3. Qualification of corner joints

This is done by means of mechanical tests. It primarily concerns leaf assemblies that are fastened to one of their vertical edges. Three types of properties are currently estimated:

• the torque to obtain 1˚ angular variation around the nominal position of 90˚ ;

• the residual deformation at the end of this measurement;

• the breaking couple.

The method is as follows:

The sample comprises ten leaf frames. They are cut roughly in the middle of their four sides and marked.

After conditioning at 20 ˚C and 65% relative humidity, they are divided into four batches of ten test tubes:

• low-iron assemblies ;

• ...