4. Results and discussion
Results obtained from the thermal stress analyses by the finite
element technique, the temperature and stress variations for the
uncoated piston and coated pistons with various coating thicknesses
of the ceramic material are discussed systematically. For the
uncoated piston, a counter-plot of the temperature is shown in
Fig. 3. As expected, the high temperatures are observed at the
crown center and bowl lip areas, since it is subjected to the heat flux
circumferentially. The maximum temperature is at the center and
the minimum is at the bottom of the crown bowl on the piston top
surface. To be more precise, the extreme values are 292.1 C and
243.8 C respectively. In the radial direction, the temperature decreases
from the crown center to the bottom of the bowl, then it
increases towards the bowl lips and finally decreases again at the
edge of the crown surface.
Under the same conditions, counter-plots of the temperature
distributions are shown in Fig. 4aed for the ceramic coating
thicknesses of 0.4 mm, 0.8 mm, 1.2 mm and 1.6 mm. It is observed
that the values of maximum temperature at the crown center of the
pistons on the coating surface are 387.7 C, 455.2 C, 503.9 C and
Tab