Shot Peening in the Automotive Industry
in Vol. 24 - November Issue - Year 2023
Shot Peening for Electric Cars, Not Only Fatigue!
I recently attended a conference in Singapore. By now you have probably guessed which conference I am referring to. You are right, I am referring to INCASE 2023, the 3rd International Conference on Advanced Surface Enhancement. It was a nice opportunity to meet old friends and to listen to very interesting presentations on how we can improve the behaviour of surfaces, or add functionality to surfaces. The focus of the conference was on sustainability, and most of the presentations had some aspect related to alleviation of the environmental impact. To be sincere, I was a bit surprised to see so many papers dedicated to shot peening and to the different ways shot peening can be used, not only for fatigue improvement, but also for other objectives. But at the mention of sustainability, it is true that shot peening and related processes can play an important role, because they do not involve toxic waste and they are not very energy intensive. In some cases, the presentations were not limited to the assessment of the improvement in fatigue properties, but also including a quantitative evaluation of CO2 emissions and to how shot peening (or other mechanical treatments) can contribute to reduce them.However, I was surprised to see that the evaluation of the effectiveness of shot peening considered only the improvement in fatigue life, rather than the increment that shot peening induces in fatigue limit. This scenario is more appropriate for aerospace parts, since in aerospace some parts are designed to last for a limited number of cycles and to be substituted before they fail. But this is not usual in automotive, where components are designed not to fail under fatigue loads. In this case, the improvement in fatigue limit should be considered, and the conclusions could be different, probably better, at least if the system is redesigned for shot peening application. To sum up, it seems that the contribution of shot peening to sustainable automotive production has not been completely analysed. That is the point; we should not focus just on fatigue. I had the opportunity to listen to a presentation discussing a special application of shot peening for electric cars.
The presentation (from Japan) described how shot peening can be used for improving the lithium-metal electrode performance of all-solid-state batteries by treating the solid-electrolyte surface. This type of battery is a strong candidate for practical use in an electric vehicle, where the battery must achieve higher energy density and higher power output than the existing lithium-ion batteries with liquid organic electrolytes.
In this study, the speaker showed that by adding lithium metal to the shot-peened solid electrolyte (SE) pellet to form the lithium metal electrode, a lower interface resistance and a higher critical current density can be obtained than for the electrode formed by using non-shot-peened SE. Furthermore, a better mechanical strength was demonstrated. Finally, the experiments performed by the authors showed that the application of shot peening can reduce or eliminate the thin gold layer that is usually used to improve electrical performance; this is also a good point for sustainability. In conclusion, in the new automotive era, where electric traction will be more and more used, shot peening can make an important contribution. The secret is not to focus only on fatigue, but to explore different other possible effects that have not been well investigated so far.
Contributing Editor MFN and
Full Professor of Technical University of Milan
20156 Milan, Italy