Information on the most widely used ASTM standards within the materials testing industry
ASTM E290 Standard Test Methods for Bend Testing of Material for Ductility
ASTM E290 test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle of bend or to a specified inside radius of bend (r) measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend-and-flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen.
Ductility refers to the mechanical property whereby a material can deform under tensile or compressive stress without breaking. Bend testing under ASTM E290 significantly determines a material's suitability for flexible, non-cracking applications. This testing method ensures that products are reliable, safe, and quality-compliant in construction, aerospace, automotive, and manufacturing, making them essential.
Types of Bend Tests
There are different bend test standards where the details change depending on the material type or sample geometry you are testing. These differences affect your test fixture choices, software calculations, and data analysis. Using our Newton controller, each test report can contain different data from one test sample to the next.
3-point bend test: These are easier to set up than 4-point, and the bent fixtures cost less. The 3-point test can yield precise modulus and flexural strength measures when the materials are uniform and ductile.
4-point bend test: These apply to ceramics and specific composites, as well as test samples that are brittle, heterogeneous, or have surface imperfections that are a problem. By establishing a zone of constant bending moment between the inner upper loading sites, 4-point tests lessen the chance of premature failure at a single location and stress concentrations. Because it evaluates a greater volume of the material, the 4-point test provides a better estimate of the bending behavior if your material's characteristics vary across its cross-section, like wood or layered composites.
Guided Bend Test:
This applies to testing weld ductility where controlled bending to a specific angle is part of the evaluation.
Sample size
The following are the technical specifications of ASTM E290:
Sample size For ASTM E290 testing, the longitudinal edges of a rectangular test specimen may be rounded to a radius not exceeding 1.5 mm 1/16 inch) for specimens equal to or less than 50 mm (2 inches)
Sample thickness For specimens over 50 mm (2 inches) in thickness, the sample must be rounded to a radius not exceeding 3 mm (1/8 inch).

Result checking:
After bending, the convex surface of the bend is examined for evidence of a crack or surface irregularities. If the specimen fractures, the material has failed the test. When complete fracture does not occur, the criterion for failure is the number and size of cracks or surface irregularities visible to the unaided eye occurring on the convex surface of the specimen after bending, as specified by the product specification. Any cracks within one thickness of the edge of the specimen are not considered a bend test failure. Cracks occurring in the corners of the bent portion shall not be considered significant unless they exceed the size specified for corner cracks in the product specification.
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