EN 14425-3:2010

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.UQRVWL&1%Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit von monolithischer Keramik - Teil 3: Verfahren für Biegeproben mit Chevron-Kerb (CNB-Verfahren)Céramiques techniques avancées - Méthode d'essai de détermination de la ténacité à la rupture des céramiques monolithiques - Partie 3: Méthode de l'éprouvette à entaille en chevronAdvanced technical ceramics - Test methods for determination of fracture toughness of monolithic ceramics - Part 3: Chevron notched beam (CNB) method81.060.30Sodobna keramikaAdvanced ceramicsICS:Ta slovenski standard je istoveten z:EN 14425-3:2010SIST EN 14425-3:2010en,fr,de01-september-2010SIST EN 14425-3:2010SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14425-3
June 2010 ICS 81.060.30 Supersedes CEN/TS 14425-3:2003English Version
Advanced technical ceramics - Test methods for determination of fracture toughness of monolithic ceramics - Part 3: Chevron notched beam (CNB) method
Céramiques techniques avancées - Méthode d'essai de détermination de la ténacité à la rupture des céramiques monolithiques - Partie 3: Méthode de l'éprouvette à entaille en chevron
Hochleistungskeramik - Prüfverfahren zur Bestimmung der Bruchzähigkeit von monolithischer Keramik - Teil 3: Verfahren für Biegeproben mit Chevron-Kerb (CNB-Verfahren) This European Standard was approved by CEN on 30 April 2010.
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During the test, the crack front widens as the crack propagates from the tip, resulting in an increase in the force required to maintain growth. Countering this, the test piece becomes more compliant as the crack lengthens, and so the two effects result in a peak load being attained after some distance of propagation. The toughness is determined from the peak force applied. This test method employs the chevron notch in a flexural strength test piece, loaded in four-point bending geometry. The advantage is that it can be performed on standard flexural strength test pieces. SIST EN 14425-3:2010

5 Test apparatus 5.1 Flexural strength test apparatus of four-point bending type, in accordance with the requirements in EN 843-1. 5.2 Mechanical testing machine, capable of accurate recording of load/displacement data for loads in the range 0 N to 500 N. The load shall be calibrated in accordance with EN ISO 7500-1. NOTE A stiff loading system (i.e. frame, load cell and fixtures, etc.) is advantageous for this test. The compliance is ideally less than 5 × 10-5 m/N (see [1]). 5.3 Micrometer in accordance with ISO 3611 but measuring to an accuracy of 0,002 mm.
5.4 Calibrated device for measuring dimensions of the cut chevron after fracture, reading to an accuracy of 0,002 mm or better. NOTE This may be achieved by use of an appropriate travelling microscope, or a conventional microscope with a calibrated stage micrometer, or a microscope with a micrometer eyepiece. 5.5 Humidity measuring device for measuring relative humidity to an accuracy of ± 2 %, e.g. those according to ISO 4677. 6 Test pieces 6.1 Material selection Select the material or components from which test pieces are to be machined with reference to the considerations given in EN 1006. 6.2 Test piece dimensions 6.2.1 The test pieces shall preferably be of dimensions as for determination of flexural strength and described in EN 843-1. Alternatively, if availability of material permits, the dimensions may be scaled larger for convenience of machining of the notch. NOTE It is usually advantageous to test coarse-grained or heterogeneous materials in larger test piece sizes because it improves the chances of obtaining a valid test (see 7.9). 6.2.2 The standard size test pieces shall be (3,00 ± 0,15) mm × (4,00 ± 0,15) mm in cross-section, and have a minimum length of 45 mm. The surfaces shall be machined to a flatness of better than 0,01 mm over the test piece length, and opposite pairs of faces shall be parallel to better than 0,01 mm over the test piece length. The section should be visibly rectangular.
NOTE Chamfering in accordance with EN 843-1 is unnecessary for this test. SIST EN 14425-3:2010
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