Title: DESIGN OF AN INSULATOR WHICH MUST SURVIVE HIGH g-FORCES

During the 3-year period of 1987 through 1989, the Advanced Shield Phenomenology Program included a research and development effort, with both experimental work and analytical support, to design a low weight, survivable shield against a stainless steel projectile at low earth orbit velocity. The specific threat used was a 1.75 gram, length to diameter ratio of one, stainless steel cylinder. The impact velocity was {approximately}7 km/s. Testing was performed at the Arnold Engineering Development Center, Arnold Air Force Base, Tullahoma, Tennessee. Sixteen shield configurations were tested. The Hull hydrocode was used for detailed analysis of five impact configurations. A successfulmore » shield was designed, which had a stainless steel front and back plate and 15.24 cm of carbon felt disrupter. The success of this configuration against the stainless steel threat was repeated. In comparison with the solid homogeneous aluminum shield necessary to stop the same threat, the layered shield developed has an areal density (mass per unit area) of 15.7% of the solid aluminum shield. Six conclusions of particular interest from the stainless steel work are summarized briefly as follows: the yaw angle of a cylindrical projectile at impact has a significant effect on shield survivability; areal density alone may not be enough to adequately model front plate behavior; thickness and material should be considered as separate variables; stainless steel very possibly is more damaging than can be accounted for by its density alone; a double-layer front plate produced no significant change in survivability; analytical results and test results are overall in excellent agreement; and hydrocode analysis is a useful tool in design and development of hypervelocity shields. 10 refs., 31 figs., 9 tabs.« less

The project has as its original focus the high temperature behavior of 2.25 Cr-1 Mo steel, heat treated to produce a predominantly bainitic microstructure and the load carrying response of components made of this material. Experiments were carried out on uniform and notched specimens under both steady and cyclic loading using specially acquired electromechanical test machines. It emerged that a very important feature of mechanical behavior under the conditions of interest was the strong tendency of this material to cyclically soften, particularly at high temperature in the creep range, giving the illusion of a severe creep-fatigue interaction under certain conditions.more » This finding led to a significant component of the project being devoted to investigation of the effects of local, as opposed to generalized, cyclic softening, and the implications this phenomenon might have on the setting of allowable design stress limits. The format of this report is as follows: The second chapter is a review of the work carried out in approximately chronological order under the headings of work was carried out under the following: (1) 2.25 Cr 1 Mo Steel -- Elevated Temperature Fatigue and Environmental Effects; (2) Preliminary Studies of Advanced Austenitics; (3) A Uniaxial Constitutive Model for Cyclic Softening; (4) The Iso-Cyclic Stress-Strain Approach to Evaluation of Components in Cyclic Softening Materials; (5) Testing of High Temperature Austenitic Alloys; and (6) Design Methodology for Aging Materials -- Application to Cyclic Softening. 65 refs., 39 figs., 7 tabs.« less

The project described in this report has, as its beginning, two investigations, the first a study of the effect of material softening on the overall structural stability of complex components, and the second an evaluation of damage induced through cyclic loads combined with high temperature environmental effects. The initial work was carried out on one grade of 2.25Cr 1Mo steel, with the intention of extending the investigation to other grades once the investigative techniques had been settled. However, considerable interest has grown in the application of modified forms of austenitic steel to very high temperature use in superheaters and reheaters.more » The ability to utilize these materials can mean an increase of 100{degree}C in the top temperature in a power plant, which converts into a significant improvement in thermal efficiency for a very small investment in material. Therefore, the direction of this project has been modified to continue on this class rather than the ferritic alloys originally under consideration. The basic problem to be investigated in the austenitics is the concern for possible strength variations, either positive or negative, induced in the very complex microstructures by service conditions of cyclic load and high temperature. 23 refs., 31 figs., 6 tabs.« less

The design criteria are presented for a multichannel telemetry system to provide data for the reliability assessment of a major electromechanical system to be used in a high g flight environment. Included is a set of detailed procedures for designing an FM/FM telemetry system capable of optimum performance when operating close to the signal-to-noise threshold of the receiver. The theory supporting this design is also presented, along with the details of the theory of the associated pre-emphasis of multichannel FM signals. The application of the design procedure imposed by this philosophy is illustrated by inclusion of a telemetry design tomore » meet the electrical, environmental, and mechanical requirements of an actual telemetry system under development.« less