Effect of Damping

This speed becomes critical when the frequency of excitation is equal to one of the natural frequencies of the system. In forced vibration, the system is a function of the frequencies. These frequencies can also be multiples of rotor speed excited by frequencies other than the speed frequency such as blade passing frequencies, gear mesh frequencies, and other component frequencies. Figure 5-20 shows that for forced vibration, the critical frequency remains constant at any shaft speed. The critical speeds occur at one-half, one, and two times the rotor speed. The effect of damping in forced vibration reduces the amplitude, but it does not affect the frequency at which this phenomenon occurs. 

Figure 9-13). A response, of course, is a sudden rise in amplitude at a speed. The analysis is performed using a mathematical model that includes the effects of damping in the equations, making the model much more complex than any previous analysis. The University of Virginia carries out continuous research in which a consortium of users, vendors, and researchers provide funds, and data and interchange ideas to advance the science of rotor dynamics. Other organizations, such as the Bently Rotor Dynamics Research Corporation and Texas A M University, are also carrying on similar work on a continuing basis.

Dr. R. Brout has called our attention to the time dependence of resonantly filtered gamma rays from Fe67 studied by Lynch, F. J., Holland, R. E., and Hamermesh, M., in Phys. Rev. 102, 513 (1960), where oscillations arise from the combined effect of damping and free propagation. 

The annual loss of water from hot country lakes and reservoirs due to evaporation is usually about 3 m per year. This evaporation can be reduced considerably by coating the water surface with an insoluble monolayer for example, a monolayer of cetyl alcohol can reduce the rate of evaporation by as much as 40 per cent. Insoluble monolayers also have the effect of damping out surface ripples. 

This paper summarizes different methods of pulsation dampening in high pressure plants, and shows how to control and optimize the effectiveness of damping measures by numerical pulsation analysis. 

Ungar, E. E. In Noise and Vibration Control Beranek, L. L., Ed. McGraw-Hill New York, 1971 Chapter 14. Mead, D. J. Criteria for Comparing the Effectiveness of Damping Treatments Report No. 125 Department of Aeronautics and Astronautics, University of Southampton Hampshire, England, 1960. 

Henderson, J.P. and M.L. Drake, "Investigation of the Effects of Damping Treatments on the Response of Heated Fuselage Structure," NoisEXPO, National Noise and Vibration Control Conference, New York, New York, March, 1976. 

Peat JK, Dickerson J, Li J Effects of damp and mould in the home on respiratory health A review of the literature. Allergy 1998 53 120-128. 

S. chartarum, which are then ingested via airborne dust samples, has been associated with adverse health effects of damp rooms. 

Note that the effect of damping of dm-waves and their nonlinear harmonics as well as free waves depend on the film elasticity. Therefore, one can expect that the resulting phase velocity of the system free waves/bound waves should depend on the characteristics of films. This effect will be studied in further experiments. 

Figure 11.3 Effect of damping factor on overshoot and decay ratio.

Good resistance to heat normally, although it will tend to yellow if left to cook in the barrel, sk of decomposition at temperatures above 250° C (482° F). At a temperature of 250° C (482° F) the maximum residence time in the barrel should not exceed 5 minutes. When the temperature is 275° C (527° F) then the maximum residence time in the barrel should not exceed 1 to 2 minutes. Splay marks or streaks on moldings (similar to the effects of dampness) is an early indication of the material being overheated. 

The effect of damping is small e.g., 10% damping reduces the response by about 15%. 

The proportionality (which usually requires fairly complex electronics) has the overall effect of "damping" the controller system, and this decreases the overswing. Sometimes the knob on a controller that adds this function is labeled "damping," but most often it is called "proportional band (PB)." If the "band" is made narrower, there is a steeper gradient of power increase as the temperature goes down if the band is set by the operator to be wider, there is a more gradual application of power (but over a wider temperature range). 

The 98 th Battalion encountered some of the same tribulations on New Guinea that had marked the fighting in the South Pacific Area. These included the unfamiliarity of infantry commanders with the capabilities and limitations of the weapon, the inadequate training of mortar personnel in infantry tactics and procedures, the excessive length of time firing personnel remained in the line without relief, and the deleterious effects of dampness on mortar shell components and their containers. The disadvantages of attaching mortar units to artillery... 

Nonstationary spectral densities of displacement showing effect of damping = 0.025 and - 2.0. 

Nonstationary spectral densities of displacement Syc T ) showing effect of damping Cs 0.025... 

Vakakis A, Paipetis S (1986) The effect of a viscously damped dynamic absorber on a linear multi-degree-of-freedom system. J Sound Vib 105(l) 49-60 Val DV, Segal F (2005) Effect of damping model on pre-yielding earthquake response of structures. Eng Struct 27(14) 1968-1980... 

The measurement of the dynamic-mechanical properties of polymers requires the separation of the response of the material to cyclic or transient loading into two components an elastic response and an inelastic response. Frequently, these two are best resolved experimentally as a complex response and a damping. Whilst the complex or total reponse is familiar to most experimentalists, damping frequently poses a conceptual problem. However, the effect of damping is manifested in many ways. For example (i) the phase lag between stress and strain (Le. load and displacement) (ii) the decrease with time of the amplitude of stress and strain in a freely vibrating system and (iii) the limited amplitude of a system excited at resonance. 

Recently, a great number of papers were published on the systems exhibiting mode coupling instability due to friction and the complex effect of damping on such systems. See papers by Hoffmann and his coworkers [79-81] and Jezequel and his coworkers [82-89]. Other recent works on this subject include [90-94]. 

The remainder of this chapter is dedicated to the mode coupling instability mechanism and is focused on the linear system given by (7.18). In Sect. 7.3, the similarities between the two models are explored. The undamped case will be treated first and then the effect of damping is studied. 

Lemmas 7.5 and 7.6 showed that in the extreme cases where damping is present only in one of the two DOFs of the system, the steady-siding equilibrium point is unstable. In addition, the complex effect of damping in expanding or reducing the parameter regions of stabihty was shown by the examples in Sect. 7.2.4. The actual variations in the steady-state amplitude of vibrations can have an even more complex behavior. 

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