Overview
ISO 7801:2024 - Metallic materials - Wire - Reverse bend test defines a standardized method for assessing the ability of metallic wire (diameter or characteristic dimension from 0.3 mm to 10 mm) to undergo plastic deformation when subjected to repeated reverse bending. The second edition updates testing symbols, typical cross‑sections (round, shaped, clad), support radii and procedural rules to ensure reproducible ductility and fatigue‑related evaluations for wire products.
Key topics and technical requirements
- Scope: Applies to metallic wires with nominal diameters/characteristic dimensions between 0.3 mm and 10 mm; specific ranges can be refined in relevant product standards.
- Test principle: Repeated bending through 90° in alternating directions over cylindrical supports; each bend is counted and the number of reverse bends (Nb) is recorded.
- Equipment and geometry: Machine must conform to Figure 2 and the parameter tables. For round wires, Table 1 prescribes support radius (r), guide hole diameter (dg), distance L, and top‑edge offset y by wire size. Annex A provides support radii for shaped steel wires (Z, H, T types).
- Procedure details:
- Insert and grip the straightened test piece; bending arm pivots 90° alternately.
- Rate of bending: uniform, without shock, not exceeding one bend per second.
- Ambient testing: generally 10 °C to 35 °C; controlled testing at (23 ± 5) °C when required.
- To maintain contact, a tensile force up to 2% of nominal tensile strength may be applied (unless otherwise agreed).
- End criteria: Test continues until the specified number of bends in the product standard is reached or until complete fracture. Crack detection is not required as the default stopping criterion; visible cracking may be used if specified.
- Reporting: Test reports must reference ISO 7801:2024 and include identification, nominal diameter/characteristic dimension, preparation method, testing conditions (r, F, etc.), ending criterion and Nb.
Applications and users
- Who uses it: wire manufacturers, materials testing laboratories, quality control/assurance teams, product standards writers, R&D engineers, and procurement/inspection authorities.
- Why use it: To evaluate ductility, bend‑fatigue performance, and integrity of round, shaped and clad wires for static and dynamic applications (e.g., springs, electrical conductors, fasteners, coated/clad products). Results support acceptance criteria, supplier qualification, and material selection.
Related standards
- Product‑specific standards will typically reference ISO 7801:2024 for applicable diameter ranges and detailed acceptance criteria.
- Prepared by ISO/TC 164/SC 2 (Mechanical testing of metals - Ductility testing); replaces ISO 7801:1984.
Keywords: ISO 7801:2024, reverse bend test, metallic wire testing, wire ductility, cylindrical supports, shaped wire, round wire, clad wire, test parameters.
