MEASUREMENT TECHNIQUE - Click here to return to overview or click on a title to download the document An appraisal of the GrindoSonic Material Tester Authors: P.J. Emerson, BCIRA Language: English A limited number of tests have been carried out on iron test bars and castings with the Grindo-Sonic material tester. This instrument measures the resonant frequency of the component being tested. It has been found that the Grindo-Sonic readings correspond with the BCIRA sonic test equipment, and hence this instrument could have use in iron foundries. For foundry use, however, the instrument would have to be more robust, and the hand operation used in laboratory tests might not be satisfactory. An Evaluation of Three Methods to Measure the Dynamic Elastic Modulus of Steel, Authors: A. Wolfenden, W. Schwanz, Texas A & M University, Mechanical Engineering Dept. Language: English An evaluation is made of three methods used to determine the dynamic elastic modulus of steel. The three methods make use of the Grindo-Sonic machine, the Modul-r machine, and the Piezoelectric Ultrasonic Composite Oscillator Technique. Testing of specimens, all from the same piece of stock, was done using each method and a comparison was performed. Since the assumption that all specimens had the same elastic modulus was not valid, a comprehensive statistical comparison could not be done. Still, all methods produced results that were highly repeatable. In addition, it was determined that long thin specimens did not vibrate in their fundamental mode when tested with the Grindo-Sonic machine and that testing specimens with the Modul-r machine heats the internal coils of the machine which affects the determined modulus values. The width tolerance needed for the Modul-r specimens could not be maintained, and the results of tests on these specimens are not completely valid. The overall mean elastic modulus was 207.1 Gpa with a standard deviation of 2.75 GPa. Determination of the elastic moduli of materials at high temperatures by means of a non-contact sensor Authors: F. Lostak, W. Vandermeulen Language: English The determination of the elastic moduli of materials by means of the measurment of the frequencies of the elastic modes has become a celebrated technique (pulse excitation technique). Its non-destructive character and its ease of use in almost all circumstances make it very attractive for research as well as industrial environments. This work describes the state of the art and reports on the development of a non-contact laser-based sensor to detect the elastic deformations of materials even at temperatures up to 1200°C. ELASTIC CONSTANTS - THEIR DYNAMIC MEASUREMENT AND CALCULATION Authors: Bernd Weiler, Christian U. Grosse Language: English The modulus of elasticity and the shear modulus can be calculated from the free vibrations of bar-shaped specimens. Therefore, a review of the theoretical bases for the calculation of the moduli is given. Measurements using the Grindo-Sonic device and a device developed at the FMPA were carried out and compared. Both devices turned out to be very efficient, although their features are quite different. ELASTISCHE PARAMETER - IHRE DYNAMISCHE MESSUNG UND BERECHNUNG Authors: Bernd Weiler, Christian U. Grosse Language: German Elastizitäts- und Schermoduln können aus den Eigenschwingungen von stabförmigen Probekörpern berechnet werden. Dazu wird eine Übersicht über die theoretischen Grundlagen der Berechnung gegeben. Mit dem Grindo-Sonic-Gerät und mit einer an der FMPA entwickelten Anlage wurden Messungen gemacht und verglichen. Beide Geräte erwiesen sich als sehr leistungsfähig, obwohl ihre Eigenschaften recht verschieden sind. Evaluation of the Elastic and Plastic Properties of Si3N4 by depth sensing indentation Authors: R. Berriche, R.T. Holt, Institute for Aerospace Research, National Research Council of Canada Language: English A high resolution instrument, called the nanomechanical probe, which permits continuous monitoring of load and depth of penetration during indentation and scratch tests have been developed at IAR/NRC. Its principle of operation, specifications and capabilities are discussed. Indentation tests on HIPed silicon nitride samples with densities ranging from about 82 to 99.7% theoretical density have been performed. Hardness values for each sample have been calculated from load vs. depth plots using a new method involving the plastic work dissipated during the indentation process. The elastic properties of the samples have been determined from the slope of the unloading curve using the elastic punch model. The results are compared to those obtained to those by conventional methods. GrindoSonic : test on tubes, applicability of the system to detect cracks Authors: Lucent Technologies Language: English The GrindoSonic measurement by itself does not provide an indication of cracks. However, calculating ratio's from two different vibration modes can provide an indication of a problem. Indeed, if we have a defect, it is very unlikely that two independent vibration patterns will shift to the same extent. In this case we will measure the longitudinal vibration mode and the flexural vibration mode. Both results are used to calculate the modulus of elasticity. Because the formulas are totally independent we expect some small variation between the two results that can be expressed in a ratio. This ratio has to be constant. Any significant deviation is an indication of defects. In addition, the GrindoSonic instrument will not provide a repeatable measurement for seriously cracked tubes. Impulse excitation technique for dynamic flexural measurements at moderate temperature, Authors: K. Heritage, Clayton Frisby and Alan Wolfenden, Texas A & M University, Mechanical Engineering Department Language: English The impulse excitation technique (IET), which is presently a precise and reliable technique for measuring dynamic moduli at room temperature, has been adapted to measure dynamic flexural modulus at temperatures in the range of 25° to 300°C. This modified technique involves a sensitive microphone and electronics to record and analyze the sound waves emitted from a specimen vibrating in the fundamental flexural mode. The fundamental resonant frequency and geometry of the specimen are used to obtain the modulus. The location of the microphone relative to the specimen is critical and is major factor once the specimen is placed within the heated environment. Problems were identified and solved, and test data for aluminum are presented to support the modification of the IET for use at elevated temperatures. New Technique for measuring the dynamic Young's modulus between 295 and 6 K, Authors: J. Zhang, A. Nyilas, and B. Obst, Karlsruhe Nuclear Research Centre Language: English A transducer system based on train gauge technology was developed and applied to bar type specimens to determine the dynamic Young's modulus. The system was installed in a continuous flow cryostat working in the temperature range 295-6K. The adapted technique is the remote mechanical excitation of the bar as a cantilever beam and the on-line determination of the fundamental free vibration frequency using a commercially available electronic instrument. This simple and economic method is able to measure the material's dynamic Young's modulus, E, and shear modulus, G, with a high degree of accuracy (error < ± 2.0%). The Poisson's ratio, ?, can therefore be determined, according to the measured values of E and G. Six different engineering materials were characterized with respect to their elastic properties between 295 and 6 K. The dynamic Young's modulus versus temperature measurements were compared with the results of static stress - strain measurements carried out in the same test facility. PARAMETRES ELASTIQUES - MESURE DYNAMIQUE ET CALCUL Authors: Bernd Weiler, Christian U. Grosse Language: French Les modules d'élasticité et de rigidité peuvent être calculés à partir des vibrations libres issues des specimens en forme de barre. Dans ce but, on a présenté un survol des bases pour le calcul théorique de ces modules. Au FMPA, un nouveau dispositif a été développé permettant la mesure de ces modules. Ce dispositif a été comparé au dispositif Grindo-Sonic. Les deux dispositifs ont permis une évaluation très satisfaisante des modules, bien qu'ils présentent des caracteristiques très differentes. Research Technique in non-destructive testing, Authors: R.S. Sharpe Language: English

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