Machine offers pull-to-break tensile testing

A research project is to investigate aspects of wire/rod network design and specification, with "pull-to-break" tensile testing using an EZ50 materials testing machine from Lloyd Instruments.

Cable terminations are one of the principal interfaces on the rigging between a yacht or ship and the mast.

They are also used in a variety of architectural products, including the "London Eye".

A 4 year research project between Petersen Stainless Steel Rigging and the Engineering Department at the University of Hull is under way to investigate many aspects of wire/rod network design and specification, with "pull-to-break" tensile testing using an EZ50 materials testing machine from Lloyd Instruments playing an important role.

This study has already produced reliable scientific data on the design and properties of stainless steel rigging components.

The way in which one component interacts with another both in terms of how they are connected and how loads are transmitted between them can have a huge effect on the functionality not only of the system but also the components themselves.

In the early stages of the project, the performance of swage and compression fittings has been compared, leading to an improved design of the 3 mm compression fitting which has now been incorporated into the Petersen Hi-MOD product range.

The key test used to evaluate the performance of these components was a "pull-to-break" test.

This was carried out using an EZ50 twin column universal materials testing machine from Lloyd Instruments, complete with Nexygen MT/ Ondio application and analysis software to allow complex load- displacement traces to be obtained.

The EZ50 features a twin column, twin lead screw frame and incorporates a crosshead guidance system to prevent side loading of the sample under test.

A high resolution encoder is used to measure sample extension and also to provide high accuracy speed control.

In these experiments, the extension resolution was better than 0.1 microns.

Load data were captured using a crosshead-mounted 50 kN load cell with 0.005% resolution.

Nexygen software was set up to perform a Pull-with-Yield test from the software's comprehensive library of standard tests.

The system allowed overlaid load/extension curves to be produced from multiple samples of 3 mm and 6 mm compression fittings and 3 mm swage fittings.

Analyses of these curves allowed common characteristic features to be identified and the general trends gave a detailed insight into termination failure mechanisms.

In particular, analysis of data from the 3 mm compression fittings led to design improvements which were confirmed by repeating the tests on the new design.

This research is part of a four year project.

To further assist their research, the Department of Engineering at the University of Hull has now also installed a 100 kN LR100K materials testing machine from Lloyd Instruments.

Future work will include further understanding of the failure mechanisms involved.

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