REVEAL DEFECTS BY BENDING DEFORMATION
The metal bend test is one of the most widely used mechanical tests for evaluating ductility, soundness, and the quality of welds and base materials. By deforming a specimen to a specified angle, the test forces defects to reveal themselves. Cracks, laminations, lack of fusion, and other discontinuities become visible on the tensile (outer) surface of the bend.
Bend testing produces qualitative data that directly reflects material or weld integrity. These characteristics are vital considerations in engineering design across construction, offshore, and oil & gas industries, where ductility can be the difference between safe service and catastrophic failure.
Professional Testing Services has decades of experience performing bend tests on:
- Raw materials
- Welds
- Reinforcement bars (rebars)
- Wire meshes
We perform welding bend test and material bend test services to internationally recognised ASTM standard for bend test requirements, supporting fabricators, contractors, and manufacturers across the region. Whether you need a sectioned bend test or bending of a full-sized pipe, our accredited laboratory can support your qualification and QC requirements.
What Is a Bend Test?
A metal bend test deforms a specimen to a specified angle, typically 90°, 120°, or 180° depending on the standard, around a mandrel or former. The concave (compressed) side and convex (tensile) side are then visually inspected for defects.
The technique is deceptively simple, but the data is powerful:
- Ductility assessment: how much a material can deform before cracking
- Weld quality: soundness of the weld, HAZ, and fusion zones
- Material verification: confirming grade and processing meet specification
- Product certification: required for reinforcement bars, wire mesh, welded pipe
For reinforcement bars and wire mesh, we also perform rebend testing, where the specimen is bent, aged, then bent back to a specified angle, simulating service conditions.
Types of Bend Test We Perform
Our laboratory performs the full range of bend test configurations:
Test Type | Application | Guided bend test | Weld qualification (WPS/PQR, welder qualification) |
|---|---|
Face bend test | Weld cap side placed in tension, reveals cap defects |
Root bend test | Weld root placed in tension, reveals root defects |
Side bend test | Weld cross-section placed in tension, for thicker welds |
3-point bend test | Material ductility and bend properties |
Semi-guided bend test | Base material qualification per ASTM E290 |
Bend and rebend test | Reinforcement bars, wire mesh (BS 4449, ASTM A615) |
For pipe and tube materials, we also offer flattening tests for pipe and tube materials.
ASTM and ASME Standards for Bend Testing
The ASTM standard for bend test varies by material type and application. Our laboratory operates to the following commonly referenced standards:
Standard | Application | ASTM E190 | Guided bend test for ductility of welds |
|---|---|
ASTM E290 | Bend testing of material for ductility (general purpose) |
ASTM A370 | Mechanical testing of steel products (includes bend test methods) |
ASTM A615 / A706 | Bend and rebend testing of reinforcement bars |
ASME Section IX | Bend testing for welding procedure and welder qualification |
ISO 5173 | Destructive tests on welds, bend tests |
AWS D1.1 | Structural welding code, includes bend test requirements |
API 1104 | Pipeline welding, bend test requirements |
We also perform bend testing to client-specific or classification society requirements (DNV, ABS, Lloyd’s, Bureau Veritas).
Bend Test Acceptance Criteria, What Passes and What Fails
Bend test acceptance criteria depend on the governing code, but the principles are consistent. After bending to the specified angle, the specimen is examined for open discontinuities on the convex (tensile) surface.
Typical acceptance limits (per most codes):
- No single discontinuity exceeding a specified length (commonly 3 mm or / 1/8″)
- Sum of all discontinuities below a specified total length (commonly 10 mm or / 3/8″)
- Corner cracks are often excluded from acceptance criteria unless caused by lack of fusion or slag
Common causes of bend test failure:
- Lack of fusion between weld passes or at the weld root
- Slag inclusions
- Porosity clusters
- Excessive hardness in HAZ (brittle behaviour)
- Improper welding parameters (heat input, travel speed)
- Base material defects (laminations, inclusions)
If your welds are failing bend tests, we can support root cause investigation through metallographic examination and macro-etch testing.
Our Bend Testing Process
Step 1: Sample Receipt and Preparation Specimens are received, identified, and prepared according to the applicable standard (dimensions, edge preparation, weld reinforcement removal where required).
Step 2: Machining Test coupons are machined to standard dimensions. For weld bend tests, weld reinforcement is typically ground flush with the base metal.
Step 3: Bending The specimen is bent around a mandrel of specified diameter to the required angle using calibrated bend testing equipment.
Step 4: Examination The bent specimen is visually examined for cracks, tears, or other open discontinuities on the convex surface.
Step 5: Reporting A detailed report documenting test parameters, observations, measurements, and pass/fail assessment against acceptance criteria.
Bend Testing for WPS, PQR, and Welder Qualification
Welding bend test is a mandatory destructive test for welding procedure qualification (WPS/PQR) and welder performance qualification under most major codes.
Typical WPS/PQR destructive test package:
Test | Purpose | Bend test (face, root, or side) | Weld ductility and soundness |
|---|---|
Weld tensile strength | |
Weld profile, fusion, penetration | |
Evaluates metallurgical changes across the base metal, HAZ, and weld metal cross-section | |
Reveal internal discontinuities on fracture surface | |
Notch toughness (where code requires) |
Number and type of bend specimens depends on the code, material thickness, and joint configuration. Under ASME IX, for example, plate qualification typically requires two face and two root bend specimens (or four side bends for thicker sections).
What to Send Us, Specimen Requirements
At PTS, we strive to provide fast and accurate testing, but we do have requirements. Please provide the following with each submission:
Specimen:
- Welded coupon or material sample sized per the applicable code
- For WPS qualification, sufficient material to extract all required test specimens
- Uncut coupons preferred (we perform machining under controlled conditions)
Documentation:
- Material grade / specification
- Welding procedure (WPS) if applicable
- Governing code or standard for testing
- Acceptance criteria
- Sample identification and orientation (top, bottom, root, cap)
Not sure what to send? Contact us with your project details and we’ll advise on specimen size and preparation.
Application of Bend Test
Ease of specimen preparation
cost-effective compared to many other mechanical tests
Specimens undergo extensive plastic deformation
so any defects in the material are revealed
Flexible angle configurations
90°, 120°, or 180° depending on test standard
Multiple material types
plate, pipe, reinforcement bars, wire mesh
Weld qualification support
required for WPS, PQR, and welder performance testing
Industries We Serve
Our bend testing services support:
- Construction: reinforcement bar certification, structural steel welds
- Marine and Offshore: hull welds, structural fabrications
- Oil and Gas: pipeline welds, pressure equipment
- Manufacturing: welded assemblies, fabricated components
- Steel Mills and Distributors: product certification and QC
Accredited Testing You Can Trust
Our laboratory is accredited to ISO/IEC 17025:2017. Test reports carrying our accreditation mark are accepted by classification societies, regulatory authorities, and end clients across the region.
For more detail on our accreditation scope, see our accreditations.
Talk to Us Today
Our expert testing team performs bend tests using calibrated force measurement instruments and materials testing machines, from standard 3-point bend to full-pipe bend configurations.
Need a single metal bend test or a full WPS qualification package? Contact us or send us an enquiry to see how we can help you with a bending testing solution that suits your needs.
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Frequently Asked Questions About Bend Tests
Which ASTM standard covers bend testing of welded joints?
The primary ASTM standard for bend tests of welded joints is ASTM E190 (Guided Bend Test for Ductility of Welds). For general ductility testing, ASTM E290 applies. Under ASME Section IX and AWS D1.1, bend test procedures are defined within the welding codes themselves. For reinforcement bar welds, ASTM A615 or A706 may apply.
What is a bend test for welding qualification?
Welding bend test is a destructive mechanical test used to verify weld ductility and soundness during welding procedure qualification (WPS/PQR) and welder performance qualification. A welded coupon is bent to a specified angle, and the tensile surface is examined for open discontinuities. Acceptable results confirm the welding procedure produces sound, ductile welds.
What caused my weld to fail a guided bend test?
Common causes include lack of fusion between weld passes or at the root, slag inclusions, porosity clusters, excessive HAZ hardness, incorrect welding parameters (heat input, travel speed), or base material defects. If a weld passed radiographic testing but failed the bend test, likely culprits are fine planar defects (tight lack of fusion, cold cracks) that RT can miss but bend testing exposes. We can support failure investigation through macro-etch examination and metallographic analysis.
I need to qualify for a WPS. Which destructive tests are required and where can I get them done?
WPS qualification typically requires bend tests (face, root, or side), transverse tensile tests, macro-etch examination, and, where specified, Charpy impact testing and hardness testing. The exact scope depends on the governing code (ASME IX, AWS D1.1, ISO 15614), material, and joint configuration. Our laboratory performs the complete WPS destructive test package in-house, so contact us with your WPS details for a full quotation.
