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1.
无约束Timoshenko梁横向冲击响应分析   总被引:6,自引:0,他引:6  
将运动刚体与受其横向冲击的无约束Timoshenko梁看成一个接触.冲击系统,用广义Fourier,级数方法推导了系统的特征方程和特征函数,得到了冲击响应的解忻解.冲击响应可以分解成弹性响应与刚性响应两部分,验证了接触.冲击系统中弹性响应的动量之和为零,从而得到刚性响应的简便求法.  相似文献   

2.
利用第(Ⅰ)部分推得的公式,对一无约束平面框架结构受运动刚体冲击时的瞬态响应进行了数值计算分析.计算了结构与运动刚体之间的冲击力时程曲线、梁中的剪力及弯矩分布、轴力杆件中的轴力分布.分析了杆中的纵波、Timoshenko梁中弯曲波及剪切波的传播现象.数值分析表明:冲击力的延续时间主要是由挠曲波及纵波控制的;在结构的冲击响应分析中,梁的剪切效应不容忽略.  相似文献   

3.
论述了轴向运动梁横向振动问题以及研究轴向运动梁横向振动问题的方法,指出对轴向运动梁横向振动问题研究中存在的一些错误并进行了更正.针对一端可看作固定边界条件的轴向运动悬臂梁,基于连续体的模态叠加法,推导出含自重效应的轴向运动梁动力响应的计算公式,进行实例计算,并对计算结果进行了详细的讨论,得出影响轴向运动梁振动响应的因素主要有速度和运动方向.  相似文献   

4.
考虑到轨道结构长度随系统响应持时的增加而增长,提出了一种改进的车辆 轨道垂向耦合系统的动力响应求解算法.该算法事先选定某一定长度的轨道结构,并获得该轨道结构的质量矩阵、阻尼矩阵和刚度矩阵;通过在求解过程中不断地对车辆子系统定位,判断是否需要对车辆子系统的位置和轨道结构的响应矩阵进行调整,以此来达到仅增加系统响应持时而不增加轨道结构长度的目的.算例表明:该改进加快算法是精确、高效的,不仅可以真实地模拟车辆在轨道上的前进运行状态,而且可以保证轨道子系统的轨道单元数量不随系统响应持时的增加而增长,这为快速求解车辆 轨道垂向耦合系统提供了一种有效的计算方法.  相似文献   

5.
利用弹性悬臂梁模态叠加构造出约束阻尼悬臂梁的振动模态,基于Lagrange方程推导出了约束阻尼悬臂梁的控制方程,求解了在集中力突然卸载的情况下约束阻尼悬臂梁的动力响应.计算并测试了一系列铝合金约束阻尼悬臂梁模型的振动频率和瞬态响应,分析了阻尼层材料参数对铝合金约束悬臂梁瞬态响应时间的影响.采用了解析法及实验法两种方法,结果表明,所采用的方法是可靠的.  相似文献   

6.
基于可靠性的工程结构动力响应优化设计   总被引:2,自引:0,他引:2  
在考虑结构物理参数和作用荷栽同时具有随机性的情况下,建立了具有动应力、动位移可靠性约束和设计变量上下限约束的工程结构优化设计数学模型;分别对结构动力响应的数字特征和基于可靠性的结构动力响应的灵敏度进行了推导。利用内罚函数法求解,算例表明中构建的优化模型和提出的求解方法是合理与可行的。  相似文献   

7.
冲击荷载作用下水中悬浮隧道的位移响应   总被引:1,自引:0,他引:1  
建立冲击荷载作用下悬浮隧道的动力学模型,将悬浮隧道简化为等距离弹性支撑梁,通过Galerkin(伽辽金)法求解悬浮隧道的振动位移方程,数值模拟悬浮隧道跨中时程响应,分析张力腿竖向刚度、冲击物质量、冲击速度对悬浮隧道跨中位移的影响.结果表明:冲击荷载作用下,张力腿竖向刚度对悬浮隧道位移响应的影响显著,但具有极限性.其次,冲击物质量和冲击速度也会显著影响悬浮隧道的跨中振动位移.研究结论为未来悬浮隧道的研究和建设提供重要的理论参考.  相似文献   

8.
根据L-I经验公式得到参数待定的L-I模型,并利用遗传算法搜索最优参数得到参数模型,对结果进行拟合优度检验,求出误差.在该模型基础上对环境温度进行修正并且考虑电流瞬时变化的影响,建立微分方程模型,采用Ode23求解,并利用遗传算法搜索最优参数得到参数,对结果进行拟合优度检验,得出了该激光器不同温度下的L-I特性曲线和激光器小信号幅频响应.同时根据速率方程推导出了带宽响应的数学模型,对参数归一化后,利用遗传算法搜索最优参数得到参数.  相似文献   

9.
带裂纹三点弯曲试样的动态应力强度因子分析   总被引:1,自引:0,他引:1  
提出了计算带单边裂纹三点弯曲试样动态应力强度因子的新方法.首先由权函数的普遍形式和两种参考载荷下的应力强度因子,得到了带单边裂纹三点弯曲试样的权函数,然后考虑试样的转动惯性和剪切变形,根据振动理论推导出无裂纹梁内的动应力响应和分布,最后由权函数的思想推导出了带裂纹三点弯曲试样动态应力强度因子公式.通过有限元数值计算,验证了该方法的正确性,结果比较表明公式具有较高的精度.另外,还研究了冲击载荷下三点弯曲试样的动态应力强度因子随裂纹长度和加载速率的变化规律.  相似文献   

10.
本文利用正交多项式级数部分和的“最佳近似”性,推出了求解结构动力响应的付里叶-厄密多项式展开法.文中详细推导了振动系统的位移和速度响应的分步解析表达式,并讨论了计算格式的稳定性条件,通过了实例考核与精确度对比分析.  相似文献   

11.
Fluid-induced vibration (FIV) prediction is an important prerequisite work in wear and fatigue analysis of tubing string in oil & gas well. The finite element method, energy method and Hamiltonian principle are comprehensively used to establish a single nonlinear vibration model of pipe conveying fluid, taking into account the longitudinal/lateral coupled vibration. Based on the contact/impact theory of elastic/plastic body, the nonlinear contact-impact model of tubing-casing is established and introduced into the single nonlinear vibration model to form a bi-nonlinear vibration model of tubing string in oil & gas well. The bi-nonlinear model is numerically discretized by the finite element method, solved by Newmark− β method, and verified preliminarily by a classical contact/impact example in literature in which the influence of inflow is not taken into account temporarily. A similar experiment of tubing vibration is designed and completed to further test the validity of the bi-nonlinear vibration model by comparing the frequency-domain and time-domain responses of the experiment with those from the model. The analysis shows that the bi-nonlinear model has good calculation accuracy and the vibration response law is basically consistent with the experimental results, which can provide an effective theoretical analysis tool for FIV behavior of tubing string in oil & gas well.  相似文献   

12.
根据冲击接触计算模型所需满足的基本控制方程和非线性互补条件,应用非线性互补问题与约束优化的等价关系将非线性互补接触问题转变成一个非线性规划问题,系统地推导建立了冲击接触问题的一种双共轭投影梯度计算方法.增广Lagrange乘子法克服了罚函数要求减小迭代步长以达到计算稳定的限制,即使对于冲击接触问题亦可以采用较大迭代步长,在形成的与原互补问题等价的无约束规划模式下,应用双共轭投影梯度算法提高非线性搜索速度和计算效率.算法模型计算结果表明,所建立的双共轭投影梯度计算理论及方法是正确有效的.  相似文献   

13.
The paper deals with a coding method for a sequent calculus of the propositional logic. The method is based on the sequent calculus. It allows us to determine if a formula is derivable in the calculus without constructing a derivation tree. The main advantage of the coding method is its compactness in comparison with derivation trees of the sequent calculus. The coding method can be used as a decision procedure for the propositional logic.  相似文献   

14.
In order to enrich the bridge damage detection method and further improve the accuracy of bridge damage identification, a detection method for simply supported beams with cracks under dynamic loads was proposed not based on the complete finite element model. Under the premise of not blocking traffic, the method only needs to analyze and deal with the acceleration responses of the simply supported beam span, which reduces the mounting, dismounting and maintenance of sensors in practical engineering. At the same time, based on the model, an analytical formula of the acceleration at the midspan of the simply supported cracked beam was derived. Based on the theoretical derivation, the instantaneous energy and the mean energy difference were constructed through the variational mode decomposition and the Hilbert transform, and these 2 crack identification indexes were used to effectively identify small cracks with a crack depth ratio of only 5%. Then the influences of different wheel loads, environmental noises and damage degrees on detection results were studied. The results show that: ① the instantaneous frequency has a better recognition effect for crack positions; ② the mean energy difference is sensitive to crack depth ratio δ and the wheel load magnitude; ③ this method has strong noise robustness. © 2022 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.  相似文献   

15.
Ever since Kirk proposed an approximate price formula for a European call spread option in 1995, Kirk’s approximation has become the most widely used among the practitioners, especially in the energy markets. It is well known that Kirk’s approximation extends from Margrabe’s exchange option formula but no explicit derivation is available or has ever been published. In this paper we apply the idea of WKB method to provide a simple derivation of Kirk’s approximation and discuss its validity.  相似文献   

16.
Lattice theory with the meet and join operations is formulated as a system of rules of inference. The order of application of these rules can be permuted so that a subterm property follows: If an atomic formula is derivable from given atomic formulas by the rules, it has a derivation all terms of which are terms in the given formulas or the conclusion. A direct decision method for universal formulas in lattice theory with the meet and join operations follows.  相似文献   

17.
In a recent paper [2], Nourein derived an iteration formula, which exhibited cubic convergence for the simultaneous determination of the zeroes of a polynomial. In this paper - following quite a different appraoch - we derive a method which can be viewed as an improvement on that of [2]. The derivation is based on the approximation of the polynomial in question by a Lagrange interpolation formula. We give the algorithm in ALGOL 60. For a given real polynomial, the algorithm caters for the general case of complex zeroes.  相似文献   

18.
The traditional antenna calibration for time division duplex multiple input multiple output (TDD-MIMO) systems assume that free-space channel keeps constant during calibration, which is unreasonable under the high-speed rail and other time-varying channel scenarios for time variability can cause calibration error. This paper analyzes the performance of traditional antenna calibration methods, and then proposes an antenna calibration method based on Wiener channel prediction for time-varying TDD-MIMO system. Through theoretical derivation, we get the capacity formula of the TDD-MIMO system using traditional antenna calibration and antenna calibration based on channel prediction. The theoretical analysis and simulation results both indicate that the performance degradation of antenna calibration can be caused by time-varying channel and the prediction algorithm proposed in the paper can well compensate for the performance loss and significantly improve the antenna calibration performance for time-varying TDD-MIMO system.  相似文献   

19.
A derivation schema in an axiomatic theory is defined as a finite sequence of analysis of applications of rules and axioms. A derivation by a schema U is any derivation whose list of analyses of applications of rules and axioms is precisely U. A derivation schema is admissible if a corresponding derivation can be constructed. Let G be a Hilbert-type axiomatic theory. The following problems are considered: a) to decide whether a given derivation scheme is admissible in G; b) to decide whether a formula is derivable by a given derivation schema in G. In the usual formulations of the predicate calculus without equality, the first problem is shown to be decidable, the second undecidable.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akad. Nauk SSSR, Vol. 174, pp. 132–146, 1988.  相似文献   

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