Everything you need to know about destructive testing

Tuesday, 25 June 2019

What is destruction testing?

Destructive testing is used for many purposes, we might seek the load at which a device slips, deforms, collapses, ruptures or (and typically most importantly) we might wish to discover and understand the way something fails.  Destruction testing provides real experimental data which makes it possible to engineer complicated component interactions.

How is destructive testing carried out?

With the destructive tests we do, we have the test subject and either side of it we have the tooling.

Since we deal most commonly with lifting gear the tooling often consists of shackles, links and pins which may or might not be sacrificial depending upon how difficult the test is. On other occasions we engineer specialised tooling.

Most tests we perform are done with the test piece wrapped in a protective blanket to catch any flying debris but some are performed under other controlled conditions, with a camera set up to witness the moment of destruction in a safe way.

Observations can be made of the deformation of the sample and at pre-determined loads, or frequently the measurement that is made is of the peak load achieved before load release (usually by rupture of the test piece).

Why destructive testing is important?

When performed correctly, destruction testing provides several benefits for which there are few (if any) practical alternatives:

- The test outcome is absolute and observable. This avoids staring at something wondering ‘what if?’.

- We find out how something breaks. Did it break in a predictable way? Did it break in a reliable way? Did it break with safe mode of failure?

- It becomes possible to determine the outcome of highly complex interactions between components and materials. This is especially important with some of the structurally complicated materials used in lifting.

- It is cheaper than paying for many hours of engineering time to obtain a result which is still only ‘theoretical’.

- It can reveal the presence of 'nasties' which might result from a manufacturer’s poor-quality control.

This is a particularly nasty break discovered in a grade 100 chain fitting. Not only has failure occurred at the weld (which is undesirable) but the break is a sudden and brittle fracture below the minimum requirement. A link like this could suddenly fail in the field and will have had limited resistance to the dynamic loads applied during real lifting.

Who needs destructive testing?

The truth is that everyone needs destructive testing, not only does it improve engineering outcomes across industry - it is also fundamental to the product standards upon which we all rely.

End users should always try to obtain products from sources who perform destructive testing at trustworthy facilities and try to eliminate suspect products which have cheated the rules and put the safety of workers and the public at risk.

A routine batch destruction test for this shackle shows a good result, the minimum breaking load was achieved, and the safest ductile mode of rupture is evident.

When should you use destructive testing?

Destruction testing is not merely the preserve of manufacturers and R&D engineers! Other benefits can be gained from commissioning a destruction test, for example:

- Maintenance planners can destructively test samples of worn equipment to calibrate the replacement and inspection regimes they set in place.

- Safety officers can support incident investigations by replicating conditions and putting them to the ultimate test.

- In cases where a piece of rigging must be used in an unusual way – the safety margins of the configuration can be tested, and safe working procedures developed.

- Any disputed scenario can be resolved with an ultimate test.

Of course, for the R&D engineers, scientists and inventors in general industry – destruction testing offers a way to save many hours of theorising and consternation.

Who is qualified to carry out destructive testing?

Destructive testing relies on much more than simply a big machine that can break things and testing with poor and inaccurate results can be very costly indeed.

Every destruction test deserves:

- A laboratory that is accredited to ISO 17025, so that results are presented faithfully and are trusted worldwide.

- Load measurements taken with tools calibrated to a recognised standard such as AS2193 and with the required accuracy.

- Knowledgeable test personnel who can offer up tooling which is safe, efficient and does not detract from the results obtained.

- Experienced people who can interpret results and provide feedback, particularly if the mode of failure is of concern.

Nobles operates NATA accredited laboratories which are accredited to ISO 17025 and use load measuring tools which are calibrated to applicable standards. We have the testing facilities and expertise to test a broad range of lifting and rigging equipment as well as a broad range of other items. This provides you with further confidence that the services provided by Nobles are independently audited, accredited, and are bench marked against international laboratory rules.

Where does Nobles complete destructive testing?

Nobles operate tensile test machines of all shapes and sizes with our largest machine rated for destructive test loads up to 1,000 tonnes with a wide internal clear-space that is 30 metres long. We also possess a variety of other test beds of various sizes.

Nobles operates a fleet of tensile testing devices for proof load testing lifting gear and other products. ‘Proof’ loading verifies the load bearing strength in a manner which is intended to be non-destructive, but this commonplace testing is rather different to destructive load testing.

Almost all of our fixed test bed facilities are capable of destructive testing up to their nameplate load rating and it is a regular task at our facilities nationally.

To arrange destructive testing for your lifting and rigging equipment, please give our team a call on 1300 711 559 or send them an email at sales@nobles.com.au.