Bend testing is a procedure to determine the relative ductility of metal that is to be formed (usually sheet, strip, plate or wire) or to determine soundness and toughness of metal (after welding, etc.). The specimen is usually bent over a mandrel of specified diameter. Defects which are not shown by radiography test may appear in the surface of a specimen when it is subjected to progressive localized over-stressing.
A bend test is an easy and inexpensive test to apply. The method is fast and shows most weld faults quite accurately. Bend tests may be used to find a number of weld properties such as:
- Fusion
- Ductility of the welded zone
- Weld penetration
- Crystalline structure (fractured surface, if any)
NUSATEK provides bend testing which is a common requirement for destructive tests in producing welding procedure specification (WPS) and to qualify welder in welder qualification tests (WQT).
Test Standards
- ASTM E190
- ASTM E290
- BS EN ISO 5173
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Bend Test
A Bend Test may be carried out on a tensile testing machine with the help of certain attachments and fixture. The bend test assists in determining the soundness of the weld metal, the weld junction and the heat affected zone. The test shows the quality of the welded joint. Any cracking of the metal will indicate false fusion or defective penetration. The stretching of the metal determines to some extent its ductility. Fractured surface shows the crystalline structure. Large crystals usually indicate wrong welding procedure or poor heat treatment after welding. A good weld has small crystals.
To conclude, the bend test is an easy and useful method of comparing one welded joint with another of the same type and of revealing abnormalities and defects at or near the surface in tension.
Types of Bend Tests
Bend tests may be categorized as
- Guided Bend Test
- Semi-Guided Bend Test
- Free Bend Test
- Bend and Flatten
Bend tests may be further classified as:
a) Transverse bend test
- Face bend test
- Root bend test
- Side bend test
b) Longitudinal bend test
- Face bend test
- Root bend test