Overview
SIST ISO 7802:2015 defines the wrapping test method for metallic wires, specifically targeting wires with diameters or thicknesses ranging from 0.1 mm to 10 mm inclusive. This internationally recognized standard assesses the wire's ability to undergo plastic deformation during wrapping without cracking or failure. Originally published in 1983, the updated 2013 edition provides refined procedures to ensure consistent, reliable testing across industries that rely on metallic wire performance.
Key Topics
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Scope and Purpose
SIST ISO 7802:2015 covers the wrapping test as a method to evaluate ductility and deformation properties of metallic wire materials. It is applicable to wires with specified dimensional limits, ensuring that wires can maintain integrity under coiling and uncoiling stress conditions.
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Test Principle
The wire is wrapped tightly around a mandrel of predetermined diameter to form a closely packed helix. This test evaluates the wire’s plastic deformation characteristics by simulating real-world stressing during manufacturing or end use. Some tests may include sequences of winding, unwinding, or rewinding.
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Equipment Requirements
The testing machine must facilitate consistent winding ensuring coil turns are in contact. The mandrel can be a piece of wire matching the prescribed diameter and hardness. The equipment setup allows for precise control of wrapping speed and tension.
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Testing Procedure
- Conduct tests at ambient temperatures between 10°C and 35°C (preferably 23°C ± 5°C under controlled conditions).
- Wrap the wire at a controlled rate (not exceeding 1 turn per second), avoiding heat buildup.
- Apply tensile stress during winding up to 5% of the wire’s nominal tensile strength to ensure tightness.
- When unwinding is included, it should be done slowly to prevent temperature rises that could affect outcomes.
- Post-test evaluation is based on visual inspection for cracks, using magnification (approx. 10x) for wires below 0.5 mm diameter.
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Test Reporting
Reports must reference SIST ISO 7802:2015 and include detailed test piece identification, wire dimensions, mandrel diameter, test conditions (turn count or wound length), and the test result. This facilitates traceability and comparison across batches or suppliers.
Applications
SIST ISO 7802:2015's wrapping test is critical in industries where wire ductility and flexibility determine product quality and safety. Common applications include:
- Electrical wiring manufacturing, ensuring that wires can withstand bending and coiling during installation.
- Automotive wire harnesses, where wires must endure repeated flexing without failure.
- Construction and engineering, where metallic wires are used in reinforcing, binding, or structural applications requiring reliable deformation characteristics.
- Metal wire products like springs and cables, where the wrapping test helps predict performance and lifespan.
This standard supports quality control, material selection, and product development by verifying metal wire performance under mechanical stress conditions mimicking practical use.
Related Standards
- ISO 8532 – Methods for mechanical testing of wire and wire products, complementing wrapping test procedures.
- ISO 6892 – Metallic materials tensile testing, useful in conjunction with ductility assessments like wrapping tests.
- ISO 7801 – Metallic wire bending test, another method evaluating wire flexibility and endurance.
- IEC standards for electrical wires, which may reference ISO 7802 for verifying wire deformation resistance in electrical applications.
By integrating SIST ISO 7802:2015 with these related standards, organizations can establish a comprehensive testing protocol ensuring metallic wire quality for diverse industrial needs.
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