Two types of bend fixtures are available for evaluating the ductility of plate specimens and welded ferrous and non-ferrous materials. The main difference between the two fixtures is in the base, the guided bend test fixture has a fixed span base, while the weld bend test fixture has an adjustable span base.
Both fixtures use plungers or loading struts with a fixed diameter nose for testing a particular specimen thickness. The plungers are attached to the adjustable crosshead using the grip bumper plate or a threaded adapter.
The base is equipped with a dowel hole in the center so that it can be doweled to the compression table and kept from sliding during a test. This also will maintain the alignment of the plunger in relation to base so that the force is applied in the center of the span.
The hardened rollers in the base are captured but free to rotate to allow the specimen to slide as the plunger moves between the rollers. The depth of the base will typically allow up to a full 180 degree bend in the specimen.
Principle of Operation
The bending force is applied as the specimen is forced against the plunger, either as the base is raised with the table or as the crosshead moves down depending on the frame being used. The plunger forces the specimen into a 180 degree bend against the rollers on the base.
On the weld bend test fixture, one half of the base can be adjusted to one of four different positions to allow for testing different thickness specimens. A separate plunger or strut is required for each thickness specimen, several struts are available depending on the fixture.
Guided bend fixtures have a fixed span base and a single diameter loading strut or plunger to form a complete assembly. Specimen loading is carried the same as with the weld bend fixture though a separate assembly must be purchased for each specimen thickness.