Our regular series of technical articles is all about clarifying some of the most commonly held misconceptions in the field of materials mechanics and mechanical testing.
Most metals exhibit pronounced plasticity during deformation. The degree of plastic deformation that a metal can sustain before fracturing can largely be characterised in a tensile test. However, some metals (not many) are brittle, or can fracture prematurely during tensile tests.
There is quite frequent reference in the literature to “tension/compression asymmetry”, meaning a difference between the inherent (plasticity) responses of a material when subjected to (uniaxial) compression or tension. This is largely a myth. Find out why in this article.
Necking is observed in most tensile tests on metals, but detailed interpretation of stress-strain curves in the post-necking regime is complex, and frequently misunderstood.
We explain why indentation on the nanoscale can never be used to reliably extract bulk mechanical properties from indentation tests, and we review the potential origins of indentation size effects and pop-in phenomena.
Here is our view on why hardness numbers are as good as meaningless, and how they could be misleading your decision making processes around material safety and component integrity.
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