共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Experimental Mechanics - In this study, the effect of fragment or bullet impact before blast loading on laminated glass is studied experimentally. First, laminated windows consisting of two 3.8 mm... 相似文献
4.
5.
弹性撞击作用下弯扭耦合梁的动力响应 总被引:1,自引:0,他引:1
对于质量块以一定初速度撞击悬臂梁端部问题,基于弯扭耦合Timoshenko梁模型,把质量块与悬臂梁作为一个整体振动,动力响应以Duhamel积分表示,使用模态叠加法给出动力响应与撞击力的结果.对于悬臂梁受质量块撞击的算例,分别分析了弯扭耦合梁、弯扭耦合系数很小的梁和各向同性Timoshenko梁,对比讨论了撞击力结果. 相似文献
6.
7.
低速冲击下复合材料合板的响应过程模拟 总被引:4,自引:0,他引:4
运用一种精度较高的高阶位移模型分析了复合材料层合板在低速击下的响应过程,该位移模型能够同时考虑层间正应力和横向剪应力,另外,采用修正的Hertz接触定律与Newmark积分方法相结合,建立了冲击接触的有限元模型,本文的数值模拟计算结果与解析结果相比较证明了该方法的有效和精确性。 相似文献
8.
通过在有限元软件Abaqus/Explicit中编写用户材料子程序VUMAT,建立了一种基于能量演化的复合材料低速冲击渐进损伤模型.该模型以三维Hashin准则来预测层内损伤的起始,以一种简化的损伤变量来模拟层内损伤的演化,将具有双线性牵引-分离本构的零厚度界面单元插入层间来模拟分层损伤.采用该模型对14.7 J冲击能量下的纤维增强复合材料低速冲击过程进行了仿真分析,计算得到的冲击力-时间曲线、能量-时间曲线和损伤分布与试验结果吻合较好.根据数值模拟结果,分析了纤维、基体和分层损伤的扩展规律,为低速冲击下的复合材料结构设计提供了理论依据. 相似文献
9.
车辆与轨道的动态相互作用,是铁路轮轨接触式运输系统中最基本的问题之一,它直接制约着铁路运营速度的提高和运载重量的增加,也影响着铁路安全运行。本文采用有限元方法,对我国C61型运煤货车,按照车辆/轨道系统的实际几何形状、材料性质和边界条件建立了包括车辆和轨道系统的有限元模型,应用大型非线性动力分析程序LS-DYNA3D来模拟车辆通过轨道错牙接头时的轮/轨动态响应过程。计算结果表明车轮和轨道之间的竖向动态接触力大约是静轮载的2倍,与已有的现场试验结果基本吻合。因此应用有限元方法研究车辆/轨道耦合系统是可行和可靠的。 相似文献
10.
11.
For Kolsky bar testing beyond strain-rates of 10,000/s, it is useful to employ bars with diameters of only a few millimeters
or less. Furthermore, very small (sub-millimeter) systems are compatible with micron-sized specimens, to be used, for example,
for the determination of mesoscale properties. However, at these sizes, traditional strain-gage measurements of the longitudinal
waves within the bars become impractical. In this paper we describe the application of optical measurement techniques to two
Kolsky bars, with 3.2 and 1.6 mm diameters. A transverse displacement interferometer is used to measure the displacement of
the mid-point of the incident bar and provide measurements of the incident and reflected pulses. Similarly, a normal displacement
interferometer is used to measure the displacement of the free-end of the transmitter bar and provide a measurement of the
transmitted pulse. The new methods are used to characterize the behavior of 6061-T6 aluminum at rates greater than 100,000/s.
The feasibility of application to smaller bars is also discussed. 相似文献
12.
As a method for measuring full-field out-of-plane displacement, projection moiré provides high measuring quality with simple experimental setup. Based on an image processing program developed by Heredia and Patterson, this article presents the implementation of projection moiré in low-velocity impact testing. Results from projection moiré agree reasonably well with those obtained from the commonly used load cell method. In an attempt to better document composite response to impact loading, the possibility of correlating the external out-of-plane displacement measurement with the internal delamination is discussed. The technique is further applied to composites with various microstructures, including laminated, two-dimensional woven and quasi-three-dimensional (Q3D) woven composites. Projection moiré is able to provide some insights of the delamination propagation of the composites under impact loading. 相似文献
13.
Experimental Mechanics - Plastic dissipation at inter-granular contacts during elasto-plastic wave propagation plays a significant role in wave attenuation. However, it is unknown if plastic... 相似文献
14.
对任意荷载作用下具有封闭杆件的刚架给出用分配系数和传递系数表示的精确解。刚架用变矩分配法求解时,将各结点用假设的刚臂固定,求得任意荷载引起的固端弯矩,然后求得结点不平衡力矩,从而将求任意荷载作用的问题转化为求任意的结点不平衡力矩作用的问题。用弯矩分配法求解时,将杆端弯矩,表示为无穷多次分配弯矩和传递弯矩之和,其表达式为公比小于1的无穷等比级数的和,为方便地求得该和的表达式,从而求得任意荷载作用下刚架结构的精确解。文中给出了算例。 相似文献
15.
16.
17.
Yu. V. Zakharov K. G. Okhotkin A. D. Skorobogatov 《Journal of Applied Mechanics and Technical Physics》2004,45(5):756-763
Exact solutions of the problem of nonlinear bending of a thin bar under a point follower load are given. The problem is studied for an arbitrary follower angle and the particular cases of axial and transverse follower forces are considered. The solutions are written in unified parametric form and expressed in terms of Jacobi elliptic functions. 相似文献
18.
This paper represents a first attempt to derive one-dimensional models with non-convex strain energy starting from “genuine” three-dimensional, nonlinear, compressible, elasticity theory. Following the usual method of obtaining beam theories, we show here for a constrained kinematics appropriate for long cylinders governed by a polyconvex, objective, stored energy function, that the bar model originally proposed by Ericksen [3] is obtainable but enriched by an additional term in the strain gradient. This term, characteristic of nonsimple grade-2 materials, penalizes interfacial energies and makes single-interface two-phase solutions preferred. The resulting model has been proposed by a number of authors to describe the phenomenon of necking and cold drawing in polymeric fibers and, here, we discuss its suitability to interpret also the elastic-plastic behavior of metallic tensile bars under monotone loading. 相似文献
19.
Response and Damage Tolerance of Composite Sandwich Structures under Low Velocity Impact 总被引:1,自引:0,他引:1
The deformation and failure response of composite sandwich beams and panels under low velocity impact was reviewed and discussed.
Sandwich facesheet materials discussed are unidirectional and woven carbon/epoxy, and woven glass/vinylester composite laminates;
sandwich core materials investigated include four types of closed cell PVC foams of various densities, and balsa wood. Sandwich
beams were tested in an instrumented drop tower system under various energy levels, where load and strain histories and failure
modes were recorded for the various types of beams. Peak loads predicted by spring-mass and energy balance models were in
satisfactory agreement with experimental measurements. Failure patterns depend strongly on the impact energy levels and core
properties. Failure modes observed include core indentation/cracking, facesheet buckling, delamination within the facesheet,
and debonding between the facesheet and core. In the case of sandwich panels, it was shown that static and impact loads of
the same magnitude produce very similar far-field deformations. The induced damage is localized and is lower for impact loading
than for an equivalent static loading. The load history, predicted by a model based on the sinusoidal shape of the impact
load pulse, was in agreement with experimental results. A finite element model was implemented to capture the full response
of the panel indentation. The investigation of post impact behavior of sandwich structures shows that, although impact damage
may not be readily visible, its effects on the residual mechanical properties of the structure can be quite detrimental. 相似文献