General Information
1. Title of the Dataset:
Nanoindentation dataset of paper submitted to Journal of Geophysical Research: Solid Earths entitled "Comparison of biotite elastic properties recovered by spherical nanoindentations and atomistic simulations - influence of nano-scale defects in phyllosilicates"
2. Author information:
a. Eril Lanin (lanin@wisc.edu)
b. Hiroki Sone (hsone@wisc.edu)
3. Date of data collection (range or single date)
June 14 - 28, 2019
Sharing/Access Info
1. Licenses placed on data:: CC-BY-NC
2. Was data derived from another source? NO
Methodological Information
1. Description of methods use for collection/generation of data:
a. Sample preparation
Two sets of small rectangular samples were prepared, whose largest faces were oriented parallel to the foliation (layer-normal loading) and perpendicular to the foliation (layer-parallel loading), and fixed in resin. The samples were then ground using sandpaper with different grit sizes, sequentially from 180, 320, 600, to 1200 grits. The ground surfaces were then polished using abrasives of 6 μm, 1 μm (diamond suspension), 0.5 μm (colloid alumina), and 0.04 μm (colloidal silica suspension) grain sizes, followed by inspections under the microscope after each polishing step to ensure no scratches were remaining from the previous polishing step. The sample preparation is completed by identifying the area of interest under an optical microscope and marking the area by giving a scratch mark.
b. Nanoindentation tests
Nanoindentation was carried out in areas of interest, using the Hysitron TI-950 TriboIndenter capable of providing continuous stiffness measurement (CSM). The tests were performed at room temperature, in load-control mode, with maximum applied loads of 2-2.5 mN. Two diamond spherical indenters were used in these tests, whose tip radiuses were either 1 or 5 μm, with Young’s modulus of 1.14 x 103 GPa and Poisson’s ratio 0.007. The experiments for this study were carried out with a linear load control (Linear CSM) consisting of 6 segments (Hysitron, 2014). Segments 1-3 are the pre-loading phases, where the indenter contact with the specimen surface is established. The specimen is loaded in segment 4 using the Linear CSM mode. After the load is held for 2 seconds in segment 5, the specimen is unloaded in segment 6.
2. Methods for processing data:
Data processing methods started with loading the data, defining which segment it belongs to, and plotting CSM data overlying the non-CSM data. It can be seen that CSM data comes from segment 4 of the non-CSM data, where the specimen is loaded using the Linear CSM mode. Following the data inspection, the next step is the zero-point determination. In this study, the zero-point determination was carried out by applying the method described in Kalidindi and Pathak (2008). By plotting P'-(2/3)*S*he' versus S, where P', he', and S are the measured load, displacement, and stiffness signal, respectively. The slope and y-intercept of the linear relationship represent quantities -(2/3)*he^* and P^*, respectively, where P^* and he^* are the load and displacement of the actual initial contact. Note that this relation only holds when the material response is still linearly elastic. The linear elastic region is identified as a continuous trend line without any observed discontinuity. The final step of this method is to determine the indentation modulus as a slope of the indentation stress versus indentation strain plot. The indentation stress is expressed as P/(pi*a^2), and the indentation strain is equal to (4/3*pi)*(ht/a), where P is the load and ht is the total indentation depth. The contact radius, a, is calculated from (3*P*Rr/4*Er)^(1/3), where Er and Rr are the reduced moduli and the relative radius of indentation curvature, respectively. The last two parameters defined by (1/Er)=((1-νs^2)/Es)+((1-νi^2)/Ei) and (1/Rr)=(1/Ri)+(1/Rs), where E, ν, and R are Young’s modulus, Poisson’s ratio, and radius respectively, and the subscripts s and i refer to the sample and indenter, respectively.
3. Instrument or software-specific needed to interpret the data:
There is no instrument or software-specific needed to interpret the data. Any data computing (e.g., MATLAB) and spreadsheet (e.g., EXCEL) program can be used.
4. Other such as experimental conditions:
Data included in this archive are only those that has pass the screening process. Every dataset has two files, namely:
1. AB-C_D_CSM.txt for the CSM data
2. AB-C_D.txt for the non-CSM data
where the letters in the naming represent:
A = Sample orientation (N=normal, P=parallel)
B = Indenter radius (1=1 micrometer, 5=5 micrometer)
C = Dataset number (1-7)
D = Indentation number (1-9)
The AB-C_D.txt files consist of:
1. Time (second)
2. Depth (nanometer)
3. Load (microNewton)
The AB-C_D_CSM.txt files consist of:
1. Time (second)
2. Displacement (nanometer)
3. Load (microNewton)
4. Stiffness (microNewton/nanometer)