Dynamic tests on stranded wires Manufacturers are required by product standards to perform these tests. These tests are often outsourced to a service provider in order to save equipment costs. Additionally, the manufacturers are externally monitored by independent institutes.
During fatigue tests (e.g. according to ISO 15630-3, XP A 35-045-2011, FprEN 10138-3:2009) on wire strands, the specimen must endure two million test cycles at a frequency at max. 20 Hz without breaking. If the specimen breaks nearby or during gripping, the test is invalid and must be repeated. The test lasts several days, therefore making invalid tests very costly. Since stranded wires are extremely stiff, they are also very sensitive to notches. The gripping force causes a load to be superimposed on the dynamic test load in the clamping area, which can lead to premature specimen failure. Therefore, for classic tensile specimens made of solid material, the ends often have larger cross-sections to ensure that the specimen breaks in the free portion between the specimen grips. With wire strands it is not so simple. To obtain correct test results, extensive specimen preparation, such as sealing, is required.