蒸压加气混凝土在乏燃料容器坠落工况下的减振性能分析

在核电厂燃料厂房结构安全性分析中需考虑乏燃料容器坠落所产生的巨大冲击作用的影响,在坠落位置铺设蒸压加气混凝土砌体作为减振层是一种有效的结构防护方法．为了确定合理的减振层厚度并评价其减振效果,本文首先应用ANSYS/LS-DYNA对蒸压加气混凝土砌块的落锤冲击试验进行了有限元模拟,标定了蒸压加气混凝土的MAT96材料模型参数;再通过对减振层缩尺试验的模拟,验证了模拟方法的可行性;最终建立了燃料厂房分层壳模型,模拟设置不同厚度的减振层时乏燃料容器坠落对燃料厂房的冲击响应,并从坠落处楼板冲击力、混凝土应变、跨中挠度以及乏燃料水池加速度响应方面对厂房结构的安全性进行分析．分析结果表明：乏燃料容器坠落时,铺设1 m、2 m厚度的蒸压加气混凝土减振层后,减振效果显著：楼板冲击力分别减小71.5%和76.4%,楼板混凝土破坏明显减轻,跨中挠度明显减小,乏燃料水池竖向加速度峰值分别削减29.2%和43%;同时,2 m厚的减振层并未取得1 m厚度减振层2倍的减振效果．     

构型弹体跌落冲击载荷及结构响应特性

为深入认识跌落冲击条件下构型弹体内部的载荷传递规律及结构响应特征,促进战斗部装药安定性评估和结构设计,结合数值模拟和应力波分析手段,研究了构型弹体在跌落过程中的冲击响应特征,主要关注内部药柱的变形和损伤特性,并讨论跌落姿态、装药构型和跌落高度等因素的影响。结果表明,在跌落冲击条件下,构型弹体装药的变形并非由药柱同壳体的直接撞击作用主控,而主要受到弹体内部应力波传播的影响。装药结构最大变形和损伤区域并不位于药柱外侧同壳体相接触的位置,而位于内部区域。冲击应力波在壳体和药柱之间的透射特征、在壳体和装药内部的反射和叠加特性等决定了药柱的主要变形区域及其变形程度。跌落姿态对药柱的响应特征和变形形貌具有重要影响,导致装药安定性风险从高到低排序的跌落姿态依次为尾部向下垂直跌落、水平跌落、头部向下垂直跌落和倾斜跌落。药柱构型也具有重要作用,其中药柱分段界面容易使得药柱变形程度增大,但对装药过载以及变形分布特征的影响相对较小;隔板结构则容易增大装药过载,同时导致药柱的局域变形位置和变形程度均发生改变。跌落高度对药柱变形区域分布特征的影响较小,对载荷幅值、变形程度和分布范围大小等则具有重要作用,随跌落高...     

压电智能结构有限变形下热-机耦合的有限元分析

采用有限元方法研究了结构在热载荷作用下变形与热传导之间的耦合特性．分析表明，结构变形较小，非线性效应很弱时，变形对材料的热传导系数影响很小，对结构的温度分布几乎没有影响；当变形增大，非线性效应增强时，变形对材料的热传导特性影响显著，热载荷作用下结构的温度变化和变形与现行不考虑热-机耦合效应所得结果产生明显差异．因此，为实现压电智能结构形状(振动)的精确控制，分析及实施控制时须考虑热-机耦合及变形对热传导系数的影响．     

考虑初始几何缺陷时复合材料层合浅拱的动态“跳跃”

考虑几何非线性但不计横向剪切效应，给出了复合材料合浅拱的动力方程，利用伽辽金法求出了均布阶跃载荷作用下，两端铰支、正交铺层的对称层合浅拱在计及初始几何缺陷情况下的动力响应，并由Ｂ－Ｒ准则分析了动力稳定性计算结果表明：初始缺陷对于结构参数γ较大的拱的临界动力载荷有很大的影响。     

流固冲击载荷下弹性约束加筋板的非线性动力响应

本文在考虑大变形、忽略阻尼影响的情况下,基于高散加筋板模型,对具有弹性约束边界的加筋板在流固冲击载荷下的非线性瞬态响应进行了理论研究.取样条函数作为挠度试函数,运用加权残值法求得加筋板动力响应的控制方程,采用四阶Runge-Kutta法求解该方程,并用Fortran语言编制了相应的计算程序.构造的B样条函数能适应板侧边上的任意弹性转动约束.文中不仅分析了不同的冲击载荷形式对加筋板动力特性的影响,还讨论了载荷峰值、冲击栽荷持续时问、加强筋和弹性转动约束的影响.     

轴对称横观各向同性浅球壳受物体撞击的非线性动力响应分析

基于非线性扁壳理论和弹性接触力学,建立了横观各向同性浅球壳在其顶部受集中载荷作用的非线性运动微分方程,根据Hertz定律,考虑撞击物与浅球壳之间的弹性接触效应,确定了壳体顶部所承受的冲击力,它与撞击物的质量、初始速度、壳体的几何和物理性质等因素相关.对此非线性动力问题,采用正交配点法与时间增量法求解.算例中,讨论了撞击物的冲击速度、壳体的厚度及中曲面曲率半径对壳体所受冲击载荷及其位移响应的影响.     

浅埋炸药爆炸形貌及其冲击作用效应

为研究浅埋炸药爆炸形貌及其冲击作用效应,提出了一套新型试验工装,通过浅埋砂爆试验,系统探究了浅埋爆炸过程中冲击波的传播、爆炸产物与砂土的喷射轨迹、靶板的变形形貌以及爆炸载荷的空间分布情况。结果表明:浅埋爆炸在空气中产生冲击波,其传播速度大于爆炸产物与砂土的喷射速度;起爆后的爆炸产物与砂土迅速向外喷射,体积随时间不断膨胀,撞击到靶板后向四周扩散;通过特 殊设计的试验工装与靶板,定性得出浅埋砂爆载荷产生的冲量在空间中呈非均匀分布,即中间最大,向四周逐渐减小。对比分析2次不同试验,发现炸药埋深影响爆炸产物和砂土喷射时的相对位置:埋深较小时,爆炸产物会冲破覆盖的砂层,直接作用到靶板;埋深较大时,爆炸产物基本被砂层包覆,随砂土共同作用到靶板;此外,增大炸药埋深会延缓爆炸产物与砂土的喷射时间。砂土的类型直接影响靶板的变形形貌,按北约标准AEP-55配做的砂土不仅使靶板产生整体弯曲变形,还在靶板上形成大量凹坑,产生侵彻效果,而普通的河砂仅使靶板产生整体弯曲变形,无明显的侵彻效果。     

受面内冲击载荷下加筋板的非线性动态屈曲

分析了受面内冲击载荷下加筋板的非线性弹性动态屈曲．考虑板与筋的膜力，忽略面内位移，运用Hamilton变分原理，得出非线性控制方程，采用双级数形式的挠度假设，由Galerkin方法得到离散方程组，根据B-R准则，判断加筋板的动态屈曲．     

含黏弹性夹芯FG-GRC后屈曲梁的低速冲击响应

研究了含黏弹性夹芯的功能梯度石墨烯增强复合材料(functionally graded graphene reinforced composite, FG-GRC)后屈曲梁在低速跌落冲击下的跳跃振荡行为.采用修正Halpin-Tsai细观模型预测FG-GRC的材料宏观属性.使用赫兹点接触模型确定冲击器和梁之间的接触力.提出了考虑轴向预应力的复合材料层本构关系和阻尼层的Kelvin型黏弹性本构.通过一种广义高阶剪切变形锯齿梁模型建立夹芯梁的非线性位移场. 基于Hamilton 能量变分原理, 推导了动力学控制方程组. 通过两步分析,首先获得弹性后屈曲平衡路径作为冲击问题的初始状态. 随后, 结合四阶龙格库塔法,拓展了两步摄动-伽辽金法计算接触力的时程曲线以及后屈曲梁的位移时程曲线.研究了后屈曲梁在单次和两次撞击下双稳态大幅振荡过程的动力学特征.讨论了轴向载荷、冲击速度、黏弹性阻尼特性、冲击器材料等因素对于碰撞接触力以及后屈曲梁动力响应的影响规律.结果表明, 接触力仅对冲击速度较为敏感,一定的结构碰撞参数设计可以在接触力变化不大的情况下,使得后屈曲梁由单势能阱运动转变为双阱大幅振荡.      

柴油机气缸盖多场耦合三维有限元分析

气缸盖是柴油机重要的零部件之一，在工作过程中承受着高温与交变的机械载荷，其强度是设计人员非常关心的问题。本文利用有限元分析软件MSC．MARC，对某柴油机气缸盖进行三维非线性有限元分析，在考虑各组件接触关系的基础上，计算了气缸盖在螺钉的预紧力、热载荷、爆发压力多场耦合作用下的应力场和位移场分布情况，为改进设计提供参考。     

Experimental and numerical investigations into collapse behaviour of thin spherical shells under drop hammer impact

A study of the collapse behaviour of hemi spherical and shallow spherical shells and their modes of deformation under impact loading are presented in this paper. Aluminium spherical shells of various radii and thicknesses were made by spinning. These were subjected to impact loading under a drop hammer and the load histories were obtained in all the cases. Three-dimensional numerical simulations were carried out for all the tested specimen geometries using LS-DYNA^®. Material, geometric and contact nonlinearities were incorporated in the analysis. The uni-axial stress–strain curve for the material was obtained experimentally and was assumed to be piecewise linear in the plastic region. The results from impact experiments are used for the validation of the numerical simulations. Three distinct modes of deformation, namely local flattening, inward dimpling and formation of multiple numbers of lobes were analysed and influence of various parameters on these modes is discussed.     

Numerical and experimental analysis of flow and heat transfer in a fuel assembly mock-up with transverse flow above the rods

Thermal-hydraulic conditions in a partially uncovered nuclear fuel assembly mock-up are studied with particular focus on the influence of the horizontal air flow above the rod bundle. The investigations are performed at the ALADIN test facility, which models a boiling water reactor fuel assembly at a 1:1 scale both axially and radially. In the scenario studied, the main heat transfer mechanisms – conduction, convection and radiation – are strongly coupled and all are of similar importance. A combination of measurements and CFD simulations serves to analyze the heat transfer processes in detail. Contrary to previous studies in this field, all heat transfer mechanisms were considered in the simulation with sophisticated models. The numerical results show a good agreement with the measurements, given the inevitable differences between the approaches. Although the successive evaporation of cooling water in a fuel assembly is a transient, multiphase process, the steady, single-phase simulation yields acceptable results. While single effects are overestimated in the simulation, the important dependencies are predicted similarly. A general result is that the maximum cladding temperature rises with decreasing water level. Further results indicate an impact of the horizontal air flow on the residual heat removal for moderate rod powers. Higher horizontal velocities above the fuel assembly lead to slightly higher temperatures inside. A characteristic flow field forms in the test facility that prevails for all studied water levels and horizontal velocities. However, it has only a minor effect on the temperature distribution in the central rod bundle. By combining experiments and numerical simulations, the study provides important information about the decisive parameters for the heat exchange in a spent fuel pool in case of an accident with loss of cooling. The exposed length of the fuel rods is of much more importance than the magnitude of the horizontal velocity above the fuel assembly.     

代理模型在机翼油箱晃动适航审定中的应用

飞机飞行过程中,机翼油箱易受扰动或激励作用而产生低频晃动,引起机翼油箱壁面变形失效.本文将响应面代理模型引入飞机复合材料燃油箱晃动适航审定工作,以晃动频率、晃动幅值和油箱载液比为自变量,以油箱外壁面最大主应变峰值为响应,建立了油箱上下蒙皮响应面统计模型,给出油箱上下蒙皮最大主应变峰值与激励频率、幅值和油箱载液比等因素的显式响应函数.开展物理全尺寸试验和流固耦合数值模拟验证代理模型的有效性.结果 表明,上下蒙皮最大主应变峰值呈非线性趋势,存在最危险载液比使得主应变峰值最大化,且油箱破坏多发生在下蒙皮.     

抛撒药壳体对一次起爆型云爆弹威力的影响规律

在对抛撒药壳体的变形及破裂后运动规律进行理论分析的基础上,对2种不同结构的一次起爆型云爆装置进行静爆威力实验,实验结果表明:采用中心起爆抛撒结构时,适度减小中心抛撒药壳体的强度可以提高云爆弹的威力;而采用中心与周边辅助抛撒药同时起爆结构,适度增加抛撒药壳体的强度可以提高云爆弹的威力.     

Enrico Fermi shield-plug response to a 1000-Ib TNT accident

The Enrico Fermi Atomic Power Plant—world's largest fast breeder—is a 100,000-kw facility currently nearing completion at Lagoona Beach, Mich. Access to the sodium-cooled core is provided by a 143-ton shield plug. The maximum credible nuclear accident for the Fermi reactor has been postulated not to exceed in violence the detonation of 1000 lb of TNT at the core location. This paper is addressed to predicting the structural response of Fermi to this maximum credible accident. Scaled charges of TNT (cased in molten sodium) were detonated in idealized models of the Fermi reactor. The results of these experiments together with available theory indicate that the accident would be contained in the reactor shielding complex but that the 143-ton shield plug, if unimpeded, might be propelled through the roof of the containment building. In response to the findings of this extensive study, the Fermi reactor will be equipped with an arrester that will prevent a hazardous plug jump in the unlikely event of a nuclear accident.     

吸能包装模型结构的冲击响应

利用空气炮冲击实验对吸能包装结构的跌落过程进行模拟，进行了缩比模型的正撞和30°斜撞实验，针对模型实验进行了数值分析，获得了吸能包装结构模型在撞击过程中的应力分布和塑性变形，并将计算情况与实验结果进行了分析。结果表明:在撞击中吸能包装结构主要通过缓冲木材的塑性变形及外钢壳屈曲产生的塑性铰吸收能量，塑性变形主要集中于撞击端，而远离撞击端未见塑性变形；计算中木材本构参数采用顺纹方向压缩应力应变曲线具有一定的有效性。     

Rolling deformation of truck tires: Measurement and analysis using a tire sensing approach

Measurements on rolling tire deformation provide deep insights into the mechanism of generating tire forces and moments. For free rolling tires, substantial attention has been given to the rolling resistance because of its significant impact on the fuel consumption and CO₂ emissions. This paper attempts to investigate the rolling resistance force through measurements of the rolling deformation of truck tires using a tire sensing approach. An optical tire sensor system is used to measure rolling tire deformation, which includes the deformed inner profile, sidewall deformation, and tread deformation. Measurements were conducted on a test truck for both new and used tires. In addition, the influences from operational factors such as wheel load and inflation pressure on tread deformation were examined and analyzed.     

Influence of the projectile composition and shape during an impact

Slug impact is considered a potential risk for pressurized water reactors in the event of a severe accident. The German team of FZK investigates this issue through the reduced-scale experiments BERDA, whose goal is to quantify the maximum mechanical energy that the upper head of a PWR is able to withstand. As these tests are performed with a material different from the one that would intervene in a real accident, the French team of CEA studies the influence of the slug material with the SKIPPY mock-ups. In order to understand better the impact process, relevant theoretical study has been conducted with the EUROPLEXUS code Published in Prikladnaya Mekhanika, Vol. 42, No. 5, pp. 3–15, May 2006.     

爆炸冲击下复合材料层合扁球壳的动力屈曲

研究计及横向剪切的复合材料层合扁球壳在爆炸冲击载荷作用下的非线性轴对称动力屈曲问题。通过在复合材料层合扁球壳非线性稳定性的基本方程中增加横向转动惯量项并引入R.H.Cole理论的爆炸冲击力,得到爆炸冲击下复合材料层合扁球壳的动力控制方程,应用Galerkin方法得到用顶点挠度表达的爆炸冲击动力响应方程,并采用Runge-Kutta方法进行数值求解,采用Budiansky-Roth准则确定冲击屈曲的临界载荷,讨论了壳体几何尺寸对复合材料层合扁球壳冲击屈曲的影响;数值算例表明,此方法是可行的。