Effect of the casing on the initial parameters of the underwater explosion of a cylindrical charge of explosive

An experimental determination was made of the initial parameters of shock waves in water with the explosion of cylindrical charges of TNT in casings. It is shown that these parameters depend mainly on the dynamic rigidity of the material and the relative weight of the shell. It is established that during the process of the expansion of the casing of the charge with an explosion in limited volumes of water there is formed a region of extremely rapid expansion, whose boundary can be identified with the boundary between the detonation products and the water after destruction of the casing, coinciding in time with the arrival of the cavitation front.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 165–168, January–February, 1973.     

Deformation of rock in the explosion of a cylindrical charge in a coaxial cavity filled with liquid

A study is made of the effect of a water sheath around a cylindrical explosive charge on the parameters of shock waves in rocks. A coupled problem for the detonation-product-water-rock system is examined within the framework of continuum mechanics. A binomial isentropic equation is used for the detonation products, water is modeled by a Tate-type equation, and the rock is modeled by an elastoplastic medium which undergoes dilatation. A numerical solution is obtained by a finite-difference scheme. The dependence of the wave processes in the rock and the dimensions of the crushing zone on the radius of the water sheath is studied with the use of sandstone and siltstone as examples. Institute of Hydromechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 3, pp. 83–88, March, 1999.     

分段装药爆炸应变场与裂隙场分布规律

为探究分段装药爆炸应变场与裂隙场分布规律,采用数字图像相关分析方法与电子计算机断层扫描实验方法,分析了孔内分段装药爆炸全场应变传播规律,建立了爆后“岩石—爆炸裂隙”的三维重构模型,描述了爆炸裂纹位置与形态的空间分布情况,得到岩石材料爆炸裂隙的分形维数与损伤度。研究结果表明：分段装药改变了连续装药对介质的全场应变形态,由一次应变改变为两次应变,在满足第一段炸药对介质的破坏作用下,同时加大了第二段炸药对介质的作用效应;上分段装药占比0.4时,下分段介质受爆炸作用应变峰值更大,更好满足工程实践中下半段岩体对爆炸能量的需求;相同装药系数下,连续装药结构爆炸裂纹没有贯穿试件整体,炮孔封堵段的爆炸裂纹较少,分段装药结构下,由于提高了炸药的位置,使得上部分岩体能够更好地利用炸药爆炸的能量破碎岩石;分段装药岩石整体损伤度较连续装药提高了23.5%,其中上分段岩石损伤差异较大,分段装药上分段损伤度比连续装药提高46.4%。     

The shape of the throwout crater from the explosion of a cord charge in a two-layer medium

The problem concerning the explosion of a cord charge in the ground, with a hard upper layer, is considered in pulse formulation. A numerical solution is obtained and profiles are given for the throwout craters for several values of thickness of the layer and emplacement depth of the charge, in two limiting cases: when the resistance of the lower ground is negligibly small in comparison with the resistance of the layer and when the resistance of the ground and layer are quite close in magnitude.Translated from Zhurnal Prikladnoi Mekhanika i Tekhnicheskoi Fiziki, No. 2, pp. 143–146, March–April, 1973.     

圆柱装药在偏心定向起爆时水中近场压力特性

对UHL-5装药在侧向9点偏心定向起爆和几何中心点起爆时的水下爆炸近场峰值压力分布特性进行实验研究和数值模拟,得到2种起爆条件下不同距离与方位角测点处冲击波峰值压力和侧向9点起爆时的定向增益区域.结果表明,对于5 kg圆柱形UHL-5装药,采用侧向9点偏心定向起爆方式时,在爆距750 mm、方位角90°范围内的流场区域...     

Effect of rock shapes on brittle fracture using Smoothed Particle Hydrodynamics

Breakage of rocks or particulates plays a major role in various industries, such as mineral and ore processing. Many of the processes used for fracturing materials in these industries have the requirement to produce specified size and/or shape of the products. Numerical modelling can assist in understanding and predicting complex fracture processes, and can be used in designing the equipment and setting the process parameters to ensure desired product quality. In this paper, a mesh-free numerical method, called Smoothed Particle Hydrodynamics (SPH), is extended to predict impact fracture of rocks. SPH is a particle based Lagrangian method which is particularly suited to the analysis of fracture due to its capacity to model large deformation and track the free surfaces generated. A continuum damage model is used to predict the fracture of rocks. Evolution of damage is predicted using the strain history of each particle. Damage inhibits the transmission of tensile stress between particles, and once it reaches unity, the particle is unable to transmit tensile stress, resulting in a macro-crack. Connected macro-cracks lead to complete fragmentation.Firstly, an Unconfined Compressive Strength (UCS) test under uniaxial compression of a rock sample is modelled using SPH and compared against experiments to validate the capability of SPH for prediction of fracture in rocks. The SPH prediction matched the well-known experimentally observed diagonal fracture pattern. SPH is subsequently used to simulate brittle fracture of rocks during impact. Rock specimens of different shapes are examined to determine the effects of shape on both the fracture pattern and the energy dissipation during impact fracture. Rock shape is found to have considerable influence on the fracture process, fragment sizes, energy dissipation, and post-fracture motion of the fragments.     

Creep and long-time fracture of a cylindrical shell under external pressure in the presence of an aggressive medium

We consider the process of deformation and fracture of an oval ring modeling the behavior of a long cylindrical shell subjected to distributed external pressure. The shell deformation is studied in both the presence and absence of an aggressive medium. The hypothesis of nonlinear viscosity with a singular component is taken for the constitutive relation used to estimate the metal characteristics. This relation allows for the difference between the tensile and compression strength of the material. The singularity permits taking into account not only the nonlinear viscosity but also instantaneous fracture characteristics. We show that an aggressive medium can substantially decrease the shell operation life.     

Calculation of channel produced by explosion of a linear charge below the surface of an anisotropic medium

A study is made of the problem of determining the channel produced by the explosion of a linear charge below the surface of a homogeneous anisotropic medium, i.e., a medium in which the strength depends on the direction of the applied load. Examples of such media are single crystals of various materials, rocks, and thinly laminated rocks.     

Effect of bearing pressure on the strength of a rock mass containing cylindrical cuts

The three-dimensional problem of stress distribution in a rock mass in the vicinity of two cylindrical holes located in the zone of elevated mountain pressure is solved using the boundary-element method. The technogenic disturbance of the mass with regular strength anisotropy was estimated quantitatively using specially introduced parameters.     

Calculation of the motion in the near field of an explosion in a solid medium

Some results are presented of calculations of motions in the near field of an explosion in a solid body for which a previously obtained equation of state is employed. The corresponding theoretical and experimental results are compared.     

圆柱壳体装药偏心多点起爆下破片速度的分布

针对偏心起爆战斗部破片速度增益的问题,提出爆轰波碰撞形成马赫超压是引起破片速度增加的原因。利用AUTODYN软件,模拟偏心起爆战斗部从壳体径向膨胀、表面产生裂纹到最后形成破片的整个过程,并将模拟得到的破片速度与实验数据对比,两者吻合较好;简化Whitham方法并结合Gurney速度公式得到偏心起爆战斗部定向破片速度和定向区域的计算方法,同时在保证破片初速的前提下,研究偏心多点起爆下起爆点数的选择标准。研究结果表明：偏心多点起爆下定向破片初速增益约34%,定向区域范围约30°,起爆点数的选择与壳体长度和装药口径相关。