Indentation size effect
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Comment: This is overly technical, and may be hard for non-experts to understand. Remember that Wikipedia is read by everyone, and thus its language should be accessible. We should keep in technical information, but it also needs to be succinctly explained in as plain of English as possible. Remember that Wikipedia is an encyclopedia, not a scientific journal. Please explain the image. Also, did you create that image yourself from scratch or? Please respond on my talk page if you did not. Captain Eek Edits Ho Cap'n!⚓ 23:00, 20 November 2019 (UTC)
The indentation size effect (ISE) is the observation that hardness tends to increase as the indent size decreases at small scales.[1] The effect has been seen through nanoindentation and microindentation measurements at varying depths. Dislocations increase material hardness by increasing flow stress through dislocation blocking mechanisms.[2] Materials contain statistically stored dislocations (SSD) which are created by homogeneous strain and are dependent upon the material and processing conditions.[3] Geometrically necessary dislocations on the other hand are formed, in addition to the dislocations statistically present, to maintain continuity within the material.
These additional geometrically necessary dislocations (GND) further increase the flow stress in the material and therefore the measured hardness. Theory suggests that plastic flow is impacted by both strain and the size of the strain gradient experienced in the material.[4] Smaller indents have higher strain gradients and therefore have a higher measured hardness in some materials.
For practical purposes this effect means that hardness in the low micro and nano regimes cannot be directly compared if measured using different loads. However, the benefit of this effect is that it can be used to measure the effects of strain gradients on plasticity.[3]
References
- ^ Pharr, George M.; Herbert, Erik G.; Gao, Yanfei (June 2010). "The Indentation Size Effect: A Critical Examination of Experimental Observations and Mechanistic Interpretations". Annual Review of Materials Research. 40 (1): 271–292. doi:10.1146/annurev-matsci-070909-104456. ISSN 1531-7331.
- ^ Askeland, Donald R. (2016). The science and engineering of materials. Wright, Wendelin J., (Seventh edition ed.). Boston, MA: Cengage Learning. pp. 111–118. ISBN 9781305076761. OCLC 903959750.
{{cite book}}:|edition=has extra text (help)CS1 maint: extra punctuation (link) - ^ a b Nix, William D.; Gao, Huajian (October 1997). "Indentation size effects in crystalline materials: A law for strain gradient plasticity". Journal of the Mechanics and Physics of Solids. 46 (3): 411–425. doi:10.1016/s0022-5096(97)00086-0. ISSN 0022-5096.
- ^ Fischer-Cripps, Anthony C. (2000). Introduction to contact mechanics. New York: Springer. ISBN 0387989145. OCLC 41991465.