Measurement and Control of Residual Stresses in Cylinder-Block Castings 540240
THE control of residual stresses in automotive cylinder blocks is discussed in this paper. According to the authors, this study was started because a small percentage of castings was being scrapped because of cooling cracks in the valve compartment wall.
They discovered that the greatest single factor in inducing trapped stresses in castings is too great a difference in the cooling rates for different portions between 1400 F and 600 F.
They also found out that residual tensile stresses can be eliminated in a particular section by keeping its cooling rate at least as fast as that of other significant sections. Moreover, it is possible to move trapped stresses from one section to another by overcooling.
They have also developed a method that gives quantitative results that serve as good index values of the trapped stresses present even in complex castings.