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61.
A method of controlling chaos in the voltage-mode buck converter is presented by using an improved notch filter feedback control in this paper. The proposed control part comprises a notch filter and a low-pass filter. The discrepancy between the outputs of the two filters is introduced into the control prototype of the power converter. In this way, the system period-1 solution is kept unchanged. The harmonic balance method is applied to analysing the variation law of the system bifurcation point, and then the stable range of the feedback gain is ascertained. The results of simulation and experiment are also given finally.[第一段] 相似文献
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By using the finite element method, three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated. The aim of this research is to investigate the thickness effect on the location of maximum stress and notch stress intensity factor (NSIF) of corresponding blunt and sharp periodic notches respectively. With this aim, different number of periodic notches as well as different notch opening angles are examined. While for two-dimensional plates weakened by periodic notches some results are available in the literature, this paper first faces the problem of three-dimensional cases. A total of about 100 geometrical configurations are investigated. It is found that, the effect of plate thickness of periodic notched components can be characterized by the relative value with respect to the depth of the notch (H/t). For the blunt periodic notches with relatively higher values of H/t ratio, the value of the maximum tensile stress is located near the free surface. On the contrary for lower values of H/t, it is placed at the middle plane. The same behaviour is observed for sharp periodic notches in terms of notch stress intensity factors. 相似文献
64.
周边切口短圆柱试件的杆杆型冲击拉伸试验系统的弹塑性有限元分析 总被引:6,自引:3,他引:6
基于一维试验原理提出了用带有周边切口的短金属圆柱试件进行平面应变型弹塑性动态断裂韧度的测试方法;对该复杂的动力学系统进行了轴对称的弹塑性有限元分析,并计算了动态围道^J积分;根据对试件功能转换关系的分析和Rice公式的物理意义,提出了用试件两端平功载荷-两端相对位移曲线(P^-△)推广Rice公式计算试件的远场J积分,由此得到的P^-△曲线基本上消除了与裂纹运动无关的质心运动动能的影响。论证了J积分作为裂端的表征参量,且当切口深度比大于70%时,Rice公式有较高的计算精度,为平面应变型弹塑性动态断裂韧度的表征与测试提供了依据。 相似文献
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66.
Stress-strain field near the notch tip of a rubber sheet 总被引:1,自引:0,他引:1
Analized in this paper is the elastostatic field near a notch tip in a rubber-like thin sheet. The asymptotic equations for
the notch tip field are derived based on the constitutive relation given by Ref. [1]. Near field solutions are obtained in
regions that decreases and increases in size as the notch tip is approached. Their singular character depends on the constitutive
parameters as well as the angle of notch that is evaluated numerically.
The project supported by the National Natural Science Foundation of China 相似文献
67.
压电切口张开角和深度对其尖端力电损伤场的影响 总被引:2,自引:1,他引:1
基于三维各向异性压电损伤本构理论,导出了广义平面应力问题的损伤本构方程,并据此分析了压电薄板板边V形切口尖端附近的力电损伤,研究了切口张开角和深度对切口尖端力电损伤的影响规律.结果发现:和张开角对切口尖端损伤的影响相比,深度的影响更为明显;在张开角对切口尖端力损伤的影响规律方面,压电材料与一般弹塑性材料存在明显差异,原因在于压电切口尖端力电载荷比会随着深度的改变发生很大变化;不同深度下张开角与切口尖端力、电损伤关系曲线随着张开角的增大由发散逐渐会聚,不同张开角下深度与切口尖端力、电损伤关系曲线随着切口加深由会聚逐渐发散,并且电损伤曲线表现得更为明显. 相似文献
68.
A TTF-type coaxial higher order modes (HOM) coupler has been used in a TESLA 9 cell cavity. It is impossible to measure the stop band characteristics of the HOM coupler with the cavity. A measurement device for the coaxial transmission line type for the HOM coupler has been designed at Peking University. Experimentally it was shown that the average voltage standing wave ratio of the coaxial transmission line is smaller than 1.08. The experimental results of the stop band characteristics of the TTF-type HOM coupler have been fitted for the simulation. This paper describes the design of the measurement device and discusses the experimental and simulation results of stop band characteristics of the HOM coupler. 相似文献
69.
基于ANSYS的缺口和裂纹对结构应力分布影响有限元研究 总被引:2,自引:0,他引:2
缺口和裂纹都会对结构的应力分布产生影响,过去对这两个领域的研究一直平行发展,交叉领域的研究比较少。本文应用有限元软件ANSYS,分析了金属材料中缺口根部和裂纹尖端的应力分布。有限元计算结果与Taylor^[1]的理论分析一致,即在缺口和裂纹根部存在一临界距离,大于这一临界距离时,缺口和裂纹具有类似的应力值,并都易受尺寸因素的影响;临界距离内的应力与最大应力之比只同缺口半径有关,而与结构绝对尺寸无关。文中并对缺口和裂纹交叉领域以后的研究方向提出了看法。 相似文献
70.