Alignment extensiometers are used with materials testing apparatus to measure the bending strain on the sample. Prior alignment extensiometers measure bending by using four linear displacement transducers to measure the distance between two cross heads attached to the sample. The cross heads are attached to the sample by use of a vice like action to press an insert against the sample. This is a cumbersome process and is prone to jamming and sticking of the insert into the cross head.
Prior inventions have been used to measure bending strain on a dummy sample while the load train is aligned The extensiometer is then removed and the dummy sample replaced with the test sample.
The present invention can be used on test samples to reduce the bending strain and, if desired, to subject the sample to a known bending strain.