轻轨车固定铰接结构有限元分析及方案改进

为保证轻轨列车的行驶安全,对固定铰接结构进行强度校核。选择接触非线性有限元方法,采用空间六面体单元和四节点壳单元建立模型,对某铰接结构及其连接螺栓进行静强度分析。初步计算结果表明左铰接件连接螺栓的应力不满足设计要求。通过调整铰接座的螺栓孔距、取消螺栓安装铰接座上的下沉孔、加大螺栓孔与铰接座边界的距离对固定铰接结构进行改进,结果表明：螺栓和铰接座的最大应力分别降低2.62%和41.85%,满足设计要求。     

某发动机曲轴箱有限元分析

基于有限元分析和应力疲劳理论,通过Abaqus和FEMFAT软件,对某发动机缸体曲轴箱进行结构强度分析,得到其应力分布、接触情况和高周疲劳安全因数分布.结果表明此曲轴箱结构满足设计要求.     

Abaqus在某发动机主轴承螺纹孔强度分析的应用

用AVL/Excite软件对某款发动机主轴承进行EHD分析,选择最危险时刻的主轴承载荷,将主轴承油膜压力结果映射到主轴承壁计算网格表面上,用Abaqus计算全局模型位移,并以此作为边界条件计算主轴承螺栓孔子模型的应力,通过FEMFAT对主轴承孔螺纹进行高周疲劳分析,对结果做出评价,提出结构改进建议.     

夹紧顺序、夹具布局和夹紧力对装夹变形影响与同步优化分析研究

为减小工件装夹变形,提高薄壁件加工精度,以薄壁零件装夹变形最小化为目标 函数,通过遗传算法和有限元方法相结合,提出夹紧顺序、装夹布局和夹紧力同步分析方法。用 该方法对一航空薄壁零件装夹进行优化分析,优化结果与经验设计及传统分析结果进行对比,有 效地降低了工件因装夹不当引起的变形,验证了夹紧顺序、夹具布局和夹紧力同步优化方法的 有效性。     

发动机缸体线性与非线性对比分析

采用线性分析发动机缸体时,在螺栓接触和绑定的位置会出现明显的应力集中点,且计算得到疲劳安全因数远远低于合理值.在考虑材料非线性的基础上对发动机缸体进行非线性分析,发现在螺栓接触和绑定位置处的应力明显降低,计算得到的疲劳安全因数也趋于合理.通过汽油机缸体线性与非线性对比分析可以发现,缸体非线性模型的计算结果更合理.若要改善螺栓孔周边的安全因数,一定要保证螺栓绑定和接触位置接近实际情况,特别在2个面过渡的位置不能绑定,这样可以避免造成应力集中.     

Shape optimization under fatigue using continuum damage mechanics

An introduction and overview of the developments in shape optimization for fatigue problems is given, beginning with the main ideas in the field of static shape optimization. The use of numerical tools together with the incorporation of non-linear material properties in the continuum mechanics design has led to new possibilities for the analysis of fatigue behaviour in mechanical engineering structures. Based on publications by Lemaitre and Chaboche, the material behaviour is described by defining different partial differential equation systems on micro-scale and meso-scale. From this an optimal algorithm results for the shape optimization of mechanical engineering structures using continuum damage mechanics. Our numerical and experimental tests show a significant increase of lifetime in comparison to classical shapes.     

基于图知识推理的输电线路缺销螺栓识别方法

针对输电线路缺销螺栓识别任务中存在的视觉不可分与样本不平衡问题,提出了基于图知识推理的输电线路缺销螺栓识别方法。首先通过知识表达模块学习到各类螺栓有判别力特征的类别表示;然后深入挖掘螺栓数据集中螺栓种类之间的相关性,提取出标签共现信息;最后将类别表示作为输入特征,以静态图和动态图的相关概率矩阵表征标签共现信息,通过知识推理模块完成图知识的传播与增强,从而实现缺销螺栓的识别。在实验阶段,将所选取的3类金具上的6种螺栓作为实验对象。对比实验结果表明,本文方法对缺销螺栓的识别效果优于其他方法,较原始模型提升了9.13%的准确率。消融实验结果表明,本文所提取的螺栓类别表示、静态图及动态图信息均能够提升缺销螺栓的识别效果。     

Bolt–plate contact assemblies with prestress and external loads: Solved with super element technique

In dynamically loaded bolted assemblies fatigue is the designing factor. The primary quantity that controls the fatigue is the part of the external load that is transferred to the bolt, as described by the ratio between transferred load to external load. In an idealized setting this ratio can be expressed by a stiffness ratio between the plate members and the bolt. The ratio of transferred load is, however, highly dependent on the size and position of the external loading.The bolt–plate/member connection is modelled using the finite element technique. The modelling includes contact between bolt and members and between the clamped member plates. The modelling includes the prestress that is described by a single scalar value. This prestressed state is followed by an arbitrary external load case.In this paper a finite element technique with super elements is applied to solve the contact problem of the combined prestress and external load in an overall non-iterative way. The conclusions are that it is difficult to make general design rules but in most cases the standard calculation methods will underestimate the strength of the connections. However for some specific loading situations this might not be the case.     

高频噪声下的螺栓表面缺陷检测

螺栓在很多领域内应用广泛,但在制造和加工过程中可能会出现缺陷问题,螺栓表面缺陷的存在将很大程度影响其使用寿命,并可能造成安全隐患.为了更好地检测螺栓表面缺陷,同时提高检测的速度与精度,应用机器视觉相关技术,针对螺栓表面纹理复杂、具有高频噪声难以检测的问题,提出了基于连通域自定义形状描述子的滤波算法.首先通过图像预处理与局部自适应二值化算法得到需要滤波的图像,再根据自定义的形状描述子对连通域进行高效滤波,最后经过后处理得到螺栓表面的缺陷检测结果.提出的算法能准确检测出高频噪声下的螺栓表面缺陷,并为复杂纹理下基于图像的无损质量检测技术提供了新的思路.     

某缸盖高周疲劳分析

基于有限元法和应力疲劳理论,通过Abaqus和FEMFAT软件对某发动机缸盖进行温度场和结构耐久性计算分析.计算结果表明:在当前的载荷下,从温度分布和高周疲劳角度考虑,此缸盖可以满足安全运转需求,但是对于进一步提升发动机性能,其潜在承受能力较小.     

CAE技术在汽车座椅骨架开发中的应用

为提高汽车座椅骨架的开发质量,在某型汽车座椅骨架开发中应用CAE技术进行骨架静强度和疲劳等模拟.采用壳单元与梁单元相结合建立座椅骨架有限元模型;根据座椅骨架台架耐久试验要求和试验条件,对座椅安装孔进行全约束处理,并在试验加载位置施加相应的载荷;采用Abaqus/Standard分析座椅骨架强度;在静强度分析基础上应用F...     

Design of airfoils in incompressible viscous flows by numerical optimization

A method is outlined for the design of airfoils in incompressible viscous flows by numerical optimization wherein a reduced number of design coordinates are used to define the airfoil shape. The optimization problem is formulated as a nongradient search in a finite constrained parameter space. The approach is to define the airfoil as a linear combination of basic shapes which may be analytically or numerically defined. The design problem is to determine the participation of each of these basic shapes in defining the optimum airfoil. The aerodynamic analysis program is specially developed to fit the requirements of the optimization program and is based on the vortex singularity method for inviscid flow analysis and the momentum integral method for boundary layer analysis. Four examples have been worked out to illustrate the proposed design method. In these, modifications to four different airfoil geometries are made to achieve either a minimum drag coefficient or a minimum pitching moment coefficient under prescribed constraints. The results show that significant drag or pitching moment reduction is possible through shape manipulation alone.     

Axisymmetric shell optimization under fracture mechanics and geometric constraint

This paper describes a problem of axisymmetric shell optimization under fracture mechanics and geometric constraints. The shell is made from quasi-brittle materials, and through crack arising is admitted. It is supposed that the shell is loaded by cyclic forces. A crack propagation process related to the stress intensity factor is described by Paris fatigue law. The problem of finding the meridian shape and the thickness distribution (geometric design variables) of the shell having the smallest mass subject to constraints on the cyclic number for fatigue cracks and geometrical constraint on the shell volume is investigated. Special attention is devoted to different possibilities of problem transformation and analytical methods of their solution. Using minimax approach, optimal shapes of the shells and their thickness distributions have been found analytically.     

预紧力和螺栓位置对螺栓群连接构件的影响

为研究螺栓群连接构件的力学性能,以某高速列车中较具代表性的螺栓群连接构件为研究对象,利用非线性有限元接触算法和等效外载法施加预紧力,分别对不同螺栓预紧力和不同螺栓布置位置情形下的连接构件进行仿真.通过对孔周应力的比较,得出最佳螺栓布置位置和螺栓预紧力.     

嵌入双注意力机制的Faster R-CNN航拍输电线路螺栓缺陷检测

目的 螺栓是输电线路上最普遍、数量最多的部件,螺栓缺陷检测是输电线路视觉检测任务的一大难点。针对螺栓目标存在背景复杂、目标过小、不同类别之间差异小以及精细特征难以提取的问题,提出一种双注意力机制方法,分别对不同尺度和不同位置的视觉特征进行分析和增强。方法 对于不同尺度的特征,网络使用不同尺度的特征图计算出相应的注意力图,然后将相邻层的注意力图差异性作为正则化项加入网络中,从而增强螺栓区域的精细特征。对于不同位置的特征,先使用特征图计算出图像的空间注意力图,注意力图中每个元素表示两个空间位置的相似程度,然后利用注意力图将局部特征与全局特征融合,从而在全局视野上增强相似的区域,达到增大螺栓与背景的特征差异程度,实现提高螺栓区域的预测效果。结果 本文在航拍输电线路典型螺栓数据集上进行测试,与基线相比,结合双注意力机制的航拍输电线路螺栓检测方法的平均准确率提高了2.21%,其中正常螺栓类提升了0.29%,缺销螺栓类提升了5.23%,螺母缺失螺栓类提升了1.1%。结论 本文提出的基于双注意力机制的航拍输电线路螺栓缺陷检测方法取得了良好的效果,有效避免了螺栓缺陷检测中的误判漏判问题,为进一步对输电线路其他缺陷任务奠定了良好的基础。     

发动机螺栓连接强度有限元分析

用ANSYS校核6缸发动机的连接螺栓和飞轮的强度,结果表明:在预紧工况和最大扭矩工况下,连接螺栓的受力情况基本相同,飞轮的峰值应力出现在飞轮螺纹附近;当螺栓的拧紧力矩为95 N.m时,飞轮螺纹附近区域的最大拉应力为242 MPa,满足强度要求但裕量较小,螺栓最大应力在其材料的许用应力范围内.在实际安装过程中,螺栓拧紧力矩应小于95 N.m.该仿真分析结果可为6缸发动机飞轮制造提供参考.     

基于准则法的飞机薄壁结构可靠性优化设计

针对传统的安全因数法考虑载荷和强度不确定性因素对飞机安全性的影响太笼统,无法从根本上减轻飞机结构质量的问题,提出一种飞机结构可靠性优化设计方法.根据应力-强度干涉模型计算结构单元的可靠度,建立以单元满可靠度为准则的优化模型,实现包含可靠性约束的结构尺寸优化.该功能已经加入到COMPASS中.算例结果表明该方法能够减轻结构质量,改善结构可靠度.该方法为开展飞机结构不确定性设计提供技术手段.     

Optimum design of locomotive frames using fuzzy goals and FE methods

Methods of optimum design and experimentation were used to ensure sufficient fatigue life in a series of locomotive steel frames having variable cross-sections. These were tested using resonance fatigue loading to establish the optimal fabrication methods for improving fatigue life. Dynamics simulation was used to adjust the system's natural frequency to exciter frequency by optimizing the mass distribution. Shape optimization was done by two methods. The shape was optimized using a nonlinear learning random search algorithm with both weighted and fuzzy goals and with constraints on fatigue life and with a mix of continuous, integer and discrete design variables. The goal was formulated to express customer satisfaction on the cost and technical performance. The shape was also optimized using FEM programs.     

Truss structure optimization using adaptive multi-population differential evolution

This paper applies multi-population differential evolution (MPDE) with a penalty-based, self-adaptive strategy—the adaptive multi-population differential evolution (AMPDE)—to solve truss optimization problems with design constraints. The self-adaptive strategy developed in this study is a new adaptive approach that adjusts the control parameters of MPDE by monitoring the number of infeasible solutions generated during the evolution process. Multiple different minimum weight optimization problems of the truss structure subjected to allowable stress, deflection, and kinematic stability constraints are used to demonstrate that the proposed algorithm is an efficient approach to finding the best solution for truss optimization problems. The optimum designs obtained by AMPDE are better than those found in the current literature for problems that do not violate the design constraints. We also show that self-adaptive strategy can improve the performance of MPDE in constrained truss optimization problems, especially in the case of simultaneous optimization of the size, topology, and shape of truss structures.