某型民机复合材料机翼下壁板开口补强及优化研究

根据机翼结构设计要求,下壁板的层合板上开口是不可避免的。主要对民用飞机的机翼蒙皮下壁板开口补强结构进行分析,利用有限元分析软件MSC.PatranNastran建立二维复合材料有限元模型,模型采用壳单元。通过计算分析,对比了未补强壁板、补片补强和加强筋补强三种不同的方案情况下,机翼蒙皮下壁板在外载荷下的位移以及应力变化,及不同角度铺层的各层应力变化,研究了补强方式及铺层角度对机翼下壁板应力分布的影响。结果表明加强筋补强能较好减小位移和最大应力,避免应力集中;在采用加强筋补强方案时,-45°的铺层方向上应力最大;在设计机翼下壁板开口补强方案时应尽量选用加强筋补强,并尽量减少-45°方向的铺层。     

孔口缝合补强对层间应力影响的数值模拟

使用空间杆单元模拟缝合线,对含孔复合材料层合板开口缝合补强结构进行有限元模拟计算。研究含孔复合材料层合板在轴向拉伸载荷作用下,圆孔附近各个铺层交界面处层间正应力和剪应力的分布情况,将缝合后的层间应力值与缝合前的相关数值进行比较,并研究不同缝合参数(针距、行距、边距、单缝合和双缝合)对孔边层间应力的影响。结果表明,缝合补强后孔边的层间应力明显减小。孔边附近层间应力的分布与相邻铺层的铺层角有很大关系,不同铺层之间的层间应力有显著差别。不同铺层之间的层间应力沿孔边区域存在应力转换点(即层间应力由正值变为负值)。     

压缩载荷作用下复合材料层合板结构开口翻边补强试验及数值模拟

对复合材料开口补强层合板进行压缩试验研究,分析损伤和破坏部位,然后建立补强后层合板有限元模型,分别利用非线性分析和线性分析两种方法对应力应变响应、失效强度、损伤扩展进行模拟,通过试验数据对数值结果进行考核,结果发现非线性分析较线性分析方法能更好地符合试验结果.     

复合材料基础设计及优化

通过原材料的选材、铺层和层合板结构设计,阐述了复合材料的基础设计。结合复合材料的原材料和结构设计原则,说明了复合材料结构的可设计性。针对复合材料各组分材料的特性,详细介绍了原材料选择的重要性,从载荷性能要求方面并结合层合板结构设计原则,对复合材料层合板进行了设计,并应用有限元分析软件(ABAQUS)对层合板进行了仿真分析,阐述了复合材料层合板仿真分析的方法和步骤,同时根据仿真结果对复合材料铺层进行了合理的优化设计。     

基于HyperWorks 的不同铺层方式复合材料剪切强度有限元分析

剪切强度和剪切韧性是反映复合材料构件在复合受力状态下承载能力及耗能能力的重要指标,不同铺层方式的单向玻璃纤维与短切玻璃纤维混杂增强复合材料层合板的层间剪切性能有明显差异。文中基于HyperWorks 商用有限元软件建立了精确的复合材料层合板模型,通过数值模拟分析不同铺层方式复合材料层合板的层间剪切性能。研究结果表明,铺层材料对复合材料层合板的层间剪切性能影响较大,而铺层顺序对复合材料层合板的层间剪切性能影响较小。     

基于三维CDM的复合材料开口层合板失效分析

建立了复合材料层合板三维连续介质损伤力学模型,并将该模型应用于复合材料开口层合板的损伤破坏分析中。与相关试验中开口层合板强度和损伤破坏情况对比分析表明:本文模型能够有效地模拟开口层合板从初始损伤到完全破坏的全过程,具有较高的计算精度和良好的数值模拟收敛性。基于该模型,详细分析了在单向拉伸载荷作用下开口层合板不同铺层的损伤破坏情况。     

带圆孔层合板孔边层间应力分析、失效研究及软件开发

依据边界层理论分析的带圆孔对称复合材料层合板的应力解析解,开发相应的软件,计算铺层交界处的层间应力.进一步增加Hashin失效判据,得到层合板各个铺层不同失效形式下的区域分布.该软件是基于Matlab开发的,非常适用于带圆孔复合材料层合板结构打样阶段的分析.     

含孔复合材料层合板在压缩载荷下的三维逐渐损伤

通过逐渐损伤分析可以清楚地了解承载复合材料层合板内部损伤的产生及扩展过程,应用三维逐渐累积损伤理论和有限元分析技术,对不同材料不同宽孔比的含孔复合材料层合板在压缩载荷作用下的逐渐破坏过程进行分析,综合考虑了基体开裂、基纤剪切、分层及纤维断裂等四种复合材料层合板的主要破坏模式。在通用有限元分析软件ANSYS基础上进行二次开发,编制了参数化的分析模拟程序,该程序可以预测任意铺层角度和铺层厚度层合板在压缩载荷作用下的逐渐损伤破坏过程及最终失效载荷,通过与已有参考文献结果进行比较,验证了方法及程序的正确性。该程序可以较大程度地提高最终失效载荷的预测精度,为复合材料层合板结构的设计和使用提供了有力的技术支持。     

复合材料层合板基于遗传算法的可靠性优化设计

采用遗传算法对复合材料层合板的可靠性优化问题进行了分析。本文研究的算例中 ,在层合结构总厚度一定的情况下 ,以复合材料层合板的系统可靠性指标最大为目标函数 ,对复合材料的纤维方向角或相对厚度进行了优化设计。可靠性分析中 ,采用一次二阶矩法 (FORM)和Tsai Wu准则分析层合板结构的失效概率。算例阐明了遗传算法应用于层合板结构可靠性优化设计的有效性。     

冲击后复合材料板剩余抗拉强度影响因素分析

应用提出的全程分析方法和三维逐渐累积损伤理论,对层合板的冲击过程以及冲击后含损伤层合板在拉伸载荷下的破坏过程进行详细分析.研究不同冲击能量、不同材料的冲头、不同复合材料体系和不同铺层方式等因素对层合板冲击损伤及剩余抗拉强度的影响规律,为更有效地进行复合材料抗冲击结构设计提供一定的指导作用.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.     

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and extern...     

奥氏体不锈钢表面双辉等离子渗锆的动力学

利用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备了一层均匀、致密、呈良好冶金结合的渗锆合金层,并对1 060℃下的渗锆动力学进行了研究。结果表明:随着距锆合金层表面距离的增加,锆元素的含量呈梯度递减,扩散系数逐渐减小,而扩散激活能逐步增大;在1 060℃采用双辉等离子技术渗锆时,渗锆合金层表层的空位密度为2.945×(1012~1013)cm-2,与相同温度下采用常规渗金属工艺相比,提高了1~2个数量级。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.