基于间接三轴拉伸破坏试验的某TATB基PBX强度准则适应性分析

强度问题关系炸药部件的结构完整性和服役安全性,是炸药部件结构强度评估的基础。基于单轴加载技术,设计了圆柱试件的端部约束拉溃试验,研究了三轴间接拉伸破坏时某TATB基高聚物粘结炸药(PBX)的强度特性。依据试验边界条件,利用有限元方法定量分析了临界载荷下试件内部的应力场,最后采用最先破坏位置的三向主应力数据分析了三种典型强度准则(Uniaxialstrength,Mohr-Coulomb,Twin-shear)描述三轴拉伸破坏的适应性。就安全阈度而言,现炸药工程中使用的Uniaxial-strength准则,三轴压缩时安全阈度最高,达43.77%,但也不能安全预测三轴拉伸应力下该PBX的破坏行为;就描述精度来看,Uniaxial-strength准则最优,Mohr-Coulomb准则次之,Twin-shear准则最差,试验值均比理论值偏大,三者依次为16.90%、19.62%和24.56%;试验中该TATB基PBX三轴拉伸应力下的强度为单轴拉伸强度的0.831倍,Mohr-Coulomb准则不能准确描述三轴拉伸应力下强度下限,分析表明静水压力的影响是造成这一结果的关键原因,建立高描述精度的多轴强度准则须考虑静水压力的影响。

Adaptability Analysis of Strength Criterion on TATB Based PBX by Indirect Triaxial Tensile Collapse Test

Strength plays an important role in structural integrity and safety for explosive parts, and is also the basis for estimation of the structural strength. Based on uniaxial loading technique, strength property of TATB based polymer bonded explosive(PBX)under triaxial tension stress state was studied by an end-restraint cylinder tension collapse method. The stress field under critical load was quantitatively analyzed through finite element simulation according to the tested boundary conditions. At last, the adaptability of three typical criterions(uniaxial-strength,Mohr-Coulomb,twin-shear)in strength analysis was illustrated using principal stresses of initial failure position. Results show that among these three criterions, uniaxial-strength criterion, which is most often used in explosive engineering, has the best safety threshold, about 43.77%, under triaxial compression stress state, but even so, it still can not supply a safety forecast for this TATB based PBX strength failure under triaxial tension stress state. For the representation accuracy, uniaxial-strength criterion has the best precision with an error about 16.90%, Mohr-Coulomb criterion and twin-shear criterion take second and third place with the error of 19.62% and 24.56%, respectively. Moreover, the triaxial tension strength is 0.831 times of the uniaxial tension strength, while Mohr-Coulomb criterion can not predict the strength lower bound precisely. It may be mainly caused by hydrostatic pressure,which must be considered further to establish multiaxial strength criterion with high precision.