HIAF强流重离子加速器真空室烘烤功率计算及热-结构耦合分析

针对薄壁真空室的使用特点,首先利用ANSYS有限元软件进行结构优化设计。其次通过理论计算和数值模拟相结合的方法计算出真空室烘烤功率,并给出在达到热平衡后真空室的温度分布规律。此外采用间接耦合法得到薄壁真空室在热-结构耦合状态下的变形及应力分布规律,结果表明升温阶段损失功率随时间而逐渐增加,真空室达到热平衡后损失功率保持恒定;仅大气压作用下真空室被压缩,高度方向的变形占主导地位,在烘烤过程中热载荷带来的影响较大,真空室长度方向的变形占主导地位;由于气体载荷和热载荷在某一点处所引起的应力方向不一致,所以真空室在热-结构耦合作用下的最大应力不是各个载荷应力值的线性叠加。     

烘烤工况下的ITER中子屏蔽块整体结构分析

中子屏蔽块分布于国际热核聚变实验堆(ITER)超导托卡马克真空室双层壳体内部,由多个组件装配而成,用于屏蔽核聚变产生的中子。在烘烤工况下,承受螺栓预紧力作用的中子屏蔽块受200℃烘烤温度的影响,产生热应力。为校核在烘烤温度下中子屏蔽块的应力强度,本文采用ANSYS软件对其整个装配体进行整体结构分析。分析中将螺栓预紧力导致的模型位移作为边界条件,分预紧力载荷、温度载荷、重力载荷等载荷步进行热-结构耦合分析,分析结果按照ASME评定标准可以表明,中子屏蔽块各组件的最大应力强度在许用应力之内,满足结构强度要求。该分析的类型是典型的多接触高度非线性分析,对模型网格化和接触对设置的质量要求较高,处理不当会导致分析计算不收敛,同时该分析能正确地反映各结构件之间的实际连接关系,避免零件单独分析时用刚性连接代替弹性连接的状况。该分析方法为承受预紧力的复杂模型进行接触和耦合分析提供参考。     

反应堆压力容器筒体应力分析

本文采用有限元法,运用ABAQUS6.13建立一个包含进出口接管、筒体和底封头的三维全模型,计算压力容器下筒体在自重、内压、堆芯支承凸缘载荷、和外部机械载荷等各种载荷作用下的应力强度,并严格参照ASME规范第Ⅲ卷第一册中的NB分卷规定的应力准则,对压力强度进行强度评定。评定结果表明,压力容器下筒体符合ASME标准的强度要求。最后,分析下筒体在各载荷作用下分别产生的应力强度,得出各载荷对压力容器下筒体的应力分布的影响。     

基于ANSYS Workbench的薄壁二极铁真空室优化设计

薄壁二极铁真空室由于其特殊的作用被应用在HIAF装置的部分位置,由于真空室的壁非常薄,在抽真空状态下易变形,因此对其进行有限元分析明确其在抽真空状态下的应力、变形情况很有必要。本文利用ANSYS Workbench对薄壁二极铁真空室进行结构静力分析,在静力分析的基础上对真空室进行多目标优化及结构优化得到了最佳设计点和可以减少的质量,为薄壁二极铁真空室的后续设计提供一定的参考。     

横置螺旋弹簧隔振器在冲击激励下的最大应力研究

本文研究横置螺旋弹簧隔振器简化模型在主工作方向上的有预载荷的不同初值，或幅值的上架或基础冲击激励下的最大应力及发生位置，并对隔振器弹簧进行了强度分析。     

制备铝基复合基板真空室的结构设计

铝基复合基板是一种大功率模块芯片理想的散热基板,在非真空环境下高温热压制备容易出现氧化腐蚀等问题,造成基板致密度不高,无法满足芯片匹配要求,设计了一种供在真空热电挤压下制备铝基复合基板的真空室。通过对真空室形状大小的确定、材料的选择、壁厚的计算,设计完成满足制备基板工艺的真空室结构以及静、动态密封结构。通过ANSYS有限元分析软件对真空室结构进行计算机仿真,分析其最大应力应变处,满足真空室基本强度刚性要求,从而为真空热电挤压制备铝基复合基板创造了一个密封、稳定的真空制备环境。     

循环载荷压半周对疲劳裂纹扩展速率的影响

本文使用ＬＹ１１ＣＺ铝合金及１８ＭｎＨＰ钢两种板材的中心裂纹拉伸试件，在不同应力水平及应力比下，就应力比，特别是循环载荷压缩部分对疲劳裂纹扩展速率的影响进行了试验研究和分析，指出，现有裂纹闭合理论不足以解释载荷压半周的作用，并就两种材料给出了估算裂纹扩展速率的经验公式。在此基础上还指出，用线弹性断裂力学应力强度因子Ｋ作为裂纹扩展的控制参量，在理论上，有待进一步研究。     

驾驶室锤击振动的测试及数据分析

本文以上海-50拖拉机驾驶室安全架为研究对象，对其进行了锤击振动试验，通过数据分析，获得了该安全架的应力分布情况，引起破坏的部位及导致安全性差的原因。提出用抛物线脉冲函数作为计算载荷，对驾驶室进行动强度分析。     

反场箍缩装置KTX真空室结构稳定性分析

KTX为中国科学技术大学在建的反场箍缩实验装置,在同类装置之间,其参数介于美国MST和意大利的RFX之间。KTX真空室壁厚仅为6 mm,属于非标准环形薄壳结构,其结构的稳定性分析是确定结构设计是否合理的关键因素。本文利用有限元的方法,对KTX真空室结构进行了线性和非线性屈曲分析。得到了两种情形下应力和变形加载曲线。通过对计算结果的对比和分析,验证了目前真空室结构的稳定性符合要求,并具有一定的安全裕度。     

负离子源测试平台真空室结构设计及优化北大核心CSCD

负离子源测试平台是用于开展未来磁约束聚变装置中性束注入系统负离子束源性能研究的测试装置。研究分析了负离子束源性能特征及测试方法,基于测试平台工程及物理设计需求,完成了国内首台以盒形壳体作为结构模式的大功率负离子源中性束注入系统(Negative ion based Neutral Beam Injection system,NNBI)束源测试平台真空室的结构设计及重要部件的集成。运用ANSYS Workbench软件建立有限元模型,数值分析了真空室结构静态力学特性,得到了应力与变形分布规律,并通过应力线性化分类处理与响应面的方法分别进行了各类应力评估和束线真空室变形最大的后端封头的结构优化。结果表明:真空室的结构强度与变形量均满足工程设计需求,优化后的封头变形幅值显著降低,为负离子源测试平台的集成设计优化与研制奠定了基础,具有工程应用价值。     

高地应力下圆形巷道临界冲击地压解析解

基于统一强度理论和靼性应变损伤模型,合理考虑中间主应力效应和剪胀特性,对高地应力下的圆形巷道进行弹塑性分析,由冲击地压扰动失稳理论建立圆形巷道临界冲击地压解析解.经与模型试验和工程实测数据比较,验证了解析解的正确性,并得出统一强度理论参数、剪胀参数、支护力、升降模量比和内摩擦角对临界冲击地压的影响规律.结果表明:确定高...     

封堵药包的作用机理研究

根据硐室爆破存在冲炮现象，设计了导硐封堵药包。利用封堵药包起爆产生的应力波和爆生气体作用于封堵材料，有效抑制和减少主爆药包爆炸能量的散失和冲炮现象的发生，从而改善爆破效果。本文给出封堵药包的合理位置、起爆时差和药量公式，并列举了工程实例。     

Phosphate-activated high-calcium fly ash acid-base cements

Some fly ashes are used in the concrete industry but some are deemed unsuitable owing to their chemical compositions. This study investigated the use of such a high-calcium fly ash containing large amounts of anhydrite, free lime, and calcite, to produce room-temperature acid-base cements by activation with phosphate sources. Orthophosphoric acid solutions and potassium dihydrogen phosphate were used as activators. Paste microstructures were studied using x-ray diffraction, scanning electron microscopy, isothermal calorimetry, and pH measurements. These findings were related to strength development up to 28 d. Room-temperature cured pastes activated with a 60% H₃PO₄ solution and a solution-to-powder ratio of 1.0 gave the highest 1-d strength of 15 MPa and 28-d strength of 22 MPa. Partial replacement of the ash with glass powder further increased the 28-d strength. Crystalline calcium phosphates, Brushite and Monetite, were among the products of the solution-activated pastes, as well as some amorphous phases. Potassium salt-activated pastes did not contain the calcium phosphate crystals and gave lower strengths. The ultimate pH of well-reacted mixtures were close to neutral.     

Fatigue behaviour of 3-d SiC/SiC Composites

A tension–tension fatigue damage analysis was performed using 3-d silicon carbide fibre reinforced (orthogonal) silicon carbide matrix (SiC/SiC) composites. Two groups of SiC/SiC specimens were tested. The first group consisted of samples without any oxidation protective top layer coating, whilst the latter one contained samples covered with a well fitting, chemical vapour deposited (CVD) SiC system. This coating is necessary for the material to sustain high temperatures. Both the coated and uncoated material had a fibre volume fraction of about 36% equally distributed in three rectangular directions. Load control fatigue tests were conducted at room temperature. The fatigue life was found to decrease by increasing the cyclic stress level. A power-law equation is proposed, which correlates the applied maximum stress during the fatigue test with the number of cycles to failure. In general, the presence of the coating layer decreases the static strength of the material. However, the nominal maximum cyclic stress for which the endurance fatigue limit appeared, remained unaffected by the presence of the oxidation protective SiC coating. Microstructural examination has also been performed on the fractured specimens and it reveals some of the failure mechanisms of the composite that appeared under quasi-static and dynamic loading.     

Residual strength of metal particulate reinforced ceramics with parallel cracks

This work investigates the residual strength of metal particulate reinforced ceramic matrix composites with periodically spaced, parallel cracks. A Fourier transform/integral equation method is used to obtain the stress intensity factor at the tips of the cracks bridged by the plastically stretched metal particulates. The crack bridging of metal particulates is described by a linear softening bridging law that relates the bridging stress and crack opening. The residual strength of the cracked composites is calculated using a stress intensity factor criterion with consideration of crack bridging. Numerical results are presented for three composite systems, i.e., WC/Co, Al₂O₃/Ni, and glass/Al composites to illustrate the effects of interactions between multiple cracks/bridging zones on the residual strength behavior of the reinforced ceramics with parallel cracks. It is found that for given volume fraction of metal particulate and debonding length of the particulate–matrix interface the residual strength increases with decreasing crack spacing. For a given crack spacing, the residual strength initially decreases dramatically with an increase in initial crack length and levels off for long initial cracks.     

预测复合材料缺口强度的场强法

本文以复合材料缺口附近的应力应变场为参量,提出了预测复合材料缺口强度的场强法,给出了一个估计复合材料缺口强度的普遍表达式,并由此导出了一个易于使用的工程估算方法。通过对两种材料四组实验结果的分析表明:场强法的预测结果是比较满意的。     

COMPARISON OF FATIGUE LIFE PREDICTIONS IN WELDED JOINTS USING 2D AND 3D K SOLUTIONS

The paper presents the results of fatigue life predictions in non-loaded carrying tee and cruciform joints and also longitudinal seams of tubes, obtained with 2D and 3D stress intensity factor solutions. The 2D computational method uses the standard Bueckner weight function solution to obtain the 2D values of the stress magnifying factor M_K. In the 3D approach a modified 3D weight function solution was used in conjunction with the Raju and Newman base stress intensity formulation. Comparison of results is shown between the 2D and 3D fatigue life predictions and experimental results of fatigue strength obtained by the authors. Results are also given showing the influence of crack aspect ratio, thickness and the ratio of tube radius to tube thickness.     

三维碳/碳复合材料板件拉伸强度预报

针对三维碳/碳复合材料板件开孔敏感性问题进行了试验与有限元分析。建立了三维碳/碳复合材料代表体积单元(RVE)和完好板件、开孔板件的有限元模型,给出了宏观应力到细观应力的转换方法,并基于此方法,实现了完好板件、开孔板件拉伸破坏过程的数值模拟。进行了三维碳/碳复合材料完好板件和开孔板件的单向拉伸试验,模拟计算结果与试验结果吻合良好。分析了不同宽径比(WTDR)对开孔板件拉伸强度的影响,其中当宽径比达到6时,开孔板拉伸极限强度相比完好板下降11.5%,可以认为如果宽径比不低于6,开孔对板件拉伸极限强度影响较小。该结论可以为碳/碳复合材料开孔板件设计提供指导。     

Evaluating strength of thermally sprayed Al2O3 on aluminum

We evaluated the strength of thermally sprayed Al₂O₃ on aluminum. The thermally sprayed Al₂O₃ films were processed using low-pressure plasma spraying. The thickness of the thermally sprayed Al₂O₃ was 0.3 mm and 0.7 mm. We arranged a 4-point bending test and a heating test to evaluate the strength of the thermally sprayed Al₂O₃. We also investigated the effect of residual stress on the strength by measuring deformation of the thermally sprayed Al₂O₃ after removing the aluminum substrates. The bending strength was 120 MPa, regardless of thickness. We assumed that the bending strength would be equal to the tensile strength because the thermally sprayed Al₂O₃ films were very thin. A crack was generated at 433 K, regardless of thickness. The thermal stress was 160 MPa when the crack was generated. It was 40 MPa higher than we estimated. We found that the residual stress was compression stress that measured 40 MPa, which contributed to the prevention of the crack generation. We presume that the tensile strength was lower than the thermal stress because the residual stress was reduced by stress-relaxing of the aluminum near the interface in the bending test. The influence of heat-resisting strength is dominant over residual stress. Therefore, strength design should take into account residual stress.