Expert: Veto Varma - 2/3/2008

Question
HELLO AND THANK YOU.I HAVE A 2000 KENWORTH TRUCK.IT HAS AN ALUMINUM FRAME WHICH IS RARE IN THE INDUSTRY.IT WAS RECENTLY EXPOSED TO EXTREME HEAT BECAUSE THE BRAKE DRUM HAD A FRICTION OVERHEAT CAUSING TIRE FAILURE AND FIRE TO THE WHOLE WHEEL SET.THIS WAS A CONCENTRATED FIRE APROX.ONE FOOT AWAY FROM THE FRAME OF THE TRUCK.IT WAS HOT ENOUGH TO BURN THROUGH THE TRAILER FRAME AND DECK.BRAKE DRUMS CAN GET AS HOT AS 2000 DEG. IN SOME OVERHEAT CONDITIONS.THE FRAME OF THE TRUCK IS 1/2" THICK AND IS A [ SHAPE. THE OUTER SIDE WAS EXPOSED FOR APROX.15 MIN. TO THE HEAT AND SHOWS A SLIGHT WARPING.MY QUESTIONS ARE. 1)WHAT IS THE LOSS OF STRUCTURAL INTEGRITY TO THE FRAME RAIL OVER A 3 FT. SPAN AND IS THERE ANY.2)WILL ALUMINUM CRACK IF PUT UNDER NORMAL STRESS AFTER BEING EXPOSED TO HEAT AS EXPLAINED OR WILL IT STILL BE PLIABLE AND STRETCH(BRITTLE?).THANKS AGAIN.

Answer
Hello Scott,

Due to liability issues I can not fully answer your question in this forum, but can give you an idea about it. As you have explained about the heating and warping of aluminum section, there will be changes in the structural capacity of the section. I suggest to consult professional engineer about it and he might give you the remedy for the section. For the number 2 part of your question, after this kind of heat treatment it is possible that there is change of behavior mostly because of geometric nonlinearity and also some possible material nonlinearity.

Best thing is to show it to a professional engineer in your area and take his opinion.

If you have any more questions please do no hesitate to mail me.

Regards
Veto