MIL-STD-167-1A
3.16 Plane, measuring. A measuring plane is a plane transverse to the shaft axis in which the amount and angle of unbalance is determined.
3.17 Residual unbalance. Residual unbalance is unbalance of any kind that remains after balancing.
3.18 Resonance. Resonance is the magnification of structural response, which occurs when a linear lightly damped system is driven with a sinusoidal input at its natural frequency. Resonances are the cause of many, but not all, response prominences.
3.19 Response prominence. Response prominence is a general term denoting a resonance or other distinct maximum, regardless of magnitude, in a transmissibility function, including local maxima which may exist at the frequency endpoints of the transmissibility function. Typically, a response prominence is identified by the frequency of its maximum response, which is the response prominence frequency. A response prominence of a system in forced oscillation exists when any change, for both plus and minus increments however small, in the frequency of excitation results in a decrease of the system response at the observing sensor registering the maximum. A response prominence may occur in an internal part of the equipment, with little or no outward manifestation at the vibration measurement point, and in some cases, the response may be detected by observing some other type of output function of the equipment, such as voltage, current, or any other measurable physical parameter. Instruction on how to identify response prominences is provided in Appendix A.
3.20 Rotor, flexible. A flexible rotor is one that does not meet the criteria for a rigid rotor. The unbalance of a flexible rotor changes with speed. Any value of unbalance assigned to a flexible rotor must be at a particular speed. The balancing of flexible rotors requires correction in more than two planes.
3.21 Rotor, rigid. A rotor is considered to be rigid when its unbalance can be corrected in any two arbitrarily selected planes. After correction, its residual unbalance does not exceed the allowed tolerance, relative to the shaft axis, at any speed up to the maximum service speed and when running under conditions which approximate closely to those of the final supporting system.
3.22 Simple harmonic motion. A simple harmonic motion is a motion such that the displacement is a sinusoidal function of time.
3.23 Test fixture resonance. A test fixture resonance is any enhancement of the response of the test fixture to a periodic driving force when the driving frequency is equal to a natural frequency of the test fixture.
3.24 Transmissibility. Transmissibility is the non-dimensional ratio of the response amplitude in steady-state forced vibration to the excitation amplitude. The ratio may be one of forces, displacements, velocities, or accelerations. Transmissibility is displayed in a linear-linear plot of transmissibility as a function of frequency, or in tabular form. Instructions for determining and displaying transmissibility are given in A.2.1 of Appendix A.
4. GENERAL REQUIREMENTS
4.1 Notification of tests. When specified (see 6.2.b), notification of Type I or Type II testing shall be made in accordance with DI-MISC-81624 (see 6.3).
4.2 Identification of component compliance. When specified (see 6.2.c), the information verifying that the component complies with Type I and Type II testing shall be identified on the component drawing, the Test Report (DI-ENVR-81647) (see 6.3), or an identification plate attached to the component.
4.3 Disposition of tested equipment. The requirements for tested equipment, fixturing, associated test records, and other documentation shall be as specified (see 6.2.d).
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