CMRT Predictive Maintenance Techniques 2

Question 1

In vibration analysis, a dominant 1× running speed (1X) frequency component most commonly indicates which condition?

Accepted Answer

Mass imbalance

Answer

A dominant 1× component in the frequency spectrum is the classic signature of mass imbalance, which produces a force once per shaft revolution.

Question 2

The Ball Pass Frequency Outer Race (BPFO) bearing defect frequency is determined by which set of parameters?

Accepted Answer

Number of rolling elements, shaft speed, and contact angle

Answer

BPFO = (N/2) × shaft speed × (1 − (Bd/Pd) × cos α), where N is the number of rolling elements, Bd is ball diameter, Pd is pitch diameter, and α is the contact angle.

Question 3

When performing vibration analysis, which measurement parameter is generally most sensitive to high-frequency bearing defect impacts?

Accepted Answer

Acceleration

Answer

Acceleration is most sensitive to high-frequency shock events such as early-stage bearing defects because it amplifies high-frequency content that displacement and velocity would attenuate.

Question 4

A 'waterfall plot' (cascade plot) in vibration analysis is used primarily to:

Accepted Answer

Show frequency spectra stacked over time or speed to reveal trends

Answer

A waterfall plot stacks successive FFT spectra along a time or speed axis, making it easy to identify how frequency components change over time or during run-up/coast-down.

Question 5

Resonance in a mechanical structure is most likely to occur when:

Accepted Answer

A forcing frequency coincides with the structure's natural frequency

Answer

Resonance is a condition where an external forcing frequency matches the natural (resonant) frequency of the structure, causing amplified vibration response.

(CMRT) Certified Maintenance and Reliability Technician Practice Test

(CMRT) Certified Maintenance and Reliability Technician Practice Test

CMRT Predictive Maintenance Techniques 2