Stress analysis of glass-ceramic insulator and molybdenum cylinders in vacuum tube subassembly
This study determined the state of stress between molybdenum cylinders and a glass-ceramic insulator of a vacuum tube during cooling when the glass-ceramic coefficient of expansion differed from molybdenum by +-2 x 10/sup -7///sup 0/C. A thermoelastic stress analysis was performed on the vacuum tube subassembly using the finite element method. Two cases, which examined the effect of cooling over a 700/sup 0/C range, were considered. In Case One, the expansion coefficient of the glass-ceramic was 2 x 10/sup -7///sup 0/C less than that of molybdenum while for Case Two, it was 2 x 10/sup -7///sup 0/C greater. For Case One, it was found that the tangential stresses in the insulator were entirely compressive but the maximum principal stresses in the r-z plane were mainly tensile. For Case Two, the tangential stresses were tensile in the insulator as were most of the maximum principal stresses in the r-z plane except for stress in the upper regions of the insulator. The magnitude of the stress at the maximum principal stress location appears to be substantially lower than what has been observed in practice (i.e., cracking of this design had never been a major problem, but it has been observed that if the coefficient of expansion of the glass-ceramic was 2 x 10/sup -7///sup 0/C lower than molybdenum, cracking usually resulted). This analysis showed that the expansion coefficient of the glass-ceramic could be varied quite liberally from molybdenum before the ultimate strength (13,000 lb/in./sup 2/) of the glass-ceramic was exceeded.
- Research Organization:
- General Electric Co., St. Petersburg, FL (USA). Neutron Devices Dept.
- DOE Contract Number:
- AC04-76DP00656
- OSTI ID:
- 5378192
- Report Number(s):
- GEPP-TIS-495
- Country of Publication:
- United States
- Language:
- English
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