What Is Bend Test?
The bend test is a ductility test in which the specimen is bent around a defined mandrel diameter to a specified angle, checking whether cracks form on its surface. It produces a pass/fail result rather than a numerical strength value.
Purpose of Bend Test
The purpose is to verify that the material or welded joint can deform during forming without cracking.
Which Products Is Bend Test Applied To?
- Metal sheet and strip
- Welded joints
- Pipe and section
- Reinforcing steel
In Which Sectors Is Bend Test Used?
Standards Related to Bend Test
- ISO 7438
- ASTM E290
- ISO 5173
Bend Test Conditions
- Bend angle
- 90°, 120° or 180° per the specification
- Mandrel diameter
- Defined in the standard as a multiple of specimen thickness
- Method
- Mandrel bending, V-block or wrap-around method
- Temperature
- Room temperature, or per the specification
Equipment for Bend Test
- Bending press or universal testing machine
- Mandrel set
- V-block and support rig
- Magnifier-assisted inspection rig
Sample Requirements for Bend Test
- Specimen width and thickness must conform to the standard
- Edges must be dressed so they do not initiate cracks
- For weld specimens, face and root bending each require a separate specimen
- Generally two specimens per direction
Duration of Bend Test
Testing per specimen is short; a set is generally completed within half a working day.
Bend Test Procedure
- 1Specimen dimensions are measured and edges are prepared.
- 2The mandrel diameter and bend angle are determined according to the specification.
- 3The specimen is bent in the defined direction to the specified angle.
- 4The outer bend surface is inspected visually and, if required, with a magnifier.
- 5If a crack is present, its location and size are recorded.
Bend Test Acceptance Criteria
The acceptance criterion is defined in the specification. In weld examination, the typical criterion is the absence of a crack exceeding a specified size on the bend surface.
Evaluation of Results
The evaluation is based on visual inspection. Small cracks starting at the edge are excluded from evaluation in some standards; this distinction is stated in the specification.
Bend Test Report
- Standard applied
- Mandrel diameter and bend angle
- Specimen direction and thickness
- Inspection result and, if present, crack description
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Welding-procedure-qualification requirements
- Structural-steel product standards
Mekanik Testler — What Does This Testing Field Cover?
The section below describes the field that the Bend Test test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Mechanical testing measures how a material or a part behaves under force. The family ranges from static loading (tension, compression, bending) to time-dependent behaviour (fatigue, creep), and from hardness and wear to fracture toughness.
What these tests have in common is that the result is reported as a MATERIAL PROPERTY. Yield strength or hardness is not a conformity decision; it is numerical data against which the design and the product standard will compare. Mechanical test reports are therefore usually an input to an engineering decision rather than to a product approval — material selection, safety factor, life prediction.
The distinction between static and dynamic behaviour is the key to understanding the field. A part may appear entirely unstressed under a static load yet break under repeated loading; fatigue fracture occurs at stresses well below the yield strength and gives no warning. For rotating, vibrating or cyclically loaded parts, a tensile test alone is therefore not sufficient evidence.
Test conditions determine the result, and this is critical for the readability of the report: specimen geometry, loading rate, temperature, conditioning and the gripping arrangement. The same material gives different values under different conditions. In plastics the rate effect is very pronounced, in metals the temperature effect; in composites the specimen orientation changes the result entirely.
Hardness is the most misused measurement in the field. Because it is fast, close to non-destructive and inexpensive, it is often used in place of strength. Conversion tables from hardness to strength exist, but they are APPROXIMATE and depend on the material group; using them as the sole evidence in material acceptance is wrong.
The fracture mechanics side requires a specific competence. Fracture toughness and fatigue crack growth rate measurements make it possible to calculate how long a cracked structure will last; they are the basis of damage-tolerant design in fields such as pressure equipment, aircraft structures and pipelines.
Method groups in this field
Static tests
Tension, compression, bending, shear and torsion. Yield and tensile strength, elongation and modulus of elasticity are obtained.
Impact tests
Charpy and Izod notch impact; the brittle-to-ductile transition behaviour of the material is determined as a function of temperature.
Hardness
Brinell, Vickers, Rockwell, Shore and micro hardness. Valuable for surface treatment depth and local differences in strength.
Fatigue
Force- and strain-controlled axial fatigue, fatigue in bending; S-N curves and the endurance limit.
Creep and stress relaxation
Behaviour under long-term load at high temperature; decisive for boiler, turbine and pressure equipment materials.
Fracture mechanics
Plane-strain fracture toughness, the J integral, CTOD and fatigue crack growth rate.
Wear and friction
Taber and rotating drum abrasion, coefficient of friction measurements.
Commonly confused in this field
- Calculating strength from hardness is approximate; it cannot be used as the sole evidence in material acceptance.
- Adequate static strength does not demonstrate fatigue strength; a cyclically loaded part requires a separate test.
- If test rate and temperature are not reported, the result cannot be compared — especially for polymers and composites.
- A test specimen and the actual part may not give the same value; moulding orientation, weld lines and differences in surface treatment all have an effect.
- A strength value given for a composite without stating the specimen orientation is meaningless.
- ASTM and ISO counterparts measure the same quantity but use different specimen geometries; the results are not treated as directly equivalent.
Which decisions these results support
- Design verification and material selection
- Incoming material control and supplier approval
- Meeting the mechanical requirements of the product standard
- Failure analysis, life prediction and damage tolerance calculation
- Verifying heat treatment and surface treatment processes
Related Tests
Frequently Asked Questions About Bend Test
Are the bend test and the flexural test the same thing?
No. The flexural test produces numerical values such as strength and modulus. The bend test evaluates ductility as pass/fail and is generally used in weld examination.