Tensile testing machine for multi-wire strand

Steel wires/cables and strand consist of individual wires stranded together. Among the principal quality assurance tools for steel strand is the tensile test with strain measurement, for which ZwickRoell supplies a tensile testing machine for loads up to 600 kN as default configuration, in accordance with established standards (ISO 6892-1, ISO 15630, ISO 12076). As steel strand unwinds under tension, ZwickRoell uses special specimen-grip inserts to prevent premature failure at unwanted locations.

The testing machine is equipped with monobloc specimen grips with special inserts for steel strand to ensure secure gripping of the specimen. Tensile tests can be performed on steel strand with diameters from 3 to 20m; deflected tensile tests, for example to EN ISO 15630-3, can also be carried out. The moving crosshead of the testing machine is provided with a through hole for these tests.

Failure of steel strand generally results in individual wires whipping about, with the risk of damage to contact-type extensometers. ZwickRoell therefore employs optical long-travel extensometers for safe, reliable, accurate measurements on high-extension and elastic materials. The lightXtens extensometer achieves a resolution of 5 µm over the entire measurement travel of up to 900 mm and satisfies the requirements of Accuracy Class 1 as per ISO 9513 from 3mm. When used with temperature chambers it is also suitable for applications in extended temperature ranges. Other advantages of this extensometer include automatic identification of gage marks on the specimen plus the initial gage length and transmission of all data to the testXpert II software.