月壤参数对月面着陆气囊缓冲性能的影响

为研究月壤参数对气囊缓冲性能的影响,根据“嫦娥三号”的着陆工况设计了月面着陆气囊,并基于可压溃泡沫模型建立了考虑月壤特性的气囊缓冲动力学模型。对不同月壤下气囊的缓冲过程进行分析,发现月壤越软有效载荷冲击加速度越小,但气囊会陷入月壤中,不利于对外排气,影响其缓冲效果。因此,采用气囊峰值压力、有效载荷最大加速度和最大下落高度3个指标对气囊缓冲性能进行综合评价,定量研究了月壤参数的影响规律。结果表明:月壤密度、剪切模量及屈服参数a₀和a₁对缓冲性能的影响较大,且对前两个指标为正影响,对后一个指标为负影响。进一步研究发现,这4个月壤参数与3个缓冲性能指标之间〖BHDWG8,WK10YQ,DK1*2,WK1*2D〗〖XCZX.TIF;%129%129〗听语音 聊科研与作者互动 均为指数函数关系。     

Investigation of normal,lateral, and oblique impact of microscale projectiles into unidirectional glass/epoxy composites

Spacesuits and spacecraft must endure high velocity impacts from micrometeoroids. This work considers the impact of 100 μm diameter projectiles into composite targets at velocities from 0.5 km/s to 2 km/s. This work begins by presenting an energy-based theoretical model relating depth of penetration (DoP) and impact force to impact velocity, characteristic time, and threshold velocity and force. Next, this work compares numerical simulations of normal impact on composites to the theoretical model. Numerical simulations are conducted with LS-DYNA and the well-known composite model, MAT-162. The numerical models consider unidirectional S2-glass fiber reinforced SC-15 epoxy composite laminates. The numerical model shows good correlation with the theoretical model. The numerical model also investigates lateral impact, parallel to the fiber direction, and oblique impact at angles from 30° to 82.5°. This work decomposes oblique impact into normal and lateral components, and compares them with normal and lateral impact results. The results show good correlation of the normal component of oblique results with the theoretical model. This numerical and theoretical study focuses on DoP, velocity, and penetration resistance force as functions of time. The theoretical model and numerical simulations are used to determine new DoP parameters: characteristic time of depth of penetration and threshold impact velocity. These models are a first step in developing the capability to predict DoP for oblique, microscale, high-speed impact on composite materials.     

An investigation on anti-impact and penetration performance of basalt fiber composites with different weave and lay-up modes

The woven basalt fiber composites (WBFC) and the unidirectional [0°/90°/45°/-45°]_s basalt fiber composites (UBFC) were prepared by hot-pressing. Three-point bending test, low velocity impact test, and ballistic test were performed to the prepared composites. After the tests, the specimens were recovered and analyzed for micromorphology. Three-point bending tests show that both the bending strength and stiffness of the WBFC surpass those of the UBFC. Low velocity impact test results show that the low velocity impact resistance to hemispherical impactor of the UBFC is higher than that of the WBFC, but the low velocity impact resistance to sharp impactor of the UBFC is lower than that of the WBFC. For the ballistic test, it can be found that the ballistic property of the UBFC is higher than that of the WBFC. After the tests, microscopic analysis of the specimens was applied, and their failure mechanism was discussed. The main failure modes of the UBFC are delamination and fibers breakage under the above loading conditions while the main failure mode of the WBFC is fibers breakage. Although delamination damage can be found in the WBFC under the above loading conditions, the degree of delamination is far less than that of the UBFC.     

满足大动压模拟要求的试验弹道优化设计

为了解决弹道导弹在高海拔发射场进行飞行试验时的大动压检验问题,提出一种模拟大动压条件的试验弹道设计方法。针对发射场的实际特点,建立残骸再入的动力学模型与落区边界模型;将大动压模拟条件转化为过程约束,提出一种主动段联合优化策略。基于自适应模拟退火算法,分别设计了三组满足不同大动压模拟条件和各项约束的试验弹道,并给出了对应的落区调整方案,验证了该方法的可行性。设计结果表明,最大动压主要出现在一级,一级最大负攻角增加,则最大动压也明显提高;同时调整发射方位角和二、三级程序角可以保证试验弹道满足弹头落点约束条件。     

强爆轰驱动超高速碎片发射装置设计因素分析

为了得到发射装置设计因素和超高速碎片性能间的关系,考虑了药型罩的材料、炸药种类、装药长径比、药型罩的锥角、药型罩的厚度、药型罩顶部靠近装药侧的曲率半径等设计因素,采用AUTODYNTM,结合正交试验,对超高速碎片的发射过程进行数值模拟。结果表明,3种发射装置结构分别可以提供质量为1. 533 g的紫铜碎片、速度为11. 649 km/s的铝碎片、动能为85. 6 k J的铝碎片; 2种发射装置结构均可以提供质量大于1 g、速度高于11 km/s的密实结构圆柱状碎片。验证了仿真方法的可信性,对影响碎片性能的设计因素进行了分析、排序,并得到了这些设计因素与碎片质量、速度、动能的关系。     

多空域窗射击技术研究

未来空域窗射击体制相对集火射击体制,提高了对机动目标的拦截概率,能够对付有限机动目标,然而依然难以对付具有高度机动能力的目标,尤其是有人驾驶飞机,如果在射弹飞行时间内进行拐弯、爬升、俯冲等强机动.为了进一步提高对目标的拦截概率,提出了多空域窗射击体制,即在传统火控系统中增加目标实时态势估计模块,实时预测目标在射弹飞行时间内的可能机动模型,并根据预测结果进行多个未来空域窗射击.     

基于最大后验概率候选集更换法的多故障诊断策略研究

给出了一种基于最大后验概率候选集更换法的多故障诊断策略,并深入阐述了基于最大后验概率候选集更换法的形式化描述,分析了对单故障诊断和多故障诊断的计算模型,提出了基本的故障诊断算法——改进二进制粒子群算法,并对抽象实例进行验证,结果表明,采用改进BPSO算法能有效地求解基于最大后验概率候选集更换法的多故障诊断问题。     

基于ANSYS／LS—DYNA的电子装备爆炸冲击振动损伤建模研究

针对电子装备爆炸冲击振动损伤问题,设计了损伤模拟的基本方案;采用ANSYS／LS—DYNA建立了二维“爆炸源-地面-弹性体-电子装备”模型;通过模型试验,获得了与实际爆炸冲击振动特性相吻合的加速度、位移和应力等数据。     

许地山小说中宗教救赎的流变

宗教救赎是许地山小说的创作意图和重要特质,它或隐或显地贯穿于许地山的整个小说创作中。他的小说对现实人生和终极理想进行了交错关注,而宗教救赎的意涵也在关注中不断变化。     

RBF神经网络在深V型滑行艇阻力预报中的应用

基于SV、JYK系列滑行艇的阻力、浸湿面积、航行纵倾角试验数据,采用RBF神经网络建立了深V型滑行艇阻力预报数值图谱;针对艇艉底部横向斜升角变化的有限试验数据,提出了一种基于小样本试验数据的阻力修正方法。试验表明,该方法对深V型滑行艇(折角线长度与最大折角线宽度比在4~5.5,面积负荷系数在5.5~7,重心纵向相对位置在3%~9%,艉部艇底斜升角在5°~25°之间变化)阻力预报是可行的。在相同精度下,针对该文研究的问题,RBF神经网络所需时间少于BP神经网络。