The flexibility of a wire/cable is dependent on a combination of the conductor and insulation constructions. Conductors with more strands are often better able to endure flexing without breaking. More rigid insulations can place additional strain and also crack during flex testing.
The flexure endurance test (or cyclic bending in the ISO standard) evaluates the wire/cable’s ability to withstand flexing on a tight mandrel. The flexing performed in this test is very severe and the results should only be considered for comparative analysis and not an estimate of in-service longevity (test parameters can be adjusted to better reflect in-service conditions).
In this test, the specimen is flexed 180Deg between two mandrels until there is a break in electrical conductivity of the conductor. The pass/fail criteria is based on the particular specification, typically set at a minimum threshold for the number of flexing cycles with conductor loss.
Parameters that can be changed for this test include:
- Mandrel diameter
- Weight on specimen
- Number of trails
Note that there are significant procedural differences between the European and SAE flex test methods. Information and pricing on the SAE test can be found here.