Guided Bend Test is a type of the destructive testing which is applied on specially prepared specimens of a test welded plate or pipe, in order to evaluate the quality and soundness of weld. Specimens are prepared in such a way that the cut surfaces are considered as sides and the remaining two surfaces would be the face and root. Guided bend test can be performed with five different ways depending on which surface is to become convex of a bent specimen and also on the type of specimen (whether the lengthwise axis of specimen is parallel or transverse to the weld axis). Following are the five types of weld guided bend test, have a look!
Type One: Transverse and Side Bend Test
In this type the specimen with its lengthwise axis transverse to weld axis, is allowed to bend in such a way that one of the cut surfaces (sides) is to become convex.
Type Two: Transverse and Face Bend Test
The specimen with its lengthwise axis transverse to weld axis, is allowed to bend in such a way that the face surface is to become convex. That is why it is called transverse face bend test.
Type Three: Transverse and Root Bend Test
This type is similar to transverse face bend test but the root surface is to be made convex of the bent specimen instead of a face surface.
Type Four: Longitudinal and Face Bend Test
The longitudinal bend test can be used to substitute for the transverse bend tests (side, face and root) where the bending properties may vary either between two base metals or between a base metal and weld metal.
In a longitudinal and face bend test, the specimen with its lengthwise axis parallel to weld axis is allowed to bend is such a way that the face surface is to become convex.
Type Five: Longitudinal and Root Bend Test
Same as longitudinal and face bend test but the root surface is to be made the convex side of bent specimen instead of a face surface.
The purpose of a guided bend test is to determine the soundness of the quality welds as specified in procedure qualification and performance qualification. The specimen is allowed to bend around the former using a ‘test jigs method’ where the side of specimen (root, face or side) is rounded towards the gap of jigs. Sometimes the thickness or width of specimen is too large to allow it to wrap around the former. In this situation the specimen is cut into equal sections by making sure that each section of the sub-sized specimen is to be bent test. In transverse bend test the weld and heat affected zone (HAZ) must be within the bent portion of the specimen. If they do not come inside the bent portion, the specimen will be sub-sized in equal sections and tested.