🔩 Bend test of welded joints — face bend, root bend and side bend

Materials and NDT PN-EN ISO 5173

Overview

The standard specifies a method for making transverse root, face and side bend tests on test specimens taken from butt welds, butt welds with cladding (welds in clad plates and overlays) and cladding without butt welds — in order to reveal imperfections on or near the surface of the test specimen that is in tension during bending, and to assess ductility. The standard also gives the dimensions of the test specimens.

In addition, it specifies methods to be used instead of transverse bend tests with a former for welded joints in which the parent materials, the heat-affected zones or the weld metal differ significantly in their physical and mechanical properties in relation to bending. The standard applies to metallic materials in all product forms, with joints made by any welding process. The third edition, ISO 5173:2023, replaced the 2009 edition.

The types of test specimen have their own designations, among others TFBB — transverse face bend test specimen for a butt weld (face in tension) and the root bend test specimen (root in tension). The dimensions are described by the symbols: b — width of the test specimen, Lt — total length of the test specimen, ts — thickness of the test specimen, t — thickness of the material, d — diameter of the former or the inner roller, l — distance between the rollers, R — radius of the rollers, α — bending angle. The bend test belongs to the standard set of tests on test joints: in the presentation of the Lublin University of Technology, 4 transverse bend test specimens are specified for a butt joint.

Method principle

A test specimen taken transversely or longitudinally from a welded joint is subjected to plastic deformation by bending, without reversing the bending direction, in such a way that one of the surfaces or cross-sections of the joint is in tension. The temperature at which the test is carried out is recorded in the report; the test speed should be constant and — if known — also recorded. The test is carried out by one of the methods described in Clause 7 of the standard (among others bending with a former and alternative methods for joints with a large difference in the properties of the zones). The test specimens are prepared so that the preparation affects neither the parent material nor the weld metal.

Applications

• Welding procedure qualification and welder qualification testing (testing of test joints)
• Assessment of the ductility of the joint and revealing surface imperfections: cracks, lack of fusion, incomplete penetration
• Testing of butt joints, welds in clad plates and overlays
• Acceptance inspection of welded structures and pipelines
• Assessment of joints of materials with different properties of the zones (alternative methods to bending with a former)

Key parameters

Standard

Standard number

PN-EN ISO 5173:2023-06

Title (PL)

Badania niszczące spoin w materiałach metalowych — Badanie na zginanie

Title (EN)

Destructive tests on welds in metallic materials — Bend tests

Step-by-step procedure

1. Taking test specimens

   Take test specimens transversely or longitudinally from a butt weld, a weld with cladding or from an overlay; select the type of test specimen (face, root, side) according to the purpose of the test and the material thickness.

2. Preparation of test specimens

   Prepare the test specimens so that the preparation affects neither the parent material nor the weld metal; maintain the dimensions and edge radii according to the figures and tables of the standard.

3. Selection of the method

   Select the test method from those described in Clause 7 of the standard — bending with a former or an alternative method when the parent materials, the HAZ or the weld metal differ significantly in their bending properties.

4. Setting up the fixture

   Select the diameter of the former or inner roller d, the roller spacing l and the roller radius R in accordance with the requirements for the material and thickness tested.

5. Bending

   Bend the test specimen without reversing the bending direction until one of the surfaces or cross-sections of the joint has been stretched to the required angle α; keep the test speed constant.

6. Recording the conditions

   Record the test temperature and — if known — the test speed (requirement of Clause 9 of the standard).

7. Assessment

   Inspect the surface of the test specimen in tension and record the imperfections revealed (cracks, lack of fusion, incomplete penetration) together with their position and size.

8. Report

   Give the identification of the joint and the test specimens, the type of test, the bending parameters (d, l, R, α), the test temperature and speed, and the result of the assessment.

Required equipment and apparatus

Health and safety (OHS)

• High bending forces and possible fracture of the test specimen — guard around the working zone, safety glasses
• Ejection of fragments with brittle joints — do not stand in the bending axis
• Sharp edges of test specimens after cutting — gloves, rounding of edges in accordance with the radius r requirement
• Cutting and milling of test specimens — guards, cooling, chip extraction

Frequently asked questions