典型压装与浇注PBX炸药缝隙挤压损伤-点火响应

Damage⁃ignition Simulation for Typical Pressed and Casted PBX under Crack⁃extruded Loading

为探究动态挤压载荷作用下典型装药结构在壳体裂缝周围的点火响应过程,采用高聚物粘结炸药(Polymer bonded explosives,PBX)微裂纹-微孔洞力热化学耦合细观模型,对缝隙挤压载荷作用下PBX药柱与缝隙结构相互作用、炸药宏观力热化学响应、以及损伤-点火细观机理进行了研究,对比分析了压装PBX-5与浇注GOFL-5两类炸药损伤-点火响应的差异性。结果表明,200 m·s^-1挤压速度下压装PBX-5炸药表现为脆性破坏,60μs时挤压前沿距缝隙表面3 mm,在缝隙位置处形成应力集中,与挤压位置成45°方向区域内微裂纹发生快速扩展;相同撞击条件下,浇注GOFL-5炸药在缝隙位置处发生快速流动,大量材料被挤入缝隙,60μs时挤压前沿距缝隙表面9 mm。两种炸药在缝隙周围均形成了潜在点火位置,剪切裂纹热点为压装炸药点火主导机制;局部剪切塑性耗散机制为浇注炸药潜在的点火主导机制。

When polymer-bonded explosives(PBX)charges are rapidly extruded in a crack in the warhead's case,it's required to accurately predict unexpected ignition of cased PBX for safety reasons.Using the combined microcrack and microvoid model(CMM),damage-ignition responses of crack-extruded PBX are investigated in three aspects:(i)interactions between crack and extruded PBX;(ii)mechanical-thermal-chemical responses of PBX at the macroscale;and(iii)underlying mechanisms of dam-age-ignition at the mesoscale.Meanwhile,the difference between two typical PBXs(pressed PBX-5 and casted GOFL-5)in response to crack-extruded loading is compared.The results show that,under 200 m·s^-1 extruded velocity,pressed PBX-5 exhibits brittle failure(extruded 3 mm at 60μs)and shows a stress concentration near the crack;microcrack shows a rapid growth along the 45°angle with the extruded surface.In contrast,under the same extruded condition,casted GOFL-5 exhibits a rapid flow rate near the crack;large quantities of material are extruded(extruded 9 mm at 60μs).Both pressed and casted PBXs show an ignition near the crack.Shear-crack hotspot is the dominated ignition mechanism for PBX-5,while locally plastic dissipation is a possible dominated ignition mechanism for GOFL-5.