The effect of systematic parameters on the structural equivalent damping ratio in translational and torsional direction is studied for torsionally coupled vibration.

Response analysis in the frequency domain is also studied by using random vibration theory,from two aspects of vibrartion-absorbing coefficient and equivalent damping ratio to study the effect of μ_d 、 λ_d 、ζ_d and φ_(k_1) to vibration control.

Based on the Code for Loads of Building Structure in China,a practical method of designing nonlinear passive dynamic absorbers for controlling wind-induced vibration responses of highrise structures is presented,using the concept of equivalent damping ratio of a structure and equivalent dynamic parameters of TMD.

(3) The equivalent linearization method is studied and the inelastic system is replaced by elastic system. The relations of equivalent damping ratio and ductility coefficient for equivalent single-degree-of-freedom system is suggested.

The equivalent damping ratio and the control gain are changed coordinatedly in control. Each performance index of the system will be well regulated and the effect of the system control will be promoted with the premise of the system stability ensured.

Through theory deducing and analyzing,the calculation formulas of equivalent stiffness and equivalent damping ratio as well as the graph of system period are brought forward.

The equivalent damping ratio and stiffness coefficient of the LED device are studied, and the general equivalent formula of energy dissipation devices is established.

Based on the definition of the equivalent viscous damping, the formula of equivalent damping ratio of the structure with hysteretic dampers is derived. Second, the optimum strength ratio of damper system is defined as strength ratio when the equivalent viscous damping ratio is maximum, Thus was clear about has caused the hysteretic dampers to consume the energy to achieve the biggest mild hysteretic dampers structure should have, namely the damper seismic response mitigation effect could achieve the optimum condition.

As a result,computation work is decressed to50% of the original. During the determination of feedback gains,the concepts ofequivalent inherent frequency and equivalent damping ratio specified by MIL-F-8785C are utilized. Considering the influence of actuator dynamics and reasonablepole-assignment,we deduce approximate feedback gain formulas.

Taking a tall building of 24 stor ies as an example, all parameters contributing to the equivalent damping ratio a re studied, and its design optimized obtaining good control efficiency.

The factors which affect the level stiffness,energy dissipation and equivalent damping ratio of SMA-rubber seismic isolation bearings including level displacement amplitude,level loading frequency and vertical load were studied. Result showed that the new SMA-rubber seismic isolation bearings have better hysteresis and energy dissipation capabilities. It provided the base to optimize the SMA-rubber seismic isolation bearings.

It is shown that the equivalent damping ratio increases inproportion to the square of frequency.

A theory for describing deformation behaviour of sands under cyclic loading is proposed on the basis of the assumption that the permanent deformation of sands after each cycle of loading is mainly determined by the effctive stress states at the peak and the valley of that cycle of loading and a loading history parameter named as effective number of cycles. A series of cyclic triaxialtests on a medium sand has been per- formed in order to estabilish two sets of empirical relationships required in this theory....

A theory for describing deformation behaviour of sands under cyclic loading is proposed on the basis of the assumption that the permanent deformation of sands after each cycle of loading is mainly determined by the effctive stress states at the peak and the valley of that cycle of loading and a loading history parameter named as effective number of cycles. A series of cyclic triaxialtests on a medium sand has been per- formed in order to estabilish two sets of empirical relationships required in this theory. The first one, giving the expressions for mean shear modulus and equivalent damping ratio, is derived from the model proposed by Hardin and Drnevich with a revision to consider the coaction of cyclic normal stress and cyclic shear stress. The second one gives the expression for increments of permanent volumetric strain and deviatorie strain, taking account of the influence of assymetry of stress levels at the peak and the valley of loading in each cycle. The theory may be used to predict the liquefaction potential and deformation of sands subjected to repeated loading under plane strain condition.

文中探讨了建立砂土动力应变关系的途径,并根据砂土的动力变形主要取决于每个荷载循环中动应力达到峰值和谷值时的有效应力状态的假设,提出一个计算动力变形的平均发展过程的理论。从这一理论出发,根据一种砂料的三轴反复荷载试验结果,建议了一组计算残余体应变和残余剪应变的经验公式,并对哈定和达尼维奇(Hardin and Drnevich)的动剪切横量公式进行了修改。这些公式可以用于计算低频动荷载作用下砂土的液化和变形。

In this paper, based on the detailed analysis of the dynamic cutting force of the helical tooth end milling cutters and its direction coefficients, a method of analysing the behaviour of regenarative chatter for helical tooth end milling cutters with waved cutting edges is proposed.The cutting tests are carried out to check the theoretical analysis on validity and they have proved to be in good agreement with the results calculated from the theoretical analysis. The results obtained are summarized as follows:...

In this paper, based on the detailed analysis of the dynamic cutting force of the helical tooth end milling cutters and its direction coefficients, a method of analysing the behaviour of regenarative chatter for helical tooth end milling cutters with waved cutting edges is proposed.The cutting tests are carried out to check the theoretical analysis on validity and they have proved to be in good agreement with the results calculated from the theoretical analysis. The results obtained are summarized as follows: 1. The proposed theoretical formulae for the calculations of instantane -ous and mean direction coefficients can be applied to up- and down- milling operations with helical tooth end milling cutters. By using these formulae the relations between the chatter and cutting conditions can be found, which enables us to select the optimum cutting conditions easily. 2. The equation which can be applied to the determination of the critical width of cut for helical tooth end milling cutters with waved cutting edges is given below: Where: Kd is the coefficient of chip thickness, b is the critical width of cut, D is the equivalent damping ratio, K is the equivalent static stiffness, Rm is the mean direction coefficient, Z is the number of teeth, ψ is the phase shift between the two vibration waves in successive cutting teeth, ξ is the ratio between the length of the chip and the lead of the waved cutting edges, ηi, η2, ……,ηz are the ratio between the partial length on the underside of the chip and the length of the chip respectively. 3. It is dear from the theoretical analysis and the experimental results th at the critical width of cut for the helical tooth end milling cutters with waved cutting edges is considerably larger than that of the conventional milling cutters. Practically, this method of analysis can also be applied to the determination of the chatter behaviour for the helical tooth end milling cutters with any kinds of grooves on the cutting edges and it may be expected o obtain the similar results mentioned above.

Referring to the adaptive scheme proposed by U.Hartmann et al.,this paperpresents a simplified model for parameter-estimation and an extended Kalman filterparameter-estimation algorithm.As a result,computation work is decressed to50% of the original.During the determination of feedback gains,the concepts ofequivalent inherent frequency and equivalent damping ratio specified by MIL-F-8785C are utilized.Considering the influence of actuator dynamics and reasonablepole-assignment,we deduce approximate feedback...

Referring to the adaptive scheme proposed by U.Hartmann et al.,this paperpresents a simplified model for parameter-estimation and an extended Kalman filterparameter-estimation algorithm.As a result,computation work is decressed to50% of the original.During the determination of feedback gains,the concepts ofequivalent inherent frequency and equivalent damping ratio specified by MIL-F-8785C are utilized.Considering the influence of actuator dynamics and reasonablepole-assignment,we deduce approximate feedback gain formulas.A simplified andappropriate logic condition for the start of gain adaptation is recommended.Thusthe system stability and good flight handling quality are ensured.The estimation oftime varying parameters during the climbing maneuver with decreasing speed anddescending maneuver with increasing speed,the climbing or descending maneuverwith nearly invariant speed,is studeid in detail including the role of probe-sig-nals.The divergence phenomenon encountered in the conditions mentioned above isanalyzed and means for overcoming it are investigated.