Coupled thermal-mechanical analysis of two ITER-like first wall mockups under heat shock of plasma disruptions

The first wall of the fusion reactor is a plasma-facing component and is a key link to maintain the integrity of structure during thermal shock induced by plasma disruptions. Be and W/Cu functionally graded materials are two kinds of important plasma-facing materials(PFM) of first wall in fusion reactor currently. Previous researches seldom comparatively evaluated the normal servicing and heat shock resistance performance of first walls with those two kinds of PFMs. And also there lacks coupled thermal/mechanical analysis on the heat shock process in consideration of multiple thermal/mechanical phenomena, such as material melting, solidification, evaporation, etc., which is significant to further understand the heat shock damage mechanism of the first wall with different PFMs. With the aim of learning more detailed mechanical mechanism of thermal shock damage and then improving the thermal shock resistance performance of different first wall designs, the coupled thermal/mechanical response of two typical ITER-like first walls with PFM of Be and functionally graded W-Cu respectively under the heat shock of 1–2 GW/m~2 are computed by the finite element method. Special considerations of elastic-plastic deformation, material melting, and solidification are included in numerical models and methods. The mechanical response behaviors of different structures and materials under the normal servicing operation as well as plasma disruption conditions are analyzed and investigated comparatively. The results reveal that heat is mainly deposited on the PFM layer in the high energy shock pulse induced by plasma disruptions, resulting in complex thermal stress change as well as mechanical irreversible damage of thermal elastic and plastic expansion, contraction and yielding. Compared with the first wall with Be PFM, which mitigates the damages from heat shock at most only in the PFM layer with cost of whole PFM layer plastic yielding, the first wall with graded W-Cu PFM is demonstrated to be possessed both of higher heat shock resistance performance and normal servicing performance, provided its material gradient and cooling capacity are well optimized under practical loading conditions.     

不同波长激光对半导体Si表面的损伤机制

为了研究不同激光对半导体Si表面的损伤机制,实验中采用扫描电镜记录1064 nm激光和248 nm激光对单晶Si材料的表面损伤.通过比较,发现在紫外光辐照下Si表面熔融效应明显并且出现了清晰的周期性条纹.经分析认为表面损伤主要是热应力、激光自持爆轰波的冲击压力和蒸发波的反冲力所导致,损伤形貌的差异则源于材料对不同激光的吸收系数有显著差别.     

激光重熔热障涂层热震行为研究

在GH635高温合金基材上等离子喷涂NiCrAlY/85Y2O3-ZrO2热障涂层，进行激光重熔，对不同激光工艺参数下的试样进行表面形貌观察并进行热震试验，试验结果表明：采用4.0J/mm^2的激光能量密度可以得到较好的表面质量，并且具有高于等离子喷涂试样的热震寿命。     

Supersonic flow imaging via nanoparticles

Due to influence of compressibility, shock wave, instabilities, and turbulence on supersonic flows, current flow visualization and imaging techniques encounter some problems in high spatiotemporal resolution and high signal-to-noise ratio (SNR) measurements. Therefore, nanoparticle based planar laser scattering method (NPLS) is developed here. The nanoparticles are used as tracer, and pulse planar laser is used as light source in NPLS; by recording images of particles in flow field with CCD, high spatiotemporal resolution supersonic flow imaging is realized. The flow-following ability of nanoparticles in supersonic flows is studied according to multiphase flow theory and calibrating experiment of oblique shock wave. The laser scattering characteristics of nanoparticles are analyzed with light scattering theory. The results of theoretical and experimental studies show that the dynamic behavior and light scattering characteristics of nanoparticles highly enhance the spatiotemporal resolution and SNR of NPLS, with which the flow field involving shock wave, expansion, Mach disk, boundary layer, sliding-line, and mixing layer can be imaged clearly at high spatiotemporal resolution.     

长脉冲激光辐照单晶硅的表面形态

针对长脉冲激光在空气中对单晶硅进行辐照所产生的表面形态问题,研究了不同能量密度的激光辐照后单晶硅的表面形态变化及其形成机理.结果表明:单晶硅表面的涟漪波纹状微结构与光的散射和干涉有关;随着激光能量密度的增加,单晶硅表面出现解理现象,其主要是由较高的温度梯度而引起的应力所致;熔融和汽化时的单晶硅表面形态主要是由载流子动力及等离子体波引起的;激光辐照单晶硅中心点温度曲线在单晶硅熔点和沸点附近时出现平台期,这是由于材料在熔融和气化过程中要吸收潜热;激光能量密度越大,单晶硅表面的损伤面积越大.     

射频放电等离子体激励对激波/边界层干扰的控制效果

在空气静止、气压为12 kPa（对应超声速风洞试验段的气压）条件下,研究射频放电等离子体的光谱特性;在马赫数为2的超声速来流中,研究射频放电等离子体激励对激波/边界层干扰非定常性的控制效果. 实验结果表明：在相同的激励频率下,随着加载功率的增大,表征电子温度的相对光谱强度增大,而表征振动温度和电子密度的相对光谱强度基本保持不变;保持加载功率不变,随着激励频率的增大,表征电子温度的相对光谱强度先增大后减小,而表征振动温度和电子密度的相对光谱强度没有明显变化. 在未施加激励时,激波振荡的主导频率为低频;在施加射频放电等离子体激励后,激波低频振荡减弱,高频振荡增强,激波特征频率从低频转向高频,再附边界层出现高能量漩涡结构.     

Shock wave-boundary layer interactions control by plasma aerodynamic actuation

This study demonstrates the potential for shock wave-boundary layer interaction control in air by plasma aerodynamic actuation. Experimental investigations on shock wave-boundary layer interactions control by plasma aerodynamic actuation are conducted in a Mach 3 in-draft air tunnel. Schlieren imaging shows that the discharges cause the oblique shock to move forward. Schlieren imaging and static pressure probes also show that separation phenomenon shifts backward and the size of separation is enlarged when plasma aerodynamic actuation is applied. The intensity of shock wave is weakened through wall pressure probe. Furthermore, numerical investigations on shock wave-boundary layer interactions control are conducted with plasma aerodynamic actuation. The discharge is modeled as a steady volumetric heat source which is integrated into the energy equation. The input energy level is about 7 kW through discharge process. Results show that the separation phenomenon shifts backward and the intensity of shock is reduced with plasma actuation. These numerical results are consistent with the experimental results.     

Dynamical Mechanical Properties for AD90 Alumina

The dynamic response of polycrystalline alumina was investigated in the pressure range of 0-13 GPa by planar impact experiments. Velocity interferometer system for any reflector(VISAR) was used to obtain free surface velocity profile and determine the Hugoniot elastic limit, and manganin gauges were employed to obtain the stress-time histories and determine Hugoniot curve. Both the free surface particle velocity profiles and Hugoniot curves indicate the dispersion of the "plastic" wave for alumina. With the measured stress histories, the complete histories of strain, particle velocity, specific volume and specific internal energy are gained by using path line principle of Lagrange analysis. The dynamic mechanical behaviors for alumina under impact loading are analyzed, such as nonlinear characteristic, strain rate dependence, dispersion and declination of shock wave in the material.     

储罐外爆冲击波数值模拟及超压公式研究

为研究储罐外爆冲击波的传播规律和对储罐安全性的影响,应用软件LS-DYNA建立炸药-储罐的数值模型,并进行空爆数值计算。研究分析储罐外爆冲击波超压的衰减关系和罐体的动力响应,与经验公式的对比验证了模型的可信性,并结合经验公式平均值对数值模拟结果做了进一步修正。结果表明:冲击波运动到迎爆面中心后,外罐主应力在10 ms时迅速达到最大值,随后主应力值迅速减小,并不断振荡;迎爆面中心首先产生较大的拉应力,混凝土外罐的破坏属于脆性破坏;比例距离大于1时,现有超压计算公式拟合超压的衰减规律误差较小,比例距离小于1时,超压计算公式误差较大,修正后的超压计算公式可为储罐抗爆设计提供参考。     

出血性休克时血浆层的实验研究

在对１２只雄性大鼠提睾肌出血性休克微循环血流在体观察基础上，用高倍显微闭路电视摄像系统和微循环数字图象处理（ＭＣＣＩＰ）技术，实现了对微动脉血流中的边缘流血浆层在体条件下的动态测试，并从血液流变学的角度跟踪研究了出血性休克的形成、发展、恢复各时期微动脉中缘流血浆层厚度随ＲＢＣｓ速度的发展机理，实验研究表明，血浆层的厚度随血流速度的降低而减少，当血浆层消失时，血流并没有停止，因此，由于血浆层的发展超前于流速的发展，血浆层的消失是造成微循环障碍的主要原因之一，在休克的预后治疗中，微动脉中的血浆层是一个重要的评价指标，以此来监测血浆层的发展，恢复血流紊乱中的血浆层是重要途径之一。     

CO_2 激光切割金属材料的工艺参数与性能关系的研究

本文研究了用 CO_2激光切割金属材料时,切割工艺参数对热影响区显微组织及力学状况的影响和相互关系.结果得出,激光切割淬火回火态金属材料时,热影响区由表及里出现三层不同的显微组织,即白亮的熔化层,相变硬化层(它由白色的淬火层和灰色的回火层组成),以及黑色的回火层.对各层形成的原因及其显微硬度,残余应力场的分布进行了分析试验结果说明,对一些特殊性能下使用的金属材料,既须考虑切割参数对切割表面质量的影响,还须考虑它们对热影响区显微组织和力学状态的影响.不同材料应根据情况选用优选工艺参数.     

吹除法对斜激波/边界层干扰控制数值模拟

为了对进气道内斜激波/边界层干扰进行控制,采用RSM模型,以二维平板/楔结构为基础,研究了斜激波冲击平板诱导边界层分离现象,探讨了吹除状态下流场波系结构和壁面参数分布,分析了吹除位置和总压对分离区及流场的影响.研究表明加入吹除控制之后,流场参数得到了有效改善,吹除喷嘴靠近分离区,吹除效果更好.吹除总压并不是越高吹除效果就越好,存在一个最佳吹除压力,该压力就是使吹除喷嘴出口气流达到近似音速,这一结论如进一步得到实验证实,对实际工程具有指导意义.     

枪速对热障涂层组织性能及残余应力的影响

为了研究等离子喷涂制备热障涂层(TBCs)时不同枪速对陶瓷面层组织性能和残余应力的影响,在GH4169高温合金基体上采用超音速火焰喷涂(HVOF)Ni Co Cr Al Y粘结层(BC层)和大气等离子喷涂(APS)8YSZ陶瓷层(TC层).通过对比不同参数样品的微观组织以及显微硬度、残余应力和热震性能差异,研究了枪速对热障涂层的影响.结果表明:枪速过低或过高时,涂层表面残余应力较大,热震性能较低;随着枪速的增大,涂层表面粗糙度逐渐增大,而孔隙率和显微硬度逐渐减小;枪速过低时,涂层出现纵向裂纹,热震失效方式为整体剥落;而枪速较大时,涂层从边缘向中心不断剥落,涂层表面出现白点.     

应力冲击波在结构节点的反射和透射

应用固体冲击波理论，分析杆中一维压应力冲击波，通过结构十字形刚节点时的反射和透射行为，建立估算反射波和透射波波后参数估算公式．     

激光诱导等离子体淀积薄膜过程的研究

用激波理论推出了激光诱导等离子体化学气相淀积过程中两个重要参量薄膜面积、膜淀积速率的表达式.分析了激光强度、气体压强、基片温度对淀积过程的影响,为最佳淀积条件的选取提供了理论依据.     

多波段激光合束镜温度适应性分析

环境温度是激光合束镜设计过程中需要考虑的重要因素。研究了实际应用中环境温度对合束激光光束质量产生的影响。对高功率红外激光常用的材料Zn Se建立光-机-热集成仿真,利用瞬态导热方程和应力应变平衡方程对温度场,应力场进行仿真计算。将离散的有限元数据提取后通过Zernike多项式拟合镜面畸变。并将透镜折射率的变化转变为光程差的变化,求得出射激光远场光强分布、β因子、环围能量比BQ作为激光光束质量的评价标准。在环境温度(-40℃~+50℃)条件下,长波段激光光束质量保持较好,其β因子最大值为1.761;短波段激光光束质量接近衍射极限,其β因子最大值为1.072。结果显示在环境热冲击下通过合束镜的长波激光以及短波激光保持了良好的光束质量,满足合束镜环境温度使用要求。     

Laser-induced spark ignition of H<Subscript>2</Subscript>/O<Subscript>2</Subscript>/Ar mixtures

Laser-induced spark ignition of hydrogen-oxygen-argon mixtures was experimentally investigated using a Q-swiched Nd:YAG laser to break down the gas at 532 nm. The laser-based high-speed schlieren system was employed to record flame front evolution for the gas mixtures with different initial pressure or laser output energy or argon dilution. The results show that the breakdown of the gas leads to the generation of ellipsoidal plasma. The rarefaction waves create the toroidal rings at the leading and trailing edges of the plasma, which provides a reasonable explanation for inward wrinkle of the plasma and the resultant flame. The toroidal rings at leading edge decays more rapidly and a gas lobe is generated that moves towards the laser. The hot gas in the plasma induces the generation of the spark kernel. Affected by the very weak shock wave or compression waves reflected off the wall, the initial laminar flame decelerates. The arc flame front interactions with the wall, reversed shock wave or compression waves, rarefaction waves, etc. induce the transition from laminar flame to turbulent one. These induce the transition from laminar flame to turbulent flame. For stoichiometric hydrogen-oxygen mixtures diluted by 76.92% argon at an initial pressure of 53.33 kPa, the minimum output energy of the laser is 15 mJ for successful laser-induced spark ignition. With increasing initial pressure or the output energy of the laser, or decreasing argon dilution, the speed of the flame front increases.     

平板式汽车ZrO2氧传感器多孔保护层研究

为开发平板式汽车ZrO2氧传感器的保护层,以MgAl2O4为主要原料,研制了适合于ZrO2氧传感器电极保护的多孔复合保护层,并对其气孔率和抗热冲击性能进行了研究。结果表明,保护层中造孔荆含量增多,其气孔率增大,附着强度降低,当造孔剂含量为4％～6％时,满足了多孔性保护层的要求,并且也能保持较好的抗热冲击性。     

高精度切割新技术的研究现状

电火花切割、等离子切割、激光切割和超高压水切割是工业上广泛应用的高精度切割方法：电火花切割具有很高的材料利用率和接近于磨削水平的加工精度和加工表面粗糙度,但加工效率过低;等离子切割速度快,但切割过程中噪声大、烟尘多、辐射大,而且作为等离子切割机关键部件的喷嘴、电极和割炬在目前技术条件下都是易损件,无形中增加了切割成本;激光切割切割速度快、切缝小、切割材料表面质量好,但是切割材料厚度偏低,目前仅用于薄板切割;超高压水切割是一种冷态切割方式,切割材料无热变形,表面质量极佳,但切割成本过高。结合实践经验,提出了三条选用切割工艺的原则：特殊的场合选用特定的切割方法;利用热切割方法满足加工工艺要求时,则无需采用超高压水切割;在等离子切割和激光切割都能满足加工要求的情况下,最好选用等离子切割.     

多阶模态瑞利面波频散曲线的BP神经网络反演

瑞利面波勘探已经广泛应用于工程地质勘探和工程质量检测等领域中。瑞利面波勘探频散曲线反演解释时主要考虑基阶模态面波。当地层中含有软弱层以及表层为高速层时,在高频段高阶模态面波相对基阶模的能量更占优势。在瑞利面波勘探频散曲线反演解释中,必须考虑高阶模态面波的信息;在高阶模态面波占优势时,同时利用多阶模态组合频散曲线（包括基阶、二阶、三阶、四阶等）进行反演解释。本文通过对软夹层型和地表为高速层两种高阶模态面波能量较强的地层结构的理论和实测多阶组合模态频散曲线的反演研究,获得了比仅利用基阶模态面波解释更好的效果。