• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.343-346
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• 2004

In recent years, various forms of indentation testing have been increasingly used to determine the material properties of specimens. This technique, particularly the nano-indentation method , has been extended to the testing of coating systems in order to calculate the individual properties of the thin coatings and the substrates. However, the interpretation of the test data to achieve this is complex and continues to be a widely studied subject. Based on the finite element method of coated surfaces indented by a Berkovich diamond tip, this paper describes methods for combining FEM and experimental indentation testing to determine coating modulus and hardness independent of substrate effects. Using this proposed methodology, testing and FEM to measure coefficients of friction of sheet steel for outer panel were studied.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.117-119
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• 2003

When material properties depend much on positions in a material or it is difficult to make test specimens from a material or component, an instrumented indentation test described in ISO 14577-1, 14577-2 or KS B 0950 can be used to measure material properties and damage. In this study, first of all, the principals of the instrumented indentation test, KS B 0950 are introduced and yield strengths, tensile strengths and work hardening exponents of base materials, heat affected zones and weld materials are measured. In addition, the influence of post-weld heat treatment on the material properties are investigated.

• Nuclear Engineering and Technology
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• v.36 no.3
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• pp.237-247
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• 2004

To investigate the applicability of automated ball indentation (ABI) tests in the evaluation of the tensile properties of cast stainless steel (CSS), ABI tests were performed on four types of unaged CSS and on 316 stainless steel, all of which had a different microstructure and strength. The reliability of ABI test data was analyzed by evaluating the data scattering of the ABI test and by comparing tensile properties obtained from the ABI test and the tensile test. The results show that the degree of scattering of the ABI test data is reasonably acceptable in comparison with that of standard tensile data, when two points data that exhibit out-of-trend are excluded from five to seven points data tested on a specimen. In addition, the scattering decreases slightly as the content of ${\delta}-ferrite$ in CSS increases. Moreover, the ABI test can directly measure the flow parameters of CSS with error bounds of about ${\pm}10\%$ for the ultimate tensile stress and the strength coefficient, and about ${\pm}15\%$ for the yield stress and the strain hardening exponent. The accuracy of the ABI test data is independent of the amount of ${\delta}-ferrite$ in the CSS.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.268-271
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• 2010

In this paper, forward and reverse analysis is introduced in order to estimate the elastic-plastic properties from a power-law hardening bulk specimen materials with one simple spherical indentation impression test. In order to verify the reliability of the reverse analysis, we have simulated about a large range of materials that essentially cover all engineering materials, using ABAQUS(6.91) program. Then, we could obtained the fitting functions and plastic parameters from the numerical analysis results. Next, through the procedure of reverse analysis we can obtain the yield stress and power-law exponent. Finally, obtain good agreement between the result from reverse analysis and initial input data from experiment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.578-585
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• 2004

Hardness test is performed for determination of the other properties, such as strength, wear resistance and deformation resistance, as well as hardness itself. And it is performed for prediction of residual lifetime by analysis of hardness reduction or hardness ratio. However, hardness test has limitation that observation of residual indent is needed for determination of hardness value, and that is the reason for not to be widely used in industrial field. Therefore, in this study, we performed researches to obtain Brinell hardness value from quantitative numerical formula by analysing relationship between indentation depths from indentation load-depth curve and mechanical properties such as work hardening exponent, yield strength and elastic modulus.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2089-2095
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• 2002

Ceramic/metal composites have many attractive properties and great potential fur applications. Interfacial fracture properties of different layered composites are important in material integrity. Therefore, evaluation of fracture toughness at interface is required in essence. In this study, the mechanical characteristics for interface of ceramic/metal composites were investigated by indentation test of micro-hardness method. Apparent interfacial toughness of TBC system could be determined with a relation between the applied load and the length of the crack formed at the interface by indentation test.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.158-162
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• 2004

Reliability of welded structures in power plant facilities is very important, and their reliability evaluation requires exact materials properties. But, the conventional PQR (Procedure Qualification Record) can hardly reflect the real material properties in the field because the test is only done on specimens with simulated welding. Therefore, a continuous indentation technique is proposed in this study for simple and non-destructive testing of in-field structures. This test measures the indentation load-depth curve during indentation and analyzes the mechanical properties such as the yield strength, tensile strength and work hardening index. This technique has been applied to evaluate the tensile properties of the weldment in the main steam pipe and hot reheater pipe in power plants under construction and in operation.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.516-522
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• 2002

For the experimental study of rotor steel, seven kind of specimens with different degradation levels were prepared by isothermal heat treatment at $630^{\circ}C$. Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel, and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steel's were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.291-296
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• 2004

Cast austenitic stainless steel piping pump, valve casings, and elbows are susceptible to reductions in toughness and ductility because of long term exposure at the operating temperatures in LWR(light water reactor). In this paper, we have measured the material properties of long term aged CF-8A cast stainless steel, accelerated aging at $400^{\circ}C$. These studies have been carried out using Indentation tests(automated ball indentation and nano-indentation) and EDS(energy dispersive spectroscopy). The fracture toughness of CF-8A cast stainless steel was also determined by using standard fracture toughness and Automated Ball Indentation.

• 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.