The testing technique and some results from an experimental study to determine tire temperature profiles to aid in defining the strength and fatigue limitations of the tire carcass structure are described. This effort is part of a program to explore analytically and through experiment the temperature distribution in an aircraft tire during free roll and braked and yawed rolling conditions

Mccarty, J. L.

English

NASA Technical Reports Server

RESULTS FROM RECENT NASA TIRE THERMAL STUDIES 
John L. McCarty 
NASA Langley Research Center 
ABSTRACT 
This paper describes the testing technique and some results from an experimental 
study to determine tire temperature profiles to aid in defining the strength and 
fatigue limitations of the tire carcass structure. This effort is part of a program 
to explore analytically and through experiment the temperature distribution in an 
aircraft tire during free roll and braked and yawed rolling conditions. The analytical 
effort, together with a comparison with the experimental results, is discussed in 
the paper by Clark in this publication (ref. 1). 
211 
https://ntrs.nasa.gov/search.jsp?R=19830013130 2020-03-21T03:38:48+00:00Z
LOCATION OF THERMOCOUPLES IN TIRE THERMAL STUDY 
Figure 1 shows the approximate locations of the eighteen thermocouples installed 
within the carcass of several tires to support the thermal study. As noted in the 
figure, the thermocouples were mounted on the inner and outer walls of the tires and 
along an approximate midline at six radial stations. Most of the thermocouple 
installation was accomplished by implanting the sensors in holes drilled into the 
tire carcasses after the carcasses had been buffed prior to retreading. 
Figure 1 
212 


TYPICAL TEMPERATURES THROUGH THE TIRE CARCASS 
DURING FREE ROLLING 
Figure 4 presents the time history of temperature buildup in six of the 
thermocouples as the tire in the free-rolling mode made two and a half passes of 
about 6500 feet each down an asphalt runway. As noted on the figure, the test tire 
was raised from the pavement surface following each pass while the test vehicle 
was being turned around for the return trip. The thermocouples were selected to 
illustrate the temperature rise through the tire carcass in the shoulder and bead 
areas. The figure clearly demonstrates that in both areas the rate of temperature 
buildup, and hence the magnitude of the temperature, is greatest along the interior 
wall, decreases through the carcass, and is lowest along the exterior wall. As 
would be expected because of tire flexure, the temperatures in the shoulder area 
are greater than the corresponding temperatures in the bead area. 
TIRE: 22 x 5.5, 12 PLY TIRE DEFL. = 25% Vg= 20 MPH 
250 
200 
150 
TEMP. , OF 
100 
50 
TIRE OFF GROUND 
I /- 
I 
0 100 200 300 400 500 600 
TIME, SEC 
Figure 4 
215 
TYPICAL INTERIOR TIRE CARCASS TEMPERATURES DURING 
FREE ROLL 
Temperature data from the six thermocouples installed along the tire internal 
wall are presented in figure 5 as a function of the free-roll distance. It is 
interesting to note that the maximum temperature was measured not in the center of 
the tread nor in the shoulder area, but between the two. The temperature in the 
bead area is again shown to be well below the other measured tire internal tempera- 
tures. 
TIRE: 22 x 5.5, 12-PLY TIRE DEFL = 25% v 
9 
= 20 MPH 
T, "F 
5ooo 10 ooo 13 ooo 
DISTANCE, FT 
Figure 5 
216 
EFFECT OF TIRE DEFLECTION 
Figure 6 illustrates the effect of tire deflection 6 on the distribution 
of temperature within the tire carcass after the tire had free-rolled for a distance 
of 5000 feet. The different deflections in this case were obtained by changing the 
tire inflation pressure while maintaining the 4000-pound vertical loading. Although 
data are lacking in the tread region, similar tests on other tires showed little 
effect of tire deflection on temperatures in that area. However, the figure shows 
a pronounced effect on temperatures in the sidewall region. The higher temperatures 
associated with the greater deflections are attributed to the more severe sidewall 
flexing which increases with tire deflection. Similar trends were observed when 
the tire deflection was changed by varying the vertical load while maintaining a 
fixed inflation pressure. 
FREE ROLL d = 5000' 
m 60 to 71 
m 71 to 82 
Figure 6 
217 
EFFECT OF YAW ANGLE 
To examine the effect of yaw angle I/J on tire temperature distribution, a series 
of free-rolling tests was conducted where the tire was yawed to 3" and 6". Because 
only one side of the tire was instrumented, two passes were required at each yaw 
angle with the tire yawed first in one direction (+3", for example) and then in 
the other direction (-3", for example) to complete the temperature picture. The 
results are illustrated in figure 7 which presents the tire temperature profiles 
after having traveled 7000 feet. The figure shows a considerable temperature build- 
up with yaw angle in the tread area and in the "downwind" sidewall of the tire with 
an accompanying cooling effect on the "upwind" side. The reduced temperature on the 
"upwind" side is apparently due to the stress relieving which occurs in the "upwind" 
sidewall when the shoulder area on that side is forced to roll partially into the 
footprint. Conversely, the greater tire distortion on the "downwind" side as the 
yaw angle is increased would account for those higher temperatures. The higher 
temperatures in the tread area can be explained by the increased scrubbing action 
in the tire footprint that is associated with increasing yaw angle. 
Figure 7 
218 
EFFECT OF BBAKING 
Driving the test tire at fixed slip ratios provides a means for evaluating the 
effect of braking on the temperature buildup in the tire carcass. Figure 8 presents 
the temperature profiles after the tire had traveled 7000 feet first in free roll 
and subsequently at slip ratios of 5 and 10 percent. The figure shows that the 
influence of braking is essentially limited to the tread area. Minimal changes 
are noted in the temperature profiles of the sidewall regions. 
6 = 30%; d = !OOO' 
'C (OFI 
‘. 
4 x I m 71 6d to  71 82 
A 
p 'm 82to93 
*. 
m 93 to 104 
>104 
i < 1201‘ 
(120 to 1401' 
(140 to 16of 
(160 to 1801 
(180 to 200) 
1200 to 2201 
l > 22oi 
Figure 8 
219 
EFFECT OF SPEED 
Over the speed range of these tests, the influence of wheel speed on the tire 
temperature distribution is almost insignificant. As observed in figure 9, the 
sidewall temperature after free-rolling 7000 feet is essentially unaffected and only 
moderate increases can be seen in the tread temperature as the speed is increased. 
The rise in tread temperature at higher speeds is perhaps the result of the higher 
frequency squirming action which has been observed in the tire footprint. 
FREE ROLL d = 30%: d =‘7000 
f-7 n 
‘C (OF) 
I <49 ( < 120) m 82 to 93 (180 to 200) 
m 49 to 60 1120 to 140) m 93 to 104 (200 to 220) 
60 to 71 (140 to 140). m > 104 ( > 220) 
71 to 82 1160 to 180) 
Figure 9 
220 
TIRE EQUILIBRIUM TEMPERATURES 
The question arose during the course of this investigation as to whether the 
tire carcass would assume an equilibrium temperature profile if permitted to free 
roll for an indefinite period. To answer the question, many passes were made in 
both directions along a 7000-foot runway at 20,mph with a very brief turn-around 
time between passes to minimize any tire cooling. It became apparent after the 
tire had traveled approximately 65,000,feet that each thermocouple was approaching 
an equilibrium value. The final temperature profile, obtained after the tire had 
traveled in excess of 80,000 feet, is presented in figure 10 and shows temperatures 
approaching 300" F near the shoulder area. Note again that, particularly in the 
sidewall region, the temperatures along the inner wall are considerably greater than 
those near the outer surface. Also note that the centerline tread temperatures are 
somewhat lower than other temperatures in the tread. 
FREE ROLL ' b = 30% d > 80 000 
'C (OFI 
I <66 ( X150) m 107 to 121 (225 to 250) 
m 66 to 79 (150 to 175) m 121 to 135 (250 to 275) 
79 to 93 (175 to 2001 >135 ( >275) 
191 93 to 107 (200 to 2251 
Figure 10 
221 
CONCLUDING COMMENTS 
The results from a program to study tire temperature profiles to aid in 
defining the strength and fatigue limitations of an aircraft tire carcass struc- 
ture suggest the following concluding comments. 
l A testing technique has been developed for successfully measuring the 
thermal characteristics of a rolling tire. 
l Tire shoulder and sidewall temperatures increase with increasing tire 
deflection due to either overload or underinflation. 
l Tire tread and "downwind" sidewall temperatures increase with yaw 
angle. 
l Large temperature increases are noted in the tread region during 
increased braking. 
l Changes in ground speed (over the test range to 50 mph) produce 
insignificant effects on the temperature buildup in the tire carcass. 
REFERENCE 
1. Clark, Samuel K.: Heat Generation in Aircraft Tires. Tire Modeling, 
NASA CP-2264, 1983, pp. 193-210. 
222 


Results from recent NASA tire thermal studies

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