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Page 836 of 977 Results 8351 - 8360 of 9762

Min-Jae Choi1, Kyung-Woo Lee, Ju-Young Kim, Kwang-Ho Kim, Dongil Kwon
APPLICATION OF INSTRUMENTED INDENTATION TECHNIQUE TO ESTIMATE STRENGTH AND RESIDUAL STRESS

The instrumented indentation technique has recently attracted significant research interest because of its various advantages such as nondestructive specimen preparation, easy process, and high spatial resolution. In particular, this technique is a promising alternative to measurement methods of tensile properties and residual stress. We can evaluate tensile properties and residual stress by analyzing the indentation load-depth curve. Tensile properties of materials, primarily yield strength and tensile strength, are obtained by defining representative stress and strain, through the numerous investigations of instrumented indentation curves, and the results were discussed by comparing with results of uniaxial tensile tests. Residual stress measurement technique is based on the key concepts that the deviatoric stress part of residual stress affects the change in indentation load-depth curve, and then by analyzing difference between residual stress-induced indentation curve and residual stress-free curve, quantitative residual stress of target region can be evaluated. In determining the stress-free curve of the target region, we take into consideration microstructural changes accommodating the strength difference. Micromechanical contact analyses for the residual-stress-induced load shifts yield stress values comparable to the applied in-plane stresses. This study supports the proposition that the surface stress in an arbitrary biaxial state can be evaluated through a theoretical model combined with the ratio of two principal stress components. Instrumented indentation tests and conventional tests were performed to verify the applicability of the suggested technique, and the estimated residual stress values obtained from the indentation technique showed good agreement with those from conventional tests.

Harald Kohlhoff, Christian Ullner
VERIFICATION OF THE STANDARD MACHINE FOR THE MACRO RANGE OF INSTRUMENTED INDENTATION TEST

A new calibration machine according to the requirements given by ISO 14577-3 [1] was described in [2]. The results of the verification are reported in this paper. It is shown that the calibration machine can be used as a national standard for the materials parameter of the instrumented indentation test.

Jiong-Shiun Hsu, Sheng-Jui Chen, Hui-Ching Lu, Shear-Shi Pan, Gwo-Jen Wu, Chung-Lin Wu, Chin-fen Tuan
UNCERTAINTY EVALUATION OF MODULUS AND HARDNESS FOR THE NANOINDENTATION MEASUREMENT SYSTEM

The uncertainties of nanoindentation measurement system were evaluated in this paper. A precise electonic balance and an optical interferometric system were respectively utilized to calibrate the force and displacement of nanoindentation measurement system. The uncertainties of reduced modulus and indentation hardness providing from the naoindentaion measurement were respectively obtained.

Kensuke Miyahara, Takashi Yamamoto
TUNGSTEN SINGLE CRYSTAL AS HARDNESS STANDARD FOR NANOINDENTATION

Hardness standard of tungsten single crystal were utilized in order to check stability and reproducibility of nanoindentation testers. The pop-in load and maximum penetration depth were measured and monitored during several hundreds of repeated experiments. One of the tested instruments showed gradual increase of pop-in load and decrease of maximum depth, which indicate the indenter tip was damaged by repeated tests. The both parameters, the pop-in load and the maximum depth, can be used to detect the change of the area function; the pop-in force is more sensitive and should be easy for general users. Other applications of tungsten single crystal are also discussed.

Zhi Li, Sai Gao, Konrad Herrmann
INVESTIGATION OF NANO-INDENTATION ON FREE-STANDING FILMS FOR THE DETERMINATION OF TENSILE TEST PARAMETERS

With the aim to extract the mechanical properties of small volumes of materials, nowadays several methods have been proposed and are applied in practice. How to compare the results of these methods, therefore, gains more and more interests. Instrumented indentation with a spherical indenter on circularly supported freestanding thin films is believed to be an effective way to connect and compare the material testing methods including nanoindentation and micro-tensile testing. In this paper an experimental setup for making indents on free-standing films is presented, in which a modified bright-field microscope with optical sectioning capability is applied to determine the zero-point of nanoindentation, and to in-situ and real-timely measure the deflection of the film. Preliminary experimental results are reported, which coincide with the theoretical model.

Zhi Li, Sai Gao, Konrad Herrmann
DEVELOPMENT OF A MICRO-MINIATURE NANOINDENTATION INSTRUMENT

Among the various methods for characterizing the mechanical properties of small volume of materials, nano-indentation testing has gained more and more interests, due to its simple principle, the easy realization and application for various specimen, etc. However, nano-indentation instruments often fail to measure the mechanical properties of materials which demonstrate heavy creep, plasticity, etc. To overcome the disadvantages of nano-indentation instruments, here a new approach to develop the next generation of nano-indentation systems is proposed, in which the well-developed MEMS technique is employed. As one of the key components in the to be developed system, the loading component is now realized by an electrostatic comb-drive actuator, which can generate the required indentation force with high resolution. This microminiature indentation system will feature the advantages of small size, low power consumption, high precision in manufacture, the potential for low cost through batch fabrication, the ability for on-site applications, etc. In this paper the design of the MEMS system is detailed, including the simulation of the mechanical system and the system performance.

Konrad Herrmann
NEW DEVELOPMENTS AND APPLICATIONS IN HARDNESS METROLOGY

The overview on the development tendencies clarifies that the main developments refer to the increase of productivity and of the accuracy of measurements. With the development of new materials also new optimum hardness measuring methods are developed. Great efforts are undertaken to enlarge the information content of hardness measuring methods. In this connection great perspectives can be ascribed to the instrumented indentation test.

Kozo Iizuka
WORLDWIDE ACTIVITIES AROUND HARDNESS MEASUREMENT - ACTIVITIES IN CCM/CIPM, IMEKO/TC5, OIML/TC10 AND ISO/TC164 -

All of hardness testing methods now in use were invented about a century ago but it was after the World War II that the international conformity of the test results was required and that the standardization of the testing methods and testing machines was investigated and promoted. In this paper, the historical role of four international organizations, CIPM, IMEKO, OIML and ISO for the progress of the standardization of hardness testing and on the development of the metrological standards of hardness is reviewed together with some remark on the discussions related to the definition of hardness as a quantity. Then a few comments on the feature and metrological meaning of hardness standards are described.

Mihaela Ioana Baritz
Management of the patients’ data recorded by electro-medical apparatus

In this paper it is presented the activity for recording the patients’ data using electro- medical apparatus. These recording are made in different environmental conditions to analyze the influences of the ambient temperature and the quality of air on the stability and waking behavior and on the level capacity effort. The results are presented in the final part of the paper.

Mihaela Ioana Baritz
Screening method for environmental human stability behavior studies

In this paper it is presented the screening method to study the behavior of the human body in different situation: relaxed, before and after an effort in the environmental space. The human subjects have a good health and the recordings are made using a special system for record and analyze the human body stability behavior answer. It is very important to establish in these researches the methodology to record the information’s taking in account the interactions of the human body with environment (with or without open eyes, with or without the sounds in background, temperature, air pollution or external vibrations and noises). The results are presented in the final part of the paper.

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