DIN EN ISO 844:2015 pdf free.Rigid cellular plastics – Determination of compression properties.
6 Apparatus
6.1 Compression-testing machine
Use a compression-testing machine suited to the range of force and displacement involved and having two square or circular plane, parallel plates which are polished and cannot be deformed and of which the length of one side (or the diameter) is at least 10 cm. One of the plates shall be fixed and the other
movable; the latter shall be capable of moving at a constant rate of displacement in accordance with the conditions laid down in Clause 8. Neither plate shall be self-aligning.
6.2 Devices for measuring displacement and force
6.2.1 Measurement of displacement
Procedure A — The compression-testing machine shall be fitted with a system allowing continuous measurement of the displacement x of the movable plate with an accuracy of ± 5 % or ± 0,1 mm if this latter value is a more accurate measurement (see second paragraph in 6.2.2).
Procedure B — The measure of displacement shall be obtained by attaching an extensometer to the sample or by using similar devices that measure directly the sample deformation, with an accuracy of ± 1%.
6.2.2 Measurement of force
A force sensor shall be fixed to one of the machine plates in order to measure the force F produced by the reaction of the test specimen upon the plates during the test. This sensor shall be such that its own deformation during the course of the measurement operation is negligible compared with that being measured and, in addition, it shall allow the continuous measurement of the force at any point in time with an accuracy of ± 1 %.
It is recommended that a device be used for the simultaneous recording of the force Fand the displacement x that allows, by obtaining a curve of F = f(x), the graphical determination of the pair of values F, x required in Clause 9 with the accuracy laid down in 6.2.1 and this subclausc, and provides additional information on the behaviour of the product.
6.2.3 Calibration
Devices for measuring and, if applicable, recording graphically the force and displacement produced by the test machine shall be checked periodically. The devices shall be checked by using a series of standard weights, the masses of which are known to accuracies better than ± I % and which correspond to the forces applied during the test. To check the devices, spacers shall be used which have thicknesses known to accuracies better than either ± 0,5 % or ± 0,1 mm, whichever is more restrictive.
6.3 Instruments for measuring the dimensions of the test specimens These instruments shall be in accordance with Iso 1923.
7 Test specimens
7.1 Dimensions
The test specimens shall be (50 ± 1) mm in thickness except for products with moulded skins which are intended to remain integral with the product in use. With such products, the specimens shall be the full thickness, provided that the minimum thickness is 10 mm or greater and that the maximum thickness is not greater than the width or diameter of the specimen.
The test specimen base shall be either square or circular, with a minimum area of 25 cm2 and maximum of 230 cm2. The preferred geometry and dimensions are a right prism with a base of (100 ± 1) mm x (100 ± 1) mm. The distance between two faces shall not vary by more than I % (tolerance on parallelism).
DIN EN ISO 844 pdf download.