爆炸载荷作用下铝蜂窝夹芯板动力响应研究

采用自行设计的冲击摆实验系统对铝蜂窝夹芯板在爆炸载荷作用下的动力响应进行了系统实验研究,给出了面板和铝蜂窝不同区域的不同变形模态,得到了不同炸药当量对铝蜂窝夹芯板动态响应的影响规律,证实了铝蜂窝夹芯板产生较大塑性变形时,比一般的结构具有更好的能量吸收特性.并利用LS-DYNA对其动力响应进行了数值仿真,考察了炸药起爆、接触界面及上表面接触力对夹芯板变形影响的全过程,得到了板中心的最终变形和芯层的变形模式,与实验结果吻合较好.     

爆炸载荷作用下铝蜂窝夹芯板的动力响应

为了考察铝蜂窝夹芯板在爆炸载荷下的动态响应,采用自行设计的冲击摆系统,用激光位移传感器测定了爆炸载荷作用在铝蜂窝夹芯板上的冲量,对夹芯板的变形和失效模式进行了归类和分析,并就芯层的几何尺寸、炸药当量及板厚对其响应的影响进行了系统研究。给出的理论分析结果与实验结果吻合较好。     

梯度蜂窝夹芯板在爆炸荷载作用下的动力响应

利用弹道冲击摆锤系统对分层梯度蜂窝夹芯板在爆炸荷载下的动力响应进行了实验研究,分析了梯度蜂窝夹芯板在爆炸荷载作用下的变形失效模式,并与传统非梯度蜂窝夹芯板的抗爆性能做了对比。通过一维应力波理论,分析了应力波在梯度芯层中的传播规律。应力波透射系数在梯度试件中比非梯度芯层中小,而且相对密度递减的芯层组合有最小的应力波透射系数。综合考虑结构变形失效模式,后面板挠度,芯层压缩量以及应力波传播特点得到:分层梯度蜂窝夹芯板的抗爆性能明显优于传统的非梯度夹芯板,在所研究的荷载范围内,芯层相对密度从大到小排列试件的抗爆性能相对较好。     

低速冲击下负泊松比蝴蝶形蜂窝夹芯板的动力响应

为了研究负泊松比蝴蝶形蜂窝夹芯板在低速冲击下的动力学响应,采用质量-弹簧模型获得了冲击器与蜂窝夹芯板之间的接触力,同时基于哈密顿原理和一阶剪切变形理论推导了负泊松比蝴蝶形蜂窝夹芯板的运动方程,采用Navier法和Duhamel积分对蜂窝板的振动位移进行了理论解析求解。在理论验证方面,蜂窝夹芯板前5阶固有频率的数值模拟结果与理论模型计算结果的最大相对误差为6.52%,蜂窝夹芯板中心最大横向位移的数值模拟结果与理论模型计算结果的最大相对误差为6.84%,理论模型求解的接触力与文献得到的接触力的最大相对误差为8%,验证了理论模型的有效性。结果表明,随着球形冲击器冲击速度的递增,蜂窝夹芯板的最大横向位移呈现递增的规律。而在相同冲击载荷下,蜂窝夹芯板的抗冲击特性随着胞元壁厚的增大而增强,随着胞元角度的增大而减弱;随着负泊松比蝴蝶形蜂窝夹芯板长宽比以及夹芯层与顶部蒙皮层的高度比的增大,蜂窝夹芯板的横向位移减小,冲击器与蜂窝夹芯板之间的接触力增大。当蜂窝夹芯板的宽长比从1∶1变化到1∶2时,蜂窝夹芯板最大横向位移减小6.1%;当顶部蒙皮层与蜂窝芯层的高度比从1∶6变化到1∶14时,蜂窝夹芯板的最大横向位移减小5.4%,这表明蜂窝夹芯板的抗冲击性能增强,吸能效果明显。

     

高效能电炮实验装置的研制

较全面地开展了电炮加载技术的实验研究,解决了低电感开关、电容器和外回路设计中的关键技术,使整个回路短路电感为38nH,接近电容器的内电感30nH,最大放电电流接近兆安。优化设计后的装置在储能仅为14.4kJ的情况下,在25 kV充电电压下,在1.2μs内可将直径10mm,厚度0.1 mm的Mylar膜飞片加速到10 km/s,通过光纤测试发现飞片在飞行3mm后平面度优于24ns。根据测试的数据进一步改进了桥箔板和炮膛的设计,使得在相同加载条件下,飞片的加速历史几乎完全重合,其弹道稳定性优于气炮等加载装置。同时解决了电炮加载下的关键诊断测试技术。本文工作为进一步开展高应变率加载下材料动力学响应和炸药冲击感度研究提供了新的有效的加载手段,同时也为研究更高储能的电炮实验装置奠定了基础。     

考虑蜂窝高度效应的蜂窝夹芯板稳定性分析

蜂窝芯层等效弹性参数因受表板影响与其高度紧密相关,而传统蜂窝夹芯板稳定性模型未对其加以考虑。本文基于精化锯齿层合板理论,建立了蜂窝夹芯板稳定性模型。模型借助于解析均匀化方法获取蜂窝芯层等效模量,并因引入该方法而能够反映由蜂窝高度改变引起的蜂窝芯子等效模量变化对屈曲载荷产生的影响,即捕捉到了蜂窝芯子的高度效应。以四边简支蜂窝夹芯方板受单向面内压缩载荷作用为例进行了算例分析。算例结果表明,蜂窝芯子高度效应在蜂窝高度较低时明显,随着蜂窝高度增加,高度效应逐渐减弱。此外,高度效应在蜂窝芯层厚度比例较大时明显,随着蜂窝芯层厚度比例的持续下降,高度效应减弱直至消失。     

60kJ高速电炮的装置性能

研制了具有较高驱动能力的100kV/60kJ高速电炮装置。性能实验结果表明,飞片的完整性和飞行平面度均较好,其中平面度优于42ns。该装置可将直径18mm、厚0.15mm的Mylar膜飞片(约53mg)加速到8.1km/s,将直径12mm、厚0.2mm的Mylar膜飞片(约32mg)加速到9.6km/s,表明该装置具有较高的加载能力。本项工作可为开展高应变率加载下的材料动力学响应及其他相关研究提供有效的加载手段。     

电炮驱动薄膜飞片的运动速度

用双灵敏度激光干涉测速技术测量了充电电压为18 kV的电炮加载下薄膜飞片自由面的速度历史。介绍了相关的实验装置及测量方法,给出了实验结果,并讨论了影响测速的一些关键技术。整个测速过程约为1.6 s,最终速度为6.7 km/s。     

电炮驱动Mylar膜飞片完整性实验研究

利用铜靶验证法研究了加速腔材料、结构以及桥箔尺寸与加速腔尺寸的匹配关系等因素对电炮驱动飞片完整性的影响。实验结果表明,对于每秒数公里的高速下,加速腔材料、预制刃口与否对飞片的完整性影响不大,当加速腔尺寸稍小于桥箔尺寸时能够获得非常完整且呈圆形的飞片。光纤探针测量结果显示,此条件下,飞片具有较好的平面度,从该角度讲,电炮是一种较好的平面波发生器。     

爆轰载荷作用下球形空腔的动力响应

以位移为未知量,利用拉普拉斯变换法,研究了球形空腔在爆轰载荷作用下的动力响应问题,获得了问题的参数解,并通过直接代入,验证了解的正确性。     

Dynamic response of doubly-curved anisotropic sandwich panels impacted by blast loadings

Problems related with the modeling and dynamic response to blast loadings of doubly-curved sandwich panels with laminated face sheets are developed. In this respect, the implications of the panel curvature, of anisotropy and stacking sequence of face sheets, of transverse orthotropy of the core, and of structural damping on dynamic response to time-dependent loads are highlighted. As concerns the blast pulses considered in this analysis, these are related to in-air explosions or of traveling shock-waves. Other parameters, mainly geometrical, are also considered in the numerical simulations, and their implications on the dynamic response are put into evidence. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of advanced sandwich shells operating in a dynamic environment. Moreover, the closed-form solutions developed in the paper, can serve as excellent references for comparison with numerical based solutions.     

Dynamic crushing of sandwich panels with prismatic lattice cores

The dynamic out-of-plane compressive response of stainless steel corrugated and Y-frame sandwich cores have been investigated for impact velocities ranging from quasi-static to 200 ms⁻¹. Laboratory-scale sandwich cores of relative density 2.5% were manufactured and the stresses on the front and rear faces of the dynamically compressed sandwich cores were measured using a direct impact Kolsky bar. Direct observational evidence is provided for micro-inertial stabilisation of both topologies against elastic buckling at impact velocities below 30 ms⁻¹. At higher impact velocities, plastic waves within the core members result in the front face stresses increasing with increasing velocity while the rear face stresses remain approximately constant. While the finite element calculations predict the rear face stresses and dynamic deformation modes to reasonable accuracy, the relatively slow response time of the measurement apparatus results in poor agreement between the measured and predicted front face stresses. The finite element calculations also demonstrate that material strain-rate effects have a negligible effect upon the dynamic compressive response of laboratory-scale and full-scale sandwich cores.     

冰雹撞击下泡沫铝夹芯板的动态响应

在传统单层泡沫夹芯结构的上、下面板之间插入中面板,通过移动中面板的位置,获得了外形尺寸相同、质量相等的5种构型夹芯结构,其上层芯材与芯材总厚度比分别为0:30、10:30、15:30、20:30和30:30。在量纲分析的基础上,应用非线性动力有限元程序LS-DYNA对5种构型夹芯结构进行了冰雹撞击数值分析,研究了中面板位置对夹芯板的能量吸收、能量耗散和动态响应的影响。结果表明:中面板的存在对下层芯材能形成有效的保护;随着中面板位置由上向下移动,夹芯板的抗撞击性能呈现由大到小再增大的态势。数值计算结果对抗冰雹撞击夹芯结构的优化设计具有一定的参考价值。     

Dynamic response of anisotropic sandwich flat panels to underwater and in-air explosions

The problem of the dynamic response of flat rectangular sandwich panels subjected to underwater and in-air explosions is analyzed. The study is carried out in the framework of a geometrically non-linear model of sandwich structures featuring anisotropic laminated face sheets and an orthotropic core, in conjunction with the unsteady pressure generated by an explosion. Effects of the core and of the orthotropy of its material, as well as those related to the ply-thickness, directional material property and stacking sequence of face sheets, geometrical non-linearities and of the structural damping ratio are investigated, and their implications upon the dynamic response are highlighted. To the best of the authors’ knowledge, the specialized literature addressing the dynamic response of sandwich structures to underwater and in-air explosions is rather scanty. This work is likely to fill a gap in the specialized literature on this topic.     

Design of metallic textile core sandwich panels

Metallic sandwich panels with textile cores have been analyzed subject to combined bending and shear and then designed for minimum weight. Basic results for the weight benefits relative to solid plates are presented, with emphasis on restricted optimizations that assure robustness (non-catastrophic failure) and acceptable thinness. Select numerical simulations are used to check the analytical results and to explore the role of strain hardening beyond failure initiation. Comparisons are made with competing concepts, especially honeycomb and truss core systems. It is demonstrated that all three systems have essentially equivalent performance. The influence on the design of a concentrated compressive stress that might crush the core has been explored and found to produce relatively small effect over the stress range of practical interest. “Angle ply” cores with members in the ±45° orientation are found to be near optimal for all combinations of bending, shear and compression.