Spring MRS-2017 Notes

Hakan

Hakan will serve as a judge in the Graduate Student Awards Committee with Prof. Kiran Solanki (ASU), Dr. Hua Zhou (Argonne National Laboratory).

Talk Details:

Session: CM5.12: Plasticity
Session Chairs: Marc Legros, Reiner Moenig
Time: April 20th 2017- 4PM
Title: Using nanoindentation as a mechanical spectroscopy tool- investigating incipient plasticity using in-situ 4-pt bend stage



Hengxu

Talk Details:

SESSION CM6.3: Discrete Dislocation Dynamics

Session Chairs: Wei Cai and Yao Shen

Time: 4:30 PM, April 18, 2017

 Title:  2D Discrete Dislocation Dynamics Simulations of Nanoindentation with tensile pre-stress:  Can we probe ‘mobile’ dislocations through nanoindentation?

Slides can be downloaded here:
https://drive.google.com/file/d/0B0bdwsoc2sM-WkxSQk9OcDBZV1U/view?usp=sharing

Two questions/comments from audiences:
1,
question:
why the hardness hardness increases with indentation depth, this is different with Nix-Gao model prediction
Answer: There are two kinds of indentation size effect: wedge indentation (Nix-Gao model), indentation size effect is related to the indentation depth: hardness decreases with indentation depth; spherical indentation: indentation size effect is related to the indenter radius: indentation hardness increases with decreasing indenter radius. Here, hardness does increase with indentation depth.
2,
question: why nanoindentation is so important, I have seen many people discussing indentations.
Answer: There are two main advantages of indentation as far as I know. First of all, indentation is 'non-destructive', the measurement only leaves a very small 'damage' on the sample surface, while for example in a simple tension/compression test, the sample is destroyed after the test. Secondly, nanoindentation test is very convenient method to probe material mechanical properties at small length scale. For example, tensile test at small length scale is very difficult regarding the equipment and the sample preparation. Moreover, the famous nano-pillar compression test is actually based on nano indenter, just using a flat punch instead of normally used Berkervich/Sphere indenter.