摘要
为了研究有限厚炸药在射流冲击下的起爆过程,并得到有限厚炸药的临界起爆阈值。试验采用Φ40 mm聚能装药作为射流源,通过高速录像进行拍摄,对不同厚度的50SiMnVB盖板覆盖下的43 mm厚TNT炸药进行了射流冲击起爆试验,得到炸药的临界起爆阈值和不同刺激强度下的响应情况以及反应产物的膨胀速度。采用数值仿真软件进行了有限厚炸药在射流冲击下的数值模拟计算,得到了射流冲击下炸药内弯曲冲击波发展过程以及有限厚炸药的临界起爆阈值和炸药厚度关系,并通过试验结果进行了验证。最后建立了有限厚炸药临界起爆阈值和临界盖板厚度的计算模型。结果表明:厚度43 mm的TNT临界起爆阈值为37 m
图文摘要
The response of the explosive and the expansion velocity of the product under the conditions that the cover plates have different thicknesses are obtained through the jet impact initiation tests. The propagation process of the bow wave under different conditions and the critical initiation threshold of the explosive with different thicknesses are studied in detail through simulation, and the relationship between the thickness and the initiation threshold of explosive is obtained.
野战弹药库是战时储存武器装备的基地,可以快速、不间断地提供弹药保障,是部队战斗力生成的基础,这决定了野战弹药库的突出地位和重要作用,同时也导致了它在战争中必然是敌方重点攻击目
关于射流冲击起爆已有众多学者进行了大量研究。M.Held
目前陆军弹药中TNT炸药仍占多数,因此本试验中炸药采用TNT炸药,由高速录像对炸药起爆过程进行记录,通过调节盖板厚度得到炸药在射流冲击下的不同响应以及炸药的临界起爆阈值。由于通过试验难以得到炸药内部的反应情况,因此采用仿真对射流冲击起爆有限厚炸药的过程进行了计算,分析了有限厚炸药的起爆过程和起爆阈值随炸药厚度的变化关系,并提出了有限厚炸药临界起爆阈值和临界盖板厚度的计算方法,为射流冲击起爆带壳装药提供一定依据和参考。
试验中用于形成射流的的聚能装药外径为40 mm,装药直径为34 mm,聚能装药主装药为JH‑2,密度1.71 g·c
被发炸药为压装TNT,密度1.54 g·c

图1 射流冲击起爆试验布置
Fig.1 Arrangement of jet impact initiation test
通过高速录像拍摄结果、反应产物膨胀速度、木制试验台以及试验现场并参考美军标MIL‑STD‑2105

图2 盖板厚度为30 mm试验结果
Fig.2 Test results of 30 mm cover plate
20 mm盖板下TNT炸药在不同时刻的高速录像如

a. 500 μs

b. 4000 μs

c. 20000 μs
图3 盖板20 mm时炸药的燃烧过程
Fig.3 Burn process of of explosive with 20 mm cover plate
17.4 mm盖板下TNT炸药在不同时刻的高速录像如

a. 500 μs

b. 1000 μs

c. 20000 μs
图4 盖板17.4 mm时炸药的爆燃过程
Fig.4 Deflagration process of explosive with 17.4 mm cover plate
15 mm盖板下TNT炸药在不同时刻的高速录像如

a. 40 μs

b. 400 μs

c. 500 μs
图5 盖板15 mm时炸药的爆轰过程
Fig.5 Detonation process of explosives with 15 mm cover plate
不同盖板厚度下,穿透盖板后的剩余射流头部速度以及炸药的响应情况如
Note: δ is thickness of cover plate, vj is tip velocity of residual jet.
试验中得到的射流冲击下TNT炸药不同响应对应的刺激强度

图6 试验中不同响应对应的刺激强度和反应产物或炸药粉末膨胀速度
Fig.6 The stimulus intensity and the expansion velocity of reaction products corresponding to different responses in the test
采用AUTODYN有限元程序建立模型,忽略雷管的能量,采用轴对称模型,单位为cm‑g‑μs。聚能装药的结构和布置与试验中一致,主装药中心点起爆,仿真建模如

图7 射流冲击起爆仿真计算模型
Fig.7 Simulation calculation model of jet impact initiation
仿真中炸药、空气、药型罩和外壳采用欧拉算法,盖板采用拉格朗日算法,利用流固耦合算法进行数值模拟。药型罩材料为紫铜,聚能装药中的炸药为JH‑2炸药,外壳为尼龙,盖板材料为50SiMnVB,被发炸药为TNT。药型罩和盖板材料模型采用JOHNSON‑COOK模型和EOS‑GRUNEISEN状态方程进行描述,如
Note: ρ is density, E is elastic modulus, ν is Poisson's ratio, A is yield stress, B is hardening constant, n is hardening exponent, C is strain rate constant, m is thermal softening exponent, TM is melting temperature, Tr is room temperature.
Note: ρ is density, D is detonation wave velocity, pCJ is detonation pressure, A、B、R1、R2 and ω are parameters in JWL equation.
TNT采用三项式点火增长模型LEE‑TARVER和JWL状态方程描
Note: I, b, x, a, G1, c, d, y, G2, e, g and z are parameters in Lee‑Tarver model, A、B、R1、R2 and ω are parameters in JWL equation.
空气和尼龙的参数来自AUTODYN软件中材料库内置参数。
仿真中得到的射流头部速度为5795 m·

图8 仿真得到的射流速度分布
Fig.8 Distribution of jet velocity

a. 28 μs

b. 31 μs

c. 32.5 μs
图9 15 mm厚盖板时不同时刻炸药内压力云图
Fig.9 Pressure distribution in explosive at different times with 15 mm thick cover plate

a. 29.5 μs

b. 32.5 μs

c. 40.5 μs
图10 17.4 mm厚盖板时不同时刻炸药内压力云图
Fig.10 Pressure distribution in explosive at different times with 17.4 mm thick cover plate

a. 31 μs

b. 34 μs

c. 42 μs
图11 20 mm厚盖板时不同时刻炸药内压力云图
Fig.11 Pressure distribution in explosive at different times with 20 mm thick cover plate
从
如
从仿真结果可以看出有限厚炸药在临界盖板厚度条件下,弯曲冲击波并未在轴线位置处发展为爆轰波,而是先在炸药底面附近发生衰减,同时向径向传播,随后弯曲冲击波从炸药底面开始向炸药内部传播,最终逐渐发展为爆轰波。随着盖板厚度的增加,射流前方的弯曲冲击波达到炸药背面时的压力不断下降,最终会出现弯曲冲击波从炸药底面回传时,由于稀疏波的作用,波阵面上的压力未继续增长不能发展为爆轰波的情况。
仿真得到的射流头部速度为5795 m·
考虑盖板强度,根据虚拟源点理论盖板厚度与射流的剩余射流头部速度关系为
(1) |
式中,,,和,其中为初始射流头部速度,mm·μ

a. 15 mm

b. 17.4 mm

c. 20 mm

d. 30 mm
图12 射流穿透不同盖板后的仿真结果
Fig.12 Simulation results of jet penetrating different cover plates
Note: δ is thickness of cover plate, vj is tip velocity of residual jet.
仿真和试验得到反应产物膨胀到直径1 m时的膨胀速度对比如
Note: δ is thickness of cover plate, ve is expansion velocity of product.

a. detonation

b. deflagration

c. burn
图13 仿真计算的反应产物的膨胀速度云图
Fig.13 Expansion velocity distribution of reaction products by simulation
由仿真得到的不同盖板厚度下弯曲冲击波波速和侵彻速度随位置的变化曲线如

图14 仿真得到的弯曲冲击波波速和侵彻速度随位置的变化曲线
Fig.14 Curves of velocity of bow shock and penetration velocity with position by simulation
Chic
为了分析炸药厚度对有限厚炸药起爆阈值的影响规律,对不同厚度TNT炸药进行仿真计算,仿真计算结果见
Note: L is thickness of explosive, δ is thickness of cover plate, vcr is expansion velocity of product, K is initiation threshold.
射流穿透盖板后在炸药中以定常状态持续侵彻,并且侵彻过程中侵彻速度变化很小,参照炸药的Pop曲
(2) |
式中,X为起爆深度,p为初始压力。忽略射流和炸药强度,根据Bernoulli方
(3) |
式中,ρj和ρe分别为射流密度和炸药密度,vj和u分别为射流头部速度和侵彻速度。根据炸药的临界起爆阈值K=v
(4) |
式中,a1为常数且a1=a+blg1/2。
由
(5) |
将
(6) |
式中,
有限厚炸药临界起爆阈值随厚度的拟合曲线如

图15 临界起爆阈值在不同炸药厚度下的拟合曲线和仿真试验结果
Fig.15 Fitting curve, simulation and experimental results of critical initiation threshold with different explosive thickness
采用拟合得到的a1和b值通过

图16 临界盖板厚度在不同炸药厚度下的理论计算和仿真试验结果
Fig.16 Theoretical calculation, simulation and experimental results of critical cover plate thickness with different explosive thickness
(1)采用Φ40 mm聚能装药形成的射流对不同厚度盖板覆盖下的TNT炸药进行了冲击试验,得到43 mm厚度TNT的临界起爆阈值为37 m
(2)射流侵彻有限厚炸药时,弯曲冲击波先与侵彻界面以相同速度运动,经过一定距离后弯曲冲击波波速超过射流在炸药中的侵彻速度并稳定传播,波阵面压力不断增加最终发展为爆轰波或者受到稀疏波作用发生衰减直至消失,并且射流速度越高,弯曲冲击波的压力增长越快。
(3)对于有限厚炸药,炸药厚度对炸药的临界起爆阈值具有较大的影响。有限厚炸药的临界起爆阈值和临界盖板厚度随炸药厚度的减小而增加,并且炸药厚度的对数与炸药临界起爆阈值对数近似呈线性关系。
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