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Simulated turbine blades were subjected to transient and steady-state heating and spanwise loading in a Mach 1 burner rig. Leading-edge cracks were produced which were similar to thermal-fatigue cracks observed during engine service. Crack initiation and propagation data were obtained for a variety of test conditions. The simulated turbine blades consisted of coated and uncoated IN 100 and B 1900 cambered airfoils with grips for application of spanwise load to simulate centrifugal stress. Test variables were blade temperature, spanwise load, and steady-state (hold) time. The Mach 1 gas velocity substantially reduced conventional creep rupture life. This caused a substantial reduction in thermal fatigue life. Coating effectiveness was below that for low velocity tests.

Efficient storage of propellants (especially cryogenics) in space for more than a few hours will generally require the use of multiple foil insulation and/or shadow shields. The practical problems involved in applying both foil and shadow shields, and the current state-of-the-art are discussed. Performances in both an Earth and space environment are given for various foil insulated systems. Realistic weight estimates, supported by some experimental data, indicate that foil, despite its application penalties, outperforms all other nonfoil insulations; also, that shadow shield systems can be extremely lightweight and definitely should be considered for future thermal protection systems.

This paper summarizes the results and findings of a program to design, develop, and evaluate actuator rod seals for use in advanced aircraft high-temperature hydraulic systems. The rod seals are intended to function efficiently and reliably for 3000 hr in the temperature range of -40-500 F. Preliminary studies of various material and design combinations showed that a polyimide low-pressure second-stage V-seal in a two-stage configuration had the greatest potential in long-term duty cycle testing in a simulated actuator test system. Modifications of this seal that provided for improved fatigue life and more efficient loading met the test objectives of 20 X 106 short-stroke cycles of operation at 500 F. Severity of this testing was equivalent to 3000 hr of duty cycle operation. The validity of design techniques used to achieve performance goals was shown.

The high-temperature capability and workability of cobalt-tungsten alloys for aerospace applications is discussed. The average life at 1850 F and 15,000 psi of the strongest previously reported alloy Co-25W-1Ti-1Zr-0.4C was doubled from 92 to 185 hr by small additions of chromium and rhenium. At 2200 F and 5000 psi the strongest alloy, Co-25W-1Ti-1Zr-3Cr-2Re-0.4C, had a rupture life of 23 hr; the elevated temperature rupture strength compared favorably with the strongest available conventional (high chromium) cobalt-base alloys. It is particularly significant that even the strongest alloys of this series were readily hot-rolled. Elongations as high as 31% were obtained at room temperature with annealed cold-rolled sheet specimens. The good ductility obtained suggests that these alloys could be fabricated into complex shapes required for various aerospace and other applications.

The fatigue behavior of several steels, AISI 4130, E52100, and 304 ELC stainless, as well as that of a nonferrous alloy, 5456-H311, was investigated in rotating bending fatigue after these materials were subjected to a prestress for different cyclic histories. The data obtained corroborated the hypothesis proposed by the authors that lines representing the S - log N relation of a material prestressed in varying amounts will intersect the S - log N line of the original material near a common point. A correlation was found between the stress at this intersection point and the ultimate tensile strength. Thus, the only requirements for establishing the fatigue behavior of a prestressed material in the range of stresses where the S -log N line is inclined are the S - log N line of the original material and the ultimate tensile strength. The importance of determining the new endurance limit of a material after prestressing was shown analytically.