나노압입공정 해석에서 재료의 탄소성 특성 도출을 위한 대표변형률의 결정과 Dao 의 Reverse 해석의 향상

다국어 초록 (Multilingual Abstract)

The newly developed analysis method for nanoindentation load-displacement curves are focused on not only obtaining elastic modulus and hardness values but also other mechanical properties, such as yield strength and strain hardening properties. Dao et al.<SUP>(1)</SUP> developed a forward and reverse algorithm to extract the elasto-plastic properties of materials from the load-displacement curves obtained in nanoindentation test. These algorithms were only applicable for engineering metals (Poisson's ratio 0.3) using the equivalent conical indenter of the Berkovich. However, the applicable metals are substantially limited because range of used in the finite element analysis is narrow. This study is designed to expand range of the applicable metals in the reverse algorithms established by Dao et al.<SUP>(1)</SUP> and to improve the accuracy of that for extracting the elasto-plastic properties of materials. In this study, a representative strain was assumed to vary according to specific range of E<SUP>*</SUP>/ σr and was defined as function of E<SUP>*</SUP>/ σr. Also, an initial unloading slope in reverse algorithms improved in this study was not considered as independent parameters of the load-displacement curves. The mechanical properties of materials for finite element analysis were modeled with the elastic modulus, E, the yield strength, σy, and the strain hardening exponents, n. We showed that the representative strain (0.033) suggested by Dao et al. (1) was no longer applicable above the E<SUP>*</SUP>/ σr of 400 and depended on values of E<SUP>*</SUP>/ σr. From these results, we constructed the dimensionless functions, in where the initial unloading slope was not included, for engineering metals up to E<SUP>*</SUP>/ σr of 1500. These functions allow us to determine the mechanical properties with greater accuracy than Dao's study.<SUP>(1)</SUP>

목차 (Table of Contents)

• Abstract
• 1. 서론
• 2. 나노압입시험의 유한요소해석
• 3. 나노압입시험 유한요소해석 결과
• 4. Reverse 해석 및 나노압입시험
• 5. 결론
• 후기
• 참고문헌

참고문헌 (Reference)

1 Tunvisut, K., "Use of Scaling Functions to Determine Mechanical Properties of Thin Coatings from Microindentation Tests" 38 : 335-351, 2001

2 Tabor, D., "The Hardness of Metals Published in the Oxford Classics series 2000" Oxford University Press 2000

3 Cheng, Y. T., "Scaling, Dimensional, and Indentation Measurements" 44 : 91-149, 2004

4 Ogasawara, N., "Representative Strain of Indentation Analysis" 20 (20): 2225-2234, 2005

5 Fischer-Cripps A. C., "Nanoindentation" Springer-Verlag 90-95, 2002

6 Ogasawara, N., "Measuring the Plastic Properties of Bulk Materials by Singles Indentation Test" 54 : 65-70, 2006

7 Oliver, W. C., "Measurement of Hardness and Elastic Modulus by Instrumented Indentation: Advances in Understanding and Refinements to Methodology" 19 (19): 3-20, 2004

8 Swaddiwudhipong, S., "Material Characterization Based on Dual Indenters" 42 : 69-83, 2005

9 Rieth, M., "Handbook of Theoretical and Computational Nanotechnology" 4 : 387-461, 2004

10 Yan, J., "Determining Plastic Properties of a Material with Residual Stress by Using Conical Indentation" 44 : 3720-3737, 2007

11 Bucaille, J. L., "Determination of Plastic Properties of Metals by Instrumented Indentation Using Different Sharp Indenters" 51 : 1663-1678, 2003

12 Giannakopoulos, A. E., "Determination of Elastoplastic Properties by Instrumented Sharp Indentation" 40 (40): 1191-1198, 1999

13 Chollacoop, N., "Depth-Sensing Instrumented Indentation with Dual Sharp Indenters" 51 : 3713-3729, 2003

14 Johnson, K. L., "Contact Mechanics" Cambridge University Press 1985

15 Dao, M., "Computational Modeling of the Forward and Reverse Problems in Instrumented Sharp Indentation" 49 : 3899-3918, 2001

16 Pelletire, H., "Characterization of Mechanical Properties of Thin Films Using Nanoindentation test" 38 : 1182-1198, 2006

17 Oliver, W. C., "An Improved Technique for Determining Hardness and Elastic-Modulus Using Load and Displacement Sensing Indentation Experiments" 7 (7): 1564-1583, 1992

18 Zeng, K., "An Analysis of Load-Prenetration Curves from Instrumented Indentation" 49 : 3539-3551, 2001

19 Fischer-Cripps, A, C., "A Review of Analysis Methods for Sub-Micron Indentation Testing" 58 : 569-585, 2000

20 Lee, J, H., "A Numerical Approach to Indentation Techniques for Thin-Film Property Evaluation" 31 (31): 313-321, 2007

21 Lee, H. I., "A Numerical Approach Indentation Technique for Material Property Evaluation" 53 : 2037-2069, 2005

22 Cao, Y, P., "A New Method to Extract the Plastic Properties of Metal Materials from an Instrumented Spherical Indentation Loading Curve" 52 : 4023-4032, 2004

23 Antunes, J. M., "A New Approach for Reverse Analyses in Depth-Sensing Indentation Using Numerical Simulation" 55 : 69-81, 2007