5. Conclusions
The current study addressed how the static and fatigue strength of
Al3003-O aluminum tubes used in air conditioner heat exchangers could be
affected by their multiple weldings, operating temperatures, and surface
notches. A nonlinear decrease in the hardness of the aluminum tubes with
increasing number of re-welding observed experimentally suggests a
decrease in their fatigue limits with multiple weldings. The fatigue
lives of an aluminum tube at heat exchanger operating temperature (125
°C) were lower than that of room temperature. Moreover, a decrease in
the fatigue limit of the aluminum tubes was experimentally measured in
the presence of a surface notch and, combined with this experimental
measurement, a method to predict a decrease in the fatigue limits for
other surface notch sizes was also presented.