism. Strain rate exerts a significant influence on the fracture mechanism by regulating the fracture-inducing factor, which may account for one of the key reasons for the variation in fracture stress of cortical bone under dynamic conditions. This study reveals, from a macro-micro correlated perspective, the shift in fracture mechanisms of cortical bone from shear dominance to tensile dominance with increasing strain rate, which provides experimental evidence for understanding the fracture mechanism of bone under impact loading and a reference for the design of bone biomimetic materials and the development of orthopedic protective equipment.
An uniaxial compression tests were conducted on chicken femoral cortical bone under quasi-static (0.001 s−1) and dynamic (350 and 700 s−1) conditions by using a universal testing machine and a split Hopkinson pressure bar (SHPB). Chicken femoral cortical bone specimens were obtained via cutting and grinding, with high-contrast speckle patterns prepared on them. Images of cortical bone were recorded during the experiment using two cameras, with an acquisition frequency of 5 Hz for the quasi-static test and 150 kHz for the dynamic test. Full-field strain distributions were obtained using digital image correlation (DIC), and fracture micro-morphology was observed via scanning electron microscopy (SEM) to analyze the effect of strain rate on fracture behavior. The experimental results show that the failure stress of cortical bone exhibits a non-monotonic trend with increasing strain rate, with average values of 99.6, 195.5 and 171.3 MPa at 0.001, 350, and 700 s−1, respectively, demonstrating an “increase-then-decrease” tendency. A similar trend was observed for fracture strain. Under quasi-static loading, the macroscopic crack propagation path aligns with the maximum shear strain region, and the fracture surface exhibits typical shear failure characteristics (layered delamination and abundant debris), indicating shear strain as the primary fracture driver. In contrast, under dynamic loading, the macroscopic crack correlates more closely with the maximum tensile strain region, and the fracture surface appears smooth, characteristic of tensile fracture morphology, confirming tensile strain as the dominant mechanism. Strain rate exerts a significant influence on the fracture mechanism by regulating the fracture-inducing factor, which may account for one of the key reasons for the variation in fracture stress of cortical bone under dynamic conditions. This study reveals, from a macro-micro correlated perspective, the shift in fracture mechanisms of cortical bone from shear dominance to tensile dominance with increasing strain rate, which provides experimental evidence for understanding the fracture mechanism of bone under impact loading and a reference for the design of bone biomimetic materials and the development of orthopedic protective equipment.
, Available online , doi: 10.11883/bzycj-2025-0330
Abstract:
To rapidly obtain the explosion power of incident, a non-contact inversion methodology that leverages fused audio-video data to estimate explosion power is presented by analyzing the temporal lag between the optical flash and the arrival of the blast wave. Based on the Hopkinson-Cranz proportionality law, the Rankine-Hugoniot equation, and the free-field and near-ground overpressure models, the critical proportion distance parameter during the attenuation of the shock wave to the sound wave stage is introduced, and a theoretical model for yield inversion based on the travel time of the two waves is constructed. Through near-ground and air explosion experiments, the validity and applicability of the established model are verified, and the influences of explosion height, frame rate, and frame extraction method on the model’s prediction accuracy are analyzed. The results show that in the near-ground explosion condition, the ground reflection effect significantly increases the propagation speed of the explosion wave. Compared with the empirical formula based on the travel time of the shock wave and the improved formula combining the travel time of the sound wave, the dual-wave theoretical model proposed in this paper significantly considers the differences in the propagation characteristics of the shock wave and the sound wave and the ground reflection effect in near-ground explosions. Under the influence of multiple factors such as explosion height, frame rate, and frame extraction method, it shows better stability and superior prediction accuracy.
To rapidly obtain the explosion power of incident, a non-contact inversion methodology that leverages fused audio-video data to estimate explosion power is presented by analyzing the temporal lag between the optical flash and the arrival of the blast wave. Based on the Hopkinson-Cranz proportionality law, the Rankine-Hugoniot equation, and the free-field and near-ground overpressure models, the critical proportion distance parameter during the attenuation of the shock wave to the sound wave stage is introduced, and a theoretical model for yield inversion based on the travel time of the two waves is constructed. Through near-ground and air explosion experiments, the validity and applicability of the established model are verified, and the influences of explosion height, frame rate, and frame extraction method on the model’s prediction accuracy are analyzed. The results show that in the near-ground explosion condition, the ground reflection effect significantly increases the propagation speed of the explosion wave. Compared with the empirical formula based on the travel time of the shock wave and the improved formula combining the travel time of the sound wave, the dual-wave theoretical model proposed in this paper significantly considers the differences in the propagation characteristics of the shock wave and the sound wave and the ground reflection effect in near-ground explosions. Under the influence of multiple factors such as explosion height, frame rate, and frame extraction method, it shows better stability and superior prediction accuracy.
, Available online , doi: 10.11883/bzycj-2026-0072
Abstract:
Independent embedded steel sheet piles, characterized by convenient construction and strong damage resistance, are widely used in nearshore coastal protection engineering. The damage characteristics of steel sheet piles subjected to shallow-water explosions play a critical role in determining the reliability of blast-resistant design. However, existing studies remain insufficient to fully elucidate the damage mechanisms of steel sheet piles under shallow-water blast loading. Based on the attenuation law of underwater explosion loads, an engineering calculation model was established to evaluate the blast-induced damage of steel sheet piles in shallow water. Meanwhile, a coupled numerical simulation model accounting for the interaction among multiple materials was developed. Model tests were further conducted to validate the reliability of both the engineering calculation model and the numerical simulations. The effects of explosive charge equivalent, standoff distance, and water depth on the structural damage response were systematically analyzed. The results indicate that the weak zone of steel sheet piles is mainly concentrated near the water-soil interface, with punching shear fracture and bending deformation identified as the dominant failure modes. The scaled distance was found to be the key parameter governing the damage behavior. When the scaled distance is less than 0.086m/kg1/3, punching shear fracture occurs; when it exceeds 1.026 m/kg1/3, no significant damage is observed; and within the intermediate range, plastic bending deformation develops. Increasing water depth has a limited effect on fracture failure but can significantly extend the bending deformation zone, with an increase of up to 35%. Good agreement was achieved among the theoretical calculations, numerical simulations, and experimental results, with relative errors within 10%, satisfying the accuracy requirements for engineering prediction. These findings provide a reliable theoretical basis and practical guidance for the blast-resistant design, damage assessment, and protective reinforcement of independent embedded steel sheet pile structures.
Independent embedded steel sheet piles, characterized by convenient construction and strong damage resistance, are widely used in nearshore coastal protection engineering. The damage characteristics of steel sheet piles subjected to shallow-water explosions play a critical role in determining the reliability of blast-resistant design. However, existing studies remain insufficient to fully elucidate the damage mechanisms of steel sheet piles under shallow-water blast loading. Based on the attenuation law of underwater explosion loads, an engineering calculation model was established to evaluate the blast-induced damage of steel sheet piles in shallow water. Meanwhile, a coupled numerical simulation model accounting for the interaction among multiple materials was developed. Model tests were further conducted to validate the reliability of both the engineering calculation model and the numerical simulations. The effects of explosive charge equivalent, standoff distance, and water depth on the structural damage response were systematically analyzed. The results indicate that the weak zone of steel sheet piles is mainly concentrated near the water-soil interface, with punching shear fracture and bending deformation identified as the dominant failure modes. The scaled distance was found to be the key parameter governing the damage behavior. When the scaled distance is less than 0.086m/kg1/3, punching shear fracture occurs; when it exceeds 1.026 m/kg1/3, no significant damage is observed; and within the intermediate range, plastic bending deformation develops. Increasing water depth has a limited effect on fracture failure but can significantly extend the bending deformation zone, with an increase of up to 35%. Good agreement was achieved among the theoretical calculations, numerical simulations, and experimental results, with relative errors within 10%, satisfying the accuracy requirements for engineering prediction. These findings provide a reliable theoretical basis and practical guidance for the blast-resistant design, damage assessment, and protective reinforcement of independent embedded steel sheet pile structures.
, Available online , doi: 10.11883/bzycj-2026-0057
Abstract:
To address the issues of insufficient cycle advance and low blast-hole utilization resulting from inappropriate cut blasting layouts during roadway excavation, the empty-hole effect was employed to establish a three-dimensional cut blasting model using FEM-SPH（finite element method-smooth particle hydrodynamics）coupled numerical simulation. In the numerical modeling, the rock mass was described by the RHT constitutive model, which accounts for strain-rate sensitivity and confinement effects under high-strain-rate loading. The explosive was modeled using the Jones-Wilkins-Lee equation of state. A central charged hole was surrounded by four, five, or six empty holes with a spacing of 210 mm determined theoretically. SPH particles were applied to the central zone to capture large deformation, fragmentation, and rock ejection, while the FEM was used for the outer region to reduce computational cost. Non-reflecting boundaries were set to avoid stress wave reflection. The model was then used to simulate and analyze the influence of different cut blasting arrangements on rock mass damage, rock throw efficiency, and fragmentation patterns. Furthermore, field engineering tests were conducted in a copper mine roadway to validate the simulation results by examining the residual hole depth after blasting and the achieved cycle advance. The research findings indicate that a cut blasting layout with one central charged hole and five empty holes provides a moderate number of free surfaces, allowing for more sufficient superposition of stress waves and resulting in better blasting performance. Compared to layouts with four or six empty holes, the five-empty-hole configuration demonstrates optimal rock throw effects, with the slot cavity opening size increasing by 42.5% and 20.3%, respectively, and the slot cavity cross-sectional size improving by 52.4% and 34.7%, respectively. Field test results show that the cycle advance achieved with the five-empty-hole layout is 10.2% and 3.2% higher than that of the four-empty-hole and six-empty-hole layouts, respectively. The research reveals a nonlinear relationship between the number of empty holes and blasting effects, demonstrating that the optimal balance between stress wave superposition and energy concentration can be achieved using a moderate number of empty holes, providing a basis for the design and optimization of cut blasting schemes in roadway excavation.
To address the issues of insufficient cycle advance and low blast-hole utilization resulting from inappropriate cut blasting layouts during roadway excavation, the empty-hole effect was employed to establish a three-dimensional cut blasting model using FEM-SPH（finite element method-smooth particle hydrodynamics）coupled numerical simulation. In the numerical modeling, the rock mass was described by the RHT constitutive model, which accounts for strain-rate sensitivity and confinement effects under high-strain-rate loading. The explosive was modeled using the Jones-Wilkins-Lee equation of state. A central charged hole was surrounded by four, five, or six empty holes with a spacing of 210 mm determined theoretically. SPH particles were applied to the central zone to capture large deformation, fragmentation, and rock ejection, while the FEM was used for the outer region to reduce computational cost. Non-reflecting boundaries were set to avoid stress wave reflection. The model was then used to simulate and analyze the influence of different cut blasting arrangements on rock mass damage, rock throw efficiency, and fragmentation patterns. Furthermore, field engineering tests were conducted in a copper mine roadway to validate the simulation results by examining the residual hole depth after blasting and the achieved cycle advance. The research findings indicate that a cut blasting layout with one central charged hole and five empty holes provides a moderate number of free surfaces, allowing for more sufficient superposition of stress waves and resulting in better blasting performance. Compared to layouts with four or six empty holes, the five-empty-hole configuration demonstrates optimal rock throw effects, with the slot cavity opening size increasing by 42.5% and 20.3%, respectively, and the slot cavity cross-sectional size improving by 52.4% and 34.7%, respectively. Field test results show that the cycle advance achieved with the five-empty-hole layout is 10.2% and 3.2% higher than that of the four-empty-hole and six-empty-hole layouts, respectively. The research reveals a nonlinear relationship between the number of empty holes and blasting effects, demonstrating that the optimal balance between stress wave superposition and energy concentration can be achieved using a moderate number of empty holes, providing a basis for the design and optimization of cut blasting schemes in roadway excavation.
, Available online , doi: 10.11883/bzycj-2026-0035
Abstract:
Aiming at the problems of complex characteristics of blast load induced by fuel-rich explosives in confined spaces, as well as the high cost of high-precision solution and engineering application, a numerical calculation method for confined blast loading considering the afterburning effect was established. The method was verified for its reliability by comparing the calculated quasi-static pressure, impulse within the saturation response time and residual deformation of the target with the experimental results, with all relative errors controlled within 10%. The spatiotemporal distribution law of confined blast loading in confined spaces was systematically analyzed, and a simplified equivalent loading method considering both the saturation response time and quasi-static pressure was proposed. The reliability of the simplification method was validated by comparing the calculated first peak deformation and residual deformation at the central point with the results from fully coupled calculation, with all errors within 10%. Through an investigation into the spatial distribution form of the equivalent load and the influence of quasi-static pressure on structural response, the results show that within the scope of the current research, the spatial distribution of the equivalent load has a relatively minor effect on structural response, while the contribution of quasi-static pressure cannot be neglected. On the basis of the above findings, a two-stage load simplification model based on the load characteristics at the central point of the target plate was proposed. The reliability of the simplified model was confirmed by comparing the residual deformation values obtained from 10 groups of simplified model calculations with the experimental data, with all errors within 15%. The research results indicate that the proposed model exhibits good applicability under different working conditions; it can significantly improve the calculation efficiency while ensuring the calculation accuracy, and thus provides a technical approach for the simplified analysis of engineering problems related to confined space explosions.
Aiming at the problems of complex characteristics of blast load induced by fuel-rich explosives in confined spaces, as well as the high cost of high-precision solution and engineering application, a numerical calculation method for confined blast loading considering the afterburning effect was established. The method was verified for its reliability by comparing the calculated quasi-static pressure, impulse within the saturation response time and residual deformation of the target with the experimental results, with all relative errors controlled within 10%. The spatiotemporal distribution law of confined blast loading in confined spaces was systematically analyzed, and a simplified equivalent loading method considering both the saturation response time and quasi-static pressure was proposed. The reliability of the simplification method was validated by comparing the calculated first peak deformation and residual deformation at the central point with the results from fully coupled calculation, with all errors within 10%. Through an investigation into the spatial distribution form of the equivalent load and the influence of quasi-static pressure on structural response, the results show that within the scope of the current research, the spatial distribution of the equivalent load has a relatively minor effect on structural response, while the contribution of quasi-static pressure cannot be neglected. On the basis of the above findings, a two-stage load simplification model based on the load characteristics at the central point of the target plate was proposed. The reliability of the simplified model was confirmed by comparing the residual deformation values obtained from 10 groups of simplified model calculations with the experimental data, with all errors within 15%. The research results indicate that the proposed model exhibits good applicability under different working conditions; it can significantly improve the calculation efficiency while ensuring the calculation accuracy, and thus provides a technical approach for the simplified analysis of engineering problems related to confined space explosions.
, Available online , doi: 10.11883/bzycj-2026-0056
Abstract:
To clarify the ultimate load-bearing capacity characteristics of prestressed concrete T-girder bridges under typical blast loads and address the technical difficulties in the residual load-bearing capacity evaluation of blast-damaged bridge structures, a two-stage test method combining blast damage test and post-blast static loading test is adopted in this study. A full-scale (1:1) prestressed concrete T-girder bridge specimen consistent with practical engineering structural parameters is taken as the test object to carry out large-equivalent field blast tests. Multi-stage graded static loading tests are further implemented on the blast-damaged specimen to obtain structural damage evolution features and deflection response data under post-blast service conditions. Based on the measured damage morphologies, deformation data and mechanical response laws acquired from physical tests, a refined three-dimensional finite element (FE) numerical simulation model for prestressed concrete T-girder bridges is established. Key structural characteristics including concrete and reinforcement strain-rate effects, material nonlinearity, prestress loss and structural contact interaction are fully considered in model establishment. The accuracy and reliability of the numerical model are validated through comparative calibration with experimental results. The validated model is subsequently employed to quantitatively investigate the ultimate load-bearing performance of bridges under three typical blast working conditions, including deck central contact blast, combined blast of deck central explosion and inter-girder internal explosion, and bilateral inter-girder internal explosion. The research results demonstrate distinct structural damage and bearing degradation characteristics under different blast scenarios. Contact blast acting on the bridge deck mainly induces local slab perforation failure and concentrated plastic deformation of deck concrete. For internal explosion occurring between main girders, structural damage presents a more severe and extensive pattern. In addition to concrete spalling and fragmentation on the bottom surface of the bridge deck, obvious outward bulging deformation, concrete crushing and local collapse failure occur on the webs and transverse diaphragms of T-girders. Among the three typical blast damage states, the combined blast condition with deck central explosion followed by secondary inter-girder explosion causes the most significant degradation of structural ultimate load-bearing capacity due to the superimposed synergistic damage effect. Reasonable optimization of live load layout effectively avoids severe damage areas of blast-affected bridges, eliminates the adverse influence of blast-induced structural defects, and achieves a remarkable improvement in the ultimate load-bearing capacity of damaged bridges. An integrated evaluation system covering the whole process from blast damage characterization to ultimate load-bearing capacity quantification is established in this research. The proposed evaluation method provides a systematic theoretical basis and feasible technical support for residual load-bearing capacity assessment, damage prediction and blast-resistant reinforcement design of prestressed concrete T-girder bridges suffering blast loads.
To clarify the ultimate load-bearing capacity characteristics of prestressed concrete T-girder bridges under typical blast loads and address the technical difficulties in the residual load-bearing capacity evaluation of blast-damaged bridge structures, a two-stage test method combining blast damage test and post-blast static loading test is adopted in this study. A full-scale (1:1) prestressed concrete T-girder bridge specimen consistent with practical engineering structural parameters is taken as the test object to carry out large-equivalent field blast tests. Multi-stage graded static loading tests are further implemented on the blast-damaged specimen to obtain structural damage evolution features and deflection response data under post-blast service conditions. Based on the measured damage morphologies, deformation data and mechanical response laws acquired from physical tests, a refined three-dimensional finite element (FE) numerical simulation model for prestressed concrete T-girder bridges is established. Key structural characteristics including concrete and reinforcement strain-rate effects, material nonlinearity, prestress loss and structural contact interaction are fully considered in model establishment. The accuracy and reliability of the numerical model are validated through comparative calibration with experimental results. The validated model is subsequently employed to quantitatively investigate the ultimate load-bearing performance of bridges under three typical blast working conditions, including deck central contact blast, combined blast of deck central explosion and inter-girder internal explosion, and bilateral inter-girder internal explosion. The research results demonstrate distinct structural damage and bearing degradation characteristics under different blast scenarios. Contact blast acting on the bridge deck mainly induces local slab perforation failure and concentrated plastic deformation of deck concrete. For internal explosion occurring between main girders, structural damage presents a more severe and extensive pattern. In addition to concrete spalling and fragmentation on the bottom surface of the bridge deck, obvious outward bulging deformation, concrete crushing and local collapse failure occur on the webs and transverse diaphragms of T-girders. Among the three typical blast damage states, the combined blast condition with deck central explosion followed by secondary inter-girder explosion causes the most significant degradation of structural ultimate load-bearing capacity due to the superimposed synergistic damage effect. Reasonable optimization of live load layout effectively avoids severe damage areas of blast-affected bridges, eliminates the adverse influence of blast-induced structural defects, and achieves a remarkable improvement in the ultimate load-bearing capacity of damaged bridges. An integrated evaluation system covering the whole process from blast damage characterization to ultimate load-bearing capacity quantification is established in this research. The proposed evaluation method provides a systematic theoretical basis and feasible technical support for residual load-bearing capacity assessment, damage prediction and blast-resistant reinforcement design of prestressed concrete T-girder bridges suffering blast loads.
, Available online , doi: 10.11883/bzycj-2026-0054
Abstract:
Impact fatigue refers to the phenomenon in which materials or structures, subjected to repeated impact loading, experience localized stress concentrations and rapid strain accumulation, leading to the initiation of internal micro-damage and ultimately the fracture failure. Impact fatigue loads are characterized by their short duration, rapid loading rates and significantly elevated strain-rates, which has greater threat than conventional fatigue. The wheel-rail dynamic contact forces of high-speed trains exhibit typical characteristics of impact fatigue loading, which induces the accumulation of impact fatigue damage, accelerates the deterioration of material’s mechanical properties; and consequently, compromises the operational safety of high-speed trains. The present study integrates a material-based impact fatigue damage-coupled constitutive model to develop a comprehensive three-dimensional wheel-rail rolling contact finite element model. The stress-strain states and adhesion-slip characteristics of wheel-rail rolling/sliding contact are clarified, and the distribution features and accumulation evolution of wheel-rail impact fatigue damage are analyzed. Meanwhile, the effects of train speed, friction coefficient, and traction coefficient on impact fatigue damage are studied, and the influence of material constitutive model on typical wheel-rail contact mechanical behavior is examined. The results clearly indicate that the proposed impact fatigue model is able to well represent the wheel-rail contact responses, adhesion-slip distribution characteristics and damage accumulation. Under repeated rolling contact, the impact fatigue damage of the rail exhibits a nonlinear cumulative increasing trend with the increase of rolling cycles; however, the growth rate gradually decreases and eventually tends to stabilize approximately. Compared with the elastoplastic constitutive model, the wheel-rail contact mechanical responses predicted by the impact fatigue constitutive model are more severe and dangerous. Moreover, the coupling effect of impact fatigue damage gradually intensifies with the increase of wheel passages. These findings provide valuable theoretical insights and technical support for fatigue damage assessment and life prediction of high-speed wheel-rail systems.
Impact fatigue refers to the phenomenon in which materials or structures, subjected to repeated impact loading, experience localized stress concentrations and rapid strain accumulation, leading to the initiation of internal micro-damage and ultimately the fracture failure. Impact fatigue loads are characterized by their short duration, rapid loading rates and significantly elevated strain-rates, which has greater threat than conventional fatigue. The wheel-rail dynamic contact forces of high-speed trains exhibit typical characteristics of impact fatigue loading, which induces the accumulation of impact fatigue damage, accelerates the deterioration of material’s mechanical properties; and consequently, compromises the operational safety of high-speed trains. The present study integrates a material-based impact fatigue damage-coupled constitutive model to develop a comprehensive three-dimensional wheel-rail rolling contact finite element model. The stress-strain states and adhesion-slip characteristics of wheel-rail rolling/sliding contact are clarified, and the distribution features and accumulation evolution of wheel-rail impact fatigue damage are analyzed. Meanwhile, the effects of train speed, friction coefficient, and traction coefficient on impact fatigue damage are studied, and the influence of material constitutive model on typical wheel-rail contact mechanical behavior is examined. The results clearly indicate that the proposed impact fatigue model is able to well represent the wheel-rail contact responses, adhesion-slip distribution characteristics and damage accumulation. Under repeated rolling contact, the impact fatigue damage of the rail exhibits a nonlinear cumulative increasing trend with the increase of rolling cycles; however, the growth rate gradually decreases and eventually tends to stabilize approximately. Compared with the elastoplastic constitutive model, the wheel-rail contact mechanical responses predicted by the impact fatigue constitutive model are more severe and dangerous. Moreover, the coupling effect of impact fatigue damage gradually intensifies with the increase of wheel passages. These findings provide valuable theoretical insights and technical support for fatigue damage assessment and life prediction of high-speed wheel-rail systems.
