hi i would like to know whether cast aluminium is sensitive to strain rate when tested at impact test of velocity 8 m/s. some of them r telling that aluminium is not strain rate sensitive however steel is very sensitive to strain rate. please do share ur views with validations.
We have tested numerous aluminum alloys (6061, 2024, 8090) at strain rates of 0.01 to 6500 per second using Instron, MTS, and Hopkinson test geometries. Yes, Aluminum and its alloys are strain rate sensitive. There are numerous papers published in the field.
Hi Praveen, found a thesis based on strain rate sensitivity of cast aluminum. Hopefully it will help you: http://www.diva-portal.org/smash/get/diva2:649785/FULLTEXT01.pdf
Dear A.Praveen Kumar, really, yield limit and strength of cast aluminium demonstrates strain rate sensitivity (more expressed in range of low rates 0,1 mm/min ...1,0 mm/min) which may be described by exponential law. Good luck!
Hi Dear
•For most metals, the value of m is low near room temperature but increases with temperature. The increase of m with temperature is quite rapid above half of the melting point (T > Tm/2). In some cases, m may be 0.5 or higher. If the rate sensitivity, m, of a material is 0.5 or higher, the material will behave superplastically, exhibiting very high tensile elongations. Superplasticity permits forming of parts that require very high strains.
•Superplasticity has been obtained in a number of alloy systems, including titanium alloys (Ti6%Al4%V), iron-based alloys, and aluminum alloys, high-strength nickel-based superalloys.
(Meyers M.A. and Chawla K.K., (2009). Mechanical Behavior of Materials, Prentice- Hall)
Good Luck
Dear Kumar
There are many papers about aluminum sensitivity to strain rate.
https://www.scorec.rpi.edu/REPORTS/2005-25.pdf
http://www.sciencedirect.com/science/article/pii/S0749641912000307
We have tested numerous aluminum alloys (6061, 2024, 8090) at strain rates of 0.01 to 6500 per second using Instron, MTS, and Hopkinson test geometries. Yes, Aluminum and its alloys are strain rate sensitive. There are numerous papers published in the field.
Dear Kumar!
In addition to what was told by colleagues, I want to pay your attention more to the fact that the plastic deformation of solid crystalline bodies is a wave process.
A wave of plastic deformation is a two-component translation- rotation spatio-temporal structure, which origin is connected with series of elementary acts of relaxation of stress concentrators (something similar happens at the formation of a mountain avalanche due to the fall of a stone).
Its phase speed is estimated in the range of 10-5 to 10-3m/s.
In turn, the relaxation is a result of the thermodynamic perturbation of a substance.
The dynamics of its synergistic development depends on the degree of such a disturbance, that is from the value of the corresponding changes of the thermodynamic potentials of the deformable volume.
Omitting for brevity physical and mathematical details, I will only say that at the impact loading occurs its strong energetic supersaturation. Herewith the bulk of the change of the internal energy of the substance will account to increase of the entropy of the substance. As result it will be take place a blocking of the translational component of the wave of plastic deformation and compensatory intensive development of its rotary component. This leads to the arising on the hardening curve of the parabolic segment. Again, for the sake of brevity, its appearance indicates that, saying simply, the substance of solid crystalline body isn't able to flow as we want, and therefore shows an increased resistance to the deformation.
Development of the dynamics of energetic supersaturation, among other things, depends on the strain rate.
In particular it refers to such plastic materials as aluminum or, for example, copper.
Therefore, these materials are, as other metals, of course, are sensitive to the deformation rate.
I could offer you a fairly large number of links to publications on this matter, but unfortunately, they all are in Russian language. However, if you will want, I'll do it with pleasure.
Applied aspects of this question you can to find in the book:
Bell J. F. Mechanics of Solids // Encyclopedia of Physics. Truesdell C. (Ed.) – Vol. VIa/1. – Berlin: Springer-Verlag, 1973. – 813 p.
With the best wishes.
Dear Kumar!
I don't know how your question regarding of the aluminum speed sensitivity remains topical, but in addition to the my answer of 10 months ago, I'll take the liberty of proposing an article that looks the general regularities of the thermodynamic excitation of a solid body at its plastic deformation.
If only you will not be hampered by the fact that it is also in Russian...
Article Analysis of the Thermodynamic Mechanism of Plastic Deformati...
The best regards.
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