Monte—Carlo法在空间外热流计算中的应用──空间光学遥感器光学窗口的地球红外辐射分析计算

用Monte-Carlo法对空间光学遥感器的大口径光学窗口的地球红外辐射进行了分析和模拟计算。考虑了光线在外遮光罩挡光环内的多次漫反射和在光学窗口表面的镜反射,讨论了目前普遍采用的挡光环等效面假设的局限性。     

Monte—Carlo法在空间外热流计算中的应用──空间光学遥感器光学窗口的地球红外辐射分析计算

用Ｍｏｎｔｅ—Ｃａｒｌｏ法对空间光学遥感器的大口径光学窗口的地球红外辐射进行了分析和模拟计算。考虑了光线在外遮光罩挡光环内的多次漫反射和在光学窗口表面的镜反射，讨论了目前普遍采用的挡光环等效面假设的局限性。     

上海光源前端高热负载挡光器的结构设计与优化

为了有效处理上海光源前端挡光器接收的高热负载,研究了挡光器的结构设计及其优化方法。选用高导热性、高强度的GlidCop AL-15制造挡光器吸收体,采用直接水冷和掠入射结构提高其热缓释能力。以对流换热系数和压力降为评价指标,选用佩图克方程和达尔西-韦斯巴赫方程优化冷却水路,通过热分析得到了不同参数下挡光器的温度和热应力分析结果,从而确定了挡光器的结构设计优化参数。优化后挡光器的水路直径为6mm,水路到光照面的距离为9mm,光照面接线处圆角≥2mm,且水路与光束方向基本平行。与初始结构相比,优化后挡光器的最高整体温度和最高冷却壁温度分别下降约8%和1/4,最大等效应力降低了1/2左右,完全满足上海光源前端部件的设计要求。目前,应用优化参数设计的挡光器已应用于上海光源实际工程中。     

运用矩形压电片的冲击载荷定位新方法

为了更加方便、精确地进行结构冲击载荷定位,利用应变花的原理,通过矩形压电片传感的方向性试验,提出了一种基于矩形压电片花形结构的冲击载荷定位新方法——相对幅值法。该法只需知道压电片的响应幅值,1个压电片花形结构确定1个冲击载荷的方向,因此通过2个花形结构就可以确定冲击载荷的位置。在铝板中进行了验证试验,理论计算和实际冲击点的平均误差为3.6 cm,识别精度能满足工程实际要求。     

多路阀片间漏油的原因及其解决的方法

我厂生产的ZFS—L20H_2—Y※M—T型串联油路多路换向阀,是由进油阀片、出油阀片和若干中片组合而成。为进一步提高产品质量,就必须不断地发现问题,不断地解决问题。多路阀明显的片间外漏是基本解决了,但通过仔细检查,却发现多路阀在进行换向冲击时,片间有一点一点的微渗现象。这是什么原因产生的呢?原来多路阀进行换向冲击时,双头螺栓承受周期性的拉力载荷。升压时,双头螺栓受拉伸;降压时,     

活塞式压缩机气垫阀的试验研究

一、前言 气阀是往复活塞式压缩机重要的部件之一,且极易损坏。气阀损坏多发生在其中两个运动件——阀片和弹簧上。根据实际经验得出,阀片对升程限制器和阀座的冲击是阀片损坏的经常原因,此冲击速度是影响阀片使用寿命的一个主要因素。在任何情况下,阀片对升程限制器的冲击速度,总是比冲向阀座的速度大。根据我厂和西安交通大学材料力学教研室     

喷丸强化对多冲弯曲抗力的影响

本文研究喷丸时间与多次冲击弯曲抗力的关系。零部件喷丸只有接近或达到“饱和时间”,才能大幅度提高多冲抗力,起到强化效果。喷丸时间不足,将大大地降低强化效果。试验又揭示了“过饱和喷丸”并不恶化多冲抗力。通过对喷丸后试片的残余应力测定,指出残余压应力对受交变冲击应力的零件有提高冲击疲劳寿命的作用     

LCoS微型投影光引擎杂散光分析与抑制

为抑制LCoS光引擎的杂散光,在TracePro软件中建立了光引擎的光机模型,运用蒙特卡罗方法对该系统的杂散光进行了分析。通过仿真模拟及实验发现PBS棱边、成像透镜边缘、镜片隔圈以及镜筒内表面为产生杂散光的关键面。为此使用挡光片、表面发黑、镜片边缘及隔圈涂黑等方法对杂散光进行抑制。仿真及实验均表明上述方法可有效抑制杂散光。     

高强度钢加工不同槽型铣刀片冲击破损实验研究

采用几种适合加工高强度钢的不同槽型铣刀片,通过对大型化工设备热壁加氢反应器的主体件——筒节材料3Cr-1Mo-1/4V(2.25Cr-1Mo-1/4V)钢的面铣加工,进行铣刀片冲击破损的实验研究。首先,采用正交试验设计法,进行几种不同槽型铣刀片加工高强度钢试验,通过试验揭示不同铣刀片冲击破损失效形式的差异;其次,在大量、系统的冲击破损试验基础上,采用数理统计的方法建立冲击破损寿命累积分布函数数学模型;进行冲击破损平均寿命比较,从而对不同槽型铣刀片进行优选。研究成果为实际生产中刀具破损这一关键技术问题及槽型优选技术的研究打下理论与试验基础。     

不同热处理铝合金2014状态方程研究

以轻气炮作为加载手段,采用飞片撞击法,对两种热处理的铝合金试样2014-A、2014-B进行了冲击加载实验,得到了两种材料适用于LSDYNA的Gruneisen状态方程参数。     

Profiling of barrier capacitance and spreading resistance using a transient linearly increasing voltage technique

A technique for the combined measurement of barrier capacitance and spreading resistance profiles using a linearly increasing voltage pulse is presented. The technique is based on the measurement and analysis of current transients, due to the barrier and diffusion capacitance, and the spreading resistance, between a needle probe and sample. To control the impact of deep traps in the barrier capacitance, a steady state bias illumination with infrared light was employed. Measurements of the spreading resistance and barrier capacitance profiles using a stepwise positioned probe on cross sectioned silicon pin diodes and pnp structures are presented.     

ZrO2热障涂层耐高温冲刷性能研究

采用等离子喷涂工艺制备了NiCoCrAlY／ZrO2热障涂层，利用超音速火焰喷涂（HVOF）ZrO2粒子高速冲刷涂层表面，考察ZrO2热障涂层的耐高温冲刷性能。结果表明，等离子喷涂NiCoCrAlY／ZrO2热障涂层具有较好的耐高温冲刷性能，经高温高速粒子冲刷20s后，涂层与基体结合良好，涂层完整，未出现大面积的剥落。等离子喷涂ZrO2热障涂层高温冲刷的主要磨损机理为脉动冲击作用造成的裂纹扩展、涂层颗粒变形磨损和微切削。涂层的耐高温冲刷性能主要取决于涂层的硬度。     

断裂准则对TC4钛合金板抗卵形头弹冲击的影响

为了解TC4钛合金的抗冲击力学性能,利用一级轻气炮进行了卵形头弹冲击TC4钛合金靶板的试验,撞击速度范围为125.9~240.0 m/s。通过撞击试验获得弹体的初始-剩余速度以及靶板的失效破坏模式,并利用公式拟合弹体初始-剩余速度得到弹道极限速度。利用ABAQUS/Explicit有限元软件建立弹体冲击靶体的三维模型,研究断裂准则对TC4钛合金板抗卵形头弹冲击性能的影响,分别采用不同断裂准则进行数值模拟,并将数值模拟预测结果与试验结果进行对比。研究结果表明,从弹道极限和失效破坏模式综合考虑,Hancock-Mackenzie (H-M) 准则预测的结果与试验结果更接近,说明考虑失效应变随应力三轴度的变化关系能提高数值仿真精度。     

单列光源反射式光幕靶检测弹着点

为了降低弹丸着靶点检测的成本,提出了一种新的弹着点检测原理。采用单列光源,经两面条形表面反射镜反射后,形成"Z"型的三道光幕,用于实现对弹丸等飞行目标的测速及定位。弹丸的速度和着靶点水平方向的坐标可以通过对时间的测量得到,弹丸着靶点竖直方向的坐标可以通过单列光探测器获知。文中对检测原理进行了研究,对光源、探测器、信号特征、有效测试区域、射频测试能力等进行了分析,并在桌面进行了原理性试验。高速摄影机拍摄的小球坐标与"Z"型结构测量出的坐标相对位置误差为0.1～1mm,传统区截靶法与"Z"型结构测量出的小球速度相对测速误差为0.02%～0.2%,说明基于反射镜的"Z"型结构在定位和测速方面的应用具有可行性,提出的方法具有结构简单、解算方便、节省成本的特点。     

A development of simple analysis model on bumper barrier impact and new IIHS bumper impact using the dynamically equivalent beam approach

This paper presents a simple analysis model for bumper barrier impact and new IIHS (Insurance Institute for Highway Safety) bumper impact instead of a non-linear finite element impact analysis. A dynamically equivalent beam approach was introduced to simplify the non-linear dynamic bumper impact. For a bumper barrier impact, the equivalent curved-beam element was substituted for the bumper beam and the bumper foam. For a new IIHS bumper impact, a modified curved-beam element of bumper barrier impact considering the effect of contoured new IIHS impact barrier was used. The accuracy of this simple analysis model was tested by comparing its results with those of the non-linear finite element analysis. Tested bumper beam types were press type beam and roll forming beam used widely in the current car bumpers. The maximum displacement error between the two models did not exceed 1.95% for a barrier impact and 13.2% for a new IIHS bumper impact. This accuracy is good enough to be used in the early stage of bumper beam design process. This simple analysis model is expected to reduce the car development time and tests cost significantly.     

Dynamic response of aluminum honeycomb sandwich panels subjected to hypervelocity impact by porous volcanic rock projectile

The dynamic response and damage behavior of aluminum honeycomb sandwich panels (HC/SPs) subjected to hypervelocity impact by volcanic rock projectiles were investigated by hypervelocity impact tests and hydrocode simulations. The experiments were conducted using a two stage light gas gun and the results showed that the failure modes in HC/SPs subjected to hypervelocity impact by volcanic rock projectiles mainly took forms of front-face denting and circular perforation, honeycomb core collapsing and rapture, rear-face petal-ling and perforation etc. A 3D discrete configuration of the porous volcanic rock projectiles was set up. The hypervelocity impact behavior of the HC/SPs was investigated through hydrocode modeling, within a Lagrange-SPH coupling method in LS-DYNA solver. It was found that the dynamic response and failure modes in the HC/SPs were significantly influenced by the impact location and the impact velocity of the volcanic rock projectile.

     

基于障碍Lyapunov函数的双臂空间机器人捕获卫星柔顺控制

空间机器人捕获卫星操作过程中不可避免地会与卫星接触、碰撞，此过程中若未对其关节进行有效的保护，很容易造成捕获操作失败，因此提出在各关节电机与机械臂之间添加一种弹簧阻尼机构，该机构不仅能够实现碰撞冲击能量的吸收及柔性振动的抑制，还能配合设计的柔顺策略实现捕获操作的柔顺化。分别利用含耗散力Lagrange方程与Newton-Euler方程导出了碰撞前的双臂空间机器人与卫星分体系统动力学方程；结合Newton第三定律、捕获点的速度及闭链几何约束获得了捕获完成后的混合体系统动力学方程，且通过动量守恒关系计算了碰撞冲击效应与冲击力；基于障碍Lyapunov函数设计了一种状态约束控制方法，实现了轨迹的高精度跟踪；采用模糊自适应控制器对系统的不确定项进行拟合，解决了系统参数不确定的影响。通过Lyapunov定理证明了系统的稳定性，并利用数值模拟验证了缓冲机构的抗冲击性能及所提柔顺策略的有效性。     

The role of microstructure in the impact wear of two aluminum alloys

The impact wear resistance of two aluminum alloys was investigated using flat-ended aluminum specimens impacted upon a stainless steel counterface. The counterface itself was held stationary in some tests (pure normal impact) and moved transverse to the normal impact direction in other tests (compound impact).The alloys investigated were aluminum-copper: 2011-T3 which was formulated for free-machining applications and 2124 which possessed very high fracture toughness. Thus, one alloy favors crack nucleation and growth, while the other suppresses these. A variety of tests were conducted with both alloys in compound impact loading. The peak impulsive stress was found to influence wear rates significantly; the relative sliding velocity is also an important parameter.Surface and subsurface microscopy were used to define operative wear mechanisms. With the 2011-T3 alloy, the characteristic subsurface features support the delamination theory of wear. With the 2124 alloys, subsurface features differ significantly. These features are discussed in the light of microstructural variations in the alloys.     

低速冲击下的界面响应和磨损行为*

为探究低速冲击下界面响应与磨损行为之间的联系，开展多周次的低速冲击磨损实验；通过分析冲击过程中的接触力峰值、接触时长、接触力冲量、动能耗散等，研究冲击速度对接触界面的力学响应的影响；通过对冲击磨痕的磨损轮廓和形貌、磨损体积的检测分析，以及对磨痕区域元素组分变化的测试，研究冲击速度对接触界面磨损损伤行为的影响。结果表明：冲击速度的增加会导致接触界面在更短的时间内受到更强烈的力学作用；能量吸收率对冲击速度的变化不敏感，但冲击速度的提高会导致单位能量造成的磨损损伤逐渐降低；冲击磨痕可分为以塑性变形和以剥层磨损为主要损伤形式的2种区域；磨损区内经历了严重的摩擦氧化，并随着冲击速度的增加发生冲击副材料转移。因此，冲击速度越高，接触界面间的摩擦越剧烈，形成的表面氧化层避免了冲击副与基底材料的直接接触，延缓了磨损损伤的进一步发展。     

An analytical and experimental study of impulsive stress of square plates at an impact loading point by the 3-dimensional dynamic theory of elasticity

In this paper, a new method is proposed to analyze impulsive stresses at an impact loading point, which cannot be solved by the classical plate theory. Particularly, impulsive stresses at an impact loading point under any impact conditions (regardless of mass of impactor, velocity of impactor, stiffness of plate, etc.), can be obtained by the three-dimensional dynamic theory of elasticity and potential theory of displacement. In addition, by using the Hertzian contact theory, impact loading can be analyzed to account for the local deformation, and this load is applied to the impulsive stress analysis by approximating the impact loading to an analyzable function. In the numerical analysis, the Fourier transform (FFT) algorithm and the numerical inverse Laplace transformation are utilized. Using a new equation, it was possible to analyze impulsive stresses at an impact loading point, and good agreement between the experimental and theoretical results was established.