MTS Axial Extensometers - Manual (Page 57)

Installation 57
2. Mount one spring in the appropriate hole in the attachment adapter
as determined by the specimen dimensions (see the installation
drawing).
3. Slide the spring retainer over the end of the spring and tighten the
socket head cap screw. Orient the spring retainer in such a way that
it will not interfere with movement of the extensometer arm.
About Metal Extension Springs
Metal extension springs may be used for testing throughout the
temperature range of the extensometer. The metal extension springs are
stainless steel with an outside diameter of 3.18 mm (0.125 in). The
spring wire is 0.41 mm (0.016 in) thick. More than one spring can be
connected end-to-end to accommodate large specimens.
Spring length is selected based on specimen size and required contact
force. The recommended contact force is approximately 600 grams.
• Greater contact force will provide a more secure attachment under
conditions where slippage may occur such as operating at high
cyclic frequencies. The knife edges can damage the specimen at
high contact forces.
• Less contact force will reduce the possibility of damage to soft
specimens; however, the possibility of slippage increases.
Round specimens
An extension spring attachment method can be used for large and small
diameter round specimens. It can be used by all axial extensometers.
Spring
Spring
Retainer
Attachment
Adapter
l
MODEL
634.xx
l
MODEL
632.xx