BS EN ISO 204 pdf free download

BS EN ISO 204 pdf free download.Metallic materials – Uniaxial creep testing in tension – Method of test.
5 Principle
The test consists of heating a test piece to the specified temperature and of straining it by means of a constant tensile force or constant tensile stress (see Note) applied along its longitudinal axis for a period of time to obtain any of the following:
— a specified creep extension (uninterrupted test) with continuous extension measurement;
— values of permanent elongation at suitable intervals throughout the test (interrupted test);
— the creep rupture time (uninterrupted and interrupted test).
NOTE “Constant stress” or “true stress” means that the ratio of the force to the instantaneous cross-section remains constant throughout the test. The results obtained with constant stress are generally different from those obtained with constant forcel4Zl.
6 Apparatus
6.1 Testing machine.
The testing machine shall apply a force along the axis of the test piece while keeping inadvertent bending or torsion of the test piece to a minimum. Prior to test, the machine should be visually examined to ensure that loading bars, grips, universal joints and associated equipment are in a good state of repair.
The force shall be applied to the test piece without shock.
The machine should be isolated from external vibration and shock. The machine should be equipped with a device which minimizes shock when the test piece fractures.
NOTE At present, there appears to be insufficient quantitative data in the literature demonstrating the influence of bending upon creep and stress rupture life. Any organization with such information is encouraged to forward it to ISO/TC 1641431.
The machine shall be verified and shall meet the requirements of at least class 1 in ISO 7500-2.
6.2 Extension and elongation measuring devices.
6.2.1 Extension measuring device.
In uninterrupted tests, the extension shall be measured using an extensometer which meets the performance requirements of class 1 or better of Iso 9513 or by other means which ensure the same accuracy without interruption of the test. The extensometer can either be directly attached to the test piece or be non-contacting (e.g. a non-contacting optical or laser extensometer).
It is recommended that the extensometer be calibrated over an appropriate range based upon the expected creep strain.
The extensometer shall be calibrated at intervals not exceeding 3 years, unless the test duration is longer than 3 years. If the predicted test duration exceeds the date of the expiry of the calibration certificate then the extensometer shall be recalibrated prior to commencement of the creep test.
The extensometer gauge length shall not be less than 10 mm.
The extensometer shall be capable of measuring extension of one side of the test piece or, preferably, on opposite sides of the test piece.
The type of extensometer used (e.g. single-sided, double-sided, axial, diametral) should be reported. When the extension is measured on the opposite sides, the average extension should be reported.When the extension is measured with an extensometer attached to the grip ends of the test piece, the ends shall be of such shape and size that it can be assumed that the observed extension has occurred completely within the reference length of the test piece. Percentage creep extension is measured over Lr. The extensometer gauge length should normally be as near as possible to the reference length. In the case of accurate creep measurements, a gauge length as long as possible should be used to improve the accuracy of measurements. Care should be taken to avoid spurious negative creep when using nickel base alloy extensometers. See the Code of Practice[42]. For low creep strain measurements, e.g. ≤1 % strain, on test pieces with short gauge lengths, careful consideration should be given to ensure that the measuring device used has sufficient resolution and accuracy over the range of use. BS EN ISO 204 pdf download.