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Page 711 of 977 Results 7101 - 7110 of 9762

Christiaan S. Veldman
IMPLEMENTING A SHOCK-FORCE CALIBRATION SYSTEM USING A VIBRATION EXCITER AND PENDULUM

The NMISA upgraded its impulse hammer calibration system to satisfy new demands from local industry for shock force measurements. As part of Land Mobility Testing (LMT), high impact force levels are measured. Improvements to the existing facility required the development and implementation of a system, able to deliver repeatable high impact forces, with a substantial payload. Further improvements included the development of a data capturing unit for the measurement of the impact pulses and to determine the unit under test shock force sensitivity.
This paper will discuss the measurement methodology applied for the generation and measurement of shock pulses. The determination of the force required for the generation of these shock pulses is discussed, indicating the chain of traceability to the SI. The system performance is demonstrated. To conclude, data to validate the performance is provided together with an overview of the uncertainty of measurement estimation.

C. Hirunyapruk, P. Rattanangkul, B. Thummawut, V. Plangsangmas
EXPERIMENTAL INVESTIGATION INTO THE EFFECTS OF EXCITER MOTIONS ON THE PRIMARY CALIBRATION OF SINGLE-ENDED ACCELEROMETER

It is widely known that in the primary calibration of accelerometers by using a laser interferometer, a unit under test (UUT) and the laser interferometer should measure vibration at the same position. However, this is not applicable to single-ended accelerometers because of the limitation of their design. One way of overcoming this limitation is to measure the vibration at several positions on the plate which connects UUT to a vibration exciter. However this can present the effects of rocking motions of the exciter. Although the motions of vibration exciters are presented in several studied, the different model of exciters might have different characteristics. This paper aims to study the motions of an air-bearing exciter (model 2911) used at National Institute of Metrology (Thailand) in order to expose their characteristics, their effects on the calibration results and the measurement errors due to these effects. The motions of the exciter are shown in terms of magnitude and phase shift distributions of sensitivities. These can be obtained by measuring the magnitudes and phase shifts at several positions on the plate. The effects of exciter motions are measured in terms of how much the magnitudes and phase shifts at each measured positions deviate from the average values. To illustrate these effects, parametric studies were conducted. The influences of four parameters, i.e. the angular positions of the laser points, the distance of the laser positions from the centre of the plate, the number of measured positions to be averaged and the mass loading effect, were examined experimentally. The frequency of interest is between 10 Hz and 15 kHz.

Chenguang Cai, Qiao Sun
MEASUREMENT AND EVALUATION OF DAMPING PROPERTIES OF DAMPING MATERIAL

This paper presents a testing method and process of damping properties of a kind of damping material. A damping system was regarded as the experimental subject composed of an oblate solid cylinder specimen of the damping material and an additional mass. The specimen is excited by an electromagnetic shaker in the vertical direction, and the specimen excites the additional mass vibrating. Not only the traditional damping properties, such as the damping ratio and vibration transfer rate, but also the nonlinear properties are measured to evaluate the damping specimen. Firstly the magnitude-frequency characteristics of vibration transfer rate are measured under constant stable excitation over a frequency range of 10 Hz to 320 Hz which includes the resonant frequency of the fundamental mode. Based on the magnitude-frequency characteristic, the half band power method is used to measure the damping ratio. In order to investigate the effects of vibration magnitude on the damping properties, the characteristic of the vibration transfer rate versus excitation magnitude at 210 Hz is measured. The experiment results reveal the fact that linear and nonlinear damping properties of the damping system change as the exciting magnitude increases.

Claire Bartoli, Philippe Averlant, Cédric de Waubert
REFERENCE VIBRATION CALIBRATION EQUIPMENT AT LNE: INFLUENCE OF METHODS AND EXCITERS

The traceability to the acceleration measurements for the industry is done in France by the LNE. This traceability to the national standards is necessary for the industries that have processes where knowledge of the parameters related to the acceleration is essential in terms of quality and safety, such as nuclear, space, automotive or military fields.
The reference accelerometers calibrations for the industry and other laboratories are performed at the LNE's site located in Trappes since 2006 by the absolute method using a Michelson interferometer. However, the equipment used, presented in [1], was of old design and a first step of the upgrade is presented in [2].
This article presents the end of the qualification, including the comparison of methods 1&2 versus method 3 described in standards 16063-1 and -11 [3]. It presents the comparison results of two different design exciters: one in beryllium also an air bearing guide and one with a pierced aluminum moving element with a mechanical guide.
Metrological approval was based on the consistency achieved between the calibration results for given accelerometers obtained using the new bench and those obtained using the original bench.
A comparison with a national primary vibration calibration laboratory was performed and presented.

Yi-Ching Lin, Ya-Ko Chih
COMPARISON OF NANOINDENTATION TESTERS IN TAIWAN

The Center for Measurement Standards provides two test pieces for this exercise to compare a set of common data including elastic modulus and indentation hardness. Participating laboratories will perform the common test items on their systems and follow the recommended instructions. The distribution chart compiled from the experiment data provided by each laboratory can then be used to fully demonstrate the current state of nanoindentation testers. The experimentation method shall take the testing capabilities of each laboratory into consideration, and a full analysis shall be provided. The providers of experiment data shall be represented by an index code in the report. By participating in this comparison exercise, participants will be able to understand the differences and similarities between their own results and those of other laboratories; thus the results can be used as a reference basis for evaluation of the participant's testing capabilities.

Chiu-Hsien Chen, Sheau-shi Pan
THE UNCERTAINTY OF PITCH AND YAW RE-EVALUATED FOR PRIMARY ROCKWELL HARDNESS STANDARD SYSTEM IN CMS

The Primary Rockwell Hardness Standard System was set up in the Center for Measurement Standards since July 1996 till June 1997. During the time, a laser interferometer, HP10737R 3-axis compact interferometer system was used to measure the effect of pitch and yaw of the Rockwell Hardness machine.
As the laser interferometer was performed the measurement of the pitch and yaw of the indenter when the hardness was measured; then we evaluated the uncertainty caused from the Abbe's error through pitch and yaw measurements. In this paper, we will compare the results to the results of 2003 and to evaluate the aging effect of the indenter axis during seven years' used.

Masayuki Fujitsuka, Makoto Yamaguchi, Shigeru Ueno, Ichiro Miura, Shigeo Katayama
DEVELOPMENT OF NANOINDENTATION TESTER WITH A RAMAN SPECTROSCOPY INTERFACE FOR MATERIAL CHARACTERIZATION

Instrumented indentation test is a simple and effective method for evaluating the mechanical properties such as elasticity/stiffness, hardness and adhesion. During indentation test, materials are subjected to highly localized stresses. It is fundamental interest to explore its mechanical properties under conditions of extreme contact pressure. Raman micro-spectroscopy is a powerful and rapid technique to investigate the pressure-induced phase transformations and the residual stress in the indented region. This technique has been successfully used to study pressure-induced phase transitions of during indentations.
On the other hand, the localized stress during indentation not only causes phase transformation, but also elastic and plastic deformation. The observation of shape of surface or internal material, for example the piling-up or sinking-in behaviour that appears around the indent, plastic zone boundary, the distribution of a lateral crack, and so on, is also important to understand the phenomena during indentation. This understanding also plays an important role in the accurate determination of material properties using nanoindentation test.
In this paper, authors developed the nanoindentation tester with a Raman spectroscopy interface for material characterization. Not only general mechanical properties but also crystalline and residual stress is obtained by this system. The observation data using this system revealed that the stress field around the residual impression.

Ikuo Ihara, Takanobu Matsumoto , Yoshikazu Yajima, Jun-ichi Uegaki, Yoshikazu Shima
APPLICATION OF CONTINUOUS MULTIPLE LOADING WITH SPHERICALTIP NANOINDENTATION TO MECHANICAL PROPERTY EVALUATIONS OF INDUSTRIAL MATERIALS

There are increasing demands for measuring mechanical properties of small volumes of metal or smallsized materials used for Micro-Electro-Mechanical-Systems (MEMS). This is basically because such mechanical properties are closely related to the strength and reliability of the metal or systems. In this work, a nanoindentation technique with a spherical-tip is applied to the evaluation of elastic-plastic properties such as stress-strain relationship of industrial materials such as steel and aluminium. A continuous multiple loading method is employed to determine the stress-strain curve. A set of 21 times of loading/unloading sequences with increasing terminal load are made and load-displacement curves with the different terminal loads from 0.1 mN to 100 mN are then continuously obtained and converted to a stress-strain curve. The influence of measurement condition on the obtained stress-strain curve is examined and an appropriate condition is determined. Based on the examinations, stress-strain curves have been estimated for steels and aluminium. It has been found that the estimated stress-strain curves correlate closely with those measured by tensile or compression tests when the influence of the residual stress of the specimen surface is taken into account. In addition, some issues affecting the results are discussed.

Edward Aslanyan, Peter Krasowski
NECESSITY OF RUSSIAN NANOINDENTATION STANDARD BASE DEVELOPMENT

Over the past years a large number of papers have been published on the application of the nanoindentation method. These works describe various aspects of the nanoindentation method and provide a detailed overview of the characteristics of different hardware and software tools implementing this method. However, measurements taken under the same conditions and on the seemingly same samples often provide a significant discrepancy in the results on different instruments functioning according to the same principle. This paper discusses the issues of metrological support for the nanoindentation method in Russia.

Jiri Nohava, Petr Hausild, Nicholas X. Randall , Gregory Favaro
GRID NANOINDENTATION ON MULTIPHASE MATERIALS FOR MAPPING THE MECHANICAL PROPERTIES OF COMPLEX MICROSTRUCTURES

Instrumented indentation has now become established for the single point characterization of hardness and elastic modulus of both bulk and coated materials. This makes it a good technique for measuring mechanical properties of homogeneous materials. However, many composite materials are composed of several phases whose properties are difficult or even impossible to examine in bulk form ex situ (e.g., carbides in a ferrous matrix, martensite and austenite in steels, etc.). The requirement for in situ analysis and characterization of such structured materials with different phases obviates conventional mechanical testing of large specimens' representative of these material components. This paper will focus on new developments in the way that nanoindentation can be used as a two-dimensional mapping tool for examining the properties of constituent phases independently of each other. This approach relies on large arrays of nanoindentations (known as grid indentation) and statistical analysis of the resulting data. Two examples of application of the grid indentation method will be presented: indentation on naval brass and indentation on AISI 301 stainless steel.

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