爆炸成型弹丸对Al2O3装甲陶瓷材料的侵彻实验研究

用爆炸成型弹丸(explosively formed projectile, EFP)对Al2O3装甲陶瓷材料进行了侵彻（depth of penetration, DOP）实验,得到了99Al2O3装甲陶瓷对模拟EFP的质量防护因数和差分防护因数及他们随陶瓷块厚度的变化规律,初步评估了99Al2O3装甲陶瓷对EFP的抗侵彻性能,解释了装甲陶瓷对EFP的抗侵彻过程和机理。研究结果表明,增加约束可以提高陶瓷的抗侵彻性能。     

扁球面网壳的混沌运动研究

在圆形三向网架非线性动力学基本方程的基础上,用拟壳法给出了圆底扁球面三向网壳的非线性动力学基本方程．在固定边界条件下,引入了异于等厚度壳的无量纲量,对基本方程和边界条件进行无量纲化,通过Galerkin作用得到了一个含二次、三次的非线性动力学方程．为求Melnikov函数,对一类非线性动力系统的自由振动方程进行了求解,得到了此类问题的准确解．在无激励情况下,讨论了稳定性问题．在外激励情况下,通过求Melnikov函数,给出了可能发生混沌运动的条件．通过数字仿真绘出了平面相图,证实了混沌运动的存在．     

桩基完整性测试的非线性最小二乘优化方法

针对桩基检测中低应变反射波法存在的应力波被桩土吸收和散射而衰减问题,把包含桩土衰减系数和介质不连续界面反射系数的反射波方程转化为非线性最小二乘优化问题,并采用信赖域法进行求解。由于采用信赖域法并采用了Gauss-Newton方向定义信赖域二维子空间,具有较好的收敛速度。通过模型桩算例表明该方法是确实可行的。     

Plastic-strain evolution for cyclic loading based on the equations of the field theory of defects

A relation governing the plastic-strain evolution under applied stresses is obtained within the field theory of defects to analyze the specific features of deformation under sign-varying cyclic loading. The effect of the applied stress amplitude, loading frequency, and cycle skewness on the deformation process under uniaxial loading conditions is studied. Specific features of the plastic-strain evolution in a stable deformation process are considered, and the time to failure of the system in an unstable process is determined. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 3, pp. 112–118, May–June, 2006.     

On the relationship between the work of adhesion and the critical shear stress for the onset of flow instabilities

The relationship between the critical shear stress for the onset of flow instabilities and the work of adhesion at the interface has been evaluated experimentally for a series of polyolefins on several steels, brasses, and coated steels. The critical shear stress was considerably affected by the chemical nature of the die. Low-surface-energy materials were found to produce smooth extrudates presumably by inducing slippage at the wall. Steel, tungsten carbide, and brass surfaces promoted sharkskin defect at shear stresses above the first critical shear stress. A linear relationship between the critical shear stress and the work of adhesion was found to be valid for values of work of adhesion smaller than approximately 30 mN/m. This indicates that slippage occurs due to a breakdown of the adhesion at the interface. For values of work of adhesion greater than approximately 30 mN/m a stronger interaction at the interface may induce a cohesive failure at the interface and subsequently, extrudate distortions.     

Bending of elastic plates with a physically nonlinear inclusion

An infinite elastic isotropic plate with an elliptical, physically nonlinear inclusion loaded at infinity by uniformly distributed moments is considered. Surface loads are absent. The problem of the stress-strain state of the plate is solved in a closed form. It is shown that, for reasonably general stress-strain relations for the inclusion, the bending-moment field (and the corresponding curvatures) in the inclusion is homogeneous. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 6, pp. 152–157, November–December, 2006.     

Bitumen/polyethylene blends: using m-LLDPEs to improve stability and viscoelastic properties

The stability and the rheological properties of blends of a 60/70 penetration-grade bitumen with conventional HDPEs and metallocene catalysed LLDPEs (m-LLDPE) are investigated. Considerably better stability results are obtained using m-LLDPEs instead of conventional polyethylenes, allowing one to avoid phase separation of the emulsion-like system during storage at high temperature. Thermodynamical interaction between bitumen and polyethylene is discarded as a cause of the observed difference, because the solubility parameter is practically the same for all the investigated polyethylenes. The result is explained on the basis of the lower melt elasticity of m-LLDPEs (attributed to their narrow molecular weight distribution), which facilitates the drop breakup during mixing process. The modification of bitumen with any of the m-LLDPEs considered in this work gives a new material with considerably improved viscoelastic properties.     

Bending of Composite Plates under Static and Dynamic Loading

The stationary bending of a two-dimensional elastic system of joined rectangular plates with different mechanical properties and boundary conditions is studied. A technique for solving the corresponding problem is proposed. It is based on approximate approaches in combination with a generalization of the force method. It is established that the static strain state of the system is essentially dependent on the difference between the elastic moduli of the constituent plates. It is also shown that with certain boundary conditions, the dependence of the first resonant frequency on the relative position of plates along the contact line is nonmonotonic__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 1, pp. 77–84, January 2005.     

Numerical modeling of a turbulent flow behind a heated grid

A numerical model of the dynamics of turbulence and temperature fluctuations behind a heated grid located in a wind tunnel is constructed on the basis of closed Kármán-Howarth and Corrsin equations. Results calculated by this model are in reasonable agreement with available experimental data. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 118–126, May–June, 2009.     

40Cr材料动态起裂韧性KId（）的实验测试

描述了利用Ｈｏｐｋｉｎｓｏｎ压杆技术加载三点弯曲试样测试４０Ｃｒ，材料动态起裂韧性ＫＩｄ（）的试验方法。试样上的动态载荷历程由Ｈｏｐｋｉｎｓｏｎ杆直接测得，并分别代入动态有限元程序及近似公式求得动态应力强度因子历史；由贴在试样裂尖附近的应变片确定起裂时间，最终确定起裂时的动态应力强度因子值，即动态起裂韧性ＫＩｄ（）。试验结果表明:利用Ｈｏｐｋｉｎｓｏｎ压杆技术加载三点弯曲试样测试材料动态起裂韧性的方法是可行的，起裂时，动态有限元的位移法、应力法及近似公式法求得的动态应力强度因子值比较吻合；在本文的载荷速率下，４０Ｃｒ材料动态起裂韧性ＫＩｄ（）与准静态裂韧性ＫＩｄ（）相比，降低了约２８％。