Strain gradient effects in periodic flat punch indenting at small scales

INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES

卷:51

Article

Nielsen, K. L.¹  Niordson, C. F.¹  Hutchinson, J. W.² 

[1] Tech Univ Denmark, Dept Mech Engn, DK-2800 Lyngby, Denmark

[2] Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA

关键词: Higher order theory;    Size effects;    Indentation;    Imprinting;   

DOI  :  10.1016/j.ijsolstr.2014.06.009

来源: Elsevier

【 摘 要 】

Experiments 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 10 gm. 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. (C) 2014 Elsevier Ltd. All rights reserved.

【 授权许可】

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