Reference material for tensile testing of metals

Informations projet

N° de convention de subvention: MAT1920028

Projet clôturé

Date de début 1 Janvier 1993

Date de fin 31 Decembre 1995

Financé au titre de

• Specific research and technological development programme (EEC) in the field of measurements and testing, 1990-1994

Coût total

Aucune donnée

Contribution de l’UE

Aucune donnée

Coordonné par

NPL MANAGEMENT LTD.
United Kingdom

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Résultats exploitables

Reference materials for tensile testing of materials

General Information : The objective of the project is to produce a certified reference material for the validation at room temperature of tensile testing machines. Upon the basis of the results of an intercomparison of room temperature tests on CRM 425 involving 10 laboratories from the Member States of the European Union, 5 laboratories will be selected to participate in the project to produce a certified room temperature tensile test reference material. The work programme for production of the reference material includes the acquisition of a candidate reference material master melt (1 tonne of Nimonic 75), checking the homogeneity of the master melt (for chemical composition, grain size, hardness and microstructure) and certification of the reference material by undertaking a certification exercise between the 5 laboratories. Achievement : Results have been collated and analyzed to determine the mean, standard deviations and 95% confidence limits of the room temperature tensile properties of Nimonic 75, to enable it to be used as a Certified Reference Material. It should be noted that data sets of the proof and tensile strengths exhibited non-Gaussian distribution, however an alternative approach to presenting the mean values of the measured parameters based on correlation with hardness is given which allows the uncertainty to be reduced to ~ ± 1% at the 95% confidence level. The small systematic variation of the proof and tensile strengths with hardness is attributable to small compositional changes in the silicon content. A comparison of the measured uncertainties of the Nimonic 75 with those for thirteen other alloys evaluated in previous intercomparison exercises showed that it had the best overall precision of all the materials evaluated.