Accuracy of the Dilatometer on Gleeble

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Accuracy of the Dilatometer on Gleeble
Gang Shi Prof. T. Calvin Tszeng Prof. Philip Nash
Thermal Processing Technology Center Department
of Mechanical, Materials Aerospace
Engineering Illinois Institute of Technology Sep
19, 2003
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Motivations
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Experiment Procedure
Composition C 0.77 Mn0.8 Si 0.24 Cu 0.23 P
0.015 S 0.025 Ni 0.08 Cr 0.032 V
0.032 Mo0.017 Sn 0.015 Cb 0.002 N 0.002
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Sample at 20Hz
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Sample at 15Hz
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Sample at 15Hz
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Sample at 15Hz
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Sample at 10Hz
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Sample at 100Hz
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Sample at 100Hz
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Sample at 100Hz Smoothing the data
Black curve is obtained by numerical filter Red
curve is obtained by slow heating rate
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Noise vs. Sample Rate
Noise Source
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Conclusion

• There are two type errors in the dilatation
  curves, shifting error and noises.
• Both of them appear during heating processes not
  observed during cooling processes.
• The shifting error comes from the structure of
  the dilatometer and mechanical vibration.
• It happens under high heating rate,
  usually first few cycle or when power turns on.
• Suddenly change of heating rate may apply
  a external moment at the quartz rod of the
  dilatometer and cause it to rotate. The
  mechanical vibration due to high heating rate is
  another reason.
• To minimize the error, carefully setup the
  dilatometer and avoid sudden change of the
  heating rate.
• Noises in dilatation curve come from electric
  noise and mechanical vibration.
• The error is sensitive to the sample
  rate.
• Numerical filter is another solution. But
  it is not easy.
• Use low sample rate if possible.

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Thank you!