Measurement Technique

An appraisal of the GrindoSonic Material Tester
P.J. Emerson, BCIRA

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.

Impulse excitation technique for dynamic flexural measurements at moderate temperature,
K. Heritage, Clayton Frisby and Alan Wolfenden, Texas A & M University, Mechanical Engineering Department

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,
J. Zhang, A. Nyilas, and B. Obst, Karlsruhe Nuclear Research Centre

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, ν, 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.

  Use of an ultrasonic resonance technique to measure the in-plane Young's modulus of thin diamond films deposited by a DC plasma-jet, L. Chandra and T.W. Clyne, University of Cambridge, Department of Materials Science and Metallurgy
Research Technique in non-destructive testing,
R.S. Sharpe
An Evaluation of Three Methods to Measure the Dynamic Elastic Modulus of Steel,
A. Wolfenden, W. Schwanz, Texas A & M University, Mechanical Engineering Dept.

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
F. Lostak, W. Vandermeulen

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.

Evaluation of the Elastic and Plastic Properties of Si3N4 by depth sensing indentation
R. Berriche, R.T. Holt, Institute for Aerospace Research, National Research Council of Canada

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.

Elastic Properties of CVD Diamond via Dynamic Resonance Measurements
Mark P. D'Evelyn, David E. Slutz, Bradley E. Williams, General Electric Corporate R & D, General Electric Superabrasives

Control of the mechanical properties of CVD diamond is essential to achiev optimal performance in various applications. While several methods have been applied to the measurement of Young’s modulus of thick-film CVD diamond, in general these methods are not suitable for diamond characterization on a production scale. In addition, many of these methods cannot determine the shear modulus (or Poisson’s ratio), which is necessary for a complete description of the elastic properties. We have developed a simple dynamic resonance method for determining both the Young’s modulus and shear modulus of free standing CVD diamond in the shape of rectangular plates or round discs. The specimen is supported along nodal lines of flexural or torsional modes. Oscillations are induced by impact from a falling ceramic bead, are senses by a microphone, and the resonant frequencies are determined by a signal analyzer. The Young’s and shear modulus are calculated from the frequencies of the fundamental flexural and torsional modes, respectively, using quasi-analytic formulas. CVD diamond grown by several methods routinely achieves Young’s and shear modulus values above 1000 Gpa and 500 Gpa, respectively, in good accord with theoretical values for pure polycrystalline diamond.

Determination of the moduli of elasticity of rocks,
B. Christaras, F. Auger, E. Mosse, Aristotle Univerity of Thessaloniki, Poitiers University

In the present investigation, dynamic methods for the determination of moduli of elasticity were compared with direct static methods. The dynamic moduli of rocks, such as Young’s modulus (E) and Poisson’s ratio (ν) were determined, using both mechanical resonance frequency and classic P and S wave ultrasonic velocity techniques. For this purpose rock samples from different areas of France, covering a wide range of velocity values, were used. The mechanical resonance frequencies were investigated using a Grindo-Sonic machine while the P and S wave ultrasonic velocities were measured using a Pundit ultrasonic machine, connected to an oscilloscope. The static moduli were determined using deformation gauges. Statistical inter pretation of the test results indicated significant correlation between these dynamic and static methods. Accordingly, the above non-destructive dynamic methods are suitable for the determination of static moduly of elasticity.

Evaluation of the GrindoSonic Analyzer for Characterisation of our Chemical Products Atul C. Sarma, Ph D, Whip Mix Corporation A study on gypsum products, phosphate die refractory materials and phosphate investments by impulse excitation of sonic vibration  
Revêtements vitreux sur titane pour application aux prothèses articulaires,
P. Van Landuyt, UCL, Faculté des Sciences Appliquées, Unité de Physico-Chimie et Ingénierie des Matériaux

Le module d’élasticité d’un revêtement est une propriété importante car elle est indispensable à la compréhension du comportement du revêtement lorsqu’il est soumis à des contraintes. Notamment, le module d’élasticité est une donnée de base lors du calcul des contraintes résiduelles dans le revêtement.

On the measurement of the elastic modulus of a vitreous coating on a titanium substrate by the resonance method
P. Van Landuyt, J.M. Streydio, F. Delannay, E. Munting, Université Catholique de Louvain

We have synthesized a biocompatible glass that, when used as a glaze, allows wetting and adhesion on a titanium substrate. The elastic modulus of this glaze cannot be measured isolately. It is possible to calculate the modulus of the vitreous coating by measuring the resonant frequencies of a titanium plate before and after the deposition of the glaze. The values obtained can be compared to the modulus of elasticity of bulk glass. The evolution and the dispersion of the calculated modulus values are followed in function of the density for three different coatings.

GrindoSonic : test on tubes, applicability of the system to detect cracks
Lucent Technologies

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.

Degradation und Erholung der Verformungsmoduli von Polycarbonat unter mechanische Last
Rainer Tilgner, Infineon Technologies

Am Beispiel der Veränderung der Verformungsmoduli von Polycarbonat unter mechanischer Last wird die Notwendigkeit einer derartigen Bestimmung für eine moderne Konstruktionstechnik verdeutlicht. Dazu wird neben einfachen statischen Belastungstests eine dynamische Meßmethode, die das Schwingungsverhalten von Probekörpern verfolgt, beschrieben. Gerade der zeitliche Verlauf von Degradation und Erholung verdeutlicht deren Bedeutung für Sicherheits- und Zuverlässigkeitsaspekte moderner Aufbautechnik.

Neue Methoden der Schadensanalyse und -dokumentation sowie neue Konservierungsmittel für die Baudenkmalpflege und Restaurierung
Dokumentation von Haus Römer in Wuppertal-Sandfeld
Prof. Dr.-Ing. J. Eberhardt
Dr.-Ing. N. Schöndeling
Dipl.-Ing. G. Kunze

Als Projekt im FuE-Schwerpunkt Baudenkmalpflege und Restaurierung wurde in enger Zusammenarbeit mit dem Landschaftsverband Rheinland/Bergisches Freilichtmuseum Lindlar das Gebäude Haus Römer in Wuppertal-Sandfeld dokumentiert. Hierzu fertigte das Labor für Fotogrammetrie Meßbilder an, die die Grundlage für die detailgenaue Vermessung bildeten. Die Arbeiten sollen in 1997 fortgesetzt werden.

Master’s Thesis – Non-destructive testing of particleboard with ultra sound and eigen frequency methods
Fredrik Grundström

In the production of particleboard, different properties of the board have to be measured in order to keep the board quality within required limits. Non-destructive methods for this purpose include ultra-sonic testing and eigen frequency testing. These methods have been proposed for measuring the strength of the board after pressing, for process control purposes. The ultra sound velocity and eigen frequency have been proved to be good instruments for doing this. The results show that Young’s modulusand bending strength can be predicted with high accuracy with these methods. Internal bond can only be predicted with poor to fair accuracy with normal regression models. The use of multivariate models most often give better predictions of the internal bond. Multivariate models are best suited for complex predictions if the prediction variables are weak.

Bernd Weiler, Christian U. Grosse

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.

Bernd Weiler, Christian U. Grosse

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.

Bernd Weiler, Christian U. Grosse

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.

The Stiffness of Plasma Sprayed Zirconia Top Coats in TBCs
J.A. Thompson, T.W. Clyne, University of Cambridge, Cambridge, UK.

Yttria-stabilised zirconia coatings have been deposited onto nickel superalloy substrates by air plasma spraying (APS). Free standing layers were then obtained by chemical dissolution techniques. The in-plane Young’s modulus values exhibited by these layers were measured using the techniques of cantilever ending and ultrasonic resonant frequency testing during flexural vibration. Young’s modulus data were also obtained by nanoindentation of regions remote from microcracks. The values obtained by bending and frequency measurement were found to be considerably lower than that expected for bulk zirconia, whereas those obtained by the nanoindentation experiments were much closer to that of the bulk ceramic. Tests were also performed on samples which had been heat treated at 1100°C and 1300°C. It was found that the stiffness rose significantly after such treatments. This is attributed to sintering processes which generated extensive healing of microcracks.