critical speed


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critical speed

[′krid·ə·kəl ′spēd]
(cryogenics)
(fluid mechanics)
(mechanical engineering)
The angular speed at which a rotating shaft becomes dynamically unstable with large lateral amplitudes, due to resonance with the natural frequencies of lateral vibration of the shaft.

critical speed

The angular speed of rotating machinery at which excessive vibration is produced; at this speed the periodic disturbing force coincides with a mechanical resonance of the shaft and/or of the machinery or its supports.

critical speed

i. The speed on the takeoff run at which, should one engine fail, the pilot can decide whether to abandon or continue takeoff. Below this speed, the pilot must abort takeoff. Critical speed is denoted V1.
ii. A rotational speed at which the engine suffers dangerous resonance.
References in periodicals archive ?
This behavior could be explained, because, as the travel speed increases, the torque produced in the driving wheels decreases and consequently, so does the slip, thereby increasing the traction force to a certain limit, reaching the critical speed. The mean rolling resistance value obtained in the field was 4.70kN (483kgf), which represents 8.40% (k = 0.08) of the total mass of the tractor.
In this study, the floating critical speed of an aircraft wing in a subsonic fan was determined using dynamic experimental tests and numerical simulations.
The Influence of Support Stiffness on Critical Speed. In order to make the effect of support stiffness on critical speed more obvious, in this section [N.sub.b] = 7, D_loc = 1/2.
When the ramping or the third method is used, it always yields the critical speed of about 300~350 km/h, even 400 km/h.
A critical speed analysis assuming rigid bearings with a stiffness of [10.sup.8] lb/in predicted shaft stresses at the first bending mode of 2,371 psi (Figure 28), an increase of 39% when compared to the original rotor.
If the vehicle forward speed is above this critical speed, 115 km/h, all the state trajectories (in black) will diverge, and an unstable yaw motion mode will occur.
Beyond the critical speed, the dissipated power in the drum reaches a maximum value, because of the reduction of magnetic induction under the pole.
If the critical speed is less than the idle speed of an engine, oil trapping can be avoided in engine operations.
Above the critical speed, [[omega].sub.b], the voltage limit ellipse is totally included in the current limit circle [15], as illustrated in Fig.
Dr Rabi Mehta, branch chief at the US space agency's (NASA) Ames Research Center in California, outlined roughness as a factor that dictates what the critical speed is going to be at which one gets maximum 'knuckling' of the ball when the ball is not spinning or spins very little.
Critical speed is defined as the agitator rotational speed (rpm) which coincides with its first natural frequency.
In order to explore the dynamics process with varied parameters, we put the observations in our model and then further study the influence of the competition coefficient ([[sigma].sub.12] and [[sigma].sub.21]) in case of messages propagation with low (or high) critical speed ([alpha] and [beta]).

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