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 is a destructive mechanical test standard that evaluates the ductility and structural soundness of metallic materials (and welds) by subjecting specimens to controlled bending deformationASTM International. It is a widely used quality control and qualification method for metals, alloys, and welded joints across industries.
Test Principle and Test methods:
The principle is to bend a specimen through a specified angle and/or around a mandrel of a specified diameter. The outer surface of the bend is subjected to tensile strain. The test evaluates whether the material cracks or fractures on this tension surface. The absence of cracks beyond a specified size indicates acceptable 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.
| Guided‑Bend Test (Most Common) | A specimen is placed on two fixed supports; a mandrel/plunger forces the mid‑length to bend between the supports. Typical configurations: 3‑point bend, U‑bend, V‑bend. Used for weld qualification (face bend, root bend, side bend). Support spacing C = 2r 3t ± t/2.
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| Semi‑Guided Bend Test | The specimen bends while in contact with a mandrel, to a specified bend angle or inside bend radius (r) under load.
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| Free‑Bend Test | Specimen ends are brought together with no transverse force on the bend; the concave surface does not contact any tooling.
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| Bend‑and‑Flatten Test | After initial bending, a transverse force is applied to flatten the specimen until its legs make full contact.
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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.
ASTM E290 Testing Machine required:
Universal Testing Machine (UTM) or Bending Testing Machine: Electromechanical or servohydraulic, with sufficient load capacity.
Bend Fixtures:
Supports (fixed span)
Mandrels/plungers (defined diameters/radii per material thickness)
Guided‑bend dies (U‑shaped, V‑shaped)
Measuring Tools: Calipers, rulers, angle gauges, visual inspection aid.
Test Specimen Information
1. Specimen Size Requirements
Full-section specimens: Original cross-section can be used when thickness ≤ 38mm
Rectangular specimens: Width-to-thickness ratio 2:1 (minimum width 18mm) or 8:1 (for thin plates)
Edge treatment: Radius ≤ 1.5mm (for specimens under 50mm) or ≤ 3mm (for specimens above 50mm)
2. Direction Marking
The relationship between the bending axis and rolling direction must be clearly indicated:
Longitudinal specimens: Length parallel to rolling direction (bending axis perpendicular)
Transverse specimens: Length perpendicular to rolling direction (bending axis parallel).
General ASTM E290 Bending test procedure:
Prepare and measure the specimen (thickness, width, length); select mandrel diameter per specification.
Mount the bend fixture on the UTM; set the support span.
Place the specimen symmetrically on supports (face, root, or side orientation for welds).
Apply load at a constant, slow rate until the specified bend angle (e.g., 180°) is reached or failure occurs.
Remove the specimen; visually inspect the convex surface for cracks or irregularitiesASTM International.
Evaluate against pass/fail criteria (no cracks > allowable size; no fracture).
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.
Related products and device
Related Standard
ISO 7438 is a standard that specifies a method for determining the ability of metallic materials to undergo plastic deformation in bending. It is used to evaluate the flexural strength and stiffness of a material , The bend test shall be carried out in testing machines equipped with a bending device with two supports and a former; bending device with a V-block and a former; bending device with a clamp.
ASTM C158 is a standard test method for determining the flexural strength (modulus of rupture, MOR) of glass and glass-ceramics via bending, covering two core methods (A for flat glass, B for rectangular/elliptical cross-sections) with clear specimen, equipment, procedure, and calculation rules. It is critical for glass engineering as flexural strength directly governs structural safety, design optimization, and compliance with industry standardsNational Glass Association.
ASTM D790: Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
ASTM D790 test methods are used to determine the flexural properties of unreinforced and reinforced plastics, including high modulus composites and electrical insulating materials utilizing a three-point loading system to apply a load to a simply supported beam (specimen). The method is generally applicable to both rigid and semi-rigid materials, but flexural strength cannot be determined for those materials that do not break or yield in the outer surface of the test specimen within the 5.0 % strain limit.
ISO 9585 describes a test method for straight plates but may also be used for ones having a small initial curvature. The method is neither recommended for plates of a length less than 50 mm nor for those designed to be used with, or forming parts of, intramedullary devices.
The static and dynamic strength of the bone plates are determined in 3-point or 4-point bending tests, whereby the bending device consists of two fixed and parallel supports. The bone plate (1) is fixed or clamped on the specimen holder (2). A cyclic, sinusoidal load is applied to the implant via a punch (3) until the specimen breaks or until the maximum number of cycles is reached. Testing in a liquid bath (heated to body temperature) with Ringer's solution increases the physiological relevance of the test. Force and displacement signals i.e. the deflection of the sample- must be recorded during the test.
ISO 178 Plastics - Determination of flexural properties
ISO 178 specifies a method for determining the flexural properties of rigid and semi-rigid plastics under defined conditions. A standard test specimen is defined, but parameters are included for alternative specimen sizes for use where appropriate. A range of test speeds is included.
ISO 178 test method is used to investigate the flexural behaviour of the test specimens and to determine the flexural strength, flexural modulus and other aspects of the flexural stress/strain relationship under the conditions defined. It applies to a freely supported beam, loaded at midspan (three-point loading test).
ISO 14125 is a test method to determine flexure properties of fiber-reinforced plastic composites.
There are two methods used, Method A for a three-point flexure test and Method B for a four-point flexure test.
There are four material classes, Class I – IV, which define the specimen length, span, width, and thickness.
The standard requires deflection measurement not exceed +/- 1% error of full scale.
ISO 14125 is based on the ISO 178 standard and both utilize three point flexural testing of a freely supported bar loaded between the supports.
ISO 14125 focuses on fibre reinforced plastic compositesand has an alternative 4-point loading testing procedure, Procedure B.
The material properties recorded by following the standard are the flexural stress, flexural strain, elastic modulus in flexure and interlaminar shear modulus.
Compression-testing machine which will comply with ISO 5893 and shall be capable of maintaining speeds of (0.5 +- 20 %) mm/min to (500 +- 10 %) mm/min.
Comparison Table: ISO 7438 vs. ASTM E290
| Item | ISO 7438:2020 (Metallic Materials – Bend Test) | ASTM E290-22 (Standard Test Methods for Bend Testing of Material for Ductility) |
|---|---|---|
| Core Purpose | Evaluate plastic deformation ability & ductility under bending; detect material defectsISO | Assess ductility via bending under various constraint conditionsASTM International |
| Test Methods |
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| Specimen Types | Rectangular, square, round, polygonal cross‑sections | Rectangular, round, flat, or other product‑specific shapes |
| Support Span Formula | Typically L= (D + 3a) ± a/2 | L=(E+3a)±a/2 (E = former diameter, a = specimen thickness) |
| Bend Angle Definition | Measured after unloading; target angles: 90°, 120°, 180° (per product spec) | Measured under load (semi‑guided) or after unloading (free bend) |
| Key Evaluation Criterion | No visible cracks/fractures on convex surface after bending | No cracks, fissures, or breaks; acceptability per product specs |
| Welded Joints | Not applicable (use ISO 15630) | Not primary focus; welds covered by other ASTM standards |
| Plane‑Strain Capability | Yes (Annex B for high‑constraint bending | No |
| Related Regional Standards | EN ISO 7438 (Europe), JIS Z 2248 (Japan) | ASTM E190 (weld bend), ASTM A370 (steel products) |
| Primary Application | Global material qualification, QC, forming assessment | North American manufacturing, construction, automotive |
| Equipment Focus | Universal testing machine + standard 3‑point/V‑block fixtures | Universal testing machine + guided/semi‑guided/free‑bend fixtures |
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