基于DOE参数筛选的SPH鸟体参数反演

鸟体参数的准确性对鸟撞仿真精度有重大影响,参数反演可以克服人工试凑法的局限生,搜寻出合理的鸟体参数,提高鸟撞仿真精度.在Hyper Study多学科优化平台下,先采用正交实验设计方法挑选出对位移结果敏感的鸟体参数,以简化优化问题的复杂性和计算量,然后采用自适应响应面法进行鸟体的参数反演的多目标优化,优化目标为最小化鸟撞位置处仿真位移和实验位移的平方差.RADIOSS的求解结果表明,采用优化后的鸟体参数的鸟体模型的仿真曲线与实验曲线拟合效果大大提高.     

某型开式转子发动机桨扇叶片抗鸟撞数值模拟分析

基于SOLIDEWORKS和ANSYS软件,建立鸟撞某开式转子发动机桨扇叶片有限元计算模型,分析了真实工况下鸟撞桨叶不同位置时鸟体和叶片的变形过程和动态响应.根据计算结果分析,实际中应尽量避免叶片与高动能的鸟体发生碰撞,本研究可为后续开式转子发动机的叶片设计提供理论指导.     

典型金属加筋板鸟撞实验研究

以典型金属加筋板为鸟撞实验研究对象,采用数字图像相关法的非接触测试方法实现鸟撞区域测试点三维位移信息的测量,与传统的接触式测试方法相比,测试精度和可靠性得到了提高。并通过分析高速摄像结果,得到数值模拟中鸟体应采用的描述流体行为的本构模型。最后通过对比不同撞击点的实验结果,确定了典型加筋板的鸟撞危险点,验证了加筋板不同的蒙皮-筋条间连接强度对结构抗鸟撞性能的影响。     

结合DIC技术的车用复合材料参数反演方法

针对传统电测法在复合材料参数测定中易受环境干扰等问题,提出一种基于数字图像相关(digital image correlation,DIC)技术的车用复合材料参数反演方法。首先通过DIC技术获得复合材料试样的全场位移场,结合有限元仿真,以测量值与仿真值之间的误差为目标函数,构建反问题模型。采用遗传算法和序列二次规划法相结合的策略对材料参数进行反求,获得能表征复合材料真实材料参数的最优值。试验表明,基于DIC技术的反演方法对未知参数在较大区间下具有较强的识别能力,且能一次性且完整地反演复合材料的本构参数,反演精度和计算效率都有一定优势。     

航空发动机吸鸟适航验证关键参数分析方法

发展了一种确定航空发动机风扇叶片吸鸟适航验证用关键参数的分析方法。首先分析关键参数,提出用综合关键撞击参数SCIP评估鸟撞击叶片损伤效果及确定试验用关键吸鸟参数CIP的方法,建立SPH法鸟撞旋转风扇叶片有限元模型,进行鸟撞击数值模拟,分析鸟速、风扇转速、撞击位置等参数对鸟撞击数值模拟结果的影响,得出各个状态下综合损伤参数。结果表明,在CIP=F(72 m/s,70%,100%)试验条件下,鸟撞击叶片的综合损伤最为严重,并据此确定一组吸鸟适航验证用关键吸鸟参数。     

2024铝合金薄板叠层顺序对鸟撞的动态响应

在航空航天领域,外来物损伤(FOD)严重威胁着航空飞行器的正常运营和安全,鸟撞损伤是最常见的。基于Autodyn有限元软件,建立鸟弹SPH模型和2024航空铝合金靶板Lagrange模型,研究飞机蒙皮在受鸟撞时的动力响应及损伤特性。通过仿真结果与实验数据对比,验证SPH模拟鸟弹的有效性。探究在不同靶板叠层顺序和鸟弹撞击速度下,鸟撞对靶板最大鼓包、应力和能量的影响,比较得到抗鸟撞较好的靶板叠层方式。     

鸟撞导致铆钉失效的试验研究

随着抗鸟撞结构研制过程中越来越依赖鸟撞数值仿真结果,仿真结果的正确性至关重要。通过鸟撞数值仿真结果设计试验中所选择的铝合金板厚度、铆钉直径、鸟撞速度等参数,进行铝合金薄板的鸟撞试验。试验结果表明,铆钉断裂是鸟撞中结构的失效形式之一,在仿真中应当予以考虑。     

基于神经网络和有限元法的“V”型件翻边成形性能研究

翻边是一种重要的金属成形工艺 ,曲面翻边的成形性能与几何尺寸及材料参数等因素有很大关系。本文将有限元模拟与人工智能相结合 ,建立了基于改进的BP神经网络的“V”型件翻边成形性能与几何尺寸及材料参数关系的数学模型。与单纯采用有限元法相比 ,该模型具有计算时间短和易使用的优点。与数值模拟和实验结果的比较证实了本模型的有效性。     

不同构型梁-缘结构抗鸟撞性能分析

在传统梁-缘结构的基础上,结合前缘的结构形态及其功能型要求,提出了两种斜板保护形式的梁-缘结构。利用三维有限元模型对质量相等的不同构型梁-缘结构进行了鸟撞数值分析。通过比较鸟撞后结构关键部位各时刻的应变、位移等发现:斜板保护形式的梁-缘结构表现出良好的抗鸟撞性能。数值模拟结果为今后设计新构型抗鸟撞击结构部件提供了参考依据。     

基于有限元法和Taguchi方法的移动硬盘耐撞性能稳健设计

运用Taguchi参数设计方法,提出了基于数值模拟的移动硬盘跌落冲击耐撞性能稳健设计方法。以6.3cm(2.5in)移动硬盘为研究对象,建立了基于有限元软件ANSYS/LS-DYNA的移动硬盘跌落冲击三维有限元模型。分析了关键结构参数对移动硬盘耐撞性能稳健性的影响,进行了移动硬盘耐撞性能稳健设计,获得使磁盘盘片接触面等效应力对地面硬度变化具有稳健性的最优参数水平组合,并进行了仿真试验验证分析。该方法为改进设计提高移动硬盘耐撞性能提供了理论依据。     

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...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

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.