PSI - Issue 61

Enes Günay et al. / Procedia Structural Integrity 61 (2024) 34–41

40

E. Gu¨nay et al. / Structural Integrity Procedia 00 (2024) 000–000

7

0.05

0.05

0.045

0.04

0

0.035

-0.05

0.03

0.025

-0.1

0.02

0.015

-0.15

Vertical Displacement ( m)

g

=5

0.01

d

Vertical Displacement ( m)

g

=5

g

=15

d

d

-0.2

0.005

g

=15

g

=50

d

d

g

=50

0.6 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.7 Normalized distance 0

d

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Normalized distance -0.25

(b) Vertical displacement at the end of scratching, zoomed in at the pile-up region

(a) Vertical displacement at the end of scratching

Fig. 5: Normalized vertical displacements along the indenter path at the end of scratching of polycrystals with average grain diameters of 5 µ m , 15 µ m , and 50 µ m

Conclusion and Outlook

In this work, the e ff ect of grain size on nanoscratching tests of polycrystal copper is examined using a size dependent crystal plasticity framework. FEM models of nanoscratching of specimens with di ff erent grain sizes are created and numerically solved. The findings show that specimens with smaller grains generate larger reaction forces on the indenter, showing an increase of over 50% in both normal and lateral force when the grain diameter decreases from50 µ m to 5 µ m . Additionally, as di ff erent grain boundaries are approached in a polycrystal, there are increases and decreases in the normal and lateral forces on the indenter, contrary to the steadiness of the force observed in single crystals. However, despite these grain size e ff ects and the variations in force at the grain boundaries, the coe ffi cient of friction remains nearly constant between all cases throughout the simulations. However, after a significant volume of pile-up is generated in front of the indenter, di ff erences between the specimens with di ff erent grain sizes start to show. In particular, the specimen with the 50 µ m grain diameter, where the grain size e ff ects are the least in magnitude, accumulates more material in front of the indenter due to ease of deformation, compared to the smaller and stronger specimens. The pile-up height in the 50 µ m case is 25% larger than that of the 5 µ m case. This significant increase in pile-up leads to a growth in reaction forces in the lateral direction, thus increasing the friction coe ffi cient. There are still more factors to examine in the context of grain size e ff ects on nanoscratching, such as the e ff ect of texture of the grains on this phenomenon, as an increase or decrease in neighboring grain misorientations may lead to more or less pronounced size e ff ects. Additionally, the influence of other factors such as di ff erent grain shapes, di ff erent indenter orientations, type of loading (force-controlled or displacement-controlled) can be the topic of future research. Acar, S.S., Bulut, O., Yalc¸inkaya, T., 2022. Crystal plasticity modeling of additively manufactured metallic microstructures. Procedia Structural Integrity 35, 219–227. doi: https://doi.org/10.1016/j.prostr.2021.12.068 . AlMotasem, A.T., Bergstro¨m, J., Gåård, A., Krakhmalev, P., Holleboom, L., 2017. Atomistic insights on the wear / friction behavior of nanocrys talline ferrite during nanoscratching as revealed by molecular dynamics. Tribology Letters 65, 1–13. doi: 10.1007/s11249-017-0876-y . Aydiner, I.U., Tatli, B., Yalc¸inkaya, T., 2024. Investigation of failure mechanisms in dual-phase steels through cohesive zone modeling and crystal plasticity frameworks. International Journal of Plasticity 174, 103898. doi: https://doi.org/10.1016/j.ijplas.2024.103898 . Beake, B.D., Harris, A.J., Liskiewicz, T.W., 2013. Review of recent progress in nanoscratch testing. Tribology - Materials Surfaces & Interfaces 7, 87–96. doi: 10.1179/1751584X13Y.0000000037 . Bulut, O., Gu¨nay, E., Fenercioglu, T.O., Yalc¸inkaya, T., 2023. Analysis of additively manufactured anisotropic microstructures through crystal plasticity frameworks. Materials Research Proceedings 28, 179–188. doi: 10.21741/9781644902479-20 . References