CVA Resonance & Structural Analysis

Question 1

What is resonance in the context of machinery vibration?

Accepted Answer

A condition where an excitation frequency coincides with a system natural frequency, causing amplified vibration response

Answer

Resonance occurs when an excitation frequency matches a structural or mechanical natural frequency, causing the vibration amplitude to be amplified by a factor related to the system's damping ratio.

Question 2

What is a natural frequency (also called resonant frequency)?

Accepted Answer

The frequency at which a system vibrates freely after an initial disturbance, determined by its mass and stiffness

Answer

A natural frequency is a property of the system itself (fn = (1/2π)√(k/m)) that determines the rate at which it oscillates freely; it depends only on mass and stiffness, not on the excitation.

Question 3

What is the damping ratio, and how does it affect vibration at resonance?

Accepted Answer

The ratio of actual damping to critical damping; lower ratios produce higher amplitude amplification at resonance

Answer

The damping ratio (ζ = c/cc) is the ratio of actual damping to critical damping; at resonance the dynamic amplification factor is approximately 1/(2ζ), so lower damping produces much higher resonant peaks.

Question 4

What is a mode shape in structural dynamics?

Accepted Answer

The pattern of deformation that a structure exhibits when vibrating at a specific natural frequency

Answer

A mode shape describes the relative deflection pattern of all points on a structure when it vibrates at a particular natural frequency; each natural frequency has an associated unique mode shape.

Question 5

What is a frequency response function (FRF) used for in structural analysis?

Accepted Answer

Calculating the ratio of output response (vibration) to input force as a function of frequency, used to characterize system dynamics

Answer

The FRF (H(ω) = X(ω)/F(ω)) describes how a structure responds to excitation at each frequency, revealing natural frequencies as peaks and providing the basis for modal analysis.

CVA - Certified Vibration Analyst Practice Test

CVA - Certified Vibration Analyst Practice Test

CVA Resonance & Structural Analysis