Tensile Testing Wire Joining Systems

Solution

• Universal Testing Machine 50 kN
• Wire, joiner, and tensioning component special grips

Benefits

• Eradicates the need to be dependent on testing outside the organization by having a flexible, in-house assessment.
• Reduced setup time with interchangeable grips, ensuring secure clamping of smooth metal surfaces

Requirement

The wire joining and tensioning systems have high application in the construction, agricultural, civil engineering, viticulture, and seismic application industries. These systems are an effective alternative to traditional threaded rods and channels and can be used in suspended HVAC installations, vineyard trellis systems, and other applications.

Designers of these systems should be able to make all the parts work well with loads. This involves strict tensile testing to establish breaking strength and the determination of compliance with specified factors of safety. Normally, wire rope assemblies are designed to break at a known load and hence have predictable performance. A safety margin has to be maintained at all times within the range of a 5:1 safe working load (SWL).

The internal testing processes, especially those aimed at the measurement of break loads of a variety of wire diameters (typically between 1.5 mm and 6 mm), should be refined to facilitate the ongoing improvement. The major problem is to hold the wire firmly at the time of testing so that the stress concentration or early failure at the point of clamping should not be introduced.

Solution

A powerful testing method will imply the implementation of a twin-column universal testing machine with a capacity of 50 kN of forces and sophisticated control software to perform the customized test programs. Various parameters can be assessed with this setup, and they include the ultimate tensile strength of strands of wire, the pull-out strength of joiners, and the performance of end-fixings and restraint systems.

A critical factor in achieving reliable results is the selection of appropriate grips. Traditional approaches, e.g., wire-securing choke knots, can create inconsistencies and can serve as a source of unintentional failure. There are several grip configurations that are evaluated to address this: wedge grips, hybrid grips, and capstan-style rope grips.

A comparison of testing in these setups is done at a controlled extension rate, and the force data is collected up to the failure of the specimen. Each test result is carefully validated to ensure that failure occurs within the specimen rather than at the grip interface or due to slippage.

Stable performance is normally obtained with capstan rope grips on either end of the specimen. The results of these grips are a more even distribution of load and reduced localized stress, as well as repeatable and accurate measurements across wire sizes.

Presto Stantest Testing Approach

Presto Stantest offers higher-order tensile testing systems that are designed for accuracy and versatility. The Universal Testing Machine platform combines high-capacity load cells with user-friendly software, which allows the analysis of the force-extension data in detail and allows break points to be detected automatically.

The system accommodates many different exchangeable grips so that it can easily be reconfigured to meet other test needs. It has customization options that can be used to suit longer specimens, such as adjusted crosshead travel and longer test space. To provide safety, protective enclosures and interlocked guarding systems are used to make sure that there is secure operation during high-load testing.

The software features enable a developer to create, store, and duplicate test programs in different locations, which assist in maintaining the same standards of quality in the global manufacturing setups. The information could be easily exported to be used in reporting and comparison.

Test Equipment

• Universal Tester (50 kN) Twin column
• High-precision load cell (50 kN)
• Capstan rope grips and lever-action wedge grips
• Fully programmable force testing software