Standard Test Method for Tension Testing of Wire Ropes and Strand - PDF

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ASTM A931 is the standard test method developed by ASTM International for determining the tensile properties of wire ropes and strand. This test ensures that wire rope and strand products meet strength and elongation performance requirements for safety-critical applications in industries such as construction, transportation, energy, and marine environments.

This guide provides a comprehensive overview of ASTM A931, including its purpose, testing procedures, equipment requirements, and how it compares to similar standards.

What is ASTM A931?

ASTM A931 – Standard Test Method for Tension Testing of Wire Ropes and Strand outlines the procedures for performing tensile strength tests on wire ropes and strand materials. These components are often used in applications requiring high tensile strength, such as guy wires, suspension bridge cables, elevator hoisting systems, and structural support members.

This standard ensures consistent, repeatable measurement of:

• Breaking Strength

• Elongation

• Load-Displacement Behavior

• Mode of Failure

Scope and Purpose

The purpose of ASTM A931 is to verify that a wire rope or strand meets specified minimum breaking strength requirements. It also provides insight into how the product behaves under tensile loads, especially important in evaluating safety and reliability.

The standard covers:

• Testing full-sized specimens

• Applying tensile loads to failure

• Measuring the peak load (ultimate tensile strength)

• Observing break location and failure mode

Test Specimens

Specimen Characteristics:

• Full-size specimens of wire rope or strand (not machined)

• Must include all components (core, strands, lay)

• Must be long enough to accommodate grip length and proper gauge section

Preparation:

• Cut ends must be clean and protected from unlaying

• Rope ends are often terminated using sockets, wedge grips, or resin-filled terminations

Testing Equipment for ASTM A931

Performing ASTM A931 requires a universal testing machine (UTM) with the following specifications and features:

1. Universal Testing Machine (UTM)

• High-Capacity Load Frame: Tensile capacities from 100 kN up to 2,000 kN depending on wire rope diameter

• Precision Load Cell: Accuracy typically within ±1% of reading or better

• Displacement Measurement: To track elongation during the test

• Control Software: To log and display force vs. displacement or force vs. time

2. Specialized Grips for Wire Rope

Wire ropes require custom fixtures for secure holding without slippage. Common grip types include:

• Capstan Grips: Wrap the rope around a drum to create friction

• Wedge Grips: Mechanical or hydraulic systems that clamp onto conical end fittings

• Socket Terminations: Rope ends are embedded in zinc or epoxy and bolted into threaded couplers or clevis pins

3. Extensometers (Optional)

For elongation measurements, non-contact video extensometers or travel sensors may be used, especially when clip-on devices are impractical due to rope diameter or surface irregularity.

Test Procedure

1. Mounting the Specimen
   Secure the wire rope or strand in the grips or sockets of the universal testing machine. Ensure the rope is axially aligned and that slack is removed.

2. Apply Load
   Begin applying tensile force at a controlled crosshead speed as defined by the test specification. Common speeds range from 1 mm/min to 10 mm/min depending on the rope size and material.

3. Monitor the Test
   Continuously record force and displacement until the specimen fails. The peak force recorded before fracture is used to calculate the ultimate tensile strength.

4. Report Results
   Include:

   • Maximum load (breaking strength)

   • Type of failure (e.g., in grip, at fitting, or mid-length)

   • Observations on elongation or deformation

   • Specimen dimensions and preparation method

Similar Standards to ASTM A931

Several other standards offer related procedures for tensile testing of wire ropes or similar materials:

• ISO 3108 covers tensile testing for steel wire ropes used for general purposes and is widely used as the international equivalent of ASTM A931.

• EN 12385-1 outlines safety and performance requirements for steel wire ropes in European markets.

• ASTM A370 provides general test methods for mechanical testing of steel products, including tension and bend tests.

• ASTM E8/E8M describes tension testing procedures for machined metallic specimens but is not suitable for full-size rope or strand.

Industries That Rely on ASTM A931

• Construction & Infrastructure: Suspension bridges, guyed masts, scaffolding

• Oil & Gas: Hoisting and drilling operations

• Mining: Shaft hoists and haulage

• Aerospace & Defense: Aircraft control cables, safety restraints

• Maritime: Mooring lines, towing cables, winch lines

Conclusion

ASTM A931 is a critical standard for verifying the tensile strength and integrity of wire ropes and strand. Using a universal testing machine with appropriate grips and fixtures, engineers can ensure compliance with safety and performance requirements across multiple high-load applications.

Investing in the right test equipment, following the prescribed procedures, and using robust data analysis software ensures accurate and repeatable test results. As industries continue to push the limits of structural materials, standards like ASTM A931 play a crucial role in ensuring safety, performance, and reliability.

Need equipment for ASTM A931 testing?
We offer complete solutions including high-capacity universal testing machines, custom capstan or wedge grips, and integrated control software. Contact us today to get a quote or discuss your application.