# mechanical impedance

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## Mechanical impedance

For a system executing simple harmonic motion, the mechanical impedance is the ratio of force to particle velocity. If the force is that which drives the system and the velocity is that of the point of application of the force, the ratio is the input or driving-point impedance. If the velocity is that at some other point, the ratio is the transfer impedance corresponding to the two points.

Mechanical impedance is a complex quantity. The real part, the mechanical resistance, is independent of frequency if the dissipative forces are proportional to velocity; the imaginary part, the mechanical reactance, varies with frequency, becoming zero at the resonant and infinite at the antiresonant frequencies of the system. See Forced oscillation, Harmonic motion

## mechanical impedance

[mi′kan·ə·kəl im′pēd·əns]
(mechanics)
The complex ratio of a phasor representing a sinusoidally varying force applied to a system to a phasor representing the velocity of a point in the system.
References in periodicals archive ?
As the control force [f.sub.u](t) is determined by the sliding surface S(t), let S(t) replace [f.sub.u](t) in (10), to analyse the influence of the sliding surface parameters on the mechanical impedance of pantograph head in the stage of the controller design.
where [Y.sub.U](s) is dynamic mobility, [V.sub.U](s) is admittance, s is variable determined as the Laplace operator, described by the formula s = i[omega], [Z.sub.U](s) is mechanical impedance, and [U.sub.U](s) is dynamic stiffness.
Equation (17) indicates that EMI (or EMA) is directly related to the mechanical impedance of a host structure.
It could be stated that the host structure mechanical impedance behaves in a similar way with that described for PZT mechanical impedance through (2) yielding a strong relation with host structure structural stiffness and mechanical properties too.
Physical aspects of soil fertility -- The response of roots to mechanical impedance. Neth.
In their study, the 1D model in (1) shows the coupled relationship between the electrical admittance (inverse of impedance) of the PZT element Y([omega]) to the mechanical impedance of the structure [Z.sub.s]([omega]), proving that any changes in [Z.sub.s]([omega]) will affect the electrical impedance of the attached PZT element.
This has prevented the existence of efficient mechanical impedance transformers or matching elements suitable for enhancing vibration isolation.
Specifically, the mechanical impedance interacting with the user is comprised of the internal impedance of the leg (i.e., the impedance imposed by the controller), in series with the impedance of the environment.
The mechanical impedance of a joint is a function of both passive (e.g., mechanical stiffness of ligaments, tendons, and connective tissue) and active (e.g., muscle activation, contraction mediated by stretch reflex) mechanisms.
Electrical admittance Y([omega]) of the piezoelectric transducer (PZT) is a combined function of the mechanical impedance of the PZT actuator [Z.sub.a]([omega]) and that of the host structure Z([onega]) 

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