大挠度简支矩形薄板在热、力、磁耦合作用下的分岔与混沌

本文针对大挠度四边不可移简支薄板,研究其在机械载荷、电磁场与温度场耦合作用下的混沌运动。在板壳与磁弹性力学理论的基础上,考虑温度场的影响,推导出在横向稳恒磁场和机械载荷共同作用下薄板的非线性磁弹性耦合振动方程。利用Melnikov函数法,求出该动力系统Smale马蹄变换意义下出现混沌运动的条件,并对该系统振动方程进行数值模拟。通过具体算例,得到了系统的分岔图、位移波形图、相平面轨迹及庞加莱截面图,讨论了机械载荷、磁场以及温度场的参数对系统混沌运动的影响。由仿真结果可知,通过变化机械载荷、磁场和温度场参数,可以控制系统的振动特性。     

一类非光滑机械系统的Hopf分岔与混沌

通过用四阶Runge-kutta数值积分法和Poincare映射法对系统复杂动力学现象进行的仿真，对一类简谐激振力作用下的双边不对称复杂约束系统的动力学行为进行了分析，证实单自由度含间隙系统中存在Hopf分岔，分析了系统周期运动的Hopf分岔以及通向混沌的拟周期道路。对其分岔与混沌行为的研究为工业实际中含间隙机械系统和冲击振动系统的优化设计提供了理论依据。     

《简支板辐射噪声的结构优化控制与仿真》

以简支矩形板为例,利用时域声辐射模态进行噪声的结构优化控制。已有研究表明时域辐射模态能独立地辐射声功率,并且振动结构辐射的声功率主要由第一阶辐射模态的声功率决定。在此基础上进行简支板辐射噪声的结构优化控制,并对最优控制力源的位置进行了讨论和分析。最后设计自适应前馈控制系统对控制效果进行仿真验证。     

简支梁式关键部件在蜂窝纸板缓冲作用下的冲击响应研究

具有简支梁式关键部件的电子产品,在运输过程中常用蜂窝纸板作为缓冲材料。为了分析这类易损部件在冲击载荷下的失效行为,先研究蜂窝纸板的压缩力学性能,并得到蜂窝纸板简化本构方程;然后在矩形加速度脉冲激励下,求解出最大应力与矩形脉冲峰值之间的关系,进而得到蜂窝纸板横截面积与厚度所满足的约束条件,推导出简支板弯曲应力的近似解析解;最后通过有限元分析验证解析法的可靠性。研究结果表明:蜂窝纸板在屈服阶段的应力可以表示为平台应力,且蜂窝纸板呈现率相关性;运用矩形加速度脉冲替代蜂窝纸板实际传递的加速度脉冲,在求解易损件的应力响应中具有较高的精度。     

光电层合简支板的多模态最优模糊主动振动控制

本文以配置两对光致伸缩驱动器的简支板为控制对象,提出了最优控制与模糊控制相结合的最优模糊主动控制算法。考虑到光致伸缩驱动器的非线性驱动特性,首先由最优控制获得光电层合简支板多模态振动的期望控制量, 再通过模糊控制器使光致伸缩驱动器光致应变逼近该控制量, 从而实现对简支板的多模态振动控制。在最优模糊控制器设计过程中,模糊控制的设计与最优控制设计是相互独立的。仿真结果表明, 最优模糊控制能够有效实现光电层合简支板的多模态振动抑制,控制效果明显优于直接最优状态反馈控制。     

Experimental Investigation of the Decomposition of a Nonpolar-Gas Hydrate in a Pipe Under the Action of a Microwave Electromagnetic Field

Results of experimental investigations of the decomposition of a propane hydrate in a pipe under the action of a microwave electromagnetic field are presented. Methods of obtaining a gas hydrate, its decomposition under the action of a microwave electromagnetic field, and measuring the temperature and pressure in a pipeline have been developed. It has been established that the rate of decomposition of a gas hydrate increases under the action of a microwave electromagnetic field. It is shown that a gas hydrate in a pipe can be completely decomposed under the action of a microwave electromagnetic radiation whose wavelength is comparable to the thickness of this hydrate. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 108–114, May–June, 2005.     

Thermoelastic State of a Conducting Plate under the Action of an Electromagnetic Field in the Form of Damped Sinusoid

We determine the temperature fields and stresses formed in an infinite nonferromagnetic conducting plate of constant thickness under the action of a pulsed electromagnetic field specified by the values of the tangential component of magnetic vector on the surfaces. In the case of electromagnetic action obeying the law of damped sinusoid, we perform the comparative numerical analysis of ponderomotive forces, temperature, and components of the dynamic stress tensor for plates made of stainless steel and copper. It is shown that the influence of electric and thermal conductivity, thermal diffusivity, the coefficient of linear thermal expansion, and Young's modulus on the quantitative and qualitative behavior of the analyzed parameters as functions of time is significant.     

Sensitivity of Dynamic Response of a Simply Supported Functionally Graded Magneto-electro-elastic Plate to its Elastic Parameters

Dynamic response sensitivity of a simply supported functionally graded magneto-electro-elastic plates have been studied by combining analytical method with finite element method. The functionally graded material parameters are assumed to obey exponential law in the thickness direction. A series solution of double trigonometric function agreed with the simply supported boundary condition is adopted in the plane of the plate and finite element method is used across the thickness of the plate. The finite element model is established based on energy variational principle. The coupled electromagnetic dynamic characteristics of a simply supported functionally graded magneto- electro-elastic plate are decided by its dynamics differential equation into which displacement components, electric potential and magnetic potential as nodal degree of freedom are incorporated. Dynamic response sensitivity is defined as a partial differential of dynamic response with respect to material parameter. Sensitivity of dynamic response of a simply supported functionally graded magneto-electro-elastic plate to its elastic parameters has been studied. The influence of the different exponential factor on dynamic response sensitivity has also been investigated.     

Non-homogeneous Steady-State Heat Conduction Problem in a Thin Circular Plate and Its Thermal Stresses

The present paper deals with the determination of the displacement and thermal stresses in a thin circular plate defined as 0 ≤ r ≤ b, 0 ≤ z ≤ h under a steady temperature field, due to a constant rate of heat generation within it. A thin circular plate is insulated at the fixed circular boundary (r = b), and the remaining boundary surfaces (z = 0, z = h) are kept at zero temperature. The governing heat conduction equation has been solved by using an integral transform technique. The results are obtained in series form in terms of modified Bessel functions. The results for displacement and stresses have been computed numerically and are illustrated graphically.