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The goal of the Contrails project is to help preserve and disseminate the technical record of 20th century aerospace research, highlighting in particular the research endeavors of the Illinois Tech community.

Effect Of Temperature On The Creep Of Polycrystalline Aluminum By The Cross-Sslip Mechanism

Report Number: WADD TR 60-53
Author: Jaffe, N.
Author: Dorn, J. E.
Corporate Author: University Of California
Laboratory: Materials Central
Date of Publication: 1960-06
Pages: 21
Contract: AF 33(616)-3860
Project: 7360
Task: 73604
PB Number: PB171360
AD Number: ADA328524

Abstract:
The apparent activation energy for creep of polycrystalline aluminum was determined over the range of 273° to 350°K by the effect of small abrupt changes in temperature on the creep rate. A constant activation energy of 27,400 ± 1000 cal/mole was obtained over strains of 0.003 to 0.23, stresses ranging from 2250 to 6000 p. s. i. and strain rates varying from 0.1145 x 10-5 to 29.5 x 10-5 per minute. Metallographic studies and comparison with theory suggested that creep in this range is controlled by the rate of cross-slip of dislocations.

Both X-ray diffraction analyses and room temperature tensile stress-strain data following precreep revealed that the substructure produced in this range by creep under a given stress depended only on the total creep strain being independent of the actual test temperature. As a result it was deduced that the total strain ε during creep under a given stress should be a function of temperature compensated time Θ = te-Q/RT where t is the duration of the test, Q the apparent activation energy, R the gas constant and T the absolute temperature. A number of creep tests conducted at two different temperatures verified the validity of this conclusion.


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