FATIGUE PROPERTIES OF DYNAMICALLY STRESSED AUTOMOBILE GRAY IRON CASTINGS.

The selection of gray cast irons for dynamically stressed conditions in exposed parts of automobile diesel engines constitutes a serious problem. To evaluate the fatigue properties of cast irons, a method has been worked out and tested to determine the fatigue limit from the tensile strength test on nonstandard bars. Another important piece of new knowledge, especially with respect to castings of cylinder blocks and heads, can be seen in the values of residual stresses, their dependence on the cooling rate of the casting and, in particular, on the time of removal of the casting from the mold. A temperature range for knocking out the castings avoiding the necessity of subsequent stress relieving has been determined.