How to fix a range in setting the sliding speed/ velocity while performing a tribotest on aluminum composites. In specific what is considered as slow speed and high speed, how is it justified.
Dear Dhanashekar,
Sliding velocity mainly influences strain rate and surface temperature induced by wear. So, the so called high sliding velocity will be different for different materials. In case of Al alloys/composites you should take low melting point of Al into account, which can be reached easily. Based on my experience in magnesium alloys wear properties (with very similar melting point to that of Al) I would say sliding velocities of > 1 m/s are high, since they lead to severe plastic deformation and surface melting. You can estimate surface temperature using different models available in the literature.
However, as I said above, strain rate is another factor that we should pay attention to. You need to see how high strain rates influence mechanical properties of the composite you are working on, then you can find a relationship between sliding velocity and wear properties of the composite. On the one hand, a high strain rate contributes to a higher rate of dislocation generation in a Al matrix, while a greater stress is required to trigger dislocation movement. On the other hand, if strain rate is too high, deformation mode could be changed from slip to twin, which is very unlikely to occur in Al. Also, we should not forget about the responses of reinforcements (particles/fibers) to different loads applied at different rates.
Hope you find this helpful.
Cheers,
Ahmad
Thanks Ahmad Zafari
Your explanation was useful. Can you share reference papers having "models estimating surface temperature".
Ashby, M F, Temperature Maps for Frictional Heating in Dry Sliding, Tribology Transactions 34 (1991) 577 -587
Also the following book
Stachowiak, Gwidon, and Andrew W. Batchelor. Engineering tribology. Butterworth-Heinemann, 2013.
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