1. Introduction
NB The strain gauges are exposed - handle the sections with care to avoid damaging the connections.
Take up the slack by winding the hand wheel then put the load back to zero.
Ensure that the strain gauge boxes are wired correctly, turn them on, ensure the correct gauge factor is set and that the gauges are zeroed.
Each tube is fitted with a 45 degree strain gauge rosettes, with gauges at 45, 0 and -45 degrees to the tube's axis.
When torque is applied, both ends of the tube rotate. To determine
the angle of twist of the tube the rotation at each end has to be determined and
one subtracted from the other. This can most readily be done by using the rotation protractor
gauges. Be very careful not to move these gauges during the course
of the experiment - or you will have to start again! Note the length of section
over which the measurements are made.
During the experiment keep a
check on the reading indicated by the +/- 45o gauges, do not let these readings
go above about 500 micro strain.
NB the tubes probably have a residual twist in them when under zero torque.
2. Closed Section
The closed section is much stiffer than the
open slit section and the angular rotation will probably be smaller.
3. Open Section
Check that as the tube twists the faces on either side of the slit are not interfering.
Return to module introduction.
David J Grieve, 4th January 2008. (original: 16th June 2003).