Bøyetest

Bøyetest, or bending test, is a mechanical test used to determine the ductility, bendability, and bending resistance of a material or component by applying controlled bending. It is commonly applied to metals, sheet products, tubes, and coatings to assess how they respond to forming and service strains.

The test can be performed using several configurations, such as three-point bend, four-point bend, or mandrel bend. A straight specimen is clamped and bent by applying a moment around a defined axis, causing tensile stress on the outer surface and compressive stress on the inner surface. Depending on the setup, the test measures the bend radius, deflection, or angular bend that the material can withstand before cracking or yielding.

In sheet metal and tubes, the bend radius to thickness ratio (R/t) is a key parameter; for coatings, the emphasis is on the appearance of cracks or delamination at the bend. The mandrel bend variant uses a rigid mandrel to prevent wrinkling and to reveal the true ductility of the material and coating system under bending.

Standards from organizations such as ASTM and ISO specify bend test methods and acceptance criteria for metals and coatings. Results are typically reported as the minimum bend radius or the bend angle at which cracks or defects appear, along with test conditions such as specimen size, thickness, support span, and mandrel radius.

Bøyetests help assess production quality, formability, and service durability, but outcomes depend on specimen geometry, surface finish, and test setup, so they are used alongside other mechanical tests to gauge overall material performance.