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BS ISO 17139:2014 pdf free

BS ISO 17139:2014 pdf free.Fine ceramics (advanced ceramics, advanced technical ceramics)一Thermophysical properties of ceramic composites
A test piece is heated and subsequently cooled, either at a specified uniform rate or using defined temperature increments. Its change of length and its temperature are measured continuously, or at regular frequent intervals during the imposed temperature cycle.
One of two methods can be used to determine the linear thermal expansion coefficient, either by direct measurement or by a differential method.
In this method, the variation in length of the test piece is measured directly. It is necessary to know the change in dimensions of the test piece support system by previous calibration.
The test piece is placed in a specimen holder and is made to contact a displacement transducer by using a push rod, made of the same material as the holder. This assembly is put in a furnace. The differential expansion between the test piece and the test piece holder is measured during the increase and the decrease in temperature.The apparatus is shown in Figure 1.
The test piece holder and the push rod shall be made from thermomechanically stable materials of the same type, which shall be chemically inert and thermally compatible with the test piece material under the environmental conditions of the test.
NOTE For temperatures above 1 400。C, it is necessary to employ a vacuum or inert gas atmosphere, with a non-oxide material appropriate for the test environment, such as a grade of dense graphite.
Thermocouples, in accordance with IEC 60584-1, subject to the upper temperature requirements and environmental consideration, except for tungsten-rhenium couples which may be used at higher temperatures but are not covered by IEC 60584-1, should be individually calibrated. For temperature in excess of 2 000 K, infrared detectors or any suitable device may be used.
System, capable of measuring displacements to an accuracy better than 0,1 μm. The system shall allow recording of the test piece temperature and the displacement simultaneously. The system for measuring of displacements shall be periodically calibrated in accordance with Annex A for direct measurement or Annex B for differential measurement.BS ISO 17139 pdf free download.

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