点阵增强型复合材料夹层结构的力学性能实验与分析

采用真空导入成型工艺,制备出在面板与芯材界面上具有创新构型的点阵增强型复合材料夹层结构。对其面板拉伸性能、夹层结构剪切与平压性能进行了实验研究,得出点阵增强型复合材料夹层结构经树脂柱增强后,剪切与平压性能均得以提高的结论。对不同跨高比复合材料夹层结构开展了三点与四点弯曲实验,研究其典型受力破坏形态与机理。基于Eshelby等效夹杂原理,采用Mori-Tanaka方法求解了点阵增强型复合材料夹层结构经树脂柱增强后的剪切性能。利用经典夹层梁理论和非线性有限元模拟方法,预估了试件抗弯刚度与受弯极限承载力,理论分析与实验结果较吻合。     

卵形杆弹对铝靶的斜侵彻

在Lagrange有限元基础上,扼要介绍了一种适用于三维斜侵彻数值模拟计算的滑移面处理技术。该方法放弃了传统滑移计算中从单元的设置,而代之以预设从节点,从而避免三维斜侵彻数值计算中主从单元的相交、滑移面的识别、修正与再定义的困难。在确保计算精度的同时,有效地提高了计算效率。卵形杆弹对铝靶侵彻的系列数值模拟计算表明,无论对于正撞击或斜撞击,本文中所获结果与实验结果都有良好的一致性,这说明本文中所述方法和所建程序的合理性和有效性,为侵彻贯穿过程的数值分析提供了一种实用和有效的手段。     

试油测试射孔管柱的间隙元分析

建立了管柱接触非线性问题的间隙元法。用此方法对试油测试射孔管柱的受力状态进行了分析，并通过现场应用实例证明了此方法的可靠性和准确性。根据此方法开发的应用软件可为井下管柱的结构设计提供理论依据。     

Measurement and Modelling of Gas Condensate Flow Around Rock Perforation

In the petroleum production industry wells are mostly cased and perforated in the producing formation. Perforation characteristics such as size, length, number of perforation tunnels and their arrangements as well as fluid and rock properties determine fluid flow behaviour in the wellbore region, hence, well productivity. Flow of gas and condensate around a perforation tunnel (including the damaged zone) has been studied by performing steady-state core experiments and simulating the results numerically, using a finite element modelling approach. The model allows for the changes in fluid properties and accounts for the coupling of the two phases and the inertial effect using a fractional flow based correlation. The results indicated that different sets of thickness-permeability (h−k) values obtained from matching single-phase flow performance could be assigned to the damaged zone around perforation to represent the two-phase flow performance. The status of the tip of the perforation for two extreme cases of totally closed and fully open was investigated and found to have a minimal effect on the performance of the system.     

Attenuation of weak shock waves along pseudo-perforated walls

In order to attenuate weak shock waves in ducts, effects of pseudo-perforated walls were investigated. Pseudo-perforated walls are defined as wall perforations having a closed cavity behind it. Shock wave diffraction and reflection created by these perforations were visualized in a shock tube by using holographic interferometer, and also by numerical simulation. Along the pseudo-perforated wall, an incident shock wave attenuates and eventually turns into a sound wave. Due to complex interactions of the incident shock wave with the perforations, the overpressure behind it becomes non-uniform and its peak value can locally exceed that behind the undisturbed incident shock wave. However, its pressure gradient monotonically decreases with the shock wave propagation. Effects of these pseudo-perforated walls on the attenuation of weak shock waves generated in high speed train tunnels were studied in a 1/250-scaled train tunnel simulator. It is concluded that in order to achieve a practically effective suppression of the tunnel sonic boom the length of the pseudo-perforation section should be sufficiently long. Received 23 June 1997 / Accepted 16 September 1997     

金属多级类蜂窝的压溃行为研究

通过实验和数值模拟方法系统研究了单胞壁开孔金属多级类蜂窝与双胞壁开孔金属多级类蜂窝的压溃行为. 重点分析了试件尺寸、开孔位置、孔偏距和孔梯度等因素对多级类蜂窝力学性能的影响. 结果表明,多级类蜂窝的压溃过程可分为3个阶段:弹性变形、屈曲变形以及密实;单胞壁开孔多级类蜂窝的压溃过程趋向于渐近内凹压溃,而双胞壁开孔多级类蜂窝趋向于轴向压溃;试件尺寸对多级类蜂窝的力学行为有明显的影响,当胞元数达到一定数目时,其力学性能几乎与蜂窝胞元数无关. 单胞壁开孔多级类蜂窝的峰值应力大于双胞壁开孔多级类蜂窝的峰值应力,但其平均压溃应力小于双胞壁开孔多级类蜂窝的平均压溃应力;与传统蜂窝相比,蜂窝胞壁开孔设计降低了蜂窝材料的比吸能;孔偏距的存在导致单胞壁开孔多级类蜂窝的峰值应力降低,但随着孔偏距的增加其平均压溃应力呈先减低后增加趋势;多梯度孔设计对多级类蜂窝材料的力学性能有重要影响,与均匀孔多级类蜂窝相比,正梯度孔分布设计降低了多级类蜂窝峰值应力,但提高了其平均压溃应力;多梯度孔分布设计对多级类蜂窝的峰值应力和平均压溃应力影响不大.      

Deformation and Failure Modes of Soft Steel Projectiles Impacting Harder Steel Targets at Increasing Velocity

The present paper describes an experimental and numerical study concerning the impact of blunt steel projectiles against harder steel plates, at impact velocities between 200 and 800 m/s. In contrast with previously published observations, three modes of deformation and failure of the soft steel projectiles were observed in the present study. These included: Taylor cylinder mushrooming, sunflower-like petalling and plugging perforation. Individual velocity ranges and the transitions between the deformation/failure modes are identified by both experiments and numerical simulations. Complex material failure mechanisms of projectile and target play conflicting roles in the various penetration stages. Johnson–Cook models of strength and accumulative damage failure are employed in 3D numerical simulation to describe material behavior of both projectile and target. Computational evolutions of each scenario are offered in detail to understand the deformation and failure of projectile and target plate.     

球形塑性薄壳在平头圆柱体冲击下贯穿过程的研究

对球形塑性壳在平头圆柱体冲击下的动力贯穿行为进行了分析．通过引入等度量变换,给出了壳体的变形模态．在此基础上对球壳在平头圆柱体撞击下的贯穿机制进行了分析研究,给出了贯穿模型,由此结合Hamilton原理,导出了运动方程组．采用Runge-Kutta方法求解了该方程组,最后分别给出了贯穿时间-弹体初速度;残余窝陷半径-弹体初速度;贯穿后弹体剩余速度-弹体初速度的关系曲线．     

混凝土板在接触爆炸作用下的震塌和贯穿临界厚度计算方法

采用刚塑性模型描述介质的动力学行为，结合不可压缩条件和质量守恒条件及边界条件，构造塑性区的动力学许可速度场；利用极限平衡原理推导动力学许可速度场所对应的介质抗力的量纲一表达式；根据初始条件和边界条件，求解运动方程，分别得到爆炸震塌的临界厚度和爆炸贯穿的临界厚度，并推得能够反映爆炸源参数和材料参数综合性质的量纲一冲击因子。将推得的计算公式与经验公式对比分析，证明本文计算结果合理，推导的计算公式揭示了经验公式的物理本质，且具有较为广泛的适用范围。     

动能深侵彻弹的力学设计(Ⅱ):弹靶的相关力学分析与实例

介绍了作者关于动能深侵彻弹研究的部分工作。单纯动能弹侵彻存在侵彻深度上限，在技战术指标一定的前提条件下，弹体结构的优化可令动能深侵彻弹尽可能实现最大侵深。其中弹体结构的力学设计尤为重要，如弹形、弹材、质量比、长径比等。进一步开展弹体结构设计的力学研究，包括头部设计、战斗部后盖、装填比、弹形和弹材、侵彻效应中的尺度律、混凝土靶的设计，最后给出若干实例。