火箭橇试验推力测量方法研究

以典型火箭橇试验系统为对象,对系统运动的不同阶段进行力学分析。在建立推力测量系统基础上,对不同马赫数下火箭橇试验的推力数据进行分析处理。研究结果可为综合力学环境火箭橇试验平台的建立提供参考。     

基于火箭橇试验的北斗接收机动态校准技术

提出一种基于火箭橇试验的北斗接收机动态校准技术,通过阐述动态校准过程,火箭橇试验标准弹道建立方法、接收机动态定位和速度误差评定方法、火箭橇试验外测参数的溯源及校准过程不确定度评定方法,建立了计量型可溯源的火箭橇试验系统,并对两款接收机校准结果进行了分析。结果表明火箭橇试验能够有效解决北斗接收机的高动态校准问题,具有一定的应用价值和扩展前景。     

“遥存结合”测试方法在火箭橇试验中的应用

针对火箭橇试验力学环境复杂难以测量以及侵彻类火箭橇试验橇上装置难以回收等问题,本文提出采用遥测和存储相结合的测试方法来解决此类试验的难题,并研制了火箭橇"遥存结合"发射装置,该装置已经成功应用在火箭橇试验测试中.     

基于超音速火箭橇试验的接力拍摄测试技术

对超音速火箭橇试验的测试目标进行3向位移测量,由于音爆的影响和场地的限制,既不能进行人工跟踪拍摄,也没有合适的自动追踪设备,因此采用高速相机以接力拍摄的布局方式进行分段记录,并以前方交会的方法进行分段计算.通过精度估算,弹射救生座椅航向位移在650 m的范围内,其点位测试精度约为0.5 m.对于超音速火箭橇试验,形成了以拍摄频率高、测试范围大、分段拍摄与分段计算为特点的轨迹测试新技术.     

基于火箭橇试验的航向控制点轨迹测试技术

在弹射座椅的火箭橇试验中,针对空间三向位移的测量,提出了一种基于航向控制点的轨迹测试法.这种测试法充分利用航向位移远大于竖直高度的特点,将两台高速相机在锁定俯仰角的情况下只转动方位角沿航向进行跟踪拍摄,确保每帧影像上至少有一个航向控制点.依据俯仰角的大小将倾斜像片变换为竖直像片,通过前方交会计算得到目标点的三维空间坐标.在这项测试中以实体目标进行精度检测,其平面点位和高程测试精度约为0.5 m.     

减振滑靴非线性动态特性数值分析

针对以降低火箭橇系统在轨振动为目的设计的减振滑靴,对其动态特性进行了数值分析。通过平面压缩试验及经验公式确定了减振滑靴减振层天然橡胶的本构参数,进而由有限元模型获得其非线性刚度,据此建立了减振滑靴非线性动力学模型对其求解并进行了试验验证。数值计算结果表明,减振滑靴相较于传统滑靴有着较好减振能力,其减振效率随其载荷提高而提高,但由于引入橡胶使得其在大载荷及高过载条件下易出现“跳跃”现象。根据“跳跃”现象确定了减振滑靴工作边界,典型工况下在1 Ma(350 m/s)速度下每枚减振滑靴载荷应小于311 kg,在2 Ma(700 m/s)载荷则应低于181 kg。     

轨底坡对轮轨接触行为及动力学性能的影响

为探讨轨底坡对轮轨接触行为及动力学性能的影响,利用多体动力学软件SIMPACK,分析地铁B型车LM和S1002型踏面与60 kg/m钢轨在不同轨底坡下的轮轨接触点分布情况、滚动圆半径差、最大接触压力、临界速度以及车辆运行安全性和平稳性指标等,从接触几何和动力学性能两方面提出LM和S1002型面的最佳轨底坡组合。计算结果表明,轨底坡对轮轨接触行为及动力学性能均有较大影响。对于LM型面在直线段采用1/20轨底坡可减小最大接触压力且不易发生蛇行失稳,对于S1002型面在直线段采用1/40轨底坡可获得良好的接触点分布及较大的接触斑面积,对于LM和S1002型面在曲线段均宜采用1/30轨底坡以获得较好的车辆运行平稳性。     

车轮与高速道岔长短心轨的接触分析

针对动车组、机车车轮与高速道岔的磨耗问题,测量运行线路上磨耗后的车轮与道岔的实际几何尺寸,应用有限元方法求解车轮与道岔长短心轨的接触问题。计算了车轮与高速道岔的长短心轨部分在不同位置的接触状态,分析得出了不同工况下车轮与心轨接触斑、等效应力以及接触法向力的分布和变化规律,为道岔结构的合理设计和型面尺寸的优化提供了一定的理论依据。结果表明：JM3型机车车轮与18号高速道岔的心轨型面匹配不合理;动车组和机车车轮与心轨间的最大应力值都超过了轮轨材料的屈服极限,发生塑性变形;车轮在钢轨上的横移量影响轮岔之间的磨耗,向心轨外侧的横移量越大,磨耗越严重。     

接触爆炸作用下钢板层裂效应数值分析

基于AutoDyn对接触爆炸荷载作用下钢板的层裂过程进行数值模拟,并对照试验进行分析,探讨了应力波在钢板中的传播过程和特点,剖析了钢板的层裂机理,指出钢板的层裂破坏是钢材在拉伸波作用下的一个损伤累积和能量累积过程。计算表明,装药的高度、钢板的厚度与材质是影响接触爆炸作用下钢板层裂发生、发展及其破坏效应的核心因素。试验和计算结论为钢板在某防护结构中的应用提供了技术参考。     

固体火箭发动机喷管阻尼数值计算方法及规律研究

从声学角度出发,参考稳态波衰减法,综合考虑喷管辐射损失及对流损失,建立固体火箭发动机喷管阻尼声能共振数值计算方法,通过与阻抗管法测量的试验结果对比验证仿真方法,并探究喷管喉径、监测点位置、声源强度及平均压力对喷管阻尼的影响,结果表明:数值计算结果与试验结果吻合较好,表明该研究建立的仿真方法有效;喷管阻尼随喉径的增大而增大,进而使声腔内形成稳定驻波时的压力振幅降低。传声特性分析结果表明:喷管喉径增大,声功率透射系数提高,使喷管阻尼增加;监测点位置及声源强度不会影响喷管阻尼大小,但会影响压力振幅大小;喷管阻尼及压力振幅均与平均压力大小无关。     

Numerical analysis for dynamic contact between high‐speed wheel and elastic beam with Coulomb friction

For numerical analysis of the dynamic contact between a high‐speed wheel and an elastic beam, the equation of motion of each body is time integrated by a simple ODE solution technique and frictional contact conditions are imposed by the augmented Lagrange multiplier method using the contact errors defined in this work. For the stability of the numerical solution, the velocity and acceleration contact conditions as well as the displacement contact condition are imposed with special consideration for the high‐velocity contact point moving on the deformed beam. Especially, it is shown that the Coriolis and centripetal accelerations of the contact point moving rapidly on the deformed beam play crucial roles for the stability of the solution. It is also shown that, for a wheel rolling on a beam with friction, the acceleration constraint in the tangential direction is important for the stability of the solution. Copyright © 2008 John Wiley & Sons, Ltd.     

电连接器接触件应力场的数值分析与试验验证

利用ANSYS对某型号电连接器接触件应力场进行分析,以寻找应力变化规律.对接触件应力场分布特点、插孔形变、接触压力随温度升高的变化规律进行了仿真研究,并进行数据分析与接触压力的试验验证.结果表明:随着温度升高,插孔最大形变量增加,最大接触压力和接触压力区域都有所减少;尺寸较小的接触件插孔槽缝底部最大等效应力随温度升高增幅较大,交变载荷作用时易出现疲劳、破裂等,属产品失效薄弱点.通过分析得知最大等效应力值随温度上升而变化的趋势取决于温度软化效应和热应力增强作用的综合结果;仿真结果能较好地反映电连接器的工作应力状态,接触压力试验验证了有限元仿真方法的可行性.     

Numerical simulation of the dynamic thermostructural response of a composite rocket nozzle throat

The finite element method, in the form of the commercial finite element code ADINA, is used to investigate the dynamic thermostructural response of a composite rocket nozzle throat. ADINA’s thermoelastic analysis capability is validated by the comparison of its solution for the thermoelastic response of a thick, homogeneous, cylindrically orthotropic tube heated internally, to an analytical one. The spatially reinforced Carbon–Carbon nozzle throat examined here forms part of a low-erosion solid rocket motor nozzle model that is subjected to structural and thermal loading, with the effects of material ablation being neglected. An initial transient quasi-static thermostructural analysis is performed to determine the validity of the nozzle design, following which, an uncoupled dynamic thermostructural analysis of the nozzle’s throat and entrance section for the initial transient phase of the nozzle’s operation, is carried out. The results of this analysis are then compared to those of the equivalent transient quasi-static analysis to assess the degree of variance in either solution. It is found that the dynamic response oscillates about the quasi-static response in all cases, and that, in general, the variance in stress magnitudes between the two solution techniques is significant.     

变工况下滚动轴承保持架碰撞接触动力学特性分析

滚动轴承保持架在运动过程中始终会与滚动体产生碰撞,尤其在变工况条件下更易表现出复杂的动态接触特性,对轴承使用性能和寿命产生重要影响。该研究以深沟球轴承6309为研究对象,考虑滚动体与内外圈、保持架之间动态接触关系,建立了滚动轴承耦合动力学模型,分别讨论了匀、加、减速及不同转速波动工况下滚动体与保持架间碰撞力幅值、次数及分布情况等接触特性变化。研究结果表明：变速工况下滚动体与保持架间碰撞次数增多;加速工况下滚动体与保持架兜孔前端碰撞力幅值明显小于后端碰撞力幅值,且承载区内滚动体主要与兜孔前端发生频繁碰撞,非承载内则主要与后端发生碰撞,减速工况则相反;相较于稳定工况,转速波动工况下滚动体与保持架间碰撞作用力要大得多,碰撞程度从小到大依次为三角波动工况、简谐波动工况、矩形波动工况。该研究结果可为保持架的设计和失效分析提供理论依据。     

A frictional spring and cohesive contact model for accurate simulation of contact forces in numerical manifold method

“Open-close iteration” is a crucial algorithm for handling complex contacts in numerical manifold method (NMM) and discontinuous deformation analysis (DDA). This algorithm has proved to be robust and efficient for decades. However, as some researchers have pointed out, the original open-close iteration may involve errors in sliding tests, especially in critical sliding tests with cohesive contacts. In this study, two major problems in the original algorithm are found to be nonconvergent contact force and early removed cohesive strength. The modifications are the following: (a) a frictional spring. By avoiding the trail value of normal contact force, we added a new frictional spring to the iteration scheme. This spring can apply accurate friction and can help ensure the convergence of contact forces. (b) A cohesive contact model. The original scheme can encounter an “early failure” in cohesive contacts. After investigating how contacts provide shear resistance, we found the cause and then provided a simple correction of the cohesive issue. The new algorithms in this article are essential for accurately simulating contacts by NMM/DDA.     

钢板夹薄壁钢管组合板抗接触爆炸数值模拟

为了提升钢板夹薄壁钢管组合板抗爆性能,有效减轻接触爆炸对防护结构的破坏,对钢板夹薄壁圆钢管组合板和钢板夹薄壁方钢管组合板,采用ANSYS/LS-DYNA软件进行接触爆炸数值模拟。取1kgTNT炸药,选择t=400μs时,分析该2种钢管组合板在接触爆炸作用下的抗爆吸能效果。结果表明:钢板夹薄壁方钢管组合板整体弯曲强于圆钢管组合板,但局部变形能力弱于圆钢管组合板;方钢管组合板变形输出的内能值小于圆钢管组合板,且不受钢管壁厚和数量变化影响,防护效果弱于圆钢管组合板;随着方钢管截面尺寸的减小,整体跨中挠度增加,破口直径增大,吸能减小,输出内能值增大,且不受壁厚和数量变化的影响,抗爆性能增强。同时,通过3组钢板夹薄壁钢管组合板参数对比分析后得知,在钢管数量为3,钢管壁厚2mm时,抗爆能力相对于其他工况下增大的较多,此结果可为工程实践提供参考。     

Frictional contact analysis of composite materials

In this paper, the highly non-linear frictional contact problems of composite materials are analysed. A proportional loading, the potential contact zone method and finite element analysis are used to solve the problems. A tree-like searching method is used to obtain the solution of the parametric linear complementary problem, which may overcome the anisotropic properties of contact equations caused by composite materials. In the frictional contact analysis of composite materials, the distributions of normal contact pressures, tangential contact stresses and relative tangential displacements are presented for different contact material systems and different coefficients of friction. The results show that the solutions in the paper have good agreement with Hertzian solutions. The influence of different contact material systems and different coefficients of friction on the contact stresses and displacements is large. As a numerical example, ball-indentation tests of composite materials are modelled by the three-dimensional finite element method.     

基于数值仿真的冲压成形界面接触压力

为探究冲压成形过程中板料-凹模圆角区界面接触压力,采用有限元静力算法建立了U形件小圆角半径弯曲成形过程的数值仿真模型,完成了板料和模具界面接触压力数值模拟,并参数分析了钢板强度、相对圆角半径、压边力和摩擦系数对板料界面接触压力分布的影响.研究表明:与压边力和摩擦系数相比,钢板强度和相对圆角半径更明显地影响着板料界面接触压力,并随着材料强度增加和相对模具圆角半径减小界面接触压力明显增加;随着压边力和摩擦系数的增加,界面接触压力宽度也随之增大.     

Numerical analysis of a quasistatic thermoviscoelastic frictional contact problem

We study a quasistatic frictional contact problem between a viscoelastic body and a deformable obstacle. A thin lubricant layer is assumed on the contact surface and, then, a normal damped response contact condition considered. Thermal and frictional effects are also taken into account. A fully discrete scheme is proposed, using the finite element method for the spatial approximation and the Euler scheme for discretizing the time derivatives. Error estimates on the solutions are derived and the linear convergence, under suitable regularity hypotheses, is obtained. The scheme was implemented and some numerical examples are included to show the performance of the method.Acknowledgments This work was partially supported by MCYT-Spain (Project BFM2003-05357) and it is also part of the project New Materials, Adaptive systems and their Nonlinearities: Modelling, Control and Numerical Simulation carried out in the framework of the european community program Improving the Human Research Potential and the Socio-Economic Knowledge Base (Contract n° HPRN-CT-2002-00284).