IMEKO Event Proceedings Search

   

Page 713 of 977 Results 7121 - 7130 of 9762

Gaoliang Dai, Jian Zhao , Febo Menelao, Konrad Herrmann, Uwe Brand
IMPROVED METHODS FOR ACCURATELY CALIBRATING THE 3D GEOMETRIES OF ROCKWELL INDENTERS

In this paper an improved method for calibrating the 3D geometry of Rockwell indenters using a metrological stylus profilometer is reported. The measured geometry of the indenter is not only applied to determine the quality of the indenter, but also used for correcting the hardness values for improved hardness measurement accuracy. A method for such a correction has been proposed. A virtual indentation device simulated using finite element method (FEM) has been developed. By applying both the measured and the theoretically ideal indenter geometries in the virtual device, two different hardness values HRCreal and HRCideal are obtained, respectively. The difference between HRCreal and HRCideal stands for the systematic deviation due to the indenter geometry and is used to correct the measured hardness values. Some experiments are carried out on the same group of 6 reference materials with a hardness ranging from 20 HRC to 65 HRC to verify our proposal. The geometries of three Rockwell indenters used are measured and further applied to correct the hardness values. By this correction technique the mean deviation between the three indenters on 6 reference materials could be reduced from 0.11 HRC to 0.03 HRC, indicating the effectiveness of the proposed method.

J. Song, S. Low, A. Zheng, P. Gu
GEOMETRICAL MEASUREMENTS OF NIST SRM ROCKWELL HARDNESS DIAMOND INDENTERS

The geometric parameters of 28 candidate Standard Reference Material (SRM) Rockwell hardness diamond indenters are calibrated by an automated system recently developed at the National Institute of Standards and Technology (NIST). The calibration results show that the cone flank straightness is a key issue for the calibrated indenters to be qualified for the geometrical specifications of NIST SRM diamond indenters. The effect of selecting different window sizes and locations for the evaluation of cone flank straightness is discussed.

Satoshi Takagi, Tatsuya Ishibashi
ANALYSIS OF INDENTER GEOMETRY VERIFICATION DATA BY MEANS OF THE REGRESSION PLANE FITTING

An analytical method of the geometrical parameters of hardness indenters from bitmap data obtained AFM, etc. is introduced. The method is based on the fitting to the analytical geometric shape by the least square method. The results of the analysis are not influenced by human factors which are usually included in the operation of analyzing software's GUI. Examples of analytical results are shown with the estimation of the uncertainty of measurement. The uncertainty is estimated considering the uncertainty of AFM itself and the misfit of plan regression, and the uncertainty of facet angles, interior angles of the square base of the pyramid and the area function are evaluated for nano-range Vickers indenters through the propagation of error. There are some suggestions that some of the geometrical requirements in ISO 14577 may not practical when the verification process is considered.

Dieter Schwenk, Andreas Subaric-Leitis
CHARACTERISTIC QUALITY PARAMETERS OF MEASUREMENT -VERIFICATION AND CALIBRATION OF MATERIAL TESTING MACHINES

The international standards for qualification of material testing machines like the ISO standards for hardness testing [1] -[3] use the relative span (range) as a repeatability parameter. Form the view of statistics and uncertainty the determination of the range is not suitable for this purpose. We propose a transition from range to standard deviation for describing the machines quality parameter which allows a direct estimate of the machines uncertainty and of the reliability of test results within the limits fixed by the ISO standards. For the transition from range to standard deviation the limits have to be transformed. We represent results of conformity decisions determined on the basis of data sets of hardness reference block calibration with reference testing machines using the limits concerning range and the equivalent limits related to the standard deviation.

Tanja Haas, Gottfried Bosch, Hans-Peter Vollmar
CAPABILITIES OF THE LOAD AND PARTIAL UNLOAD TECHNIQUE

The load and partial unload technique adds partial unload processes to the load curve. The mechanical properties like elastic modulus can be determined for each of these unload curves. This allows for a faster depth dependent measurement of the characteristic quantities. If the elastic modulus of a material is known and not dependent of the depth, an indenter shape correction can be performed using this technique.
The results of such a correction are compared with those gained using a correction based on the Martens hardness of the material. The elastic modulus EIT as well as the Martens hardness HM are corrected with both methods.
The results of both approaches are comparable down to an indentation depth of 100 nm. A Fischerscope HM2000 was used to perform the measurements.

Dirk Röske
UNCERTAINTY CONTRIBUTION IN THE CASE OF COSINE FUNCTION WITH ZERO ESTIMATE – A PROPOSAL

The model function of the torque generated in a static torque standard machine contains a cosine function for the inclination of the lever against the horizontal plane. An inclined lever has a shorter effective lever arm length, and a smaller torque is generated in this case. The uncertainty analysis of this model function gives a zero sensitivity coefficient for the inclination angle when the estimate of the angle is zero – a mathematical correct, but from the uncertainty point of view, obviously improper result. A method for dealing with this problem is proposed in this paper.

Carlo Ferrero, Adelina Leka , Luciano Bianchi
INTERLABORATORY COMPARISONS IN ITALY TO VERIFY THE ACCREDITATION ON TORQUE WRENCH CALIBRATION

In 2008 one ILC, for the calibration of torque wrenches, was organised in Italy by COPA-SIT (Sistema Italiano di Taratura). In the present paper the main results obtained during the ILC are discussed, in particular the differences on the repeatability and accuracy given by the different laboratories are compared and evaluated.

K.M.Khaled, G.Aggag, A.E.Abuelezz, M.G.Elsherbiny
MECHANICAL DESIGN OF NIS NEW REFERENCE TORQUE STANDARD MACHINE

Standard torque measuring machines and their traceability is relatively new in metrology field. The growing car manufacturing and assembly industry in Egypt made it necessary to develop a national standard for torque measurement which can provide traceability to the industry according to world wide standards. A new design of 3 kNm reference torque standard machine was therefore considered. The machine was designed following the component system principle based on the vertical axis measurement method, without intermediate bearing, which reduces about 70% of the cost. Prior to that, the parts chosen for the design as well as the machine structural parts are reviewed. Stresses in the critical parts of the machine are computed using Finite Element (FE) analysis to ensure that the designed machine can satisfy the International requirements.

Atsuhiro Nishino, Koji Ogushi, Kazunaga Ueda
EVALUATION OF ACTUAL SENSITIVITY LIMIT IN A 10 N·m DEAD WEIGHT TORQUE STANDARD MACHINE AND STABILITY OF A NEW 1 N·m TORQUE TRANSDUCER

A 10 N·m dead weight torque standard machine (10-N·m-DWTSM) has been under development at NMIJ/AIST since 2006 to expand the range of the torque standard. Estimation of the sensitivity limit of the fulcrum is one of the most important issues to realize a precise reference torque of small capacity by using a dead weight torque standard machine. In this study, a torque transducer was installed on the 10-N·m-DWTSM in order to keep the moment-arm on the horizontal line (balancing). The sensitivity limit of the fulcrum under real calibration conditions was estimated by reading the change in the output from the torque measuring device (TMD: the torque transducer with a cable and an indicating device) when small weights were loaded or unloaded. The small weights used in the experiment were 0.5 mg, 1 mg, 10 mg, and 100 mg. Equivalent radial loads from 0.1 N·m to 10 N·m were imposed on the fulcrum during the sensitivity measurement. As a result, the sensitivity limit of the fulcrum was confirmed to be sufficient to load at least 0.5 mg. A relative sensitivity limit of the fulcrum of less than 2.5 × 10-5 and relative reproducibility of the sensitivity limit of the fulcrum of less than 1.7 × 10-6 could be obtained within the calibration range from 0.1 N·m to 10 N·m.
It is also important to develop small-rated-capacity torque transducers that can be used as a transfer standard. Therefore, a transducer with a rated capacity of 1 N·m was developed in parallel with the development of the 10-N·m-DWTSM. The stability of the 1 N·m TMD has been evaluated over a period of one year.

Tassanai Sanponpute, Chokchai Wattong, Nittaya Arksornarong
BEHAVIOR OF PURE TORQUE AND TORQUE WITH CROSS FORCE MEASUREMENT OF TORQUE TRANSDUCER

This paper presents the study of behavior of torque four transducers under pure torque and torque with cross force. This explains how cross force causes the measurement result deviating from pure torque. Output signals at every 45° loading angle around measurement axis of pure torque and torque with cross forces at minimum arm length and middle arm length were compared. The result shows that cross force causes sinusoidal-like relationship between the output signals and loading angles. Moreover, cross force effect shifts the sinusoidal graph from x-axis or average of output signals was shifted from pure torque. Sine wave amplitude and degree of deviation from pure torque are directly proportional to cross force magnitude. The same transducers were tested with new developed method, called multi-cross force load procedure. The result from this method agrees with result from torque with cross force measurement. This paper also proposes the concept of evaluating torque with cross force of transducer, which had been calibrated by pure torque. The concept is to compensate the cross force effect using result from multicross force load procedure and to include the effect in measurement uncertainty. Furthermore, this research shows the behavior of repeatability and hysteresis error of transducers under pure torque and torque with cross force measurement.

Page 713 of 977 Results 7121 - 7130 of 9762