2009 Vol. 29, No. 4
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2009, 29(4): 337-344.
doi: 10.11883/1001-1455(2009)04-0337-08
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Abstract:
Some examples of both flexible protection and stiff protection were discussed in connection with the authors research results to explore influences of stress wave effects and material strain-rate effects on structure safety protection under intense dynamic loads. Results display that in studies on structure safety protection under intense dynamic loading, either the loading is due to shock waves or projectile impact, wave propagation effects and material strain-rate effects for the structure itself and the around media, as well as the interaction between them, should be taken into account.
Some examples of both flexible protection and stiff protection were discussed in connection with the authors research results to explore influences of stress wave effects and material strain-rate effects on structure safety protection under intense dynamic loads. Results display that in studies on structure safety protection under intense dynamic loading, either the loading is due to shock waves or projectile impact, wave propagation effects and material strain-rate effects for the structure itself and the around media, as well as the interaction between them, should be taken into account.
2009, 29(4): 345-350.
doi: 10.11883/1001-1455(2009)04-0345-06
Abstract:
A series of quasi-static axial compression tests were conducted on pseudo-elastic TiNi shells by an MTS 809 material testing system to observe their dynamic progressive buckling responses. And numerical simulations were carried out to analyze phase transformation dynamic buckling behaviors of the pseudo-elastic shape-memory alloy shells under short pulse loading. It is indicated that TiNi shells have different buckling modes under different load levels. The buckling of shells begins with the formation of axisymmetric rings under high load speeds and produces a stress plateau. With the gradual increase of martensite fraction, ring phase transformation buckling travels gradually through the whole shell and the nominal stress increases slowly. When the nominal stress exceeds a certain threshold, the axisymmetric ring buckling mode transforms into a nonsymmetrical massive buckling mode and the nominal stress decreases dramatically. The calculation sample with the impact velocity of 40 m/s and the random defect of 10% is in agreement with the experiments by Nemat-Nasser S, et al. The results show that phase transformation energy dissipation is the main mechanism of TiNi shells absorbing impact energy and TiNi shells are suitable for reusable efficient energy dissipation mechanism. And the corresponding perfect diameter-thickness ratio of TiNi shells was proposed.
A series of quasi-static axial compression tests were conducted on pseudo-elastic TiNi shells by an MTS 809 material testing system to observe their dynamic progressive buckling responses. And numerical simulations were carried out to analyze phase transformation dynamic buckling behaviors of the pseudo-elastic shape-memory alloy shells under short pulse loading. It is indicated that TiNi shells have different buckling modes under different load levels. The buckling of shells begins with the formation of axisymmetric rings under high load speeds and produces a stress plateau. With the gradual increase of martensite fraction, ring phase transformation buckling travels gradually through the whole shell and the nominal stress increases slowly. When the nominal stress exceeds a certain threshold, the axisymmetric ring buckling mode transforms into a nonsymmetrical massive buckling mode and the nominal stress decreases dramatically. The calculation sample with the impact velocity of 40 m/s and the random defect of 10% is in agreement with the experiments by Nemat-Nasser S, et al. The results show that phase transformation energy dissipation is the main mechanism of TiNi shells absorbing impact energy and TiNi shells are suitable for reusable efficient energy dissipation mechanism. And the corresponding perfect diameter-thickness ratio of TiNi shells was proposed.
2009, 29(4): 351-355.
doi: 10.11883/1001-1455(2009)04-0351-05
Abstract:
Two kinds of the penetrating rods, which were made of tungsten heavy alloy and tungsten-fiber-reinforced Zr-based metallic glass composite material, respectively, were used to penetrate the 30CrMnMo steel target plates in the penetration experiments. In the penetration process, the tungsten heavy alloy rod head formed as a mushroom head and the grains in the head were radially compressed. But in the head of the tungsten-fiber-reinforced Zr-based metallic glass composite rod, the failure along the adiabatic shear bands was observed, which indicated that the tungsten-fiber-reinforced penetrators took on self-sharpening behaviors. A thin edge layer was developed in the tungsten-fiber-reinforced penetrator head and only in this layer the metallic base was broken, the tungsten fibers were ruptured, the temperature increased and the mass was wasted. Evidently, the penetration ability of the tungsten-fiber-reinforced composite material penetrator is evidently greater than that of the tungsten alloy one.
Two kinds of the penetrating rods, which were made of tungsten heavy alloy and tungsten-fiber-reinforced Zr-based metallic glass composite material, respectively, were used to penetrate the 30CrMnMo steel target plates in the penetration experiments. In the penetration process, the tungsten heavy alloy rod head formed as a mushroom head and the grains in the head were radially compressed. But in the head of the tungsten-fiber-reinforced Zr-based metallic glass composite rod, the failure along the adiabatic shear bands was observed, which indicated that the tungsten-fiber-reinforced penetrators took on self-sharpening behaviors. A thin edge layer was developed in the tungsten-fiber-reinforced penetrator head and only in this layer the metallic base was broken, the tungsten fibers were ruptured, the temperature increased and the mass was wasted. Evidently, the penetration ability of the tungsten-fiber-reinforced composite material penetrator is evidently greater than that of the tungsten alloy one.
2009, 29(4): 356-360.
doi: 10.11883/1001-1455(2009)04-0356-05
Abstract:
A large number of experiments were conducted, and the experimental results were reported and discussed. The quantitative results were obtained based on the measurement in the tests by a ballistic pendulum with corresponding sensors, and then the deformation/failure modes of specimens were classified and analyzed systematically. According to the experimental results, a parametric study was carried out, in which the effect of face-sheet and core configurations, such as face-sheet thickness, cell size and foil thickness of the honeycomb, and mass of charge, on the structural response were investigated. Good agreement between the experimental results and theoretical analysis indicates that the proposed method is a powerful approximation method for the dynamic plasticity analysis of a sandwich structure.
A large number of experiments were conducted, and the experimental results were reported and discussed. The quantitative results were obtained based on the measurement in the tests by a ballistic pendulum with corresponding sensors, and then the deformation/failure modes of specimens were classified and analyzed systematically. According to the experimental results, a parametric study was carried out, in which the effect of face-sheet and core configurations, such as face-sheet thickness, cell size and foil thickness of the honeycomb, and mass of charge, on the structural response were investigated. Good agreement between the experimental results and theoretical analysis indicates that the proposed method is a powerful approximation method for the dynamic plasticity analysis of a sandwich structure.
2009, 29(4): 361-366.
doi: 10.11883/1001-1455(2009)04-0361-06
Abstract:
Ultrahigh-performance cementitious composites (UHPCC) with 200 MPa compressive strength were prepared by substitution of ultrafine industrial waste powder for large quantity of cement by weight and replacement of ground fine quartz sand with natural fine sand whose maximum particle diameter was 2.5 mm. And in the prepared composites, basalt stones with high elastic modules and high strength were added, whose maximum particle diameter was 10 mm. High-speed impact compressive experiments were performed on the ultrahigh-performance steel-fiber-reinforced cementitious composites (UHPSFRCC) with different fiber volume fractions by the split Hopkinson pressure bar technique. Strain rate, fiber volume fraction and coarse aggregate can influence the impact resistance of the UHPSFRCC. The impact resistance of the UHPSFRCC is improved with the increase of fiber volume fraction and the dynamic strength of the UHPSFRCC is advanced with the increase of strain rate. The dynamic performances of the UHPSFRCC are improved with the adding of coarse aggregates of basalt stones.
Ultrahigh-performance cementitious composites (UHPCC) with 200 MPa compressive strength were prepared by substitution of ultrafine industrial waste powder for large quantity of cement by weight and replacement of ground fine quartz sand with natural fine sand whose maximum particle diameter was 2.5 mm. And in the prepared composites, basalt stones with high elastic modules and high strength were added, whose maximum particle diameter was 10 mm. High-speed impact compressive experiments were performed on the ultrahigh-performance steel-fiber-reinforced cementitious composites (UHPSFRCC) with different fiber volume fractions by the split Hopkinson pressure bar technique. Strain rate, fiber volume fraction and coarse aggregate can influence the impact resistance of the UHPSFRCC. The impact resistance of the UHPSFRCC is improved with the increase of fiber volume fraction and the dynamic strength of the UHPSFRCC is advanced with the increase of strain rate. The dynamic performances of the UHPSFRCC are improved with the adding of coarse aggregates of basalt stones.
2009, 29(4): 367-374.
doi: 10.11883/1001-1455(2009)04-0367-08
Abstract:
Based on the theory for coupled vibrations of master-slave systems, numerical experiments were carried out to explore how to evaluate the shock resistance and how to design the shock protection for shipboard equipments, especially for large-scale shipboard equipments. By choosing shipboard supercharged boilers and gear cases as research objects, the non-integrated and integrated exemplification analyses were investigated numerically by devising a series of shock input data. The non-integrated analysis method for shock resistance does not take the coupling effects between the equipment and ship hull into account and cannot reproduce the real shock environments of shipboard equipments precisely. For the underwater explosions in the middle-far fields, the non-integrated analysis results are greater than the integrated analysis results, and for the underwater explosions in the middle-near fields, the non-integrated analysis results are smaller. The ship hull and equipment integrated analysis method can be used to evaluate the shock resistance of large-scale shipboard equipments subjected to underwater explosions in middle-near fields. If the existing situation can meet an integrated analysis, the non-integrated analysis results should be amended.
Based on the theory for coupled vibrations of master-slave systems, numerical experiments were carried out to explore how to evaluate the shock resistance and how to design the shock protection for shipboard equipments, especially for large-scale shipboard equipments. By choosing shipboard supercharged boilers and gear cases as research objects, the non-integrated and integrated exemplification analyses were investigated numerically by devising a series of shock input data. The non-integrated analysis method for shock resistance does not take the coupling effects between the equipment and ship hull into account and cannot reproduce the real shock environments of shipboard equipments precisely. For the underwater explosions in the middle-far fields, the non-integrated analysis results are greater than the integrated analysis results, and for the underwater explosions in the middle-near fields, the non-integrated analysis results are smaller. The ship hull and equipment integrated analysis method can be used to evaluate the shock resistance of large-scale shipboard equipments subjected to underwater explosions in middle-near fields. If the existing situation can meet an integrated analysis, the non-integrated analysis results should be amended.
2009, 29(4): 375-379.
doi: 10.11883/1001-1455(2009)04-0375-05
Abstract:
Based on the theory for coupled vibrations of master-slave systems, by choosing shipboard supercharged boilers and gear cases as research objects, the numerical statistical characteristics of numerical experiments for ship hull and equipment integrated analysis were discussed to determine the anti-shock threshold values of shipboard equipments. The standard deviations of stress values for equipments subjected to shock load were put forward as the failure criteria of shipboard equipments through large numbers of exemplification analysis. And an empirical formula of the maximum value of standard deviation was given.
Based on the theory for coupled vibrations of master-slave systems, by choosing shipboard supercharged boilers and gear cases as research objects, the numerical statistical characteristics of numerical experiments for ship hull and equipment integrated analysis were discussed to determine the anti-shock threshold values of shipboard equipments. The standard deviations of stress values for equipments subjected to shock load were put forward as the failure criteria of shipboard equipments through large numbers of exemplification analysis. And an empirical formula of the maximum value of standard deviation was given.
2009, 29(4): 380-384.
doi: 10.11883/1001-1455(2009)04-0380-05
Abstract:
The common node separate reinforced concrete model was adopted to numerically simulate the fold blasting collapse processes of frame-tube structures. The two blasting methods used in the three-dimensional simulations included the bottom blasting and the top blasting. In the bottom blasting methods, different cut height and delay time were considered. The collapse processes of the frame-tube structures and the failure processes of the sustaining pillars were discussed. The bottom of the structure was crushed more seriously by using the bottom blasting method than that by using the top blasting method. For the bottom blasting method, more fragmentation appeared in the structure with the 0.25 s delay time than that with 0.5 s. The structure collapsed southward appreciably with the different cut heights and delay times. The failure processes of the sustaining pillars were different according to the different blasting methods, which influenced the backlash distance of the structure. The backlash distance of the structure under the bottom blasting was smaller than that under the top blasting. Stress analysis of the concrete and reinforcement elements shows that the common node separate reinforced concrete model can reflect the mechanical property differences between the two materials.
The common node separate reinforced concrete model was adopted to numerically simulate the fold blasting collapse processes of frame-tube structures. The two blasting methods used in the three-dimensional simulations included the bottom blasting and the top blasting. In the bottom blasting methods, different cut height and delay time were considered. The collapse processes of the frame-tube structures and the failure processes of the sustaining pillars were discussed. The bottom of the structure was crushed more seriously by using the bottom blasting method than that by using the top blasting method. For the bottom blasting method, more fragmentation appeared in the structure with the 0.25 s delay time than that with 0.5 s. The structure collapsed southward appreciably with the different cut heights and delay times. The failure processes of the sustaining pillars were different according to the different blasting methods, which influenced the backlash distance of the structure. The backlash distance of the structure under the bottom blasting was smaller than that under the top blasting. Stress analysis of the concrete and reinforcement elements shows that the common node separate reinforced concrete model can reflect the mechanical property differences between the two materials.
2009, 29(4): 385-389.
doi: 10.11883/1001-1455(2009)04-0385-05
Abstract:
On the base of the known experimental researches, 94 field experiments of chemical explosion were carried out to investigate contact explosion damage effects of middle-high strength steel fiber reinforced concrete plates. The design of test parameters was introduced, and damage characteristics of steel fiber reinforced concrete plates were analyzed under the contact explosion conditions with different charges and structure parameters. These damage characteristics include explosion cratering, critical spalling, explosion spalling, critical perforating and explosion perforating. The damage parameters corresponding to five kinds of typical damage forms were obtained. Preliminary analysis of the main influence factors on explosion cratering and structure spalling can provide a reference for the classification of explosion local damage and the design of local-damage-resisting structures.
On the base of the known experimental researches, 94 field experiments of chemical explosion were carried out to investigate contact explosion damage effects of middle-high strength steel fiber reinforced concrete plates. The design of test parameters was introduced, and damage characteristics of steel fiber reinforced concrete plates were analyzed under the contact explosion conditions with different charges and structure parameters. These damage characteristics include explosion cratering, critical spalling, explosion spalling, critical perforating and explosion perforating. The damage parameters corresponding to five kinds of typical damage forms were obtained. Preliminary analysis of the main influence factors on explosion cratering and structure spalling can provide a reference for the classification of explosion local damage and the design of local-damage-resisting structures.
2009, 29(4): 390-394.
doi: 10.11883/1001-1455(2009)04-0390-05
Abstract:
A mathematical model, considering the inner and outer fields of explosion vessels, was introduced to explore the induced mechanism of high explosion-vented pressures and the characteristics of flame and pressure transmission in spherical vessels. Based on the conversation equations for hydrodynamics and chemical reaction dynamics, by adopting the k-e turbulent model and the EBU-Arrhenius combustion model, the SIMPLE algorithm was used to investigate numerically the methane-air premixed gas vented explosion process in the two-dimensional space of the spherical vessel with a conduit for explosion venting. The characteristics of flame and pressure transmission and gas flow in the process of vented explosion were obtained which could reflect the dynamics of gas explosion. The turbulent combustion appearing in the process of vented explosion accelerates the transmission of the combustion flame. Venting explosion conduits confines seriously the high-pressure gas venting from vessels.
A mathematical model, considering the inner and outer fields of explosion vessels, was introduced to explore the induced mechanism of high explosion-vented pressures and the characteristics of flame and pressure transmission in spherical vessels. Based on the conversation equations for hydrodynamics and chemical reaction dynamics, by adopting the k-e turbulent model and the EBU-Arrhenius combustion model, the SIMPLE algorithm was used to investigate numerically the methane-air premixed gas vented explosion process in the two-dimensional space of the spherical vessel with a conduit for explosion venting. The characteristics of flame and pressure transmission and gas flow in the process of vented explosion were obtained which could reflect the dynamics of gas explosion. The turbulent combustion appearing in the process of vented explosion accelerates the transmission of the combustion flame. Venting explosion conduits confines seriously the high-pressure gas venting from vessels.
2009, 29(4): 395-400.
doi: 10.11883/1001-1455(2009)04-0395-06
Abstract:
In order to explore the protective effects of the elastic rubber sandwich layer coated onto a ship hull, a series of 5-kg-TNT-equivalent underwater explosion tests were conducted on a floating steel box before and after the rubber sandwich was coated onto to comprehend the dynamic performance of the protective layer. Acceleration, strain and wall pressure histories at several typical locations were monitored as the main criteria and analyzed. The super-elastic protective layer is capable of lowering both acceleration and strain peaks of hull structures effectively. The wall pressure histories near the bottom hull illustrate that the transmitted impulse during the initial fluid-structure interaction stage can be reduced by almost 50%. Shock response spectrum analysis demonstrates that the elastic protective layer performs much like a low pass filter. It is capable of moderating high-frequency components of shock responses greatly, but not very effective in reducing low-frequency components.
In order to explore the protective effects of the elastic rubber sandwich layer coated onto a ship hull, a series of 5-kg-TNT-equivalent underwater explosion tests were conducted on a floating steel box before and after the rubber sandwich was coated onto to comprehend the dynamic performance of the protective layer. Acceleration, strain and wall pressure histories at several typical locations were monitored as the main criteria and analyzed. The super-elastic protective layer is capable of lowering both acceleration and strain peaks of hull structures effectively. The wall pressure histories near the bottom hull illustrate that the transmitted impulse during the initial fluid-structure interaction stage can be reduced by almost 50%. Shock response spectrum analysis demonstrates that the elastic protective layer performs much like a low pass filter. It is capable of moderating high-frequency components of shock responses greatly, but not very effective in reducing low-frequency components.
2009, 29(4): 401-407.
doi: 10.11883/1001-1455(2009)04-0401-07
Abstract:
According to the nonlinear links between blasting-vibration-induced damage degree and its influencing factors, a rough set-based fuzzy-neural network model is proposed to seek a method that can overcome the limitations in the single-factor case and improve the damage prediction precision. In the proposed prediction model, there are 10 factors to be taken into account, which include particle vibration velocity (PPV), dominant frequency, dominant frequency duration and dynamic characteristics of structures. The prediction model is trained and tested by a series of data from the observations of blasting vibration and damage degree of houses in Tonglshan Copper Mine. The training results are in agreement with the field observations. The rough set-based fuzzy-neural network can reduce data indexes and simplify input variables, and minify the decision table size and accelerate the approach to the minimal rules. The proposed method considering the manifold factors can improve the prediction precision of damage degree induced by blasting vibration.
According to the nonlinear links between blasting-vibration-induced damage degree and its influencing factors, a rough set-based fuzzy-neural network model is proposed to seek a method that can overcome the limitations in the single-factor case and improve the damage prediction precision. In the proposed prediction model, there are 10 factors to be taken into account, which include particle vibration velocity (PPV), dominant frequency, dominant frequency duration and dynamic characteristics of structures. The prediction model is trained and tested by a series of data from the observations of blasting vibration and damage degree of houses in Tonglshan Copper Mine. The training results are in agreement with the field observations. The rough set-based fuzzy-neural network can reduce data indexes and simplify input variables, and minify the decision table size and accelerate the approach to the minimal rules. The proposed method considering the manifold factors can improve the prediction precision of damage degree induced by blasting vibration.
2009, 29(4): 408-412.
doi: 10.11883/1001-1455(2009)04-0408-05
Abstract:
The equations for one-dimensional radiation hydrodynamics in spherical symmetry were applied to the early fireball phenomenology of strong explosions with different yields. Evolutions of radiation fronts and case shocks for these early fireballs were investigated numerically and analyzed by using the scaling theory. With the increase of explosion yield, the extension velocities of radiation front and case shocks increase, the beginning and ending position and sustaining area of transition of radiation front increase, and the central temperature decrease of fireballs slows. The parameters for the fireball fronts can follow the cube-root scaling of the yield after the shock transition of the fireball fronts.
The equations for one-dimensional radiation hydrodynamics in spherical symmetry were applied to the early fireball phenomenology of strong explosions with different yields. Evolutions of radiation fronts and case shocks for these early fireballs were investigated numerically and analyzed by using the scaling theory. With the increase of explosion yield, the extension velocities of radiation front and case shocks increase, the beginning and ending position and sustaining area of transition of radiation front increase, and the central temperature decrease of fireballs slows. The parameters for the fireball fronts can follow the cube-root scaling of the yield after the shock transition of the fireball fronts.
2009, 29(4): 413-418.
doi: 10.11883/1001-1455(2009)04-0413-06
Abstract:
Using the transparent material PMMA, a model experiment was carried out by the transmitted dynamic caustics to obtain a series of dynamic caustic photos. By the experimental results, the directional fracture characteristics of crack tips, such as dynamic stress intensity factors, expanding lengths and velocities, were discussed for different notch angles and depths. In addition, dynamic effects in V-notch blasting were explored according to the discussed results. It is shown that the cracks are subjected to tensile (mode-I) loading to rapidly expand at the initial stage of the V-notch blasting and later the crack tip propagation is affected by the combined action of P and S waves (complex mode). And the appropriate V-notch angle and notch depth was obtained to control the directional fracture.
Using the transparent material PMMA, a model experiment was carried out by the transmitted dynamic caustics to obtain a series of dynamic caustic photos. By the experimental results, the directional fracture characteristics of crack tips, such as dynamic stress intensity factors, expanding lengths and velocities, were discussed for different notch angles and depths. In addition, dynamic effects in V-notch blasting were explored according to the discussed results. It is shown that the cracks are subjected to tensile (mode-I) loading to rapidly expand at the initial stage of the V-notch blasting and later the crack tip propagation is affected by the combined action of P and S waves (complex mode). And the appropriate V-notch angle and notch depth was obtained to control the directional fracture.
2009, 29(4): 419-424.
doi: 10.11883/1001-1455(2009)04-0419-06
Abstract:
By means of the improved SHPB with axial pre-pressure and confining pressure, a series of experiments on sandstone were carried out to investigate the energy consumption in rock fracturing during the course of deep underground resources exploitation. In the experiments, the cylindrical sandstone specimens were subjected to the static-dynamic coupling loads with fixed confining pressure or fixed axial static pressure. Under fixed confining pressures, the dynamic load energy densities consumed by the breakage of the sandstone specimens decrease gradually with the increase of axial static pressures. When the axial static stress is above 70% of the corresponding static tri-axial compressive strength, the dynamic load energy density consumed is below 0, namely, the sandstone specimens release energy. With the further increase of the axial static stress, the negative dynamic load energy density consumed approaches gradually to 0 and keeps below 0. If the axial static stress fixed is low, the dynamic load energy density consumed by the sandstone specimens increases continuously with the increase of the confining pressure. When the axial static stress fixed is great and above 70% of the corresponding static tri-axial compressive strength, the sandstone specimen can be fractured by itself and release the rest energy after losing the former balance by dynamic disturbance.
By means of the improved SHPB with axial pre-pressure and confining pressure, a series of experiments on sandstone were carried out to investigate the energy consumption in rock fracturing during the course of deep underground resources exploitation. In the experiments, the cylindrical sandstone specimens were subjected to the static-dynamic coupling loads with fixed confining pressure or fixed axial static pressure. Under fixed confining pressures, the dynamic load energy densities consumed by the breakage of the sandstone specimens decrease gradually with the increase of axial static pressures. When the axial static stress is above 70% of the corresponding static tri-axial compressive strength, the dynamic load energy density consumed is below 0, namely, the sandstone specimens release energy. With the further increase of the axial static stress, the negative dynamic load energy density consumed approaches gradually to 0 and keeps below 0. If the axial static stress fixed is low, the dynamic load energy density consumed by the sandstone specimens increases continuously with the increase of the confining pressure. When the axial static stress fixed is great and above 70% of the corresponding static tri-axial compressive strength, the sandstone specimen can be fractured by itself and release the rest energy after losing the former balance by dynamic disturbance.
2009, 29(4): 425-428.
doi: 10.11883/1001-1455(2009)04-0425-04
Abstract:
The modified Friedlander equation was introduced to analyze the explosive shock-wave overpressure transmission varied with time in air. The logarithm of the logarithm of the exponential attenuation factor in the equation was found as a linear function of time. By using the found linear relationship, a new mathematical model was presented to describe the shock-wave overpressure evolution. Comparisons of the fitted overpressures by the presented model with the recorded ones in experiments reveal that the new mathematical model is precise, universal and applicable.
The modified Friedlander equation was introduced to analyze the explosive shock-wave overpressure transmission varied with time in air. The logarithm of the logarithm of the exponential attenuation factor in the equation was found as a linear function of time. By using the found linear relationship, a new mathematical model was presented to describe the shock-wave overpressure evolution. Comparisons of the fitted overpressures by the presented model with the recorded ones in experiments reveal that the new mathematical model is precise, universal and applicable.
2009, 29(4): 429-433.
doi: 10.11883/1001-1455(2009)04-0429-05
Abstract:
A standard Godbert-Greenwald furnace apparatus was used to measure minimum ignition temperatures of magnesium dust cloud under different conditions. Experimental results reveal that corresponding minimum ignition temperatures of dust cloud for four magnesium specimens with the medium grain diameters D50 of 6, 47, 104 and 173 m are 480,520,620,700℃, respectively. Take the magnesium powder with the grain diameter of 6 m for example, under the constant diffusing pressure of 0.1 MPa, the minimum ignition temperature of the magnesium dust cloud decreases from 600 ℃ to 480 ℃ corresponding to the dust concentration changing from 424 g/m3 to 5 085 g/m3; and for the constant dust mass of 0.3 g, when the diffusing pressure increase from 0.1 MPa to 0.2 MPa, the minimum ignition temperature of this magnesium dust cloud increases from 540 ℃ to 580 ℃. And effects of grain diameter distribution, concentration and diffusing pressure on the minimum ignition temperature of magnesium dust cloud were analyzed by the above experimental results. It is helpful in the explosion-proof equipment design for the magnesium powder production.
A standard Godbert-Greenwald furnace apparatus was used to measure minimum ignition temperatures of magnesium dust cloud under different conditions. Experimental results reveal that corresponding minimum ignition temperatures of dust cloud for four magnesium specimens with the medium grain diameters D50 of 6, 47, 104 and 173 m are 480,520,620,700℃, respectively. Take the magnesium powder with the grain diameter of 6 m for example, under the constant diffusing pressure of 0.1 MPa, the minimum ignition temperature of the magnesium dust cloud decreases from 600 ℃ to 480 ℃ corresponding to the dust concentration changing from 424 g/m3 to 5 085 g/m3; and for the constant dust mass of 0.3 g, when the diffusing pressure increase from 0.1 MPa to 0.2 MPa, the minimum ignition temperature of this magnesium dust cloud increases from 540 ℃ to 580 ℃. And effects of grain diameter distribution, concentration and diffusing pressure on the minimum ignition temperature of magnesium dust cloud were analyzed by the above experimental results. It is helpful in the explosion-proof equipment design for the magnesium powder production.
2009, 29(4): 434-438.
doi: 10.11883/1001-1455(2009)04-0434-05
Abstract:
An engineering algorithm model was proposed to simulate the damage of dual-wall structures from debris clouds generated by hypervelocity impact. The corresponding hypervelocity impact experiment was conducted on the aluminum dual-wall structure impacted by the Mylar film flyer plate driven by an electric gun. The numerical simulations are consistent with the experimental results.
An engineering algorithm model was proposed to simulate the damage of dual-wall structures from debris clouds generated by hypervelocity impact. The corresponding hypervelocity impact experiment was conducted on the aluminum dual-wall structure impacted by the Mylar film flyer plate driven by an electric gun. The numerical simulations are consistent with the experimental results.
2009, 29(4): 439-443.
doi: 10.11883/1001-1455(2009)04-0439-05
Abstract:
A mechanical delay ignition device was designed on the basis of the characteristics of the investigated obstacle-breaching rocket projectile. The designed ignition device can check the obstacle-breaching power and make the kinetic energy penetrating warhead explode at the optimal depth. Theoretical and experimental results prove that the designed kinetic energy rock projectile structure is practicable.
A mechanical delay ignition device was designed on the basis of the characteristics of the investigated obstacle-breaching rocket projectile. The designed ignition device can check the obstacle-breaching power and make the kinetic energy penetrating warhead explode at the optimal depth. Theoretical and experimental results prove that the designed kinetic energy rock projectile structure is practicable.
2009, 29(4): 444-448.
doi: 10.11883/1001-1455(2009)04-0444-05
Abstract:
By the method of piecewise ploytropic exponent, the whole recoil process was divided into four different stages and the actual thermodynamic characters of the gas in each stage were analyzed. Theoretical analysis and experiments indicate that there are some differences between the gas thermodynamic characters in counter-recoil mechanisms and those in ordinary pneumatic mechanisms. The characters of the gas in counter-recoil mechanisms are not always between the isothermal process and the adiabatic process. These can affect the performance of counter-recoil mechanisms. The calculation, considering internal friction and heat transfer, is more approximate to the facts than the known methods.
By the method of piecewise ploytropic exponent, the whole recoil process was divided into four different stages and the actual thermodynamic characters of the gas in each stage were analyzed. Theoretical analysis and experiments indicate that there are some differences between the gas thermodynamic characters in counter-recoil mechanisms and those in ordinary pneumatic mechanisms. The characters of the gas in counter-recoil mechanisms are not always between the isothermal process and the adiabatic process. These can affect the performance of counter-recoil mechanisms. The calculation, considering internal friction and heat transfer, is more approximate to the facts than the known methods.
