一种不对称滞回受迫振动系统及其应用

许多系统或结构在动载荷作用下会表现出非线性滞回行为。通过情况下，人们往往认为滞回环是对称的。但是，在工程实际中还存在一些特殊的、不对称的滞回现象。例如，在对物料进行振动压实的过程中，由于压实机构的压下和回程中物料弹塑性变形不同。该振动产系统存在不对称的滞回恢复力。本文提出用一种不对称模型描述这种不对称滞回性质，该不对称滞回模型由分段曲线组成。文章对这类系统在简谐激励下的响应特征进行了分析，得到一次     

窄带激励下带有时滞反馈的非线性动力系统的响应

研究了窄带激励下带有时滞反馈的Duffing振子的主共振响应。用多尺度法分离了系统的快慢变量。分析了稳态响应的稳定性和分叉，研究了时滞、调谐参数、噪声带宽和幅值对系统的影响。证明了由于时滞的存在，系统将表现出复杂的动力学行为：时滞会导致分叉、时滞会影响跳跃区域等;发现噪声幅值会导致系统多解或分叉现象的出现，且随着噪声带宽的增大系统非零稳态响应从-极限环变为-扩散的极限环。最后，给出了数值模拟。     

一种不对称滞回受迫振动系统及其分析

许多系统或结构在动载荷作用下会表现出非线性滞回行为。通常情况下，人们往往认为滞回环是对称的。但是，在工程实际中还存在一些特殊的、不对称的滞回现象。例如，在对物料进行振动压实的过程中，由于压实机构的压下和回程中物料弹塑性变形规律不同，该振动压实系统存在不对称的滞回恢复力。本文提出用一种不对称模型描述这种不对称滞回性质，该不对称滞回模型由分段曲线组成。文章对这类系统在简谐激励下的响应特征进行了分析，得到一次近似解析解以及特有的直流分量和二次谐波等成分。然后又通过实验和数值模拟分别验证了模型的合理性。     

《结合部系统的混沌与分岔的研究》

研究了机床导轨结合部系统的非线性动力学行为。考虑到系统在实际接触振动过程中具有滞回模型的特点,建立了分析该类系统的数学模型,并应用渐进法求出系统的等效阻尼和等效刚度系数。采用Range-Kutta法对系统方程进行了数值计算,并讨论了系统在改变阻尼条件下的非线性动力响应问题。最后发现阻尼在一定范围内变化时,系统会出现混沌运动。     

Bouc-Wen模型参数识别的非线性自适应遗传算法和试验验证

Bouc-Wen模型是一种可表征结构及构件在往复荷载作用下的刚度退化、强度退化等的一种多功能非线性光滑滞回模型,可广泛应用于各类结构滞回行为的描述。Bouc-Wen模型参数是决定结构构件滞回模型力学特征的关键,由于该模型参数众多且物理意义不明确,往往只能从滞回数据得到近似解。为适应该类模型参数高效识别的需求,该研究提出了一种非线性自适应遗传算法,并通过4片不同配筋和加载条件的RC剪力墙的低周反复加载试验对Bouc-Wen模型参数识别的效果进行了验证。模型参数识别得到的滞回曲线和算法效率与标准遗传算法识别的结果以及实验数据进行了对比,结果表明:所提出的方法显著提升了Bouc-Wen模型的识别精度与效率。该文所提出的方法可用来进行结构滞回模型的识别并用所识别的模型进行结构的非线性行为模拟。     

带滞变支撑悬臂输流管的动力响应分析

将滞变支撑所做的虚功引入到管道的能量方程中,利用Hamilton体系的变分原理,导出了带滞变支撑悬臂输流管的非线性运动方程。进而利用Galerkin法对偏微分方程进行离散,以Matlab为平台编制了带滞变支撑悬臂输流管流致振动的计算程序。通过滞变支撑退化模型与现有文献结果比较,验证了本文模型的有效性;随后,考察了该系统的动力学行为,并分析了滞变支撑刚度对悬臂输流管稳定性的影响。结果表明,滞变支撑悬臂输流管表现出丰富的动力学行为,刚度的变化不仅使使得系统的分叉类型、分叉方式与分叉路径发生了的显著变化,也改变了周期运动的周期数,并使其出现复杂响应的参数范围发生了改变。     

单自由度随机滞回系统的振动响应分析

在Bouc—Wen滞回模型的基础上，根据求解随机非线性结构动力学的二阶矩法，推导出求解由滞回环本身的随机性而引起的、单自由度随机滞回系统的响应的有效数值方法，得到了系统响应的均值和标准差。并采用Monte—Carlo数值模拟法对系统的响应进行模拟分析，其计算结果与数值模拟结果相基本吻合。从而解决了由滞回环本身的随机性引起的非线性振动系统的随机响应问题。     

某发动机转子-机匣系统局部碰摩的混沌运动研究

以某发动机实验器为基础，研究了转子-机匣系统发生碰摩时的分叉与混沌行为。分析了转子径向碰摩刚度比、偏心质量等参数对转子分叉与混沌特性的影响并与试验结果进行了比较。当转子机匣系统发生碰摩时呈现出非常丰富的动力学行为，除了通过倍周期、阵发性和拟周期分叉进入混沌外，还发现了孪生叉形分叉现象。     

强非线性Duffing系统倍周期分叉

应用广义牛顿法和周期解存在条件，得到了强非线性Ｄｕｆｉｎｇ系统在物理参数平面上周期倍化分叉的转迁集，以及在不同区域内全局分叉行为，并分析了非线性项对于周期倍化分叉转迁集的影响。     

考虑非线性涡动时裂纹转子的分叉与混沌特性

分析了裂纹转子在非线性涡动影响下的动力学行为，特别是系统响应的分叉与混沌特性。通过大量数值计算表明：当刚度变化比ΔＫ较大时，系统在亚临界转速区的１２Ωｃ、２３Ωｃ附近具有丰富的非线性力学行为，有可能出现倍周期分叉、拟周期响应及混沌现象。随着ΔＫ的增大，在１２Ωｃ、２３Ωｃ附近周期解分别由低频进动分量分叉和谐波分量分叉两种不同的方式变到拟周期。随继续增大，首先在２３Ωｃ附近出现混沌，通向混沌的道路一方面是由拟周期进入，另一方面则与周期３解有关。当ΔＫ非常大时，在１２Ωｃ附近也由拟周期通向混沌。本文还发现许多周期３解随初值的改变而变为其它周期数解的情形。     

Use of the phase shift between longitudinal and transverse strains for determining material damping properties. Communication 1

Results are presented for a procedure for determining the damping capacity (inelasticity characteristic) of a material in terms of the phase shift between longitudinal and transverse strains. The effect of each element of a phase shift measurement system is evaluated and a method is suggested for ways of excluding it or taking it into account. It is shown in particular that failure to consider the hysteresis of strain gages leads to an overestimate of the measured inelasticity characteristics using the force hysteresis dynamic loop method and to an underestimate in the case of using the strain hysteresis dynamic loop method.Translated from Problemy Prochnosti, No. 10, pp. 37–44, October, 1994.     

Hysteresis correction in the curvature adaptive optics system

An enhancing Coleman-Hodgdon model is introduced to describe the hysteresis curves of the bimorph deformable mirror (DM). Hysteresis curves are measured from a bimorph DM and then experiment is set up for the correction of hysteresis. Finally, step response and transfer functions of a curvature adaptive optics (AO) system are compared in three cases: with DM hysteresis, without hysteresis, and with hysteresis but corrected. Simulation results show that the bandwidth of a curvature AO system is improved significantly under different loop gains after hysteresis of the DM is corrected.     

Nonlinear dynamics of a Bragg cell under intensity feedback in the near-Bragg,four-order regime

A detailed examination of the nonlinear dynamical behavior of an acousto-optic Bragg cell in the near-Bragg regime of operation for the case of four scattered orders under intensity feedback is carried out. This problem is an extension of the standard ideal-Bragg feedback model whereby traditionally bistability, hysteresis, and chaotic oscillations are observed under zeroth- or first-order feedback of the scattered light. For the present case, the closed-loop equations are developed from a priori knowledge of the open-loop analytical solutions for four-order near-Bragg scattering. The results, obtained via computer simulation, reveal a variety of interesting dynamics, including bistability, bifurcation, hysteresis, chaotic oscillations (including in this case the relatively uncommon period-three behavior, in addition to the more usual period-doubling phenomenon en route to chaos), and potentially useful parametric dependence of these features. The observed results are interpreted in terms of system behavior for varying feedback gain and bias, the so-called Klein-Cook parameter Q, and time delay, and are compared with earlier work based on the ideal Bragg regime.     

A method for calculating hysteresis loops of interacting single-domain particle systems in a nonmagnetic binder

A method is given for calculating the minor and full hysteresis loops of a system of uniaxial single-domain particles with a common direction of easiest magnetization. A probabilistic approach is used in formulating the problem by means of two differential equations which are solved for the simple case of an infinite particle chain. The method is based on a model in which each particle is characterized by a rectangular hysteresis loop with a specific saturation field Hs, and the loops are influenced by the (homogeneous) external magnetic fieldHas well by the magnetization-dependent interaction of the particles among themselves.     

Experimental investigation and numerical simulation on the hysteresis zone of a variable displacement wobble plate compressor

A test system with the variable displacement compressor (VDC) for automotive air conditioning system is built to study the changing rule of piston stroke length (PSL). It is found from our experiments that the critical suction pressure where the PSL starts to decrease is less than that where the PSL starts to increase for the same PSL; between the two critical lines, a hysteresis zone is formed, within which all the steady-state points fall and there is a multiple-valued relationship between VDC parameters; and the PSL is kept invariable when the VDC parameters change within the hysteresis zone. In order to find out the reason causing the hysteresis zone and to analyze the influence of the compressor parameters on the hysteresis zone, a steady-state mathematical model of VDC is developed and verified by our experimental data. The theoretical analysis indicates that the hysteresis zone is caused by the frictional forces among the moving components of VDC, and the greater the frictional forces, the broader the hysteresis zone and the larger the changing range of suction pressure. The influence of the discharge pressure and rotary speed on the hysteresis zone is that the hysteresis zone moves in the direction of the suction pressure decreasing along with the increase of the discharge pressure or rotary speed.     

Determination of PRT Hysteresis in the Temperature Range from −50 °C to 300 °C

This paper discusses the contribution of hysteresis to the measurement uncertainty of industrial platinum resistance thermometers (IPRTs). Hysteresis is one of the sources of uncertainty that has so far not been sufficiently researched and documented. The term hysteresis applies to any system that is path dependent; the output depends on the history of the input. In our case, thermal hysteresis results in different resistance values at the same temperature point, depending on whether the temperature was increasing or decreasing. The reason for such behavior is related to the construction of the thermometer (strain due to thermal expansion and contraction) and also to possible moisture inside the encapsulation. In the process of evaluation of the calibration and measurement capabilities (CMCs) of IPRTs within Working Group 8, the Consultative Committee for Thermometry (CCT WG8) concluded that the uncertainty due to hysteresis is not uniformly defined and not always added to the total uncertainty of the resistance thermometer under calibration. In order to estimate the uncertainty contribution due to the hysteresis and compare different procedures, resistance measurements were carried out on a number of IPRTs of different qualities and tolerance classes. The temperature span was between ?50 °C and 300 °C, which is the most frequent temperature range in the practical use of IPRTs. The hysteresis was then determined in different ways (change of resistance at the ice point and at the midpoint temperature according to the ASTM International Standard E644 and according to the new version of IEC Standard 60751), and a comparison of results was made.     

Experimental and theoretical investigation of the effect of kinematic hardening on spherical indentation

When investigating material properties, the indentation test is often used in spite of the fact that very complicated nonhomogeneous processes are involved. In order to understand this test in more detail, an analysis was given by Huber and Tsakmakis using Finite Element calculations. It was shown that there exists an analogy between uniaxial homogeneous tensile experiments and spherical indentation for cyclic loading conditions. In fact, in both cases, existence, e.g., of kinematic hardening can be identified by the existence of hysteresis loops in the strain–stress diagram and the depth–load plot, respectively. The present paper deals with an experimental verification of the existence of such hysteresis loops for the case of depth-sensing indentation tests. Further, two measures are considered in order to quantify the size of hysteresis loops. The first one is the area enclosed by the hysteresis loop while the second one is a suitable defined middle opening of the hysteresis loop. Using various Finite Element calculations, it is shown that both measures can be regarded to be correlated. These theoretical relationships are proved to be in agreement with experimental results as well. Finally, the effect of kinematic hardening on the hysteresis loops is discussed experimentally by studying the opening of the hysteresis loop as a function of the depth.     

Influence of Maglev Force Relaxation on Hysteresis of Bulk HTSC Above the NdFeB Guideway at Different Lateral Displacements

After the maglev force (both levitation and guidance forces) relaxation property of a high-temperature superconductor (HTS) above a permanent-magnet guideway (PMG) was studied experimentally, the HTS bulk was horizontally moved in the lateral direction with different displacements above the permanent-magnet guideway. Both levitation and guidance force curves with lateral displacement were obtained by a SCML-2 measurement system synchronously. It was found that the levitation force hysteresis after relaxation was reduced compared to the case without relaxation, while the guidance force hysteresis curve almost did not change. This study provided a scientific analysis for the practical application of the bulk HTS.     

The Influence on Levitation Force of the Bulk HTSC Above a Permanent Magnet Guideway Operating Dive-Lift Movement with Different Angles

In practical applications, the operating of accelerating or decelerating inevitably happens in the high temperature superconducting (HTS) Maglev train. For the further research of the Maglev properties of bulk high temperature superconductor (HTSC) above a permanent magnet guideway (PMG), by moving a fixed vertical distance, this paper studies the influence on levitation force of the bulk HTSC operating dive-lift movement with different angles. Results show that with the angle increasing, the maximal levitation force decreases when the levitation gap is about 10?mm and the hysteresis is increasing. The hysteresis reaches the largest at first time of back and forth movement, and with the operating times increasing; the hysteresis is almost the same case in the following times of back and forth movements.     

压电宏纤维致动器的双极性非对称迟滞建模及补偿控制

提出了一种双极性非对称改进PI(Bipolar Asymmetric Improved PI,BAIPI)模型描述压电宏纤维(Marco Fiber Composite,MFC)的迟滞特性,BAIPI模型利用经典Prandtl-Ishlinskii(PI)迟滞模型Play算子加权叠加描述MFC的对称迟滞特性,然后叠加一系列不同权重、不同阈值的双边死区算子描述MFC的双极性非对称特性。实验辨识结果表明:BAIPI模型对MFC致动器的建模误差从PI迟滞模型的16.8%降为4.2%。在基于BAIPI逆模型的前馈补偿下,MFC致动的柔性梁构件跟踪等幅、变幅三角波轨迹的实测位移与期望跟踪位移基本重合,补偿后等幅三角波实测位移与理想位移之间的线性度为2.36%。因此,所提出BAIPI迟滞模型及补偿方法显著提高了MFC致动器的定位驱动和跟踪精度。