By Alain Portebois
Sales & Marketing Manager, Charleville Technology Centre, Wheelabrator
Shot peening makes parts stronger to improve their resistance to fatigue failure – that’s the simple conclusion of a highly complex story about residual tensile and compressive stresses. It’s also the reason why a lot of high-spec shot peening was pioneered in Aerospace, where parts have to be light and strong for obvious reasons.
I don’t think it’s too much of a leap to say that, in Aerospace, shot peening is a safety-critical process.
On the ground, it’s easy to design parts that don’t fail. You work with a generous safety factor and make it a couple of times as strong as the highest load expected. However, such an engineering approach would not work for Aerospace.
The pressure’s on
Where parts are becoming lighter and lighter, they have to be strengthened strategically and precisely, usually through airblasting, to improve fatigue strength and ensure parts last.
This means that the pressure is on for airblast shot peening as a process to induce strength with ever more surgical precision, and it’s turned the application into a complex operation.
Like elsewhere in advanced manufacturing, complete process control and repeatability are essential, but in Aerospace all of this has to meet the exacting specifications of various industry standards, audits and accreditations, from AMS, NADCAP and MIL through to various OEM specific requirements.
A lot of the process control is achieved through automatic machine set-ups and automatic control (and documentation!) of all parameters. But delivering a safety-critical process doesn’t end there – it goes way beyond equipment.
In addition to built-in process control, airblast machines for Aerospace come with an extensive package that includes training for the people in charge of the programming, for operators and maintenance personnel. In some cases this means ‘shadowing’ operating staff for a sustained period of time until all questions are answered, and there is 100% confidence in both machine and process.
Outside the niche
In the realm of shot blasting, it doesn’t get much more high-tech than this. Which is all well and good, but it wouldn’t be as interesting if it stayed within its niche. Technology refined over decades to make aircraft light and safe is now helping car manufacturers build vehicles that deliver higher performance while being lighter and hence more fuel-efficient.
The things we’ve learnt in the context of ultimate safety-consciousness in Aerospace – the fine-tuning, the testing, the imaging, the process control – all make it easier for Automotive to reduce material on high-performance parts with confidence.
There are signs across Automotive and Aerospace that, in addition to the use of new materials such as ceramics and composites, traditional materials (steel in particular) are either making a comeback or are given another lease of life, which makes me think that what we’ve seen so far is only the beginning of shot peening as a safety-critical process: it’s got the potential of turning good old steel into the lightweight design material of the future.