Abstract
CRT heater has a complex structure which is composed tungsten double spiral coil and Al2O3 insulating film on the coil surface. For the strength evaluation of the heater, thermal stress under operating conditions was analyzed, and its material strength was experimentally obtained.
Simplified analysis procedure by the finite element method is effective for a complex structure such as CRT heater. A simplified model was developed by keeping the same structural stiffness, which was useful for calculating the overall temperature distribution and deformation behavior of the heater. Thermal stress, which is an important factor in strength evaluation, was obtained by using a precise model of local structure. The analytical results showed that the highest temperature was attained in 20 seconds after current was turned on, and the uniform temperature distribution was found in the cross section of the heater. The maximum thermal stress of about 210MPa was attained and then it sharply decreased from the inside to the outside wall of the heater. The thermal stress obtained by the analysis and the strength of Al2O3 insulating film and tungsten wire determined experimentally were compared to evaluate the strength reliability of the heater.
