Modal Analysis Sprocket

8/10/2019 Modal Analysis Sprocket

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Vibration Study of aSprocket

EM 406- Mechanical Vibrations

11/12/2014



Overview of Presentation

Testing

Results

Analysis

• Test Setup• RT Pro Settings

• Reciprocity

• Sample Data & Plots

• Mode Shapes

• Compariso

• Lessons Le

• Discussion



Modal analysis was performed on asprocket

Accelerometer placement on the sprocket

Accelerometers on sprocket,

acquisition unit, and compute

Data collection was performed by using a hammer

and two accelerometers that were linked together

through a data acquisition unit.



0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-20

-15

-10

-5

0

5

10

15

20Acceleration from acc elerometer

Time (seconds)

A c c e l e r a t i o n ( g n )

Details of Test Setup (RT Pro SettinTest Setup Details

Analysis Settings

Measurement

Points

2048

Frequency Range 0 – 2000 Hz

Lines 800

Frames Multiple

Windowing None

Averages 5

Trigger Level 2%

Physical Test Settings

Hammer Tip Nylon

Test Points 88

0 500 1000 1500 2000 25000

0.2

0.4

0.6

0.8

1

1.2

Frequency (Hz)

C o h e r e n c e

Coherence

Settings were changed until

at least 5 peaks were detected

No window was necessary

as the acceleration decayed enou



Confirmation of linearity in the sprocthrough a reciprocity test

0 500 1000 1500 2000 2500 300010

-2

10-1

100

101

102

103

104

Frequency (Hz)

M a g

n i t u d e ( g n / l b f )

Reciprocity

FRF 1

FRF 2



Layout of the points

12

34 5

6

78

910

1112

1314

15 16

1718

1920 21

22

2324

2526

27 28

2930

31

3233

3435

36

3738

3940

4142

43

44

45

46

47

48

49

50

51

52

5354

5556

5758

5960

6162

6364

65

6667

68

6970

7172

7374

75

76

77

78

79

80

81

82

83

84

8586

8788



Sample plots from data collection inPro

0 500 1000 1510

-2

10-1

100

101

102

103

Frequency (Hz)

M a g n i t u d e ( g n / l b f )

FRF

0 500 1000 150

0.2

0.4

0.6

0.8

1

1.2

Frequency (Hz)

C o h e r e n c e

Coherence

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-5

0

5

10

15

20

25Hammer Forc e

Time (seconds)

F o r c e ( l b f )

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-20

-15

-10

-5

0

5

10

15

20Acceleration from Acc elerometer 1

Time (seconds)

A c c e l e r a t i o n ( g n )

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

-100

-80

-60

-40

-20

0

20

40

60

80

100

Acceleration from Accelerometer 2

Time (seconds)

A c c e l e r a t i o n

( g n )



Sample CMIF



Mode 1: f = 460.0 Hz, ζ = 0.0025



Mode 2: f = 665.0 Hz, ζ = 0.0025



Mode 3: f= 947.5 Hz, ζ = 0.0014



Mode 4: f = 1067.5 Hz, ζ = 0.0013



Mode 5: f = 1650.0 Hz, ζ = 0.0071



Mode 6: f = 1757.5 Hz, ζ = 0.0014



Comparison of the different modeshapes, frequencies, and damping

Mode # Description Frequency

(Hz)

Damping

(%)

1 Bending 460 0.0025

2 Bending 665 0.0025

3 Bending

Wave

947.5 0.0014

Mode # Description

4 Wave,

Twisting

5 Bending,

Twisting,

Wave

6 Twisting,

Bending,

Wave



ANSYS Mode 1: f = 503.5 Hz, 503.7

% 3. −..

×100%=9.52%

% −

×100% =

3. −.

. ×100%=9.46%



ANSYS Mode 2: f = 703 Hz

% =3. −.

. ×100%=5.71%



ANSYS Mode 3: f = 1091.1 Hz

% =. −.

. ×100%=15.16%



ANSYS Mode 4: f = 1218 Hz

% =8. − .

. ×100%=14.10%



ANSYS Mode 5: f = 1755.7 Hz, 176Hz

% . − .

. ×100%=6.41%

% 3.8 −.

. ×100%=6.90%



ANSYS Mode 6: f = 2055.7 Hz

% . −.

. ×100%=16.97%



What we learned

• A radially symmetrical object can have multiple mode shapenearly the same frequency

• Hammer strike technique has a large affect on the accuracy collection

• A quick hammer strike reduces hammer ‘bounce’ and leads

data



What makes our project awesome

• The sprocket geometry led to interesting mode shapes

• Sprockets have neat applications

Modal Analysis Sprocket

Documents

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