Tungsten Copper Thermal Expansion Test
Material under heat conditions will increase the volume, which is the thermal expansion. thermal expansion is one of the basic thermodynamic properties of substances. Thermal expansion of the material is due to the movement of atoms or molecules which intensified due. Thermal expansion and species related substances. even for the same material at different temperatures are also different degrees of thermal expansion. It is by a large number of randomly arranged grains constituted.
The original length L elongation after heated objects △l with temperature growth △t approximately proportional，that is △l =al △t, a is called the coefficient of linear expansion. in units of ℃ -1 or K-1. Its formal definition of the formula
If the material's temperature is t1 the length is L，when temperature rise to t2 the length increase to △l ，obtained by experiment coefficient of linear expansion is
Therefore. the problem of measuring the coefficient of linear expansion translates into how measure accurately due to temperature changes caused by small changes in length△l。If want to measure the △l Dial gauge should borrow group described above.
Tungsten Copper Thermal Expansion Coefficient Test Procedure
1. The test sample is fixed in the experimental frame. tighten the locking screw to be facing the dial gauge bezel attention.
2. Adjust the relative position of the dial gauge and bezel. both to ensure that there is no gap between the two. but also to ensure there is enough micrometer spatial elongation.
3. Adjusting the position of the thermocouple mount. so that it is in the middle of the sample.
4. The thermocouple coated with thermal grease. Thermocouples inserted in the hole in the mount. and the experimental apparatus is connected to the plug socket on the thermocouple sensor.
5. The end of the sample with a silicone tube and heated water bath outlet is connected to one end of the heated water bath connected to the inlet.
6. Turn off the pump power.
7. To ensure that there is enough water bath pot.
8. Finally, check that the instrument is connected correctly. the relative position of each part of the instrument display is appropriate.
9. Turn the instrument into the experiment.
10. Turn the water pump switch.
11. to room temperature for a starting point. a temperature set point every 5 ℃. And then measure the temperature after six o'clock. Record changes in the value of the measured temperature and the dial gauge on the sample.
12. According to the digital of △l和△t. Could calculate the thermal expansion coefficient according to the following formula
13. Switching to a different metal rod samples were measured and calculated the respective linear thermal expansion coefficient. Appendix I provides reference values were compared to calculate the measurement uncertainty.
Tungsten Copper Thermal Expansion Coefficient Test Considerations
1. Micrometer and where you want to install the appropriate shutter, it is necessary to ensure that there is no gap between the two, but also to ensure there is enough micrometer spatial elongation.
2. The end of the sample with a silicone tube and heated water bath outlet is connected to one end of the heated water bath connected to the inlet.
3. in the water bath and the sample did not do a good case connected to the pump is turned on.
4. Carefully check the connections are correct before turning on the power water bath.
5. The temperature control settings should not exceed 80 degrees.
6. The experimental process prevents water bath dry.
7. The experiment can not vibrating equipment and tables, otherwise it will affect the indicator reading.
8. The indicator is a precision instrument, can not squeeze.
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