2. The pressure reduction rate
is for shearography testing is
critical. Shearography test chambers
operate at rates of 0 to -2 psi
in 10 seconds followed by a return
to atmospheric pressure by 3-5
seconds. Slower rates increase
the image noise, slow throughput
and the chance that slow leaks
in the panel will allow defects
to go undetected.
Autoclaves are expensive and it
is a waste of money to tie up
shearography testing in an autoclave
that should be producing product.
Shearography test chambers are
designed for their function and
are relatively inexpensive.
All the shearography tooling,
test part fixtures (heavy) and
through wall electrical connections
must be removed during autoclave
production and re-installed. Even
if it would work as a shearography
chamber, and it does not, the
autoclave would have to be at
ambient temperature, generating
lost time waiting for cool down
and reconfiguration. Constant
moving of the shear camera increases
the risk it is dropped or knocked
The bottom of the chamber is curved
and the fixtures would need spacers
and shims to stabilize.
Access into the chamber to mark
multiple defects on the fan case
requires multiple entries into
the autoclave and moving around
inside with the shearography equipment
Over the years several companies
attempted shearography in an autoclave.
The instant pressure was reduced,
the images decorrelated and the
set up was worthless. They purchased
test chambers from LTI.
Autoclaves and shearography test
chambers are designed for entirely
different functions. You can not
cure composites in a shearography
test chamber and you can not do
shearography NDE in an autoclave.