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.