ISO INTERNATIONAL STANDARD 7884-4 First edition 1987-12-15 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION rso ORGANISATION INTERNATIONALE DE NORMALISATION MEXKAYHAPOAHAA OPIAHM3ALMH O CTAHAAPTW3ALMM ANE Kcomf Dc Se Glass -- Viscosity and viscometric fixed points Part 4 : Determination of viscosity by beam bending Referencenumber ISO 7884-4 : 1987 (E) Foreword ISo (the International Organization for Standardization) is a worldwide federation of national standards bodies (Iso member bodies). The work of preparing International StandardsisnormallycarriedoutthroughIsOtechnical committees.Eachmember body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with iso, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by least 75 % approval by the member bodies voting. International Standard ISO 7884-4 was prepared by Technical Committee ISO/TC 48, Laboratory glassware and related apparatus. Users should note thatall International Standards undergo revisionfrom timeto time and that any reference made herein to any other International Standard implies its latest edition, unless otherwise stated. International Organization for Standardization, 1987 Printed in Switzerland CopyrightInternational Organization for Standardization No reproduction or networking permitted without license from IHS Not for Resale ISO 7884-4 :1987 (E) INTERNATIONAL STANDARD Glass - Viscosity and viscometric fixed points Part 4 : Determination of viscosity by beam bending 0 Introduction viscosity is possible only with Newtonian or linear-viscoelastic behaviour of the glass.The procedures are sensitive to interference by International Standard Iso 7884, Glass -- Viscosity and devitrification of the sample. With viscosities above 1012 dPa's the ad- viscometric fixed points, consists of the following separate justment of the structure equilibrium within the glass is perceptibly parts: delayed with respect to the temperature setting. For tests within this range it should be agreed whether it is necessary to wait for the final Part 1: Principles for determining viscosity and viscometric equilibrium viscosity at a given temperature or to take the viscosity fixed points. value corresponding to a conventional temperature-time programme (see 6.3). Part 2: Determination of viscosity by rotation viscometers. Part3: Determination of viscosity by fibre elongation 2 Reference viscometer. IEC Publication 584-1,Thermocouples -- Part 1:Reference Part 4:Determination of viscosity by beam bending. tables. Part 5: Determination of working point by sinking bar viscometer. 3Principle Part 6: Determination of softening point. 3.1 Beams Part7:Determination of annealing pointand strain point by beam bending. For this test procedure, rod-shaped test specimens, called beams, are prepared from the sample. Along their length I they Part8: Determination of (dilatometric) transformation have a constant cross-sectional area (see figure 1) which may temperature. be a) rectangular, of thickness h, and width b; 1 Scope and field of application b) circular, of diameter d. Thispart of ISO7884specifiesamethodofdeterminingthe dynamic viscosity of glass on a rod-shaped test specimen 3.2 Supports,span .(called a beam) supported at its ends. The viscous deflection rate of the beam is measured under a given load at the midpoint The beam is placed horizontally on two supports; the beam axis between the supports. In addition the viscosity-temperature and the supports are perpendicular. relationship and the dependence of the viscosity on the thermal history of the sample canbedetermined. For rectangular cross-section beams the supports are horizon- tal and have straight edges. The viscosity range covered by this metho