2007 Vol. 27, No. 5
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2007, 27(5): 385-389.
doi: 10.11883/1001-1455(2007)05-0385-05
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Abstract:
Application of linear cutting technique with micro detonation cord( MDC) in penetration ejection system was proposed to improve successful probability of aerial aviator/seat escape system and to reduce aeroplane complexity. Different kinds of MDC were designed. Cutting process of polymethyl methacrylate (PMMA) plate by MDC was experimentally studied to determine metal cover material, explosive types, charge quantities. Spallation phenomena were observed, and relationship between the cutting depth and charge quantities was obtained. Process of cutting PMMA plate was simulated using nonlinear dynamic analysis code LS-DYNA to compare with the experiment. Relationship of cutting depth of PMMA plate and charge linear density obtained by numerical simulation is in good agreement with the experimental results.
Application of linear cutting technique with micro detonation cord( MDC) in penetration ejection system was proposed to improve successful probability of aerial aviator/seat escape system and to reduce aeroplane complexity. Different kinds of MDC were designed. Cutting process of polymethyl methacrylate (PMMA) plate by MDC was experimentally studied to determine metal cover material, explosive types, charge quantities. Spallation phenomena were observed, and relationship between the cutting depth and charge quantities was obtained. Process of cutting PMMA plate was simulated using nonlinear dynamic analysis code LS-DYNA to compare with the experiment. Relationship of cutting depth of PMMA plate and charge linear density obtained by numerical simulation is in good agreement with the experimental results.
2007, 27(5): 390-397.
doi: 10.11883/1001-1455(2007)05-0390-08
Abstract:
Three failure modes of penetration mechanisms, i.e., Taylor impact, petal-cap failure of Sunflower alike and plugging perforation, of Fragment Simulation Projectiles (FSP), were observed in the experiments of A3 steel blunt projectiles impacting 45 steel plates. Numerical simulations with LS-DYNA was conducted to analyze the various penetration mechanisms and the complicated material failures of projectile and target. Johnson-Cook models of strength and damage-cumulating failure were employed to describe the material behaviors of projectile and target, and adiabatic temperature-rise of local plastic deformation was included in the model. Different failure modes of projectiles and targets reappear in the numerical simulations in the different ranges of impact velocity, which agree well with the experimental observations. It further indicates that the failure mode of plugging perforation is the subsequent result of continuous perforation of projectile after petal-cap failure of Sunflower alike under higher velocity impact.
Three failure modes of penetration mechanisms, i.e., Taylor impact, petal-cap failure of Sunflower alike and plugging perforation, of Fragment Simulation Projectiles (FSP), were observed in the experiments of A3 steel blunt projectiles impacting 45 steel plates. Numerical simulations with LS-DYNA was conducted to analyze the various penetration mechanisms and the complicated material failures of projectile and target. Johnson-Cook models of strength and damage-cumulating failure were employed to describe the material behaviors of projectile and target, and adiabatic temperature-rise of local plastic deformation was included in the model. Different failure modes of projectiles and targets reappear in the numerical simulations in the different ranges of impact velocity, which agree well with the experimental observations. It further indicates that the failure mode of plugging perforation is the subsequent result of continuous perforation of projectile after petal-cap failure of Sunflower alike under higher velocity impact.
2007, 27(5): 398-404.
doi: 10.11883/1001-1455(2007)05-0398-07
Abstract:
Two types of ferromagnetic generators were designed. For one type, a cylinder Nd2Fe14B rare-earth permanent magnet was used as working body, and a plane shock wave forms the detonation of the explosives moved in the cylinder along the direction of its axis. For the other type, a ring Nd2Fe14B magnet was charged with high energy explosive in the center hole, and the explosives were initiated with two ends at the same time. The initial magnetic flux distribution of the Nd2Fe14B magnet was simulated by the Maxwell 3D code of the electromagnetic analysis software. The calculating method of the electromotive force from the ferromagnetic generators was given. The detonation tests of generators were carried out. The output current and voltage of generators were measured. The shock wave velocity in Nd2Fe14B magnet was measured. The results show that the ferromagnetic generators designed are capable of producing a high current pulse of up to 1 212 A, with the width of 78.3 s, and the electromotive force obtained is about 67 V/turn.
Two types of ferromagnetic generators were designed. For one type, a cylinder Nd2Fe14B rare-earth permanent magnet was used as working body, and a plane shock wave forms the detonation of the explosives moved in the cylinder along the direction of its axis. For the other type, a ring Nd2Fe14B magnet was charged with high energy explosive in the center hole, and the explosives were initiated with two ends at the same time. The initial magnetic flux distribution of the Nd2Fe14B magnet was simulated by the Maxwell 3D code of the electromagnetic analysis software. The calculating method of the electromotive force from the ferromagnetic generators was given. The detonation tests of generators were carried out. The output current and voltage of generators were measured. The shock wave velocity in Nd2Fe14B magnet was measured. The results show that the ferromagnetic generators designed are capable of producing a high current pulse of up to 1 212 A, with the width of 78.3 s, and the electromotive force obtained is about 67 V/turn.
2007, 27(5): 405-410.
doi: 10.11883/1001-1455(2007)05-0405-06
Abstract:
The features of energy distribution for blasting seismic wave which is short-time non-stationary random signal are analysed by wavelet transform technique. According to the time-frequency characteristic and multiresolution decomposition of discrete wavelet transform, the signal history of blasting seismic wave is expressed by different level reconstructed signals of wavelet decomposition. By using these signals, the relative energy distribution of blasting seismic wave in different frequency bands and the regularity of vibration strength varying with time is obtained. Blasting seismic wave measurement shows that the time-frequency characteristic analysis based on wavelet transform yields more accurate information of blasting seismic wave. The suggested method provides a new approach for analyzing the structural safety under blasting vibration conditions.
The features of energy distribution for blasting seismic wave which is short-time non-stationary random signal are analysed by wavelet transform technique. According to the time-frequency characteristic and multiresolution decomposition of discrete wavelet transform, the signal history of blasting seismic wave is expressed by different level reconstructed signals of wavelet decomposition. By using these signals, the relative energy distribution of blasting seismic wave in different frequency bands and the regularity of vibration strength varying with time is obtained. Blasting seismic wave measurement shows that the time-frequency characteristic analysis based on wavelet transform yields more accurate information of blasting seismic wave. The suggested method provides a new approach for analyzing the structural safety under blasting vibration conditions.
2007, 27(5): 411-415.
doi: 10.11883/1001-1455(2007)05-0411-05
Abstract:
The direct stress measurement method by PVDF gauge is introduced. The dynamic piezo constant of PVDF gauge is calibrated on the SHPB set-up. Influences of stress concentration, Poisson effect, friction effect on the pulse and the dynamic piezo constant of PVDF gauge are discussed. The impact compression experiment of concrete is performed with PVDF gauges. The uniformity of stress within the concrete specimen is analyzed with the data from the PVDF gauges between the bar and the specimen, and combined the data directly measured from the strain gage glued on the specimen, the dynamic stress-strain curve is derived.
The direct stress measurement method by PVDF gauge is introduced. The dynamic piezo constant of PVDF gauge is calibrated on the SHPB set-up. Influences of stress concentration, Poisson effect, friction effect on the pulse and the dynamic piezo constant of PVDF gauge are discussed. The impact compression experiment of concrete is performed with PVDF gauges. The uniformity of stress within the concrete specimen is analyzed with the data from the PVDF gauges between the bar and the specimen, and combined the data directly measured from the strain gage glued on the specimen, the dynamic stress-strain curve is derived.
2007, 27(5): 416-419.
doi: 10.11883/1001-1455(2007)05-0416-04
Abstract:
Determining of penetration deceleration on rigid-body by low-pass filtering of the measured penetration deceleration data is investigated. The concept of critical filter cut-off frequency is proposed. Critical filter cut-off frequency is acquired, penetration deceleration on rigid-body is determined. The penetration deceleration on rigid-body determined by the method presented in this paper shows a good agreement with calculation results of semi-empirical method based on cavity-expansion theory.
Determining of penetration deceleration on rigid-body by low-pass filtering of the measured penetration deceleration data is investigated. The concept of critical filter cut-off frequency is proposed. Critical filter cut-off frequency is acquired, penetration deceleration on rigid-body is determined. The penetration deceleration on rigid-body determined by the method presented in this paper shows a good agreement with calculation results of semi-empirical method based on cavity-expansion theory.
2007, 27(5): 420-425.
doi: 10.11883/1001-1455(2007)05-0420-06
Abstract:
With Ghost-fluid Euler-Lagrange (GEL) method，a two-dimensional code was developed to couple an Eulerian program(SCB scheme) with a Lagrangian code(DEFEL: 2-D finite element code). Comparing the result of a one-dimensional Riemman problem with one resolved by high-resolution PPM method, and the result of a moving boundaries test in two dimension: cylinder lift-off problem with one from reference verified the GEL method and our code.
With Ghost-fluid Euler-Lagrange (GEL) method，a two-dimensional code was developed to couple an Eulerian program(SCB scheme) with a Lagrangian code(DEFEL: 2-D finite element code). Comparing the result of a one-dimensional Riemman problem with one resolved by high-resolution PPM method, and the result of a moving boundaries test in two dimension: cylinder lift-off problem with one from reference verified the GEL method and our code.
2007, 27(5): 426-430.
doi: 10.11883/1001-1455(2007)05-0426-05
Abstract:
Based on action force analysis of slope slice，a calculation method of safety coefficient for slope stability was proposed according to the definition of safety coefficient and the Mohr-Column criteria. Reliability of the proposed method was verified and relation between pseudo-static coefficient under blast seism and safety coefficient on rock mass bedding slope was explained by using calculation examples. Computed results in some engineering cases show that the horizontal and vertical dynamic loads as well as their combined dynamic load make the greatest impact on the safety coefficient for slope stability. When horizontal dynamic load pseudo-static coefficient is added 0.05 from 0 to 0.3，the safety coefficients are reduced 7.801%~10.665% and 7.61%~10.546% respectively for case that the cracked lengths are zero and 12.76 m. When vertical dynamic load pseudo-static coefficient is added 0.05 from 0 to 0.3，the safety coefficients are reduced 1.366%~1.949% and 1.473%~2.289% respectively for case that the cracked lengths are zero and 12.76 m. Slope length, cracked length, combined load action direction have some impacts on the slope stability.
Based on action force analysis of slope slice，a calculation method of safety coefficient for slope stability was proposed according to the definition of safety coefficient and the Mohr-Column criteria. Reliability of the proposed method was verified and relation between pseudo-static coefficient under blast seism and safety coefficient on rock mass bedding slope was explained by using calculation examples. Computed results in some engineering cases show that the horizontal and vertical dynamic loads as well as their combined dynamic load make the greatest impact on the safety coefficient for slope stability. When horizontal dynamic load pseudo-static coefficient is added 0.05 from 0 to 0.3，the safety coefficients are reduced 7.801%~10.665% and 7.61%~10.546% respectively for case that the cracked lengths are zero and 12.76 m. When vertical dynamic load pseudo-static coefficient is added 0.05 from 0 to 0.3，the safety coefficients are reduced 1.366%~1.949% and 1.473%~2.289% respectively for case that the cracked lengths are zero and 12.76 m. Slope length, cracked length, combined load action direction have some impacts on the slope stability.
2007, 27(5): 431-437.
doi: 10.11883/1001-1455(2007)05-0431-07
Abstract:
A series of experiments were performed to research the dynamic response of fluid cabin at the bottom of warship subjected to underwater explosion. In these experiments, there are three states of fluid cabins, such as cabins without fluid, half fluid and full fluid. The wall pressure, acceleration and dynamic strain of the out and inner plates of these fluid cabins were obtained. Response mechanisms of the out and inner plates of fluid cabin subjected to underwater explosion were analyzed. Transmission effect of shock wave for cabin with full fluid and influences of splash load on inner plate of cabin with half fluid were discussed.
A series of experiments were performed to research the dynamic response of fluid cabin at the bottom of warship subjected to underwater explosion. In these experiments, there are three states of fluid cabins, such as cabins without fluid, half fluid and full fluid. The wall pressure, acceleration and dynamic strain of the out and inner plates of these fluid cabins were obtained. Response mechanisms of the out and inner plates of fluid cabin subjected to underwater explosion were analyzed. Transmission effect of shock wave for cabin with full fluid and influences of splash load on inner plate of cabin with half fluid were discussed.
2007, 27(5): 438-444.
doi: 10.11883/1001-1455(2007)05-0438-07
Abstract:
Impact-damage experiments on limestone specimens were carried out on one-stage light-gas gun. Pressure in specimens during shock wave action process was tested by manganin gauge. Impact-damaged and fragmentation properties of lime rock were analyzed by acoustic sounding and splitting cut observation on specimens after shock experiments. Test and analyzed results show that if flyer plate diameter is smaller than that of specimen, the freedom surface of specimen is better, and colliding pressure is 1.0~1.7 GPa, specimen damage has divisional characters with different mechanisms, including head-core space, ring-shape crack area, central section damage space and empennage failure zone. Soft reclaim installation provided a good freedom surface for the side and empennage of specimens, and pull stress made the dominant function for rock damage. Impact-damaged process of rock was numerically simulated using LS-DYNA finite element code to analyze impact-damaged properties of limestone specimens and to validate experimental results.
Impact-damage experiments on limestone specimens were carried out on one-stage light-gas gun. Pressure in specimens during shock wave action process was tested by manganin gauge. Impact-damaged and fragmentation properties of lime rock were analyzed by acoustic sounding and splitting cut observation on specimens after shock experiments. Test and analyzed results show that if flyer plate diameter is smaller than that of specimen, the freedom surface of specimen is better, and colliding pressure is 1.0~1.7 GPa, specimen damage has divisional characters with different mechanisms, including head-core space, ring-shape crack area, central section damage space and empennage failure zone. Soft reclaim installation provided a good freedom surface for the side and empennage of specimens, and pull stress made the dominant function for rock damage. Impact-damaged process of rock was numerically simulated using LS-DYNA finite element code to analyze impact-damaged properties of limestone specimens and to validate experimental results.
2007, 27(5): 445-450.
doi: 10.11883/1001-1455(2007)05-0445-06
Abstract:
The experimental research was carried out on the energy output characteristics of insensitive RDX, RDX/Al and SEFAE in the explosion chamber and under water. Numerical simulation was conducted to study the internal blast loading of explosion chamber with flat end using TVD schemes. Strains on several typical positions on the wall of the chamber were measured under the different internal blast loadings. Results show that: (1) In the confined space RDX/Al and SEFAE have after-burning effect; (2) In the experiment condition the biggest blast loading appears at the joint point of flat end and cylinder; (3) Effect of blast loading by SEFAE on explosion chamber is the lowest and those by insensitive RDX and RDX/Al are the same. The compositions of frequencies of strains of different explosives are similar and there is a slight difference of intensity; (4) The structure of blast loading is not the main reason for strain growth.
The experimental research was carried out on the energy output characteristics of insensitive RDX, RDX/Al and SEFAE in the explosion chamber and under water. Numerical simulation was conducted to study the internal blast loading of explosion chamber with flat end using TVD schemes. Strains on several typical positions on the wall of the chamber were measured under the different internal blast loadings. Results show that: (1) In the confined space RDX/Al and SEFAE have after-burning effect; (2) In the experiment condition the biggest blast loading appears at the joint point of flat end and cylinder; (3) Effect of blast loading by SEFAE on explosion chamber is the lowest and those by insensitive RDX and RDX/Al are the same. The compositions of frequencies of strains of different explosives are similar and there is a slight difference of intensity; (4) The structure of blast loading is not the main reason for strain growth.
2007, 27(5): 451-454.
doi: 10.11883/1001-1455(2007)05-0451-04
Abstract:
Introduces some new developments in nonauditory damage assessment method exposed to complex waves, analyzes feature and applicable range of these nonauditory damage assessment methods. Max inward chest velocity method, effective peak method and injury software method are the most adopted methods in nonauditory damage assessment. The organ response in thorax and abdomen and injury mechanism researched by finite element method is further direction of research on complex waves.
Introduces some new developments in nonauditory damage assessment method exposed to complex waves, analyzes feature and applicable range of these nonauditory damage assessment methods. Max inward chest velocity method, effective peak method and injury software method are the most adopted methods in nonauditory damage assessment. The organ response in thorax and abdomen and injury mechanism researched by finite element method is further direction of research on complex waves.
2007, 27(5): 455-460.
doi: 10.11883/1001-1455(2007)05-0455-06
Abstract:
Aiming at the shortages on quantity and speed existed in the tunnel blasting design now mainly completed by the artificial method and the CAD, the composition and structure of intelligent system for tunnel blasting design was studied. According to the characteristics of tunneling blasting design and construction management, the composition of intelligent system for tunnel blasting design was determined by adopting the methods of both software engineering and artificial intelligence, which consists of knowledge base, database, reasoning machine, human-computer interaction system, explanation organization. The function modules including the system management, intelligent calculation of parameter, blasting data, primary design, construction design and construction information management were established, and the data flowing chart of tunnel blasting design was put forward. The self-adapting arrangement of the blast holes on tunnel face is realized. The system provides three kinds of design method, such as traditional, artificial intelligent and complete intelligent designs. Design results of the example of tunnel blasting show that the blasting design system can obtain the high-quality design diagrams accurately and quickly which include the blast-hole arrangement, the manual of arranging blast holes and the blasting order, etc.
Aiming at the shortages on quantity and speed existed in the tunnel blasting design now mainly completed by the artificial method and the CAD, the composition and structure of intelligent system for tunnel blasting design was studied. According to the characteristics of tunneling blasting design and construction management, the composition of intelligent system for tunnel blasting design was determined by adopting the methods of both software engineering and artificial intelligence, which consists of knowledge base, database, reasoning machine, human-computer interaction system, explanation organization. The function modules including the system management, intelligent calculation of parameter, blasting data, primary design, construction design and construction information management were established, and the data flowing chart of tunnel blasting design was put forward. The self-adapting arrangement of the blast holes on tunnel face is realized. The system provides three kinds of design method, such as traditional, artificial intelligent and complete intelligent designs. Design results of the example of tunnel blasting show that the blasting design system can obtain the high-quality design diagrams accurately and quickly which include the blast-hole arrangement, the manual of arranging blast holes and the blasting order, etc.
2007, 27(5): 461-467.
doi: 10.11883/1001-1455(2007)05-0461-07
Abstract:
The long-term and transient deformation characteristics of soft soil ground under explosive loading are analyzed through the field test and numerical simulation. The main factors affecting explosion results and the remarkably impact range in the soil after explosion are investigated. Mechanism of improving soft ground by explosion is discussed. The results show that this method can accelerate consolidation speed, improve the construction speed and shorten the time limit for a project.
The long-term and transient deformation characteristics of soft soil ground under explosive loading are analyzed through the field test and numerical simulation. The main factors affecting explosion results and the remarkably impact range in the soil after explosion are investigated. Mechanism of improving soft ground by explosion is discussed. The results show that this method can accelerate consolidation speed, improve the construction speed and shorten the time limit for a project.
2007, 27(5): 468-472.
doi: 10.11883/1001-1455(2007)05-0468-05
Abstract:
The function, structure and damage mechanism of the missile were studied to analyze the missile vulnerability to the fragment warhead. The damage levels, tree and damage criterion of every component of the missile were given. Based on these, the vulnerability assessment model of the missile to the fragment warhead was built. According to the model, the vulnerability of a missile was calculated, and the relations between target vulnerability and vulnerability of components, orientation of warhead explosion and distance to the target were obtained.
The function, structure and damage mechanism of the missile were studied to analyze the missile vulnerability to the fragment warhead. The damage levels, tree and damage criterion of every component of the missile were given. Based on these, the vulnerability assessment model of the missile to the fragment warhead was built. According to the model, the vulnerability of a missile was calculated, and the relations between target vulnerability and vulnerability of components, orientation of warhead explosion and distance to the target were obtained.
2007, 27(5): 473-476.
doi: 10.11883/1001-1455(2007)05-0473-04
Abstract:
Combining with a measurement of velocity by photoelectric technology, rebuilding a type of nail gun used in civil engineering, a more simple, reliable and miniaturized measurer for shockwave velocity was developed. Thus, the difficult problem to predict the consistency and reliability of self-triggering coaxial detector for shockwave velocity was solved under lower shock pressure. The experimental results indicate that the impact velocity induced by a steel projectile with the statistical weight, (25.50.1) g, is 226.2 m/s; the reliability is larger than 66.67%, and the coherency, represented by standard error, is less than 1.14%, predicted by test results for 6 detectors, being part of a group of product. It provides an effective technique for measuring detonation and shock compression.
Combining with a measurement of velocity by photoelectric technology, rebuilding a type of nail gun used in civil engineering, a more simple, reliable and miniaturized measurer for shockwave velocity was developed. Thus, the difficult problem to predict the consistency and reliability of self-triggering coaxial detector for shockwave velocity was solved under lower shock pressure. The experimental results indicate that the impact velocity induced by a steel projectile with the statistical weight, (25.50.1) g, is 226.2 m/s; the reliability is larger than 66.67%, and the coherency, represented by standard error, is less than 1.14%, predicted by test results for 6 detectors, being part of a group of product. It provides an effective technique for measuring detonation and shock compression.
2007, 27(5): 477-480.
doi: 10.11883/1001-1455(2007)05-0477-04
Abstract:
Based on developed numerical simulation method, the impacting behavior of copper particle colliding copper substrate in process of transforming material property is investigated. The join strength, penetration depth and condition of emerging adiabatic shear instability are discussed with single particle of uniform speed and different angle. It is revealed that with increasing incidence angle, the penetration depth decreases and the join strength is weakened. Adiabatic shear instability will take place when the normal component of particle velocity excesses critical value.
Based on developed numerical simulation method, the impacting behavior of copper particle colliding copper substrate in process of transforming material property is investigated. The join strength, penetration depth and condition of emerging adiabatic shear instability are discussed with single particle of uniform speed and different angle. It is revealed that with increasing incidence angle, the penetration depth decreases and the join strength is weakened. Adiabatic shear instability will take place when the normal component of particle velocity excesses critical value.
