From: Randall Peters PETERS_RD@..........
Sent: Tue, 16 Aug 2011 21:53
Subject: acoustic emissions



Charles,
     I believe Brett is probably right, that piezoelectric sensors looking =
for =E2=80=98snap, crackle, and pop=E2=80=99 in the spring are not likely t=
o be sensitive enough to  detect imperfection changes at the level where Br=
ett wants  to improve performance.  Of course acoustic emission methods hav=
e become quite useful as a part of nondestructive testing methods.

Hi All,=20

    I would agree about the small crystal ones, but you could use a 44mm OD=
 Piezo Sounder Disk in flex mode attached between the frame and the centre =
of the spring. I have used these very successfully to produce a "Piezo geop=
hone". It had about 5x the sensitivity of a 390 Ohm geophone. You already h=
ave a sensor monitoring the whole spring force / motion. Or alternatively m=
ount a second position sensor plate and detection system attached to the ce=
ntre of the spring ? This would make the response different for dislocation=
s moving in either of the two halves of the spring.=20

    Regards,=20

    Chris





=
From: Randall Peters PETERS_RD@merc=
er.edu

Sent: Tue, 16 Aug 2011 21:53

Subject: acoustic emissions











Charles,


     I believe Brett is probably=
 right, that piezoelectric sensors looking for =E2=80=98snap, crackle, and =
pop=E2=80=99 in the spring are not likely to be sensitive enough to  d=
etect imperfection changes at the level where Brett wants  to improve =
performance.  Of course acoustic emission methods have become quite us=
eful as a part of nondestructive testing methods.


 


Hi All, <=
/FONT>



 



 &nb=
sp;  I would agree about the small crystal ones, but you could use a 4=
4mm OD Piezo Sounder Disk in flex mode attached between the frame and the c=
entre of the spring. I have used these very successfully to produce a "Piez=
o geophone". It had about 5x the sensitivity of a 390 Ohm geophone. You alr=
eady have a sensor monitoring the whole spring force / motion. Or alternati=
vely mount a second position sensor plate and detection system attached to =
the centre of the spring ? This would make the response different for dislo=
cations moving in either of the two halves of the spring. 


 



 &nb=
sp;  Regards, 


 



 &nb=
sp;  Chris