Strain gradient effects in periodic flat punch indenting at small scales
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CitationNielsen, K.L., C.F. Niordson, and J.W. Hutchinson. 2014. Strain Gradient Effects in Periodic Flat Punch Indenting at Small Scales. International Journal of Solids and Structures 51 (21-22): 3549–3556.
AbstractExperiments on soft polycrystalline aluminum have yielded evidence that, besides the
required punch load, both the size and shape of imprinted features are affected by the
scale of the set-up, e.g. substantial details are lost when the characteristic length is on
the order of 10µm. The objective of this work is to clarify the role played by strain
gradients on this issue, and to shed light on the underlying mechanisms. For this,
indentation by a periodic array of flat punch indenters is considered, and a gradient
enhanced material model that allows for a numerical investigation of the fundamentals
are employed. During a largely non-homogeneous deformation, the material is forced
up in between the indenters so that an array of identical imprinted features is formed
once the tool is retreated. It is confirmed that the additional hardening owing to plastic
strain gradients severely affects both the size and shape of these imprinted features. In
particular, this is tied to a large increase in the mean contact pressure underneath the
punch, which gives rise to significant elastic spring-back effects during unloading.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:14004550
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