To study the effect of interface behaviour on the mechanical properties and damage evolution of PBX under combined tension-shear loading, the present work establishes the numerical model of a PBX three-phase hybrid sy...To study the effect of interface behaviour on the mechanical properties and damage evolution of PBX under combined tension-shear loading, the present work establishes the numerical model of a PBX three-phase hybrid system, which introduces a nonlinear plastic damage cohesion model to study the mechanical response and damage process. The parameters in the model were fitted and calibrated.Taking the crack growth rate as the feature, the damage state in each stage was determined, and the damage instability criterion was given. The effects of interfacial tensile strength and shear strength on the damage process of PBX were studied. On this basis, serrated and hemispherical structures interface of PBX has been developed, which affects the damage process and instability during the loading process.The results indicate that damage state response of PBX experiences the process of stable load bearing,unstable propagation, and complete failure. At the critical moment of instability, the overall equivalent effective strain of material reaches 3024 με and instability loading displacement reaches 0.39 mm. The increase of interfacial tensile strength and shear strength significantly inhibits the damage of PBX. The effect of interfacial shear strength on critical instability of PBX is approximately 1.7 times that of the interfacial tensile strength. Further, interface opening along the normal direction is the main damage form at the interface. Serrated and hemispherical rough interfaces can significantly inhibit propagation of cracks, and the load bearing capacity is improved by 22% and 9.7%, respectively. Appropriate improvement of the roughness of the interface structure can effectively improve the mechanical properties. It is significantly important to have a better understanding of deformation, damage and failure mechanisms of PBX and to improve our predictive ability.展开更多
3-nitro-1,2,4-triazol-5-one(NTO)is the main component of insensitive munitions(IM)formulation because of its outstanding insensitive properties.In this paper,a series of NTO/HMX-based compositeexplosives were prepared...3-nitro-1,2,4-triazol-5-one(NTO)is the main component of insensitive munitions(IM)formulation because of its outstanding insensitive properties.In this paper,a series of NTO/HMX-based compositeexplosives were prepared and characterized.The study focuses on the effect of NTO on the perfommance of the formulations,especially the safety performance.The results revealed that the mechanical sensi-tivity of fomulations was associated with NTO content,as well as the thermal conductivity,specific heat capacity and Arrhenius parameters.Then,the high amount of NTO using in formulation was proved to be helpful for NTO/HMX-based formulation to exhibit good thermal safety.Besides,by accelerating rate calorimeter(ARC)and a modified cook-off equipment,the pressure and pressure rise rate were proved as the important indicator for judging the thermal safety performance in confined spaces.Finally,the numerical simulation was used as a credible method for predicting the respond temperature of cook-off experiment.展开更多
Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1,1-diamino-2,2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of poly...Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1,1-diamino-2,2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of polyurethane(PU)based on glycidyl azide polymer(GAP) and hydroxyl-terminated polybutadiene(HTPB) as an energetic and inert polymeric binder respectively.Casting technique was used for the preparation of different PBX formulations based on FOX-7/RDX and PU(GAP/HTPB)with 14% binder.The sensitivity to different initial impulses and performance characteristics of the explosive and lethal zone of the tested controlled fragmentation warhead by the fragmentation warhead assessment test(arena test)were studied,in which the arena test was carried out with a controlled fragmentation warhead made from Ck45 steel,with dimensions(100 mm length,30 mm outer diameter and 3 mm thickness).Results show that PBXGF4 has lower sensitivity to impact and heat than those of PBXGR4 by 188.4% and 3.2% respectively.Its friction sensitivity is the same as that of PBXGR4.It has better performance,in which detonation velocity increases by 2.1% and brisance increases by 0.5% when compared with those of PBXGR4.It was concluded that PBXGF4 which based on FOX-7 bonded with PU/GAP matrix has good characteristics as PBX,specially in the sensitivity to impact and can be applied for replacing PBXs based on RDX in the advanced PBXs for low sensitive fragmentation warheads.展开更多
A thorough understanding of drop-weight impacted responses for polymer-bonded explosives(PBXs)is significant to evaluate their impact sensitivity.The characteristics of the drop-weight impacted pressed PBXs including ...A thorough understanding of drop-weight impacted responses for polymer-bonded explosives(PBXs)is significant to evaluate their impact sensitivity.The characteristics of the drop-weight impacted pressed PBXs including deforming,fracturing,forming a local high-temperature region and igniting,were simulated using a coupled mechanical-thermo-chemical model integrating micro-defects evolution.A novel evaluation method for impact sensitivity is established using the relation between the input kinetic energy and the output energy due to deformation,crushing energy,local hot spot energy and ignition.The effects of impact velocity on sensitivity were analyzed and the critical local ignition impact velocity is determined as 4.0-4.5 m/s.The simulated results show that shear-crack friction heating is the dominant ignition mechanism.The region along the boundary of PBXs sample is the most hazardous regions where ignition first occur.The propagation of stress wave in PBXs causes shear-crack hotspot and bulk temperature exhibiting an approximate 45°direction evolution path,which is the main reason that dominated damage-ignition region transits from the boundary to the central of sample.展开更多
Polymer-bonded explosives(PBXs)are widely used in military applications due to their high energy density,but their safety under impact loading remains a critical concern due to hotspot-induced ignition risks.While exi...Polymer-bonded explosives(PBXs)are widely used in military applications due to their high energy density,but their safety under impact loading remains a critical concern due to hotspot-induced ignition risks.While existing experimental and continuum methods face limitations in capturing sub-millisecond mesoscale processes and discontinuous damage evolution,this study develops an integrated Discrete Element Method(DEM)framework integrating the Edinburgh Elasto-Plastic-Adhesive(EEPA)contact model with Arrhenius reaction kinetics,where mechanical energy dissipation deterministically drives thermal-chemical ignition.The framework successfully predicts hotspot generation and ignition thresholds in cyclotetramethylene tetranitramine(HMX)particle explosives under impact loading.The maximum temperatures of the cubic sample are consistent with the literature and the verification analysis of a Steven Test is aligned with an experiment in literature.Application to Spigot and Drop Tests reveals strain energy accumulation and damping dissipation as dominant ignition mechanisms,with chemical activation showing exponential dependence on mechanical heating.Compared to existing DEM studies focusing on single-physics processes,this work establishes a more comprehensive and better predictive tool for mapping mechanical loading conditions to ignition thresholds.展开更多
In this paper,a primary model is established for MD(molecular dynamics) simulation for the PBXs(polymer-bonded explosives) with RDX(cyclotrimethylene trinitramine) as base explosive and PS as polymer binder.A series o...In this paper,a primary model is established for MD(molecular dynamics) simulation for the PBXs(polymer-bonded explosives) with RDX(cyclotrimethylene trinitramine) as base explosive and PS as polymer binder.A series of results from the MD simulation are compared between two PBX models,which are represented by PBX1 and PBX2,respectively,including one PS molecular chain having 46 repeating units and two PS molecular chains with each having 23 repeating units.It has been found that their structural,interaction energy and mechanical properties are basically consistent between the two models.A systematic MD study for the PBX2 is performed under NPT conditions at five different temperatures,i.e.,195 K,245 K,295 K,345 K,and 395 K.We have found that with the temperature increase,the maximum bond length(L max) of RDX N N trigger bond increases,and the interaction energy(E N-N) between two N atoms of the N-N trigger bond and the cohesive energy density(CED) decrease.These phenomena agree with the experimental fact that the PBX becomes more sensitive as the temperature increases.Therefore,we propose to use the maximum bond length L max of the trigger bond of the easily decomposed and exploded component and the interaction energy E N-N of the two relevant atoms as theoretical criteria to judge or predict the relative degree of heat and impact sensitivity for the energetic composites such as PBXs and solid propellants.展开更多
基金the China National Nature Science Foundation (Grant No. 11872119)China Postdoctoral Science Foundation (Grant Nos. BX20200046, 2020M680394)Pre-research Project of Armament (Grant No. 6142A03202002) for supporting this project
文摘To study the effect of interface behaviour on the mechanical properties and damage evolution of PBX under combined tension-shear loading, the present work establishes the numerical model of a PBX three-phase hybrid system, which introduces a nonlinear plastic damage cohesion model to study the mechanical response and damage process. The parameters in the model were fitted and calibrated.Taking the crack growth rate as the feature, the damage state in each stage was determined, and the damage instability criterion was given. The effects of interfacial tensile strength and shear strength on the damage process of PBX were studied. On this basis, serrated and hemispherical structures interface of PBX has been developed, which affects the damage process and instability during the loading process.The results indicate that damage state response of PBX experiences the process of stable load bearing,unstable propagation, and complete failure. At the critical moment of instability, the overall equivalent effective strain of material reaches 3024 με and instability loading displacement reaches 0.39 mm. The increase of interfacial tensile strength and shear strength significantly inhibits the damage of PBX. The effect of interfacial shear strength on critical instability of PBX is approximately 1.7 times that of the interfacial tensile strength. Further, interface opening along the normal direction is the main damage form at the interface. Serrated and hemispherical rough interfaces can significantly inhibit propagation of cracks, and the load bearing capacity is improved by 22% and 9.7%, respectively. Appropriate improvement of the roughness of the interface structure can effectively improve the mechanical properties. It is significantly important to have a better understanding of deformation, damage and failure mechanisms of PBX and to improve our predictive ability.
基金The authors are grateful to the National Defense Foundation of China(3090021322001,3090020221912,3090021211903.)for financial support of this work.
文摘3-nitro-1,2,4-triazol-5-one(NTO)is the main component of insensitive munitions(IM)formulation because of its outstanding insensitive properties.In this paper,a series of NTO/HMX-based compositeexplosives were prepared and characterized.The study focuses on the effect of NTO on the perfommance of the formulations,especially the safety performance.The results revealed that the mechanical sensi-tivity of fomulations was associated with NTO content,as well as the thermal conductivity,specific heat capacity and Arrhenius parameters.Then,the high amount of NTO using in formulation was proved to be helpful for NTO/HMX-based formulation to exhibit good thermal safety.Besides,by accelerating rate calorimeter(ARC)and a modified cook-off equipment,the pressure and pressure rise rate were proved as the important indicator for judging the thermal safety performance in confined spaces.Finally,the numerical simulation was used as a credible method for predicting the respond temperature of cook-off experiment.
文摘Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1,1-diamino-2,2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of polyurethane(PU)based on glycidyl azide polymer(GAP) and hydroxyl-terminated polybutadiene(HTPB) as an energetic and inert polymeric binder respectively.Casting technique was used for the preparation of different PBX formulations based on FOX-7/RDX and PU(GAP/HTPB)with 14% binder.The sensitivity to different initial impulses and performance characteristics of the explosive and lethal zone of the tested controlled fragmentation warhead by the fragmentation warhead assessment test(arena test)were studied,in which the arena test was carried out with a controlled fragmentation warhead made from Ck45 steel,with dimensions(100 mm length,30 mm outer diameter and 3 mm thickness).Results show that PBXGF4 has lower sensitivity to impact and heat than those of PBXGR4 by 188.4% and 3.2% respectively.Its friction sensitivity is the same as that of PBXGR4.It has better performance,in which detonation velocity increases by 2.1% and brisance increases by 0.5% when compared with those of PBXGR4.It was concluded that PBXGF4 which based on FOX-7 bonded with PU/GAP matrix has good characteristics as PBX,specially in the sensitivity to impact and can be applied for replacing PBXs based on RDX in the advanced PBXs for low sensitive fragmentation warheads.
基金China National Nature Science Foundation(Grant No.11872119)Foundation Strengthening Project(Grant No.2020-JCJQ-GFJQ2126-007)+1 种基金Pre-research Program of Armament(Grant No.6142A03202002)China Postdoctoral Science Foundation(Grant No.BX20200046)for supporting this project。
文摘A thorough understanding of drop-weight impacted responses for polymer-bonded explosives(PBXs)is significant to evaluate their impact sensitivity.The characteristics of the drop-weight impacted pressed PBXs including deforming,fracturing,forming a local high-temperature region and igniting,were simulated using a coupled mechanical-thermo-chemical model integrating micro-defects evolution.A novel evaluation method for impact sensitivity is established using the relation between the input kinetic energy and the output energy due to deformation,crushing energy,local hot spot energy and ignition.The effects of impact velocity on sensitivity were analyzed and the critical local ignition impact velocity is determined as 4.0-4.5 m/s.The simulated results show that shear-crack friction heating is the dominant ignition mechanism.The region along the boundary of PBXs sample is the most hazardous regions where ignition first occur.The propagation of stress wave in PBXs causes shear-crack hotspot and bulk temperature exhibiting an approximate 45°direction evolution path,which is the main reason that dominated damage-ignition region transits from the boundary to the central of sample.
基金supports from the National Natural Science Foundation of China(grant No.12202415)the National Natural Science Foundation of China(grant No.22308212)are gratefully acknowledged。
文摘Polymer-bonded explosives(PBXs)are widely used in military applications due to their high energy density,but their safety under impact loading remains a critical concern due to hotspot-induced ignition risks.While existing experimental and continuum methods face limitations in capturing sub-millisecond mesoscale processes and discontinuous damage evolution,this study develops an integrated Discrete Element Method(DEM)framework integrating the Edinburgh Elasto-Plastic-Adhesive(EEPA)contact model with Arrhenius reaction kinetics,where mechanical energy dissipation deterministically drives thermal-chemical ignition.The framework successfully predicts hotspot generation and ignition thresholds in cyclotetramethylene tetranitramine(HMX)particle explosives under impact loading.The maximum temperatures of the cubic sample are consistent with the literature and the verification analysis of a Steven Test is aligned with an experiment in literature.Application to Spigot and Drop Tests reveals strain energy accumulation and damping dissipation as dominant ignition mechanisms,with chemical activation showing exponential dependence on mechanical heating.Compared to existing DEM studies focusing on single-physics processes,this work establishes a more comprehensive and better predictive tool for mapping mechanical loading conditions to ignition thresholds.
基金supported by the National Key Laboratory of Shock Wave and Detonation Physics,Institute of Fluid Physics,China Academy of Engineering Physics(076100-1197F)the Defence Industrial Technology Development Program(B1520110002)the State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology(KFJJ09-5)
文摘In this paper,a primary model is established for MD(molecular dynamics) simulation for the PBXs(polymer-bonded explosives) with RDX(cyclotrimethylene trinitramine) as base explosive and PS as polymer binder.A series of results from the MD simulation are compared between two PBX models,which are represented by PBX1 and PBX2,respectively,including one PS molecular chain having 46 repeating units and two PS molecular chains with each having 23 repeating units.It has been found that their structural,interaction energy and mechanical properties are basically consistent between the two models.A systematic MD study for the PBX2 is performed under NPT conditions at five different temperatures,i.e.,195 K,245 K,295 K,345 K,and 395 K.We have found that with the temperature increase,the maximum bond length(L max) of RDX N N trigger bond increases,and the interaction energy(E N-N) between two N atoms of the N-N trigger bond and the cohesive energy density(CED) decrease.These phenomena agree with the experimental fact that the PBX becomes more sensitive as the temperature increases.Therefore,we propose to use the maximum bond length L max of the trigger bond of the easily decomposed and exploded component and the interaction energy E N-N of the two relevant atoms as theoretical criteria to judge or predict the relative degree of heat and impact sensitivity for the energetic composites such as PBXs and solid propellants.
