Systems engineer, IBM, Green Bay, Wisconsin
Machine covers and other structural components made of superplastic Zn-22Al can easily and economically be formed by techniques commonly used in the polymeric field. This alloy, however, has a tendency to creep under sustained loads at room temperature. The primary objective of this program was to characterize the behavior of superplastic Zn-22Al under stress conditions experienced by fabricated structures so designers can predict the total strain or deflection over the life of a machine. Creep tests were conducted with simple supported beams and with fixed edge plates. Creep behavior under these bending and biaxial stress conditions was studied and related to the more comprehensive uniaxial tensile creep studies with Zn-22Al. It was concluded that the uniaxial tensile data is conservative when those creep rates are used for the maximum principal stresses in simple or plane bending applications. Included in the report are creep curves for bending of beams and plates, stress calculations and the consideration of several plastic flow theories for creep under combined stresses.
Paper ID: JTE11603J