弹性约束悬臂压弯梁的稳定性及最大二阶弯矩

利用变形微分方程,对弹性约束悬臂压弯梁的稳定性进行分析,给出了其临界载荷的精确计算式和实用近似计算式,推导了弹性约束悬臂压弯梁约束端二阶弯矩的精确计算式,并讨论了《塔式起重机设计规范》中的非弹性约束压弯梁的最大二阶弯矩近似计算式在考虑了约束端弹性时的适用性。     

简支梁在移动载荷作用下的最大剪力和最大弯矩

应用剪力图、弯矩图和代数二次函数极值的知识,对简支梁受移动载荷作用时的最大剪力和最大弯矩的计算方法进行了论证。     

游乐设施压杆稳定性计算原理解析

构件稳定性是指构件在外力作用下,保持原有平衡形式的能力,即不会产生失稳现象。游乐设施钢结构作为主要承重结构,存在失稳破坏的可能性。本文对压杆稳定性计算公式进行详细推导,得出欧拉临界力公式,利用公式对游乐设施轨道立柱进行稳定性分析,并得出立柱失稳的临界载荷和稳定系数,并用有限元方法对轨道立柱进行屈曲稳定分析,结果表明稳定性分析理论可以合理解释有限元分析结果,其计算方法为游乐设施稳定性计算分析提供了参考。     

双小车主梁最大弯矩位置的探讨分析

双小车双梁在设计主梁时,需确定主梁的最大弯矩位置,这对主梁承载的几种工况受力分析可以简化许多繁琐的计算。文中从经典的受力分析出发,对双小车的主梁最大弯矩位置进行了分析探讨。     

简支梁在移动载荷作用下的最大剪力和最大弯矩

应用剪力图、弯矩图和代数二次函数极值的知识,对简支梁受移动载荷作用时的最大剪力和最大弯矩的计算方法进行了论证。     

基于劳斯判据的柔性机械臂弹性运动稳定性分析

为了研究柔性机械臂的弹性运动稳定性,分析末端附加质量和关节惯量对弹性运动稳定性的影响,并计算柔性机械臂的动态最大许用载荷,建立了单连杆柔性机械臂的物理模型,用时空分离法和拉普拉斯变换法求解了柔性机械臂的弹性运动微分方程,用拉格朗日法建立了末端有集中质量的柔性机械臂的动力学模型并对其简化和截断。在指定状态变量、控制作用和输出变量后,建立了状态空间表达式和传递函数,并且用劳斯判据建立了稳定性判据并对其进行了简化。用得到的稳定性判据分析了末端附加集中质量和关节惯量对柔性机械臂弹性运动稳定性的影响,并从保证弹性运动稳定的角度计算了柔性机械臂的最大许用载荷。     

多节串联直角切口弹性铰链的屈曲分析

依据材料力学能量原理中的瑞利-里兹法,建立计算多节串联直角切口弹性铰链屈曲临界载荷的数学模型,并推导屈曲临界载荷的计算公式。采用商用有限元软件Abaqus6.6对不同参数的铰链模型进行有限元屈曲分析,有限元分析结果与数学模型计算的屈曲临界载荷很接近,说明所建数学模型的正确性。     

径向力和弯矩联合作用下滚子轴承的刚度计算

滚子轴承在径向力和弯矩联合作用下的承载情况极为复杂，其刚度计算也更为困难。为了建立我国航空发动机滚子轴承的寿命评价体系，在考虑弹性流体动力润滑状态的情况下，提出了航空发动机高速滚子轴承的一种实用刚度分析方法，利用该分析方法对某航空发动机主轴承在复杂载荷作用下的刚度特性进行了分析。实例计算验证了理论分析的正确性。     

弹性约束下颗粒碰撞阻尼器的理论与实验研究

为进一步研究弹性约束颗粒碰撞阻尼器的减振性能,提出了该阻尼系统的动力学模型,并模拟了该阻尼器对悬臂梁的减振效果。同时,对5种不同刚度的弹性约束颗粒碰撞阻尼器的减振效果进行了实验研究。结果表明：理论计算与实验的结果基本吻合,证明所建立的弹性约束下的颗粒碰撞阻尼系统的计算模型是可靠的;在弹性约束下的颗粒碰撞阻尼系统中,其刚度比对减振效果的影响是非线性的,且弹簧刚度对该碰撞系统的共振点存在影响。     

埋地大口径蝶阀基于刚度、密封性能的最大弯曲载荷研究

基于API 6D对管线阀门因弯曲载荷破坏时应具有足够结构强度、刚度及密封性的高要求,采用有限元法对DN2800埋地大口径蝶阀进行刚度、密封性能分析;建立蝶阀抗弯模型,对DN2800蝶阀及系列产品最大弯曲载荷进行研究。结果表明:(1)长期承受附加载荷的DN2800蝶阀密封失效先于刚度失效,所能承受的最大弯曲载荷为密封有效临界弯曲载荷;(2)DN1000 mm系列大口径蝶阀壁厚t、公称直径d与抗弯刚度K、刚度有效临界弯曲载荷M1、密封有效临界弯曲载荷M2间呈二次函数关系,且可承受最大弯曲载荷为M2。研究方法和结论对埋地大口径蝶阀承受最大弯曲载荷的研究提供了参考依据。     

Semi-analytical approach for free vibration analysis of cracked beams resting on two-parameter elastic foundation with elastically restrained ends

In present study, free vibration of cracked beams resting on two-parameter elastic foundation with elastically restrained ends is considered. Euler-Bernoulli beam hypothesis has been applied and translational and rotational elastic springs in each end considered as support. The crack is modeled as a mass-less rotational spring which divides beam into two segments. After governing the equations of motion, the differential transform method (DTM) has been served to determine dimensionless frequencies and normalized mode shapes. DTM is a semi-analytical approach based on Taylor expansion series that converts differential equations to recursive algebraic equations. The DTM results for the natural frequencies in special cases are in very good agreement with results reported by well-known references. Also, the DTM procedure yields rapid convergence beside high accuracy without any frequency missing. Comprehensive studies to analyze the effects of crack location, crack severity, parameters of elastic foundation and boundary conditions on dimensionless frequencies as well as effects of elastic boundary conditions on cracked beams mode shapes are carried out and some problems handled for first time in this paper. Since this paper deals with general problem, the derived formulation has capability for analyzing free vibration of cracked beam with every boundary condition.     

基于有限元和响应面近似的卡箍连接处最大弯曲应力估算

在水下航行器壳体连接设计中,卡箍连接设计在实际工程中得到了广泛应用.水下航行器入水过程及其复杂,目前研究对卡箍连接处的力学分析还不够充分.先对水下航行器入水瞬间,卡箍连接处进行力学分析,然后使用有限元和响应面近似法对受力分析加以验证,最后对某型水下航行器卡箍连接处最大弯曲应力进行函数拟合.最后对通过拟合的某型水下航行器...     

Nonlinear bending of Reissner–Mindlin plates with free edges under transverse and in-plane loads and resting on elastic foundations

A nonlinear bending analysis is presented for a rectangular Reissner–Mindlin plate with free edges subjected to combined transverse partially distributed load and compressive edge loading and resting on a two-parameter (Pasternak-type) elastic foundation. The formulations are based on the Reissner–Mindlin plate theory considering the first-order shear deformation effect, and including the plate-foundation interaction. The analysis uses a mixed Galerkin-perturbation technique to determine the load–deflection curves and load–bending moment curves. Numerical examples are presented that relate to the performances of moderately thick rectangular plates with free edges subjected to combined loading and resting on Pasternak-type elastic foundations from which results for Winkler elastic foundations are obtained as a limiting case. The influence played by a number of effects, among them foundation stiffness, transverse shear deformation, loaded area, the plate aspect ratio and initial compressive load are studied. Typical results are presented in dimensionless graphical form.     

Dynamic analysis of composite beam subjected to harmonic moving load based on the third-order shear deformation theory

The response of an infinite Timoshenko beam subjected to a harmonic moving load based on the third-order shear deformation theory (TSDT) is studied. The beam is made of laminated composite, and located on a Pasternak viscoelastic foundation. By using the principle of total minimum potential energy, the governing partial differential equations of motion are obtained. The solution is directed to compute the deflection and bending moment distribution along the length of the beam. Also, the effects of two types of composite materials, stiffness and shear layer viscosity coefficients of foundation, velocity and frequency of the moving load over the beam response are studied. In order to demonstrate the accuracy of the present method, the results TSDT are compared with the previously obtained results based on first-order shear deformation theory, with which good agreements are observed.     

基于主轴分析和EDISON—Zernike矩的彩色图像亚像素边缘检测

本文分析了目前常见的亚像素边缘检测方法,提出了一种综合运用主轴分析法、Zernike矩和嵌入置信度的彩色图像亚像素边缘检测算法。首先获取影像三维空间中的主轴,然后利用嵌入置信度的边缘检测算子快速检测出所有可能的边缘点,再利用Zernike矩算子以亚像素精度重新定位边缘。实验表明本文算法优于其它的边缘检测算子,充分利用了图像的彩色信息,定位精度能够达到0.13个像素,并且该方法还具有良好的抗噪声干扰性和处理效率。     

基于最大熵原理和模糊方法的极小子样产品可靠性分析

在假设产品寿命服从对数正态分布情况下，提出了用分散系数法评估极小子样产品的可靠性。介绍了2种求解分散系数的公式。分散系数的大小影响产品的可靠性，而寿命标准差又是决定分散系数大小的主要因素之一。运用极大熵原理和模糊综合分析，讨论了寿命标准差的具体求法。通过实例介绍了该方法的具体运用。     

船体外板水火成型机器人Y轴横梁变形计算和模态分析

对船体外板水火成型智能机器人的重要部件——Y轴横梁进行了有限元静力学分析和模态分析。采用三维十节点四面体结构单元计算Y轴横粱在各种典型工况下的变形，提取变形规律。在此基础上，对Y轴横梁进行模态分析，求解出前5阶的固有频率和相应频率处的振动模态，验证其设计结构的可行性。同时，也为后续的加工精度分析和误差补偿提供了理论依据。     

Research on calculation method of free flow discharge based on artificial neural network and regression analysis

Taking the Huaidian Sluice on the Shaying River in China as an example, this paper establishes the calculation model of the free flow based on artificial neural network and regression analysis. Four forms of discharge coefficient calculation equations were obtained by regression analysis, and three neural network models were established. The model is fully verified by using the measured data. The experimental results show that the third-order polynomial and multilayer perceptron neural network have better adaptability. The advantages and disadvantages of the different methods are analyzed and the cause of the error is identified. It provides a theoretical basis for dealing with the discharge calculation of small and medium dam.     

利用ANSYS和坎贝尔图对燃气轮机压气机转子模态及临界转速的分析计算

建立了某型燃气轮机低压压气机转子的几何模型,使用可计算陀螺效应的体单元建立了转子的有限元模型.利用数值仿真软件求解转子的前8阶模态,并基于其高速旋转结构模态分析功能画出了特征频率随转速的变化曲线即坎贝尔图.计算得到了一阶临界转速,并就支承刚度对其影响进行了研究.计算结果表明:转子的设计具有良好的结构刚度;设计中需要对压气机转子第4级轮盘附近转鼓的强度给予一定的重视;转子系统临界转速安全系数合理;支承刚度的改变对临界转速的影响处于非敏感区,有利于转子的稳定运行.