2010 Vol. 30, No. 2
Display Method:
2010, 30(2): 113-118.
doi: 10.11883/1001-1455(2010)02-0113-06
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Abstract:
Based on the quantitative phase analysis using the Rietveld method, in-situ X-ray diffraction (XRD) experiments were conducted to explore isothermal phase transition kinetics of HMX. Transition extent-time curves of HMX were described at different isothermal temperatures, the Avrami exponent n was obtained close to 0.6, and the related isothermal phase transition kinetics equation was developed. The Arrhenius equation was used to quantify the relationship between the rate constant k and the temperature T, the calculated activation energy Ea was about 151 kJ/mol, and the calculated pre-exponential lnA was 36.2. The results show that the experimental temperature is the dominant factor controlling the phase transition of HMX, and phase experiences a similarly one-dimensional nucleation-and-growth mechanism randomly during the phase transition of HMX.
Based on the quantitative phase analysis using the Rietveld method, in-situ X-ray diffraction (XRD) experiments were conducted to explore isothermal phase transition kinetics of HMX. Transition extent-time curves of HMX were described at different isothermal temperatures, the Avrami exponent n was obtained close to 0.6, and the related isothermal phase transition kinetics equation was developed. The Arrhenius equation was used to quantify the relationship between the rate constant k and the temperature T, the calculated activation energy Ea was about 151 kJ/mol, and the calculated pre-exponential lnA was 36.2. The results show that the experimental temperature is the dominant factor controlling the phase transition of HMX, and phase experiences a similarly one-dimensional nucleation-and-growth mechanism randomly during the phase transition of HMX.
2010, 30(2): 119-124.
doi: 10.11883/1001-1455(2010)02-0119-06
Abstract:
Shock compression experiments were performed on C30 concrete by using the one-stage light-gas gun. The stress profiles at the different distances were measured by employing in-material manganin stress gauges. Based on the measured stress profiles, the shock wave attenuation characteristics in the C30 concrete samples were investigated. The shock stress peak took on transparent attenuation characters and the shock pressure attenuation process was divided into two phases. In phase 1, the reflected rarefaction wave did not catch up with shock wave and the slow attenuation of the shock pressure was attributed to the constitutive viscosity of concrete materials only. In phase 2, the quick attenuation of the shock pressure was caused by the sum of the constitutive viscosity, reflected rarefaction wave, edge rarefaction wave and geometrical expansion. On the other hand, the rise time of shock wave increased with the propagation distance, which was the other typical characteristic of shock pressure related to the constitutive viscosity of concrete materials.
Shock compression experiments were performed on C30 concrete by using the one-stage light-gas gun. The stress profiles at the different distances were measured by employing in-material manganin stress gauges. Based on the measured stress profiles, the shock wave attenuation characteristics in the C30 concrete samples were investigated. The shock stress peak took on transparent attenuation characters and the shock pressure attenuation process was divided into two phases. In phase 1, the reflected rarefaction wave did not catch up with shock wave and the slow attenuation of the shock pressure was attributed to the constitutive viscosity of concrete materials only. In phase 2, the quick attenuation of the shock pressure was caused by the sum of the constitutive viscosity, reflected rarefaction wave, edge rarefaction wave and geometrical expansion. On the other hand, the rise time of shock wave increased with the propagation distance, which was the other typical characteristic of shock pressure related to the constitutive viscosity of concrete materials.
2010, 30(2): 125-130.
doi: 10.11883/1001-1455(2010)02-0125-06
Abstract:
The dynamics of the airplane impacting on water was investigated. The arbitrary Lagrangian-Eulerian (ALE) method was employed to describe this fluid-structure interaction problem. The velocity of the airplane after landing was researched by analyzing the velocities of the airplane head and tail. The head and tail velocities changed rapidly in the initial stage of entering water, and then they kept stable. The structural response of the airplane airframe after landing was explored under different vertical velocities, horizontal velocities and landing elevations. The von Mises stress arrived at the peak value in the initial stage, then it decreased rapidly, finally it stayed steady. The maximal structural deformation was achieved in the hundreds milliseconds after landing, and then it relapsed rapidly. Comparison shows that the vertical velocities can affect the structural response of the airplane airframe the most strongly, the following are landing elevations, and the weakest are horizontal velocities.
The dynamics of the airplane impacting on water was investigated. The arbitrary Lagrangian-Eulerian (ALE) method was employed to describe this fluid-structure interaction problem. The velocity of the airplane after landing was researched by analyzing the velocities of the airplane head and tail. The head and tail velocities changed rapidly in the initial stage of entering water, and then they kept stable. The structural response of the airplane airframe after landing was explored under different vertical velocities, horizontal velocities and landing elevations. The von Mises stress arrived at the peak value in the initial stage, then it decreased rapidly, finally it stayed steady. The maximal structural deformation was achieved in the hundreds milliseconds after landing, and then it relapsed rapidly. Comparison shows that the vertical velocities can affect the structural response of the airplane airframe the most strongly, the following are landing elevations, and the weakest are horizontal velocities.
2010, 30(2): 131-137.
doi: 10.11883/1001-1455(2010)02-0131-07
Abstract:
Mesoscale responses of heterogeneous explosives under shock loading were investigated by using a three-dimensional discrete element method. Numerical simulations without chemical reaction were conducted to explore the hot spot mechanisms in plastic bonded explosives and explosives containing voids of different shape and different size. The simulation results indicate that for shocked PBX explosives hot spots mostly locate near the interface between HMX crystals and binder, the temperature rise of HMX crystals is lower than that of the binder, and the surrounding parts of HMX crystals have higher temperature rise than the inner parts. For explosives containing a void, temperature of hot spot induced by the collapse of a big void is higher than that induced by the collapse of a small void, and temperature of hot spot induced by the collapse of a spherical void is higher than that induced by the collapse of a cubic void.
Mesoscale responses of heterogeneous explosives under shock loading were investigated by using a three-dimensional discrete element method. Numerical simulations without chemical reaction were conducted to explore the hot spot mechanisms in plastic bonded explosives and explosives containing voids of different shape and different size. The simulation results indicate that for shocked PBX explosives hot spots mostly locate near the interface between HMX crystals and binder, the temperature rise of HMX crystals is lower than that of the binder, and the surrounding parts of HMX crystals have higher temperature rise than the inner parts. For explosives containing a void, temperature of hot spot induced by the collapse of a big void is higher than that induced by the collapse of a small void, and temperature of hot spot induced by the collapse of a spherical void is higher than that induced by the collapse of a cubic void.
2010, 30(2): 138-144.
doi: 10.11883/1001-1455(2010)02-0138-07
Abstract:
By considering the elastic-plastic deformation behavior of multiple contacts and the conditions of multiple impacts and multiple separations and by using the finite difference method, the MCIS method was presented to investigate the impact problem of a simply supported beam struck horizontally by a round-nosed rigid mass. The numerical simulations show that such a horizontal strike is indeed a complicated process of multiple elastic-plastic impacts. There are usually more than two impact zones in which each of them consists of complicated multiple sub-impacts. It is found that the other impact zones might occupy considerable impact impulse or even more than ones of the first impact zone. Hence, the other impact zones have significant influence on the impact responses of the beam. It is found as well that the other impacts might have considerable impact kinetic energy dissipation totally or even more than ones of the first impact. It implies that the multiple impacts are of an important role upon the impact physical behavior of the beam. The numerical investigations also show that for the light rigid mass, the first impact course will cause more kinetic energy dissipation, and for the weight rigid mass, the following multiple impact courses will cause more kinetic energy dissipation.
By considering the elastic-plastic deformation behavior of multiple contacts and the conditions of multiple impacts and multiple separations and by using the finite difference method, the MCIS method was presented to investigate the impact problem of a simply supported beam struck horizontally by a round-nosed rigid mass. The numerical simulations show that such a horizontal strike is indeed a complicated process of multiple elastic-plastic impacts. There are usually more than two impact zones in which each of them consists of complicated multiple sub-impacts. It is found that the other impact zones might occupy considerable impact impulse or even more than ones of the first impact zone. Hence, the other impact zones have significant influence on the impact responses of the beam. It is found as well that the other impacts might have considerable impact kinetic energy dissipation totally or even more than ones of the first impact. It implies that the multiple impacts are of an important role upon the impact physical behavior of the beam. The numerical investigations also show that for the light rigid mass, the first impact course will cause more kinetic energy dissipation, and for the weight rigid mass, the following multiple impact courses will cause more kinetic energy dissipation.
2010, 30(2): 145-151.
doi: 10.11883/1001-1455(2010)02-0145-07
Abstract:
Based on the one-dimensional shock wave theory and the powder shock temperature rising model, dynamical shock response, shock temperature rising and shock-induced chemical reaction were theoretically analyzed for reactive metals under high-velocity impact by considering the effects of material compactness and impact velocity on shock pressure and shock temperature, respectively. By combining the calculated shock temperature of the power material and the chemical dynamics of shock-induced reaction, a thermo-chemical model for shock-induced reaction in reactive metal materials was presented by taking reaction efficiency into account. The calculated results by the new model presented in this paper are in agreement with the corresponding experiments by L. S. Bennett, et al. Shock-induced chemical reaction characteristics of reactive metal can be influenced evidently by material compactness, impact velocity and material kind.
Based on the one-dimensional shock wave theory and the powder shock temperature rising model, dynamical shock response, shock temperature rising and shock-induced chemical reaction were theoretically analyzed for reactive metals under high-velocity impact by considering the effects of material compactness and impact velocity on shock pressure and shock temperature, respectively. By combining the calculated shock temperature of the power material and the chemical dynamics of shock-induced reaction, a thermo-chemical model for shock-induced reaction in reactive metal materials was presented by taking reaction efficiency into account. The calculated results by the new model presented in this paper are in agreement with the corresponding experiments by L. S. Bennett, et al. Shock-induced chemical reaction characteristics of reactive metal can be influenced evidently by material compactness, impact velocity and material kind.
2010, 30(2): 152-158.
doi: 10.11883/1001-1455(2010)02-0152-07
Abstract:
Sympathetic detonation experiments of the GHL explosives in steel shell were carried out. By observing the remainder of the explosive, the deformation of the witness and steel shell, the explosive reaction state was judged and the critical distance of the sympathetic detonation was gained. A calculation model of sympathetic detonation was established. By using the non-linear finite element method, sympathetic detonation experiments of the GHL explosives in steel shell were numerically simulated by the established calculation model. In this calculation model, the method of foreordained fragments was used to describe the form of the donor’s fragments and the impact of these fragments acting on the acceptor. Numerically simulated results of the critical distances are in agreement with the experimental results. The fragments mostly in the middle part of the donor impact the acceptor, and the initiation point is in the middle part of acceptor. The steel-shell thickness affects mainly the velocity and quality of the fragments as well as the defense capability of the acceptor. Consequently the steel-shell thickness affects the critical distance of the sympathetic detonation.
Sympathetic detonation experiments of the GHL explosives in steel shell were carried out. By observing the remainder of the explosive, the deformation of the witness and steel shell, the explosive reaction state was judged and the critical distance of the sympathetic detonation was gained. A calculation model of sympathetic detonation was established. By using the non-linear finite element method, sympathetic detonation experiments of the GHL explosives in steel shell were numerically simulated by the established calculation model. In this calculation model, the method of foreordained fragments was used to describe the form of the donor’s fragments and the impact of these fragments acting on the acceptor. Numerically simulated results of the critical distances are in agreement with the experimental results. The fragments mostly in the middle part of the donor impact the acceptor, and the initiation point is in the middle part of acceptor. The steel-shell thickness affects mainly the velocity and quality of the fragments as well as the defense capability of the acceptor. Consequently the steel-shell thickness affects the critical distance of the sympathetic detonation.
2010, 30(2): 159-163.
doi: 10.11883/1001-1455(2010)02-0159-05
Abstract:
Projectiles were regarded as rigid ones to simplify the mechanics principle of the perforation for concrete targets. According to the hydrodynamics model, the cracks were considered to increase astatically when they expanded to the back of the target under the impact of a projectile. This time was defined as the moment that the perforating action began. The critical distance to the back of the target was deduced by the energy dissipation mechanism for crack extension. After the cracks arrived at the backs of the targets, the penetration resistance was calculated by considering the relative velocity between the projectile and the plug. The calculated result indicates that the deceleration changes remarkably when the warhead is intruding the target and after the perforating action begins, whereas the deceleration changes weakly between the above two stages. Comparison between the calculated results and the existent experimental results shows the calculated results are credible.
Projectiles were regarded as rigid ones to simplify the mechanics principle of the perforation for concrete targets. According to the hydrodynamics model, the cracks were considered to increase astatically when they expanded to the back of the target under the impact of a projectile. This time was defined as the moment that the perforating action began. The critical distance to the back of the target was deduced by the energy dissipation mechanism for crack extension. After the cracks arrived at the backs of the targets, the penetration resistance was calculated by considering the relative velocity between the projectile and the plug. The calculated result indicates that the deceleration changes remarkably when the warhead is intruding the target and after the perforating action begins, whereas the deceleration changes weakly between the above two stages. Comparison between the calculated results and the existent experimental results shows the calculated results are credible.
2010, 30(2): 164-168.
doi: 10.11883/1001-1455(2010)02-0164-05
Abstract:
Dust explosion experiments aiming at 4 kinds of coal dust were carried out in a 20-liter spherical vessel to explore the mechanism of dust explosion. The lower explosion limit, the maximum explosion pressure and the maximum explosion pressure rising rate were obtained for the coal dust samples. Influences of coal dust concentration, particle diameter and ignition energy on coal dust explosion intensity were analyzed. Results show that the lower explosion limit decreases with the decrease of particle size. For a given concentration, the coal dust with smaller particle size causes higher explosion pressure. Dust concentration has a significant effect on explosion intensity. The maximum explosion pressure and its rising rate increase first and then decrease with the increase of dust concentration. For sample 3, the peak explosion pressure is corresponding to the concentration range from 400 to 1 000 g/m3, and the maximum explosion pressure is 0.54 MPa. To some extent, higher ignition energy causes more sufficient reaction and results in more intensive explosion. Due to the features of coal dust sample components, experimental data indicate that gas phase combustion plays an important role during the explosion process.
Dust explosion experiments aiming at 4 kinds of coal dust were carried out in a 20-liter spherical vessel to explore the mechanism of dust explosion. The lower explosion limit, the maximum explosion pressure and the maximum explosion pressure rising rate were obtained for the coal dust samples. Influences of coal dust concentration, particle diameter and ignition energy on coal dust explosion intensity were analyzed. Results show that the lower explosion limit decreases with the decrease of particle size. For a given concentration, the coal dust with smaller particle size causes higher explosion pressure. Dust concentration has a significant effect on explosion intensity. The maximum explosion pressure and its rising rate increase first and then decrease with the increase of dust concentration. For sample 3, the peak explosion pressure is corresponding to the concentration range from 400 to 1 000 g/m3, and the maximum explosion pressure is 0.54 MPa. To some extent, higher ignition energy causes more sufficient reaction and results in more intensive explosion. Due to the features of coal dust sample components, experimental data indicate that gas phase combustion plays an important role during the explosion process.
2010, 30(2): 169-177.
doi: 10.11883/1001-1455(2010)02-0169-09
Abstract:
Numerical models for single-layer Kiewitt-8 reticulated domes with the span of 60 m and cylinder impactors were established by the ANSYS/LS-DYNA program and a series of numerical simulations were carried out. Four failure modes for the reticulated domes were put forward according as the displacement and plastic deformation. The whole failure process was divided into three steps including energy applying, energy loss and energy transfer, energy consumption, by the dynamic response characteristics of each step. Failure mechanisms of the reticulated domes were explained at the two aspects of energy transfer and failure types for members in impact zones. Energy analysis displays that the left energy (Elf) is the main factor to decide the final dynamic response and failure mode, but Elf is the initial impact energy eliminated penetrating loss by the impactor and local breakage loss by members in the impact zone. Analysis for failure types of members indicates that failure of members may lag by contrast the end of impact load, and failure types of members decide the ability of energy transfer. When remembers undergo tension failure, intensities of members are made full use of, the most energy is transferred, the left energy is more, and the whole reticulated dome experiences severe breakage. Moreover, there is a good consistent relationship among failure types of members, failure modes of the reticulated dome and left energy.
Numerical models for single-layer Kiewitt-8 reticulated domes with the span of 60 m and cylinder impactors were established by the ANSYS/LS-DYNA program and a series of numerical simulations were carried out. Four failure modes for the reticulated domes were put forward according as the displacement and plastic deformation. The whole failure process was divided into three steps including energy applying, energy loss and energy transfer, energy consumption, by the dynamic response characteristics of each step. Failure mechanisms of the reticulated domes were explained at the two aspects of energy transfer and failure types for members in impact zones. Energy analysis displays that the left energy (Elf) is the main factor to decide the final dynamic response and failure mode, but Elf is the initial impact energy eliminated penetrating loss by the impactor and local breakage loss by members in the impact zone. Analysis for failure types of members indicates that failure of members may lag by contrast the end of impact load, and failure types of members decide the ability of energy transfer. When remembers undergo tension failure, intensities of members are made full use of, the most energy is transferred, the left energy is more, and the whole reticulated dome experiences severe breakage. Moreover, there is a good consistent relationship among failure types of members, failure modes of the reticulated dome and left energy.
2010, 30(2): 178-182.
doi: 10.11883/1001-1455(2010)02-0178-05
Abstract:
Several common methods to simulate the problem of penetrating reinforced concrete were presented. Lagrange algorithm in AUTODYN was used to calculate the experiment of kinetic energy projectile penetrating reinforced concrete from the reference, the results were agreed well. With this method, the influence of reinforcement ratio, rebar schemes and impact position were analyzed. It is indicated, from the numerical results, increasing reinforcement ratio can enhance the anti-penetration property of reinforced concrete, especially in the case, where the diameter of projectile exceeds the distance of rebar. In addition, the influence of impact position is obvious.
Several common methods to simulate the problem of penetrating reinforced concrete were presented. Lagrange algorithm in AUTODYN was used to calculate the experiment of kinetic energy projectile penetrating reinforced concrete from the reference, the results were agreed well. With this method, the influence of reinforcement ratio, rebar schemes and impact position were analyzed. It is indicated, from the numerical results, increasing reinforcement ratio can enhance the anti-penetration property of reinforced concrete, especially in the case, where the diameter of projectile exceeds the distance of rebar. In addition, the influence of impact position is obvious.
2010, 30(2): 183-190.
doi: 10.11883/1001-1455(2010)02-0183-08
Abstract:
In order to fully realize the blast resistance of this kind of rock cavern, a great many 3D nonlinear finite element numerical simulations were implemented. Taking the damage of surrounding rock and concrete liner as evaluation criterion, the influence of embedded depth, rock property and lateral pressure coefficient on the blast resistance of the cavern was analyzed. The damaged plasticity model was adopted for the rock and concrete liner. Geometric nonlinear behaviors were also considered in every simulation. For this kind of high-wall cavern in a hydraulic power station, numerical results indicate that the blast resistance of the shallow cavern is weaker than that of the deep embedded cavern. The stiffer the surrounding rock, the stronger the blast resistance of the cavern. Numerical results also indicate that when the geo-stress lateral pressure coefficient λ is less than 1, the geo-stress lateral pressure coefficient affects weakly the blast resistance performance of the cavern. Once λ is greater than 1, the blast resistance of the cavern dramatically decreases with the increase of λ.
In order to fully realize the blast resistance of this kind of rock cavern, a great many 3D nonlinear finite element numerical simulations were implemented. Taking the damage of surrounding rock and concrete liner as evaluation criterion, the influence of embedded depth, rock property and lateral pressure coefficient on the blast resistance of the cavern was analyzed. The damaged plasticity model was adopted for the rock and concrete liner. Geometric nonlinear behaviors were also considered in every simulation. For this kind of high-wall cavern in a hydraulic power station, numerical results indicate that the blast resistance of the shallow cavern is weaker than that of the deep embedded cavern. The stiffer the surrounding rock, the stronger the blast resistance of the cavern. Numerical results also indicate that when the geo-stress lateral pressure coefficient λ is less than 1, the geo-stress lateral pressure coefficient affects weakly the blast resistance performance of the cavern. Once λ is greater than 1, the blast resistance of the cavern dramatically decreases with the increase of λ.
2010, 30(2): 191-196.
doi: 10.11883/1001-1455(2010)02-0191-06
Abstract:
To safely recover the waste heat of the converter gas, a series of experiments were conducted to explore the deflagration properties of CO-air mixture at different initial temperatures in a duct lined with obstacles. By measuring deflagration pressure and flame speed, influences of CO stoichiometry and temperature on deflagration properties were investigated. Results show that the pressure and flame speed increase rapidly in the duct segment lined with obstacles. When CO stoichiometry is 1.100, deflagration attains the maximum intensity. As the initial temperature increases, the pressure increase slows down, and the maximum flame speed decreases,but still keeps a high speed, over 550 m/s. The flame propagation time increases at first and then becomes stable along with the increasing of the initial temperature.
To safely recover the waste heat of the converter gas, a series of experiments were conducted to explore the deflagration properties of CO-air mixture at different initial temperatures in a duct lined with obstacles. By measuring deflagration pressure and flame speed, influences of CO stoichiometry and temperature on deflagration properties were investigated. Results show that the pressure and flame speed increase rapidly in the duct segment lined with obstacles. When CO stoichiometry is 1.100, deflagration attains the maximum intensity. As the initial temperature increases, the pressure increase slows down, and the maximum flame speed decreases,but still keeps a high speed, over 550 m/s. The flame propagation time increases at first and then becomes stable along with the increasing of the initial temperature.
2010, 30(2): 197-202.
doi: 10.11883/1001-1455(2010)02-0197-06
Abstract:
Forcreatingacreditablemodelforboltjointdamage,theexplosionshockdamagebehaviors ofbolt-jointedstructureswereanalyzedbytheLS-DYNAcodeandamethodforestablishingsimple boltdamagemodelswasputforward.ThefiniteelementmodelofM24boltjointswasproposedand prestresswasaddedbydroppingtemperature.Thedeformabledamagebehaviorsoftheboltandboltnutjointswithprestressandwithoutprestresswerecalculatedbycombiningtheconstitutivem del forelastic-plasticmaterialsandthesurface-surfacecontactalgorithm.Basedonthecalculatedresults, theinfluencesofincidentshockwaveanglesandprestressmagnitudesonboltjointdamagebehaviors weresummarizedandasimplifieddamagemodelwasdevelopedforthestructuresassembledbybolted joints.Andsomeoptimizationschemeswerebroughtforwardforenhancingboltanti-shockability.
Forcreatingacreditablemodelforboltjointdamage,theexplosionshockdamagebehaviors ofbolt-jointedstructureswereanalyzedbytheLS-DYNAcodeandamethodforestablishingsimple boltdamagemodelswasputforward.ThefiniteelementmodelofM24boltjointswasproposedand prestresswasaddedbydroppingtemperature.Thedeformabledamagebehaviorsoftheboltandboltnutjointswithprestressandwithoutprestresswerecalculatedbycombiningtheconstitutivem del forelastic-plasticmaterialsandthesurface-surfacecontactalgorithm.Basedonthecalculatedresults, theinfluencesofincidentshockwaveanglesandprestressmagnitudesonboltjointdamagebehaviors weresummarizedandasimplifieddamagemodelwasdevelopedforthestructuresassembledbybolted joints.Andsomeoptimizationschemeswerebroughtforwardforenhancingboltanti-shockability.
2010, 30(2): 203-208.
doi: 10.11883/1001-1455(2010)02-0203-06
Abstract:
Atechniquewasdescribedformodelingtheend-faceindentationduringtheSHPBtest.A numericalcorrectionprocedurewasestablishedbasedonthismodel.Bycombiningthistechniquewith othertechniquesinthedataprocessingofSHPBtest,theaccuracyofstraincalculationwasimproved dramatically.ItextendstheSHPBtesttosmallstrainrangeandmakesitpossibletoobtaintheoverallhighstrain- ratestress-straincurvewithaccuracyandreliabilitycomparablewithquasi-staticmaterialtests.
Atechniquewasdescribedformodelingtheend-faceindentationduringtheSHPBtest.A numericalcorrectionprocedurewasestablishedbasedonthismodel.Bycombiningthistechniquewith othertechniquesinthedataprocessingofSHPBtest,theaccuracyofstraincalculationwasimproved dramatically.ItextendstheSHPBtesttosmallstrainrangeandmakesitpossibletoobtaintheoverallhighstrain- ratestress-straincurvewithaccuracyandreliabilitycomparablewithquasi-staticmaterialtests.
2010, 30(2): 209-214.
doi: 10.11883/1001-1455(2010)02-0209-06
Abstract:
Byusingtheray-tracingmethod,anairopticalbreakdownmodelwasproposedforinvestigatingthelaser- materialinteraction.Thelaserbeam wasdividedintoanumberofrays,whichwere trackedtocomputeradiationintensitybytheradiationtransferequation,andtheairopticalbreakdownwassimulated. Inthelensfocusingsystem,differentgridsandraypathswereusedtovalidate theproposedmodel,andgoodagreementwasachievedbetweennumericalandexperimentalresults forthelaser-inducedairplasmafield.Itisindicatedthatthemodeldependslittleonthecomputational gridswhentheradiusoftheAirydiskismuchlargerthanthesizeofthegridaroundthefocuspoint, andthatthetemperatureinthebreakdownregionmustbehigherthan14000K,otherwisethelaser energycannotbedeposited.
Byusingtheray-tracingmethod,anairopticalbreakdownmodelwasproposedforinvestigatingthelaser- materialinteraction.Thelaserbeam wasdividedintoanumberofrays,whichwere trackedtocomputeradiationintensitybytheradiationtransferequation,andtheairopticalbreakdownwassimulated. Inthelensfocusingsystem,differentgridsandraypathswereusedtovalidate theproposedmodel,andgoodagreementwasachievedbetweennumericalandexperimentalresults forthelaser-inducedairplasmafield.Itisindicatedthatthemodeldependslittleonthecomputational gridswhentheradiusoftheAirydiskismuchlargerthanthesizeofthegridaroundthefocuspoint, andthatthetemperatureinthebreakdownregionmustbehigherthan14000K,otherwisethelaser energycannotbedeposited.
2010, 30(2): 215-219.
doi: 10.11883/1001-1455(2010)02-0215-05
Abstract:
Ninediscretemulti-layeredcylindersweremanufacturedwiththesamematerialsandthe magnificationfactorof4.Aseriesofexplosionexperimentswereconductedunderinternalexplosive loadingtoinvestigatetheiranti-explosioncapabilityandscaleeffect.Experimentalresultsshowthat theirlimitingTNTchargesareall0.89%~1.11%inrelativemass,andthattheanti-explosioncapabilityofthediscretemulti- layeredcylindersisnotattenuatedsignificantlyaftermagnified4times.It isattributedtothereasonthatthereisnostrongscaleeffectofanenergynatureintheirsteelribbon layerswhichconstructthemainload-supportingcapabilityofdiscretemulti-layeredexplosioncontainmentvessels.
Ninediscretemulti-layeredcylindersweremanufacturedwiththesamematerialsandthe magnificationfactorof4.Aseriesofexplosionexperimentswereconductedunderinternalexplosive loadingtoinvestigatetheiranti-explosioncapabilityandscaleeffect.Experimentalresultsshowthat theirlimitingTNTchargesareall0.89%~1.11%inrelativemass,andthattheanti-explosioncapabilityofthediscretemulti- layeredcylindersisnotattenuatedsignificantlyaftermagnified4times.It isattributedtothereasonthatthereisnostrongscaleeffectofanenergynatureintheirsteelribbon layerswhichconstructthemainload-supportingcapabilityofdiscretemulti-layeredexplosioncontainmentvessels.
2010, 30(2): 220-224.
doi: 10.11883/1001-1455(2010)02-0220-05
Abstract:
Abstract:Guidedbombsweretakenastheresearchobjectstonumericallysimulatethepenetration andexplosionprocessoflarge-aperture-heavy weaponsbyusingathree-dimensionalarbitraryLagrange- Eulerian(ALE)codeandtoexploredamageeffectsofarollercompactedconcretegravitydam undercontinuousattacksoftwoprecision-guidedbombs.Resultsshowthatthevibrationcausedby penetrationisweak,whiletheparticlevibrationismainlycausedbyammunitionexplosion.Theintermissiontimeofsequentialattacksisfarlongerthanthedynamicresponsestretchofthedam, andthe damvibrationcausedbysequentialattacksscarcelytakesonthesuperpositioneffect.Butthedamage effectofpenetrationandexplosionfortheformermissileprovidesthefreedomsurfaceforthesubsequentmissile, andthepenetrationdepthandexplosion-damagedrangeofthesubsequentmissileincrease. Theexplosion-damagedrangesbasicallyconnectwitheachother,whichthreattothenormal runningandsecurityofthedam.
Abstract:Guidedbombsweretakenastheresearchobjectstonumericallysimulatethepenetration andexplosionprocessoflarge-aperture-heavy weaponsbyusingathree-dimensionalarbitraryLagrange- Eulerian(ALE)codeandtoexploredamageeffectsofarollercompactedconcretegravitydam undercontinuousattacksoftwoprecision-guidedbombs.Resultsshowthatthevibrationcausedby penetrationisweak,whiletheparticlevibrationismainlycausedbyammunitionexplosion.Theintermissiontimeofsequentialattacksisfarlongerthanthedynamicresponsestretchofthedam, andthe damvibrationcausedbysequentialattacksscarcelytakesonthesuperpositioneffect.Butthedamage effectofpenetrationandexplosionfortheformermissileprovidesthefreedomsurfaceforthesubsequentmissile, andthepenetrationdepthandexplosion-damagedrangeofthesubsequentmissileincrease. Theexplosion-damagedrangesbasicallyconnectwitheachother,whichthreattothenormal runningandsecurityofthedam.
