ISO 12111:2011 pdf download.Metallic materials -Fatigue testing -Strain-controlled thermomechanical fatigue testing method.
The kinematic design of contacting extensonielry should be such that lateral or angular motions of the specimen contact zone do not cause the extensonleter contact points or knife edges to slip.
The contact pressure and operating force of the extensorneter should be low enough to avoid damaging the specimen surface and giving rise to crack initiation at the extensonieter contact points or knife edges
5.3 Heating system
The heating system shall be capable of applying the maximum heating and cooleig rates required by the TMF lest series
To minimize radial temperature gradients with a direct Induction heating system. Ills advisable to select a generator with a sufficiently low frequency (typicaly in the several hundred kHz range and lower). This will help to minimize ski, effects during heating.
During a test. the specimen temperature shall be measured using thermocouples, pyrometers, RTDs. or other such temperature.measuremenl devices,
For thermocouples, direct contact between the thermocouple and the specimen shall be achieved without causing incipient failure at the point of contact
NOTE Commonly used methods of aAtachment ate: resistance spot welding (outside the guge length) and xlng by bwidlng or by pressing a sheathed thermocouple against the specimen surface,
If the temperature within the gauge section is measured with an optical pyiomeler, steps shall be taken during calibration to address possible variation In the specimens thermal emlssivity over the duration of the tesi Potential soluhons may include Iwo.colour pyrometers and pre-oxidizlng the specimen surface
5.4 InstrumentatIon for test monitoring
A computerized system capable of carrying out the task of collecting and processing force, extension. lempemature, and cycle count data digitally is recommended. Sampling frequency of data points shal be sufficient to ensure correct definition of the hysteresis loop especially in the regions of reversals. Different data collection strategies will affect the number of data points per loop needed, however, typically 200 points per loop are required.
The contact pressure and operating force of the extensorneter should be low enough to avoid damaging the specimen surface and giving rise to crack initiation at the extensonieter contact points or knife edges
5.3 Heating system
The heating system shall be capable of applying the maximum heating and cooleig rates required by the TMF lest series
To minimize radial temperature gradients with a direct Induction heating system. Ills advisable to select a generator with a sufficiently low frequency (typicaly in the several hundred kHz range and lower). This will help to minimize ski, effects during heating.
During a test. the specimen temperature shall be measured using thermocouples, pyrometers, RTDs. or other such temperature.measuremenl devices,
For thermocouples, direct contact between the thermocouple and the specimen shall be achieved without causing incipient failure at the point of contact
NOTE Commonly used methods of aAtachment ate: resistance spot welding (outside the guge length) and xlng by bwidlng or by pressing a sheathed thermocouple against the specimen surface,
If the temperature within the gauge section is measured with an optical pyiomeler, steps shall be taken during calibration to address possible variation In the specimens thermal emlssivity over the duration of the tesi Potential soluhons may include Iwo.colour pyrometers and pre-oxidizlng the specimen surface
5.4 InstrumentatIon for test monitoring
A computerized system capable of carrying out the task of collecting and processing force, extension. lempemature, and cycle count data digitally is recommended. Sampling frequency of data points shal be sufficient to ensure correct definition of the hysteresis loop especially in the regions of reversals. Different data collection strategies will affect the number of data points per loop needed, however, typically 200 points per loop are required.
