2019 Vol. 39, No. 12
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2019, 39(12): 121101.
doi: 10.11883/bzycj-2018-0505
Abstract:
The huge energy released instantaneously in underground nuclear tests leads to a chain reaction of crustal energy, and results in geophysical phenomena such as induced earthquakes. This paper sorts out and sums up the underground nuclear test data of the Soviet Union and the United States conducted in the 20th century, including the range of engineering earthquakes induced by underground nuclear tests and the size of activating rock blocks. By judging the measured data, the mechanical nature of the engineering earthquake induced by underground nuclear explosion is pointed out and the range of the critical energy factor of irreversible displacement induced by underground nuclear explosion is calculated using the theoretical formula, thereby providing a theoretical basis and site effect test data for relevant researches.
The huge energy released instantaneously in underground nuclear tests leads to a chain reaction of crustal energy, and results in geophysical phenomena such as induced earthquakes. This paper sorts out and sums up the underground nuclear test data of the Soviet Union and the United States conducted in the 20th century, including the range of engineering earthquakes induced by underground nuclear tests and the size of activating rock blocks. By judging the measured data, the mechanical nature of the engineering earthquake induced by underground nuclear explosion is pointed out and the range of the critical energy factor of irreversible displacement induced by underground nuclear explosion is calculated using the theoretical formula, thereby providing a theoretical basis and site effect test data for relevant researches.
2019, 39(12): 122101.
doi: 10.11883/bzycj-2018-0381
Abstract:
The explosion limits of combustible material at elevated temperatures and pressures provide support for perfecting fire and explosion safety theory and improving explosion protection technology. A closed 20 L spherical vessel was designed to measure the explosion limits under abnormal conditions. The explosion limits of ethane/oxygen mixtures at temperatures ranging from 20 to 270 °C and pressures ranging from 0.5 to 2.6 MPa were measured. The influence of temperature, pressure and their coupling effect on the explosion limits in oxygen were analyzed. The results showed that the range of the explosion limits of ethane in oxygen gradually widened as the initial pressures and temperatures increased; the UELs in oxygen changed almost linearly when the initial temperatures were below 140 °C; as the temperature continues to rise, its effect gradually decreased; the UELs in oxygen changed almost linearly when the initial temperatures were below 140 °C; the UELs in oxygen linearly increased when the initial pressures were below 1.6 MPa; the rising rate of UEL increased above 1.6 MPa and 140 °C; the elevated temperatures and pressures decreased the LELs of ethane in oxygen, but their effect was reduced; the coupling effect of the initial temperatures and pressures on the explosion limits of ethane/oxygen mixtures was found slightly less than the sum of the two factors, but far greater than the effect of each individual factor; and the quantitative rules of explosion limits varying with the initial pressures and temperatures were obtained using the fitting formula.
The explosion limits of combustible material at elevated temperatures and pressures provide support for perfecting fire and explosion safety theory and improving explosion protection technology. A closed 20 L spherical vessel was designed to measure the explosion limits under abnormal conditions. The explosion limits of ethane/oxygen mixtures at temperatures ranging from 20 to 270 °C and pressures ranging from 0.5 to 2.6 MPa were measured. The influence of temperature, pressure and their coupling effect on the explosion limits in oxygen were analyzed. The results showed that the range of the explosion limits of ethane in oxygen gradually widened as the initial pressures and temperatures increased; the UELs in oxygen changed almost linearly when the initial temperatures were below 140 °C; as the temperature continues to rise, its effect gradually decreased; the UELs in oxygen changed almost linearly when the initial temperatures were below 140 °C; the UELs in oxygen linearly increased when the initial pressures were below 1.6 MPa; the rising rate of UEL increased above 1.6 MPa and 140 °C; the elevated temperatures and pressures decreased the LELs of ethane in oxygen, but their effect was reduced; the coupling effect of the initial temperatures and pressures on the explosion limits of ethane/oxygen mixtures was found slightly less than the sum of the two factors, but far greater than the effect of each individual factor; and the quantitative rules of explosion limits varying with the initial pressures and temperatures were obtained using the fitting formula.
2019, 39(12): 122201.
doi: 10.11883/bzycj-2018-0317
Abstract:
Column is the main bearing member in bridge. It is the premise for analyzing the dynamic response of the bridge under blast loading to study the distribution law of blast load acted on bridge columns. Circular sectional bridge column has been selected as the research object, and the corresponding finite element models have been built by using the LS-DYNA software. When the height of burst is less than 0.3 times of the column height, the scaled distance is 0.5−2.1 m/kg1/3 and the column diameter is 0.15−1 m, the distributions of the blast loading impulse along column height and cross-section direction are obtained through numerical simulations. The influential parameters, e.g., the explosive equivalent, height of burst, explosion distance and sectional diameter, have been considered. It is derived that, along the column height, when the contact burst and the height of burst is 0.1 times of the column height, the blast loading impulse on the column front surface approximately follows the " Single linear” distribution. When the height of burst is 0.2 and 0.3 times of the column height, the blast loading impulse approximately follows the " Double linear” distribution. Along the cross-section direction, the ratio of the average net blast loading impulse to the blast impulse on the column front surface is a constant. Furthermore, the resultant net blast loading impulse of bridge column has been obtained, which can put some theoretical basis for blast-resistant analysis and design of bridge columns.
Column is the main bearing member in bridge. It is the premise for analyzing the dynamic response of the bridge under blast loading to study the distribution law of blast load acted on bridge columns. Circular sectional bridge column has been selected as the research object, and the corresponding finite element models have been built by using the LS-DYNA software. When the height of burst is less than 0.3 times of the column height, the scaled distance is 0.5−2.1 m/kg1/3 and the column diameter is 0.15−1 m, the distributions of the blast loading impulse along column height and cross-section direction are obtained through numerical simulations. The influential parameters, e.g., the explosive equivalent, height of burst, explosion distance and sectional diameter, have been considered. It is derived that, along the column height, when the contact burst and the height of burst is 0.1 times of the column height, the blast loading impulse on the column front surface approximately follows the " Single linear” distribution. When the height of burst is 0.2 and 0.3 times of the column height, the blast loading impulse approximately follows the " Double linear” distribution. Along the cross-section direction, the ratio of the average net blast loading impulse to the blast impulse on the column front surface is a constant. Furthermore, the resultant net blast loading impulse of bridge column has been obtained, which can put some theoretical basis for blast-resistant analysis and design of bridge columns.
2019, 39(12): 122202.
doi: 10.11883/bzycj-2018-0510
Abstract:
In this paper we presented a theoretical calculation method for the physical quantities of flow filed after entering the quasi-self-similar stage concerning the interaction between the vertical planar shock wave and the horizontal thermal layer near the rigid wall. Compared with the existing Mirels’ theoretical method, ours has improved in the following three aspects: (1) the propagation process of the shock in the thermal layer is analyzed, and the shock intensity is calculated following the theory of geometrical shock dynamics, whereas the assumption that the propagation speed of the shock in the thermal layer is equal to that of the incident shock is abandoned; (2) an assumption is made that in the coordinate system fixed with the fluid behind the incident shock instead of the incident shock itself, the fluid behind the incident shock evolves into a " piston” under the action of steady isentropic wave, which moves along the wall and drives the thermal layer gas in front of it; and (3) the fluid in the " piston” and its adjacent thermal layer gas satisfy the continuity of pressure and velocity without introducing the velocity proportional coefficient. Our improved method is employed in the cases involving a Mach number 2.00 incident shock and different thermal layer densities, and gives the shock strength in the thermal layer and the field pressure, velocity and density on each side of the material interface. The deviation between the theoretical results and numerical results is below 10% in different thermal layer densities, which is much better than those of the Shreffler’s and Mirels’ methods. For a Mach number 1.36 incident shock with a propagation speed less than the speed of sound in the thermal layer, Shreffler’s and Mirels’ methods are no longer applicable, whereas the above mentioned theoretical mothod could still work and produce results that accord well with experimental data and numerical results, and the maximum deviation is about 20%, indicating that the above improved theoretical method is more reasonable and applicable than the existing theoretical calculation methods.
In this paper we presented a theoretical calculation method for the physical quantities of flow filed after entering the quasi-self-similar stage concerning the interaction between the vertical planar shock wave and the horizontal thermal layer near the rigid wall. Compared with the existing Mirels’ theoretical method, ours has improved in the following three aspects: (1) the propagation process of the shock in the thermal layer is analyzed, and the shock intensity is calculated following the theory of geometrical shock dynamics, whereas the assumption that the propagation speed of the shock in the thermal layer is equal to that of the incident shock is abandoned; (2) an assumption is made that in the coordinate system fixed with the fluid behind the incident shock instead of the incident shock itself, the fluid behind the incident shock evolves into a " piston” under the action of steady isentropic wave, which moves along the wall and drives the thermal layer gas in front of it; and (3) the fluid in the " piston” and its adjacent thermal layer gas satisfy the continuity of pressure and velocity without introducing the velocity proportional coefficient. Our improved method is employed in the cases involving a Mach number 2.00 incident shock and different thermal layer densities, and gives the shock strength in the thermal layer and the field pressure, velocity and density on each side of the material interface. The deviation between the theoretical results and numerical results is below 10% in different thermal layer densities, which is much better than those of the Shreffler’s and Mirels’ methods. For a Mach number 1.36 incident shock with a propagation speed less than the speed of sound in the thermal layer, Shreffler’s and Mirels’ methods are no longer applicable, whereas the above mentioned theoretical mothod could still work and produce results that accord well with experimental data and numerical results, and the maximum deviation is about 20%, indicating that the above improved theoretical method is more reasonable and applicable than the existing theoretical calculation methods.
2019, 39(12): 123101.
doi: 10.11883/bzycj-2018-0483
Abstract:
The mechanical behavior of Al-Mg-Si alloy after long-term neutron irradiation (i.e. LT21 aluminum alloy served in the reactor for nearly 30 years) under compression loading with different temperature and strain rates is experimentally studied using material test system and split Hopkinson pressure bar. The effects of temperature and strain rate on its yield strength and flow stress are obtained. The results show that the material exhibits obvious temperature effect within a temperature rang from −40 ℃ to 300 ℃ and positive strain rate effect in a strain rate rang from 0.001 to 3 000 s−1, respectively. At a lower temperature range (from −80 to −40 ℃) and higher strain rates (from 3 000 to 5 000 s−1), the mechanical properties are insensitive to changes in temperature and strain rate. When the temperature reaches 300 ℃, the plastic deformation behavior of the material tends to ideal plastic flow. Based on the above experimental results, a modified Zerilli-Armstrong constitutive model considering irradiation damage is established by taking into account the effect of microscale irradiation defects on the mechanical properties of materials. The Zerilli-Armstrong model predictions are in good agreement with the experimental results. Furthermore, the yield strength of LT21 aluminum alloy with different fast neutron irradiation doses and the yield strength of another two samples obtained from different irradiated regions within the reactor at different strain rates and temperature are calculated by reference to the evolution of microscale irradiation defects of high purity aluminum. The above research shows that the Zerilli-Armstrong constitutive equation considering radiation damage established in this paper can not only establish the relationship between macroscale stress and strain, strain rate and temperature of the Al-Mg-Si alloy after long-term neutron irradiation, but also describe the dislocation motion and the mechanism of irradiation hardening. It can provide reference for the design, operation and safety evaluation of the corresponding structural elements in the nuclear reactor.
The mechanical behavior of Al-Mg-Si alloy after long-term neutron irradiation (i.e. LT21 aluminum alloy served in the reactor for nearly 30 years) under compression loading with different temperature and strain rates is experimentally studied using material test system and split Hopkinson pressure bar. The effects of temperature and strain rate on its yield strength and flow stress are obtained. The results show that the material exhibits obvious temperature effect within a temperature rang from −40 ℃ to 300 ℃ and positive strain rate effect in a strain rate rang from 0.001 to 3 000 s−1, respectively. At a lower temperature range (from −80 to −40 ℃) and higher strain rates (from 3 000 to 5 000 s−1), the mechanical properties are insensitive to changes in temperature and strain rate. When the temperature reaches 300 ℃, the plastic deformation behavior of the material tends to ideal plastic flow. Based on the above experimental results, a modified Zerilli-Armstrong constitutive model considering irradiation damage is established by taking into account the effect of microscale irradiation defects on the mechanical properties of materials. The Zerilli-Armstrong model predictions are in good agreement with the experimental results. Furthermore, the yield strength of LT21 aluminum alloy with different fast neutron irradiation doses and the yield strength of another two samples obtained from different irradiated regions within the reactor at different strain rates and temperature are calculated by reference to the evolution of microscale irradiation defects of high purity aluminum. The above research shows that the Zerilli-Armstrong constitutive equation considering radiation damage established in this paper can not only establish the relationship between macroscale stress and strain, strain rate and temperature of the Al-Mg-Si alloy after long-term neutron irradiation, but also describe the dislocation motion and the mechanism of irradiation hardening. It can provide reference for the design, operation and safety evaluation of the corresponding structural elements in the nuclear reactor.
2019, 39(12): 123102.
doi: 10.11883/bzycj-2018-0462
Abstract:
Boron carbide (B4C) ceramic has been widely used in armor fence due to its high hardness and low density. Ballistic performance of B4C ceramic and its composite targets has been one of the focuses recently. Ballistic performance of B4C ceramic composite targets defending 12.7 mm calibre armor-piercing bullets were explored through depth-of-penetration experiments and the corresponding numerical simulation model was established. The numerical simulation model for 12.7 mm calibre armor-piercing bullets penetrating into B4C ceramic composite targets was verified through the comparison between numerical results and experimental data. The influences of target configuration, back layer thickness and type on the ballistic performance of the composite targets were explored. It can be figured out from the results that for the composite targets with same areal density, the thicker the ceramic target, the better its ballistic performance; the increasing rate in the ballistic performance of the ceramic composite target decreases when the areal density increases and the ceramic thickness keeps constant. Ceramic/polyethylene (PE) structures are more suitable for defending against penetration by low-velocity bullets, while ceramic/Al structures are more suitable for defending against penetration by high-velocity bullets.
Boron carbide (B4C) ceramic has been widely used in armor fence due to its high hardness and low density. Ballistic performance of B4C ceramic and its composite targets has been one of the focuses recently. Ballistic performance of B4C ceramic composite targets defending 12.7 mm calibre armor-piercing bullets were explored through depth-of-penetration experiments and the corresponding numerical simulation model was established. The numerical simulation model for 12.7 mm calibre armor-piercing bullets penetrating into B4C ceramic composite targets was verified through the comparison between numerical results and experimental data. The influences of target configuration, back layer thickness and type on the ballistic performance of the composite targets were explored. It can be figured out from the results that for the composite targets with same areal density, the thicker the ceramic target, the better its ballistic performance; the increasing rate in the ballistic performance of the ceramic composite target decreases when the areal density increases and the ceramic thickness keeps constant. Ceramic/polyethylene (PE) structures are more suitable for defending against penetration by low-velocity bullets, while ceramic/Al structures are more suitable for defending against penetration by high-velocity bullets.
2019, 39(12): 123103.
doi: 10.11883/bzycj-2018-0419
Abstract:
In order to explore the influence of granite grain size on rockburst, cubic granite specimens with an opening and different grain sizes (fine to medium and medium to coarse) were used to conduct the rockburst tests using the true triaxial rockburst testing system. The experimental results show that the failure process of the fine to medium-grained granite is mainly composed of brittle failure. However, rockburst failure (dynamic failure) dominates the failure for the medium to coarse-grained granite. The acoustic emission (AE) activity in the early loading stage is weak for the fine to medium-grained granite, and the low-frequency large-rupture events are concentrated in time and space, and the characteristic stress is higher. However, the AE activity in the early loading stage is stronger for the medium to coarse-grained granite, and the low-frequency, large-rupture events are more discrete in time and space, and the characteristic stress is lower, and the fragments are broken more. The grain size has an important influence on the rockburst proneness of granites. The hard-brittle rock with coarser grain size has a stronger rockburst proneness. In addition to strength and brittleness, grain size is an important factor to be considered in rockburst proneness evaluation of deep underground rock mass engineering.
In order to explore the influence of granite grain size on rockburst, cubic granite specimens with an opening and different grain sizes (fine to medium and medium to coarse) were used to conduct the rockburst tests using the true triaxial rockburst testing system. The experimental results show that the failure process of the fine to medium-grained granite is mainly composed of brittle failure. However, rockburst failure (dynamic failure) dominates the failure for the medium to coarse-grained granite. The acoustic emission (AE) activity in the early loading stage is weak for the fine to medium-grained granite, and the low-frequency large-rupture events are concentrated in time and space, and the characteristic stress is higher. However, the AE activity in the early loading stage is stronger for the medium to coarse-grained granite, and the low-frequency, large-rupture events are more discrete in time and space, and the characteristic stress is lower, and the fragments are broken more. The grain size has an important influence on the rockburst proneness of granites. The hard-brittle rock with coarser grain size has a stronger rockburst proneness. In addition to strength and brittleness, grain size is an important factor to be considered in rockburst proneness evaluation of deep underground rock mass engineering.
2019, 39(12): 123301.
doi: 10.11883/bzycj-2018-0425
Abstract:
Ballistic limit tests were carried out by using a ballistic gun system for the ceramic composite armors obliquely placed with the angles of 0° − 60°. The influences of the oblique angles were analyzed on the ballistic limits, steel core mass change and damage forms of armor-piercing bullets. The numerical simulations were performed to verify the above experimental results. Based on the fact that the calculated results were in agreement with the experimental ones, the influences of the oblique angles were further explored on the deflection angles of the bullet steel cores penetrating through the target plates, and the thicknesses of the equivalent Q235 steel target plates. Results show that with increasing the oblique angles of the ceramic composite targets: (1) the ballistic limit obeys an exponential increase law; (2) at the same ballistic limit, the ratio of the limit penetration depth of the Q235 steel target plate by the armor-piercing bullet to the equivalent thickness of the limit penetration depth of the obliquely-placed ceramic composite target by the armor-piercing bullet increases; (3) the integrity of the bullet steel core decreases gradually, its deflection angle increases reversely.
Ballistic limit tests were carried out by using a ballistic gun system for the ceramic composite armors obliquely placed with the angles of 0° − 60°. The influences of the oblique angles were analyzed on the ballistic limits, steel core mass change and damage forms of armor-piercing bullets. The numerical simulations were performed to verify the above experimental results. Based on the fact that the calculated results were in agreement with the experimental ones, the influences of the oblique angles were further explored on the deflection angles of the bullet steel cores penetrating through the target plates, and the thicknesses of the equivalent Q235 steel target plates. Results show that with increasing the oblique angles of the ceramic composite targets: (1) the ballistic limit obeys an exponential increase law; (2) at the same ballistic limit, the ratio of the limit penetration depth of the Q235 steel target plate by the armor-piercing bullet to the equivalent thickness of the limit penetration depth of the obliquely-placed ceramic composite target by the armor-piercing bullet increases; (3) the integrity of the bullet steel core decreases gradually, its deflection angle increases reversely.
2019, 39(12): 123901.
doi: 10.11883/bzycj-2018-0415
Abstract:
Water-entry experiments were carried out by adopting five kinds of surface roughness to explore the effects of surface roughness of water-entry spheres on the evolution of cavities induced the water-entry of the spheres and the motion characteristics of the spheres during the water-entry process of the spheres. The experiments were based on an open water-tank test system. Meanwhile, a high-speed camera was used to record the water-entry processes of the spheres with different surface roughness. The evolutions of cavity, splash and motion characteristics of each sphere were obtained. It is found that the closure of cavity and splash will exert a negative acceleration on the sphere. By comparing the displacement, velocity and acceleration curves of the spheres with different surface roughness, it is found that the sphere with the largest surface roughness will move significantly slower than other spheres after the end of slamming, and that the effects of surface roughness on the sphere motion are mainly reflected in the early period of the water-entry. By analyzing the shrinkage of the cavities connected with the free surface of each sphere after cavity seal, it is found that both the shrinking velocity and acceleration curves take on extreme points, and that the larger the surface roughness of the spheres, the earlier the extreme point appears.
Water-entry experiments were carried out by adopting five kinds of surface roughness to explore the effects of surface roughness of water-entry spheres on the evolution of cavities induced the water-entry of the spheres and the motion characteristics of the spheres during the water-entry process of the spheres. The experiments were based on an open water-tank test system. Meanwhile, a high-speed camera was used to record the water-entry processes of the spheres with different surface roughness. The evolutions of cavity, splash and motion characteristics of each sphere were obtained. It is found that the closure of cavity and splash will exert a negative acceleration on the sphere. By comparing the displacement, velocity and acceleration curves of the spheres with different surface roughness, it is found that the sphere with the largest surface roughness will move significantly slower than other spheres after the end of slamming, and that the effects of surface roughness on the sphere motion are mainly reflected in the early period of the water-entry. By analyzing the shrinkage of the cavities connected with the free surface of each sphere after cavity seal, it is found that both the shrinking velocity and acceleration curves take on extreme points, and that the larger the surface roughness of the spheres, the earlier the extreme point appears.
2019, 39(12): 124201.
doi: 10.11883/bzycj-2018-0416
Abstract:
In order to calculate the cavity sizes for the cylindrical charges in soil, a new method was established to calculate the characteristic cavity sizes for finite-length cylindrical charges in soil. In the new method, the quasi-static model for spherical charges is used to calculate the cavities induced by cylindrical charges. In this method, the characteristic cavity sizes and the plastic zones are calculated at the larger length-to-diameter ratio. The numerical simulation results show that the error decreases with the increase of the length-to-diameter ratio, when the number N of the spherical explosive packages is n and the length-to-diameter ratio is 10 or higher, the error is less than 12.2%. The results also show that the established method can accurately predict the characteristic sizes of the cavities induced by the finite-length cylindrical charge blasting.
In order to calculate the cavity sizes for the cylindrical charges in soil, a new method was established to calculate the characteristic cavity sizes for finite-length cylindrical charges in soil. In the new method, the quasi-static model for spherical charges is used to calculate the cavities induced by cylindrical charges. In this method, the characteristic cavity sizes and the plastic zones are calculated at the larger length-to-diameter ratio. The numerical simulation results show that the error decreases with the increase of the length-to-diameter ratio, when the number N of the spherical explosive packages is n and the length-to-diameter ratio is 10 or higher, the error is less than 12.2%. The results also show that the established method can accurately predict the characteristic sizes of the cavities induced by the finite-length cylindrical charge blasting.
2019, 39(12): 125101.
doi: 10.11883/bzycj-2018-0461
Abstract:
It is believed that the gradient material bumper shows some positive for shielding performance of Whipple shield. The purpose of this paper is to study the hypervelocity impact characteristic of an new Al/Mg impedance-graded materials (area density is equivalent to 1.5 mm thick aluminum alloy) enhanced Whipple shield at 5.0 km/s, and to investigate the main factors in performance improvement, except higher shock pressures and temperature rise in the projectiles caused by the high-acoustic-impedance coating of bumpers. The hypervelocity impact performances of a shield enhanced by Al/Mg impedance-graded materials and an aluminum Whipple shield are investigated experimentally, using a two-stage light gas gun at velocities of 5.0 km/s. The characteristics of perforation on bumper, debris clouds and damage patterns on the rear wall have been studied. The characteristics of the shielding performance produced by Al/Mg shields include four major features: petal-shaped curling in bumper, slight damage of the rear wall, wider expanded area of debris cloud and smaller impact craters. Some theoretical analysis and calculations are performed. Coupling process of shock energy and thermodynamic states are calculated, and wave propagation in the projectile and bumper is discussed. It is found that the shockwave propagation is affected by the shock impedance mismatch in various area density impedance-graded materials bumpers, it can break the projectile into smaller parts and increase the internal energy conversion in the bumpers. It plays an important role in contributing to kinetic energy attenuation. Thus, the preliminary results show that the shielding capability of an Al/Mg shield is greater than that of an aluminum Whipple shield where the bumper has the same areal density.
It is believed that the gradient material bumper shows some positive for shielding performance of Whipple shield. The purpose of this paper is to study the hypervelocity impact characteristic of an new Al/Mg impedance-graded materials (area density is equivalent to 1.5 mm thick aluminum alloy) enhanced Whipple shield at 5.0 km/s, and to investigate the main factors in performance improvement, except higher shock pressures and temperature rise in the projectiles caused by the high-acoustic-impedance coating of bumpers. The hypervelocity impact performances of a shield enhanced by Al/Mg impedance-graded materials and an aluminum Whipple shield are investigated experimentally, using a two-stage light gas gun at velocities of 5.0 km/s. The characteristics of perforation on bumper, debris clouds and damage patterns on the rear wall have been studied. The characteristics of the shielding performance produced by Al/Mg shields include four major features: petal-shaped curling in bumper, slight damage of the rear wall, wider expanded area of debris cloud and smaller impact craters. Some theoretical analysis and calculations are performed. Coupling process of shock energy and thermodynamic states are calculated, and wave propagation in the projectile and bumper is discussed. It is found that the shockwave propagation is affected by the shock impedance mismatch in various area density impedance-graded materials bumpers, it can break the projectile into smaller parts and increase the internal energy conversion in the bumpers. It plays an important role in contributing to kinetic energy attenuation. Thus, the preliminary results show that the shielding capability of an Al/Mg shield is greater than that of an aluminum Whipple shield where the bumper has the same areal density.
2019, 39(12): 125102.
doi: 10.11883/bzycj-2018-0418
Abstract:
To provide an optimal direction for the protection design of a projectile-borne recorder, the dynamic response mechanism of the protection system for the projectile-borne recorder under high impact loading was revealed according to the mechanical vibration theory. On the basis of analysis for the load transfer relation, a simplified dynamic response model based on the two-degree-of-freedom spring-mass-damper system was established. To verify the credibility of the model, numerical simulation was carried out, and the parameters of the response model were identified according to the impulse response analysis and the harmonic analysis. Based on the result that the values of the theoretical calculation agreed well with those of the numerical simulation, it was concluded that the proposed model was more suitable to describe the dynamic response characteristics of the protection system under high impact loading. According to the amplitude-frequency response characteristics, the change of the dynamic response characteristics along various parameters was analyzed, which could be applied to guide the protection design of the projectile-borne recorder.
To provide an optimal direction for the protection design of a projectile-borne recorder, the dynamic response mechanism of the protection system for the projectile-borne recorder under high impact loading was revealed according to the mechanical vibration theory. On the basis of analysis for the load transfer relation, a simplified dynamic response model based on the two-degree-of-freedom spring-mass-damper system was established. To verify the credibility of the model, numerical simulation was carried out, and the parameters of the response model were identified according to the impulse response analysis and the harmonic analysis. Based on the result that the values of the theoretical calculation agreed well with those of the numerical simulation, it was concluded that the proposed model was more suitable to describe the dynamic response characteristics of the protection system under high impact loading. According to the amplitude-frequency response characteristics, the change of the dynamic response characteristics along various parameters was analyzed, which could be applied to guide the protection design of the projectile-borne recorder.
2019, 39(12): 125103.
doi: 10.11883/bzycj-2018-0414
Abstract:
To overcome the high-risk and low-efficiency problems in large-volume ammunition fragmentation tests, a new method was proposed by setting water walls in front of target plates for comprehensively collecting the damage parameters of the fragments. The dynamic simulation software AUTODYN was used to simulate the penetration processes of the fragments into the target plates with the water walls and without the water walls. The influences of the thickness of the water wall and the incident angle of the fragment on the penetration capability was analyzed, and the effectiveness of the proposed method was verified by the test. The calculation results show that compared with the target plates without the water walls, the target plates with the water walls can greatly reduce the penetration capability of fragments. The results are also in good agreement with the test data, which indicates that it is feasible to use the target plates with the water walls to collect the damage parameters of the fragments in the actual tests.
To overcome the high-risk and low-efficiency problems in large-volume ammunition fragmentation tests, a new method was proposed by setting water walls in front of target plates for comprehensively collecting the damage parameters of the fragments. The dynamic simulation software AUTODYN was used to simulate the penetration processes of the fragments into the target plates with the water walls and without the water walls. The influences of the thickness of the water wall and the incident angle of the fragment on the penetration capability was analyzed, and the effectiveness of the proposed method was verified by the test. The calculation results show that compared with the target plates without the water walls, the target plates with the water walls can greatly reduce the penetration capability of fragments. The results are also in good agreement with the test data, which indicates that it is feasible to use the target plates with the water walls to collect the damage parameters of the fragments in the actual tests.
2019, 39(12): 125104.
doi: 10.11883/bzycj-2019-0270
Abstract:
A sandwich composite armor consisting of an 8 mm thickness front titanium alloy plate, a 60 kg/m2 planar density high-strength polyethylene fiber reinforced composite laminate core layer and an 8 mm thickness rear steel plate was used to simulate the structures of composite sandwich bulkheads on ship sides. According to whether there was an interspace of 20 mm between the panel and the core, the composite armor structures were defined as non-interspace type, back interspace type and front-back interspace type. In order to study the anti-penetration performance and failure mechanism of the above three structures under high-speed impact of a cylindrical projectile with the mass of 55 g, a series of ballistic tests were carried out. The failure modes of the titanium alloy plate, the ultra-high molecular weight polyethylene fiber-reinforced composite laminate core, and the steel panel were analyzed, and the influence of the structural interspace on the anti-penetration performances of the composite armor structures was obtained. The results show that the failure mode of the front titanium alloy plate is shear plugging, brittle fracture occurs on the bullet surface of the target plate and is accompanied by debris collapse; that the failure mode of the polyethylene fiber reinforced composite plate and the deformation range of the steel back plate are greatly affected by the interspace, while the front titanium alloy plate is less affected by the interspace; and that the existence of interspace is beneficial to improve the anti-penetration performances of the composite armor structures.
A sandwich composite armor consisting of an 8 mm thickness front titanium alloy plate, a 60 kg/m2 planar density high-strength polyethylene fiber reinforced composite laminate core layer and an 8 mm thickness rear steel plate was used to simulate the structures of composite sandwich bulkheads on ship sides. According to whether there was an interspace of 20 mm between the panel and the core, the composite armor structures were defined as non-interspace type, back interspace type and front-back interspace type. In order to study the anti-penetration performance and failure mechanism of the above three structures under high-speed impact of a cylindrical projectile with the mass of 55 g, a series of ballistic tests were carried out. The failure modes of the titanium alloy plate, the ultra-high molecular weight polyethylene fiber-reinforced composite laminate core, and the steel panel were analyzed, and the influence of the structural interspace on the anti-penetration performances of the composite armor structures was obtained. The results show that the failure mode of the front titanium alloy plate is shear plugging, brittle fracture occurs on the bullet surface of the target plate and is accompanied by debris collapse; that the failure mode of the polyethylene fiber reinforced composite plate and the deformation range of the steel back plate are greatly affected by the interspace, while the front titanium alloy plate is less affected by the interspace; and that the existence of interspace is beneficial to improve the anti-penetration performances of the composite armor structures.
