7/31/2019 Single Plane Balance 091401

1/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 1 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

ME 22.403

Mechanical Lab I I

Single PlaneBalancing Not es

7/31/2019 Single Plane Balance 091401

2/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 2 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

Why and How Do St r uct ur es Vibrat e?

INPUT TIME FORCE

INPUT SPECTRUM

OUTPUT TIME RESPONSE

OUTPUT SPECTRUM

f(t)

FFT

y(t)

IFT

f(j ) y(j )h(j )

FREQUENCY RESPONSE FUNCTION

Mot or or diskunbalance

can cause unwant ed

vibr at ions or wor se

7/31/2019 Single Plane Balance 091401

3/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 3 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

Any init ial unbalance in a r ot at ing syst em can have devast at ing

ef f ect s as t he syst em is st ar t ed up, slowed down or r un at or

near t he cr it ical f r equency.

Operat ing anywher e near st r uct ur al resonances can r esult in ver y

large dynamic loads which are or ders of magnit ude gr eat er t han

t he nor mal st at ic loads.Theref or e, ext r eme car e is exercised in balancing high speed

st r uct ur al syst ems t o avoid any pot ent ial problems.

This labor at or y will delve int o balancing r equir ement s.

Rot at ing Unbalance Pr oblems

7/31/2019 Single Plane Balance 091401

4/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 4 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

Bent ly Nevada Rot or kit

7/31/2019 Single Plane Balance 091401

5/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 5 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

Relat ed I nst r ument at ion & Signal Condit ioning

7/31/2019 Single Plane Balance 091401

6/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 6 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

An eddy- cur r ent probe measur es t he dist ance bet ween a sensor

head and an elect r ically conduct ing sur f ace. The sensor is based

on eddy cur r ent s t hat are induced at t he conduct ing sur f ace as

magnet ic f lux l ines f r om t he sensor int ersect wit h t he conduct ingmat er ial; t he eddy cur r ent s ar e sensed wit h an impedance

(induct ance) br idge.

Eddy Cur r ent Pr obe

The sensit ivit y of t he sensoris dependent on t he t argetmat er ial and illust r at es

higher sensit ivit y f or

nonmagnet ic mat er ials.

For magnet ic mat er ials, at hin f ilm of aluminum, f orinst ance, can be bonded t o

t he st r uct ur e sur f ace.

7/31/2019 Single Plane Balance 091401

7/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 7 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

An eddy- cur r ent probe uses a pr oximit or and power supply/ signal

condit ioning unit .

The out put volt age is pr opor t ional t o displacement and has high

sensit ivit y wit h very linear char act erist ics.

Eddy Cur r ent Pr obe

7/31/2019 Single Plane Balance 091401

8/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 8 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

The keyphasor is a once per r ev indicat or measur ed by an eddy-

cur r ent probe and shaf t displacement can be measur ed also

Eddy Cur r ent Pr obe - Keyphasor & Displacement

7/31/2019 Single Plane Balance 091401

9/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 9 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

Using bot h t he keyphasor and displacement , t he largest and

smallest displacement mot ion of t he shaf t can be det ermined

r elat ive t o t he keyphasor as some angular r elat ion

Eddy Cur r ent Pr obe Measur ement s

7/31/2019 Single Plane Balance 091401

10/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 10 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

Using t wo probes in t he x and y dir ect ions, a relat ionship can be

plot t ed wit h x/ y super imposed or plot t ed verse each ot her

Eddy Cur r ent Pr obe Measur ement s

7/31/2019 Single Plane Balance 091401

11/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 11 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

The shaf t cr it ical speed is det ermined using a simply suppor t ed

beam wit h a lumped weight f or mulat ion and is

Cr it ical Speed Det erminat ion

7/31/2019 Single Plane Balance 091401

12/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 12 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

7/31/2019 Single Plane Balance 091401

13/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 13 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

7/31/2019 Single Plane Balance 091401

14/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 14 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

7/31/2019 Single Plane Balance 091401

15/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 15 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I

7/31/2019 Single Plane Balance 091401

16/16

Dr. Peter Avi tabi le Universi ty of Massachuset t s Lowel l Single Plane Balance 091401 - 16 Copyr ight 2001

Mechanical Engineering - 22. 403 ME Lab I I