• Proceedings of the KSME Conference
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• 2004.04a
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• pp.144-149
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• 2004

Porous anodic alumina has been used widely for corrosion protection of aluminum surfaces or as dielectric material in micro-electronics applications. It exhibits a homogeneous morphology of parallel pores which can easily be controlled between 10 and 400nm. It has been applied as a template for fabrication of the nanometerscale composite. In this study, mechanical properties of the AAO structures are measured by the nano indentation method. Nano indentation technique is one of the most effective method to measure the mechanical properties of nano-structures. Basically, hardness and elastic modulus can be obtained by the nano-indentation. Using the nano-indentation method, we investigated the mechanical properties of the AAO structure with different size of nano-holes. In results, we find the hole effect that changes the mechanical properties as size of nano hole.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.503-504
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• 2006

Determination of elastic properties of nano-scale materials using nano-indentation tests is well established, but that of plastic properties is not yet clear. This paper presents a method to extract plastic properties from nano-indentation test, together with results from detailed elastic-plastic FE analysis. It shows that the plastic properties determined from this method are not unique, in the sense that a number of different plastic properties can give the same load-displacement response from nano-indentation test. possible ways to overcome such problems are discussed.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.186-193
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• 2004

Porous anodic alumina has been used widely for corrosion protection of aluminum surfaces or as dielectric material in micro-electronics applications. It exhibits a homogeneous morphology of parallel pores which can easily be controlled between 10 and 400nm. It has been applied as a template for fabrication of the nanometer-scale composite. In this study, mechanical properties of the AAO structures are measured by the nano indentation method. Nano indentation technique is one of the most effective methods to measure the mechanical properties of nano-structures. Basically, hardness and elastic modulus can be obtained by the nano-indentation. Using the nano-indentation method, we investigated the mechanical properties of the AAO structure with different size of nano-holes. In results, we find the hole effect that changes the mechanical properties as size of nano hole.

• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.3347-3358
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• 2024

Addressing the challenge of identifying an appropriate set of material and irradiation parameters for accurate simulation models using crystal plasticity finite element method (CPFEM), this study proposes a novel two-stage method for nano-indentation modeling of ion-irradiated face-centered cubic (FCC) materials. It includes implementing the strain-gradient crystal plasticity (SGCP) theory with irradiation effects and the calibration of simulation parameters using the particle swarm optimization (PSO) algorithm with experimental data. The proposed method consists of two stages: establishing CPFEM without irradiation effects in stage 1 and modeling irradiation effects based on CPFEM in stage 2. Modeling the nano-indentation test of ion-irradiated stainless steel 304 (SS304) using real experimental data is conducted to evaluate the efficiency of the proposed method. The accuracy of the calibration method using PSO is verified through comparisons between simulation and experimental results for force-indentation depth and hardness-indentation depth relationships under both unirradiated and irradiated conditions. Moreover, effect of ion-irradiation on the mechanical behavior during the nano-indentation of single crystal SS304 is also examined to demonstrate that the proposed method is a powerful approach for nano-indentation modeling of ion-irradiated FCC single crystals using SGCP theory and the PSO algorithm.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.246-251
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• 2004

Nano-indentation is used for measuring mechanical properties of thin films such as elastic modulus and hardness. For ductile materials, pile-up around the indenter causes the calculation of inaccurate projected contact area. This phenomenon was found by measurement of indentation shape using an atomic force microscope. In present study finite element analysis of nano-indentation was performed to compensate the effects of pile-up on the contact area. The result of finite element analysis was compared with that of nano-indentation for a ductile material. The analysis has demonstrated that the true contact area is greater than that calculated by nano-indentation. It is verified that the consideration of the effects of pile-up in nanoindentation for ductile materials using the finite element method is reasonable.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.05a
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• pp.62-62
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• 2003

A statistical evaluation method was proposed to evaluate mechanical properties by using small specimens and nano-indentation for irradiation study. The method is empirically based on nano-indentation which values are statistically treated. The nano-indentation in function of indentation depth (h) is expressed using the variation factor V(h). Statistical parameters of the indentation are given by histograms. Analytical and experimental relation between histograms of phase dimension distribution and parameters V(h) and G(h) is considered using the condition of additivity of phases' microhardness. The method is applied to estimate mechanical properties of irradiated materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1139-1143
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• 2007

A simple method for the fabrication of 3D micro-nano hybrid patterns was presented. In conventional fabrication methods of the micro-nano hybrid patterns, micro-patterns were firstly fabricated and then nano-patterns were formatted on the micro-patterns. Moreover, these micro-nano hybrid patterns could be fabricated on the flat substrate. In this paper, we suggested the fabrication method of 3D micro-nano hybrid patterns using micro-indentation on the anodized aluminum substrate. Since diameter of the hemispherical nano-pattern can be controlled by electrolyte and applied voltage in the anodizing process, we can easily fabricated nano-patterns of diameter of loom to 300nm. Nano-patterns were firstly formatted on the aluminum substrate, and then micro-patterns were fabricated by deforming the nano-patterned aluminum substrate. Hemispherical nano-patterns of diameter of 150nm were fabricated by anodizing process, and then micro-pyramid patterns of the side-length of $50{\mu}m$ were formatted on the nano-patterns using micro-indentation. Finally we successfully replicated 3D micro-nano hybrid patterns by hot-embossing process. 3D micro-nano hybrid patterns can be applied to nano-photonic device and nano-biochip application.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.148-151
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• 2004

Mechanical properties such as Young's modulus and hardness of thin film in coated steel are difficult to determine by nano-indentation from the conventional analysis using the load-displacement curve. Therefore, an analysis of the nano-indentation loading curve was used to determine the Young's modulus, hardness and strain hardening exponent. A new method is recently being developed for plasticity properties of materials from nano-indentation. Elastic modulus of the thin films shows relatively small influence whereas yield strength and strain hardening are found to have significant effect on measured data. The load-displacement behavior of material tested with a Berkovich indenter and nano-indentation continuous stiffness method is used to measure the modulus and hardness through thin films.

• Transactions of Materials Processing
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• v.13 no.8
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• pp.731-737
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• 2004

Mechanical properties such as Young's modulus and hardness of thin film in coated steel are difficult to determine by nano-indentation from the conventional analysis using the load-displacement curve. Therefore, an analysis of the nano-indentation loading-unloading curve was used to determine the Young's modulus, hardness. A new method is recently being developed for elastic-plastic properties of materials from nano-indentation. Elastic modulus of the thin films shows relatively small influence whereas yield strength is found to have significant effect on measured data. The load-displacement curves of material tested with a Berkovich indenter and nano-indentation continuous stiffness method is used to measure the modulus and hardness through thin films, and then these are computed using the analysis procedure. The developed neural networks apply also to obtain reliable mechanical properties.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.186-194
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• 2005

This study was designed to investigate the mechanical properties of the coating layer on electronic galvanized sheet steel as a part of the ongoing research on the coated steel. Those properties were determined using nano-indentation, the finite element method, and artificial neural networks. First and foremost, the load-displacement curve (the loading-unloading curve) of coatings was derived from a nano-indentation test by CSM (continuous stiffness measurement) and was used to measure the elastic modulus and hardness of the coating layer. The properties derived were applied in FE simulations of a nano-indentation test, and the analytical results were compared with the experimental result. A numerical model for FE simulations was established for the coating layer and the substrate separately. Finally, to determine the mechanical properties of the coating, such as the stress-strain curve, functional equations of loading and unloading curves were introduced and computed using the neural networks method. The results show errors within $5\%$ in comparison with the load-displacement measured by a nano-indentation test.