• 한국생산제조학회지
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• 제21권3호
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• pp.376-381
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• 2012

This paper deals with application of instrumented indentation technique for quality inspection methodology for automobile component. For this, the instrumented indentation tests were performed the normal and cracked compressor journal, which is made from spheroidal graphite cast iron and utilized in air-conditioning system. And the Brinell hardness was estimated using the unloading slope and maximum indentation force. With the aid of Normal distribution, this Brinell hardness was statistically compared and analyzed with hardness measured by indentation hardness tests. Also, application possibility of reliability-based quality inspection criteria for compressor journal was evaluated through the probabilistic analysis for the Brinell hardness estimated by instrumented indentation technique.

• 한국분말재료학회지
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• 제18권1호
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• pp.64-72
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• 2011

Nondestructive instrumented indentation test is the method to evaluate the mechanical properties by analyzing load - displacement curve when forming indentation on the surface of the specimen within hundreds of micro-indentation depth. Resistance spot welded samples are known to difficult to measure the local mechanical properties due to the combination of microstructural changes with heat input. Particularly, more difficulties arise to evaluate local mechanical properties of resistance spot welds because of having narrow HAZ, as well as dramatic changed in microstructure and hardness properties across the welds. In this study, evaluation of the local mechanical properties of resistance spot welds was carried out using the characterization of Instrumented Indentation testing. Resistance spot welding were performed for 590MPa DP (Dual Phase) steels and 780MPa TRIP (Transformation Induced Plasticity) steels following ISO 18278-2 condition. Mechanical properties of base metal using tensile test and Instrumented Indentation test showed similar results. Also it is possible to measure local mechanical properties of the center of fusion zone, edge of fusion zone, HAZ and base metal regions by using instrumented indentation test. Therefore, measurement of local mechanical properties using instrumented indentation test is efficient, reliable and relatively simple technique to evaluate the tensile strength, yield strength and hardening exponent.

• 소성∙가공
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• 제13권1호
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• pp.21-26
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• 2004

Instrumented indentation tests have been used for estimating material properties. In order to analyze deformation characteristics with various factors, the unloading stiffness should be properly determined from the elastic behavior. The unloading stiffness is generally obtained from the shifted power functions fitting with the experimental unloading data. However, the functions often give rise to a poor representation of actual data, and also the unloading stiffness is governed by unloading condition. In this study, both numerical and experimental conditions to obtain proper unloading stiffness were investigated. The result showed that the amount of unloading ratio and hold time played an important role in fitting the unloading curves. The current efforts can successfully provide the unloading stiffness for indentation material properties.

• 한국철도학회논문집
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• 제7권2호
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• pp.142-148
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• 2004

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 is investigated. Finally the fatigue lift of butt welded specimens are evaluated by the local strain approach. To calculate local strains and stresses, elasto-plastic finite element analysis is conducted using the measured properties.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1744-1748
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• 2007

In this study, the Johnson-Kendall-Roberts (JKR) theory was combined with the instrumented indentation technique (IIT) to evaluate work of adhesion and modulus of elastomeric polymer. Indentation test was used to obtain the load-displacement data for contacts between Tungsten Carbide indenter and elastomeric polymer. And the JKR contact model, contrived to take viscoelastic effects of polymer into account, was applied to compensate the contact area and the elastic modulus which Hertzian contact model would underestimate and overestimate, respectively. Besides, we could obtain the thermodynamic work of adhesion by considering the surface energy in this contact model. In order to define the relation between JKR contact area and applied load without optical measuring of contact area, we used the relation between applied load and contact stiffness by examining the correlation between JKR contact area and stiffness through dimensional analysis with 14 kinds of elastomeric polymer. From this work, it could be demonstrated that the interfacial work of adhesion and elastic modulus of compliant polymer can be obtained from a simple instrumented indentation testing without area measurement, and provided as the main algorithm of compliant polymer characterization.

• 대한기계학회논문집A
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• 제31권9호
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• pp.951-959
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• 2007

In this study, the Johnson-Kendall-Roberts(JKR) theory was combined with the instrumented indentation technique (IIT) to evaluate work of adhesion and modulus of elastomeric polymer. Indentation test was used to obtain the load-displacement data for contacts between Tungsten Carbide indenter and elastomeric polymer. And the JKR contact model, contrived to take viscoelastic effects of polymer into account, was applied to compensate the contact area and the elastic modulus which Hertzian contact model would underestimate and overestimate, respectively. Besides, we could obtain the thermodynamic work of adhesion by considering the surface energy in this contact model. In order to define the relation between JKR contact area and applied load without optical measuring of contact area, we used the relation between applied load and contact stiffness by examining the correlation between JKR contact area and stiffness through dimensional analysis with 14 kinds of elastomeric polymer. From this work, it could be demonstrated that the interfacial work of adhesion and elastic modulus of compliant polymer can be obtained from a simple instrumented indentation testing without area measurement, and provided as the main algorithm of compliant polymer characterization.

• 대한기계학회논문집A
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• 제36권9호
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• pp.1081-1086
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• 2012

본 논문에서는 품질 검사 방법론이 적용된 계장화 압입시험을 수행하여 점용접부의 경도를 평가하였다. 먼저 정상 및 불량 용접조건하에서 제작된 점용접 샘플에 대해 로크웰 경도 및 계장화 압입시험을 실시하였다. 계장화 압입시험을 통해 구한 압입하중-변위선도를 이용하여 계산된 경도를, 동일한 조건의 동일위치에 대한 압입경도시험을 통하여 측정된 로크웰 경도와 확률론적 방법론을 이용하여 비교평가 하였다. 또한 계장화 압입시험을 통하여 추정한 경도 및 이에 대한 확률론적 해석을 수행하여 점용접부의 신뢰성 기반 품질 관리 기준 설정 가능성을 평가하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.168-171
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• 2003

Instrumented indentation tests have been used for estimating material properties. In order to analyze deformation characteristics with various factors, the unloading stiffness should be properly determined from the elastic behaviour. In general, the unloading stiffness is obtained from shifted power functions fitting to indentation unloading curves. But, the functions give often a poor representation of actual data. In this study, control conditions for fitting unloading curves by shifted power functions were investigated. The current efforts may provide useful information about unloading process and valid unloading stiffness.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1607-1612
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• 2007

To assure safe usage of railway rolling stock, it is important to evaluate the strength of the wheel which is core part in bogies. However, conventional standard testing methods using destructive technique could not evaluate mechanical properties of degraded wheels during rolling stock maintenance work. Instrumented indentation test is a new way to evaluate nondestructively the strength of mechanical components by analyzing indentation load-depth curves. In this study, to evaluate tensile strength of the wheel, instrumented indentation test is performed nondestructively according to KS B 0950. Furthermore, test results are examined by tensile test in accordance with KS R 9221.

• 한국압력기기공학회 논문집
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• 제7권1호
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• pp.41-47
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• 2011

Residual stress is the key parameter for reliability and lifetime assessment because it can reduce the fatigue strength and fracture properties of industrial structures. Recently, instrumented indentation testing (IIT) has been widely used for evaluating it, since it does not need specific specimen and time-consuming procedure. However, conventional Oliver-Pharr method, which is used for calibrating contact depth to analyze indentation load-depth curve, cannot estimate plastic pile-up between indenter and surface of specimen. Here, we introduce f parameter which is the ratio of contact depth and maximum depth, to consider pile-up height. And, its application for evaluating residual stress of weldment is introduced.