ASTM A370, A416, ISO 15630 Tensile Testing of Multi-Wire Strand for Prestressed Concrete

To test 7-wire strands to ASTM A370, A416, or ISO 156303, we decided to use the Model 1009. Since most strand applications require specimen lengths of 500 mm and up,

 this frame was chosen primarily for its convenience, large testing space, and long travel. This allows the operator to easily install and remove specimens without the need for a ladder or pit to set up the machine.

We used a set of side-acting hydraulic grips with strand inserts. The side-acting design helps eliminate the problems associated with traditional wedge grips, including grip failure,

 time-consuming grip changes, and inaccurate total elongation measurements. Clamping forces up to 900 kN (202,300 lbf) are available for positive gripping of strand specimens. 

The strand insert arrangement allows for quick switching between different specimen diameters. The semi-cylindrical inserts also help reduce the chance of grip failure while effectively clamping all wires in the stranded specimen.

To measure strain, we use an extra-long clip-on extensometer with a 24-inch (610 mm) gauge length and 15-degree torsion capability. 

Accurate strain measurement enables the system to automatically perform required calculations, such as 1% yield strength and elongation at maximum load.

In addition, we rely on our materials testing software to set up and run repeatable, accurate tests. 

The software automatically zeros the strain measurement at the required preload value included in the test standard. 

Stress-strain graphs are clearly plotted and the calculation results are displayed on the graph.