化爆冲击波在T型通道内到时规律的实验研究

对空气冲击波在T型坑道内传播的到时规律及其影响因素进行了实验研究,在量纲一分析基础上建立了简化的工程模型。通过对实验数据拟合建立了可以对高能炸药在T型坑道内爆炸产生的空气冲击波到达时间进行预估的公式,利用该公式可以估算空气冲击波在T型坑道内的传播速度。     

圆柱形弹药空气中爆炸相似性规律

针对战场损伤试验中弹药费用高、使用风险系数大的问题,采用量纲分析的方法对圆柱形弹药相似性模型的建立方法进行分析,研究原型同相似性模型之间冲击波峰值压力的关系,利用有限元仿真软件AUTODYN对冲击波传播过程进行数值仿真,并结合实弹试验数据对相似模型的有效性进行验证。研究结果表明,AUTODYN仿真结果同量纲分析结果一致,同时与实弹试验结果也吻合较好,说明在实际试验中可以使用缩比模型替代原型进行试验。该研究为弹药缩比模型在战场损伤试验中的使用提供了理论基础,具有一定的工程价值。     

Identification of the plastic behavior of aluminum plates under free air explosions using inverse methods and full-field measurements

This article describes an inverse method for the identification of the plastic behavior of aluminum plates subjected to sudden blast loads. The method uses full-field optical measurements taken during the first milliseconds of a free air explosion and the finite element method for the numerical prediction of the blast response. The identification is based on a damped least-squares solution according to the Levenberg–Marquardt formulation. Three different rate-dependent plasticity models are examined. First, a combined model based on linear strain hardening and the strain rate term of the Cowper–Symonds model, secondly, the Johnson–Cook model and finally, a combined model based on a bi-exponential relation for the strain hardening term and the strain rate term of the Cowper–Symonds model. A validation of the method and its sensitivity to measurement uncertainties is first provided according to virtual measurements generated with the finite element method. Next, the plastic behavior of aluminum is identified using measurements from real free air explosions obtained from a controlled detonation of C4. The results show that inverse methods can be successfully applied for the identification of the plastic behavior of metals subjected to blast waves. In addition, the material parameters identified with inverse methods enable the numerical prediction of the material’s response with increased accuracy.     

Experimental data on stress-wave parameters in the earth due to underground and surface explosions

Experimental data on the parameters of stress waves in sandstone and clay ground are compared when charges of from 0.2 kg to 200 kg of TNT are exploded.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 9, No. 4, pp. 65–67, July–August, 1968.     

Nonstationary deformation of an elastic plate with a notch under the action of a shock wave

The behavior of a thin elastic plate with a rectilinear notch under the action a weak shock wave in air is studied experimentally. A technique is developed for this purpose. The effect of the notch on the strain state of the plate is analyzed __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 11, pp. 99–104, November 2007.     

Shock-wave structure in the near zone upon explosion of spatial charges in air

Profiles and values of pressure in shock waves are determined for the case of spherical, linear, and spatial charges, such as a coil of a bulk spiral and plane annular coils and Archimedes’ spiral of various lenths, exploded in air. In the case of explosion of rings and spirals, a complex wave structure in the form of a sequence of several shock waves is registered near the charges along the spiral axes; a weaker attenuation of shock waves with distance and pressure amplitudes two to three times higher than in the case of a spherical charge of the same mass are observed. It was found that an increase in the length of a plane spiral does not lead to an increase in the maximum pressure in the shock wave at distances of the order of several pitches of the spiral from its plane. With distance from spatial charges of different shape but identical mass, the pressure values in the shock-wave fronts coincide and tend asymptotically to the parameters of a spherical explosion with a significant increase in the duration of a wave packet generated by the spatial charge. Dependences for evaluation of shock-wave pressure amplitudes in the near zone of the explosion are presented. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 5, pp. 81–90, September–October, 2000.     

爆炸应力波作用下动、静裂纹相互作用的实验研究

采用数字激光动态焦散线测试系统,研究爆炸应力波作用下动裂纹与预制静裂纹(水平夹角为90°、150°)相互作用机理,以及裂纹扩展的动态行为。结果表明:(1)在动、静裂纹贯通之前,静裂纹两端便出现焦散斑,动、静裂纹贯通以后,静裂纹沿爆炸应力波传播方向扩展,并且扩展速度小于动裂纹扩展速度,也小于无静裂纹时动裂纹扩展速度; (2)静裂纹存在时,动裂纹扩展的总体长度减小。动裂纹起裂时间缩短,扩展速度基本不受静裂纹的影响,裂纹应力强度因子值大于静裂纹两端值; (3)随着静裂纹水平夹角的增大,动、静裂纹贯通时动裂纹沿水平方向偏转距离增大,静裂纹B端反向扩展与动裂纹相互“咬合”,C端裂纹扩展位移和速度增大。

     

Nonlinear longitudinal current in the Maxwellian plasma generated under the action of a transverse electromagnetic wave

The nonlinear interaction between an electromagnetic field and collisionless classic and quantum Maxwellian plasmas is analyzed. Formulas for calculating the electric current are derived. The nonlinearity turns out to lead to generation of a longitudinal electric current aligned with the wave vector. This current is orthogonal to the well-known transverse current obtained in the linear analysis. The current densities for the classic Maxwellian plasma and the plasma with an arbitrary degree of degeneration of the electron gas are graphically compared. The classic and quantum plasmas are also compared. The current density as a function of the dimensionlesswavenumber is investigated for various oscillation frequencies of the electromagnetic field.     

水击驻波场中分散相颗粒的运动分析

根据水击在管段内形成的驻波场现象,分析了流体内分散相颗粒受到的驻波作用力;运用李雅普诺夫稳定判据研究了颗粒积聚与分离的机理;考虑到颗粒运动方程的严重刚性而很难进行数值求解,采用相空间和非对称分析方法获得了分散相颗粒的运动轨迹近似解,并进行了实验验证。结果表明:水击驻波场中分散相颗粒的受力方程中惯性项对颗粒初始运动速率的影响不可忽略;在水击驻波波节的±λ/4范围内,分散相颗粒经过一定的时间会发生积聚,其运动速度呈对称分布,最大速度出现在3λ/8位置处;随着分散相颗粒粒径和密度等物性参数以及水击驻波的频率和连续相初始速度的增大,颗粒达到平衡位置的时间呈减小趋势,且连续相的初始速度对颗粒到达波节时间的影响显著。     

Penny-shaped crack at the interface between elastic half-spaces under the action of a shear wave

The three-dimensional problem of elasticity for a bimaterial body with a penny-shaped crack at the interface under the action of a normal harmonic shear wave is solved by the boundary-element method. The distribution of displacements of crack faces and tractions and displacements at the interface is analyzed