Bearing Condition Monitoring

Bearing Condition Monitoring

Precision Machining Research Consortium Industrial Advisory Board Georgia Institute of Technology 29 October 1997 Scott Billington Yawei Li Advisors: Dr. Liang, Dr. Kurfess, Dr. Danyluk

Overview - Diagnostics and Prognostics ❖

Diagnostics - Correlating Signals to Bearing Condition – Accelerometer and Acoustic Emission Sensors – Signal Processing with LabVIEW interface

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Operating Condition Effects (S. Billington) – Rotational Speed – Radial Load Level – Sensor Location

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Adaptive Prognostics (Y. Li) – Crack Propagation Model – Rate-Calibrated Life Estimation

Sensor Types

ICP Amplifier Pre-load Spring

Composite Backing

Seismic Mass Piezoelectric Element

Piezoelectric Element Ceramic Base

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ACCELEROMETER Signal Generation Type

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– Elastic Stress Waves – Stress Wave Propagation through a Piezoelectric Element

– Seismic Mass – Force on a Piezoelectric Element ❖

Frequency Range Less Than 5-10 kHz

ACOUSTIC EMISSION Signal Generation Type

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Frequency Range Greater Than 100 kHz

Test Stand Test Bearing

Loading

Data Acquisition Interface

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LabVIEW Based Virtual Instrument - HFRT Pictured

High Speed Grinding Spindle

0.012

0.01

Acceleration (g)

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Rotation Components

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0.008

0.006

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Cage

0.004

❖ 0.002

0

0

200

400

600

800

1000 1200 Frequency (Hz)

1400

1600

1800

~30,000 RPM 262,144 Data Points, 2 MB ASCII file Excellent Noise Rejection Excellent Repeatability

Comparing Instrumentation Accelerometer

0.14

0.12

Sensor Signal (V)

0.1

0.08

0.06

0.04

0.02

0

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0

20

40

60

80

100 120 Frequency (Hz)

140

160

180

200

Comparing Instrumentation : TEK FFT Oscilloscope and Virtual Instrumentation

Speed-Load Effects (1)

Acceleration (g)

Accelerometer Signals Band-Passed RMS 8.00E-02

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Load (N)

6.00E-02

4910

4.00E-02

9820

2.00E-02

14730 19640

0.00E+00 800 1000 1200 1400 1600 Rotational Speed (RPM)

24550

Increasing Speed, Increases RMS – Linear Increase in number of Outer Race Impacts – Similar increase over all Loads

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Increasing Load, Decreasing RMS – Increasing Load Reduces Signal Levels of Statistical Indicators – ~50% Error in Diagnostic Metric

Accelerometer Positioned Directly Over the Bearing on the Housing

Speed-Load Effects (2) Accelerometer Signals Band Passed RMS

Acoustic Emission RMS 8.00E+02 Load (N) Load 4910

2.00E-02 1.50E-02

9820

1.00E-02

14730

5.00E-03

19640

0.00E+00

24550

Acce le ra tion (g)

Acce le ra tion (g)

2.50E-02

Load (N)

6.00E+02

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Accelerometer Location In Unloaded Zone of Housing Relationship is Explained by Dynamic Model

9820

4.00E+02

14730

2.00E+02

19640 24550

0.00E+00

800 1000 1200 1400 1600 Rotational Speed (RPM) ❖

4910

800 1000 1200 1400 1600 Rotational Speed (RPM) ❖

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Acoustic Emission Sensor Directly Over Bearing on Housing Contact-Area Sensitive

Adaptive Prognostics Signal Metric Diagnostic Model

Estimate Growth Rate and Remaining Life

Comparison of Actual to Predicted Signal Growth

Running Conditions Adaptive Algorithm and Defect Propagation Algorithm

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Estimates Damage Level with Diagnostic Model Estimates Bearing Damage Growth According to Signal Growth Rate

Conclusions ❖

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Sensor Placement and Type Has Drastically Different Effects for Changes in Rotational Speed and Load Speed and Load Relationships can be Explained by Dynamic Models Signal Processing Techniques are Effected Differently by Speed and Load Changes Adaptive Prognostics are Calibrated on Signal Growth Rate