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This discussion summarizes the highlights of the C-141A airplane program, emphasizing fatigue, damage tolerance, and static strength considerations philosophically and in considerable detail where design criteria are involved. Dynamic considerations are also included insofar as the structural design of the airplane was affected thereby. Finally, some significant differences in criteria requirements between the C-141A and the C-5A are identified together with their expected impact on structural design.

The U. S. Army CH-47A Chinook is a transport helicopter developed by Boeing. Major considerations in the development of its structural integrity are discussed in this paper. Included is a description of fatigue analysis techniques which were developed to insure safe life of its critical components. This technique includes a mission profile, component fatigue strengths, use of top-of-scatter flight loads data, use of Miner’s rule of cumulative damage, and evaluation of possible anomalies on fatigue strengths and flight loads.

This paper discusses those materials that appear to offer the most promise for structural usage in high altitude/high temperature vehicles. Various aluminum-, titanium-, beryllium-, iron-, and nickel-base alloys are compared with respect to density, short time tensile, creep, fatigue, and fracture toughness properties. Their corrosion and stress corrosion characteristics as well as long time stability are discussed.

The advantages of an F-4C beryllium rudder are presented (torsional stiffness increased 500%, weight reduced 46%). Its analysis, design, fabrication, and ground tests discussed, and a fail-safe flight test program defined. Other potential F4C beryllium structural components within the state-of-the-art are reviewed and potential weight savings estimated.

The results of pump loop testing 50 candidate supersonic transport (SST) hydraulic fluids were presented to the May 1965, SAE Aerospace Fluid Power Systems and Equipment Conference in Los Angeles. This paper presents the results of subsequent pump loop testing of nine new fluids or compoundings. A discussion of simulated fire-resistance testing is also included. Results of pump loop testing to date indicate that four specific types of fluids are considered the best SST hydraulic fluid contenders. They are: chlorosilicone, mineral oil, perfluoroalkyl, and polyaryl.

High-temperature electrical materials presently available for application in the 500-1600 F range have been evaluated for advanced Rankine cycle systems and other high temperature applications. Magnetic materials for high saturation, low loss use include cobalt-iron and doubly oriented silicon-iron alloys. Nivco alloy (72w/o Co, 23w/o Ni and other alloying elements) has the highest creep resistance above 1000 F of all magnetic materials suitable for mechanically stressed applications. Inorganic insulations for magnet wire, flexible sheet, interlaminar coatings, potting compounds, and rigid or molded parts are discussed. Inconel-clad silver and clad and unclad dispersion strengthened copper electrical conductors offer the best performance in stressed and unstressed applications respectively.

This paper presents information compiled on the temperatures encountered by reentry and high performance aircraft, the metals and dielectrics useful for antennas and radome applications, and the effects of high temperature on the performance of these assemblies.

Coated refractory metals, coated and alloyed graphites, hafnium-tantalum alloys, refractory borides, and stabilized zirconias are considered for the 3600–4000 F high-velocity air environment. Only refractory borides and stabilized zirconias are indicated as offering long duration and reuse capabilities for such high-temperature utilization. Iridium, as coatings on substrates of either graphites or refractory metals, appears attractive for shorter times (less than 1 hr). Environmental evaluation and the need for a theoretical framework to enable the prediction of performance data for such materials are indicated to be major problems facing users and suppliers.

Candidate hydraulic fluids for systems which operate under extreme conditions vary considerably in properties and capabilities. Some compromise in fluid properties may be required but such compromise must not affect system reliability, safety and performance. This paper reviews the properties of the newer hydraulic fluid classes and their relation to maximum performance.

Considerations governing the selection of superalloys and refractory alloys for the fabrication of high-performance reentry vehicles are discussed. Oxidation resistant coatings were evaluated to determine their capacity to protect faying surfaces. The performance of the R-512A coating under simulated reentry conditions is reported.

This paper presents the results of a developmental program designed to determine physical and environmental effects on the response of balsa wood as an energy dissipator. Specifically, the effects of moisture content, density, temperature, and pressure on the energy dissipating characteristics of balsa wood are presented. It is shown that the response of balsa wood is critically dependent on physical and environmental conditions, and that the energy dissipating capacity of the material increases significantly under certain combinations of these conditions.

A series of new magnesium base casting alloys has been developed for high stress aerospace applications. The alloys are readily castable, have high strength, good ductility, and excellent fatigue properties. They show little or no tendency to microporosity and provide distinct advantages in control of quality. The alloys are based on the application of a new principle of heat treatment involving internal precipitation of hydride. Described in detail are ZE63A and ZE63B alloys.

TWO new ablative materials, designated SLA-741 and SLA-561, have been developed by Martin Marietta for Mars Lander thermal protection. The density range of these ablators is 0.18-0.22 g/cc and is substantially lower than that of other types of low density charring ablators. Plasma arc testing conducted in a simulated Mars atmosphere has established that SLA ablators are considerably more efficient than conventional ablators such as filled silicone, low density nylon-phenolic, or corkboard and that they form sturdy, erosion resistant chars.

New mechanical property data on the 62% Be, 38% Al alloy, “Lockalloy,” are presented and compared with other lightweight structural metals. The new data consist of tentative design properties for annealed sheet and provide a summary of its characteristics and properties. Material comparisons are made on the basis of gross fracture stress, an elastic weight index for compression critical structures, and on the basis of tensile strength/density and tensile yield strength/density ratios as a function of temperature for tension critical structures.

Newer concepts of thermal control coatings involving tailored optical properties are compared with the paints and coatings presently used on spacecraft. Emphasis is also given to evaluation and measurement techniques specifically dealing with the combined spatial environmental effects facility. Into a facility of the type both exposure and intermittant “in situ” optical measurements can be performed under an ultra high vacuum. A brief discussion of damage mechanisms is included along with a description of a computerized data retrieval system based on optical properties. Researchers in this aerospace field have high hopes for significant advances in the next several years through advanced materials and composites, “in situ” evaluation and measurement techniques, and computerized optical data retrieval for thermal control designers.

The following discussion outlines the applications of titanium technology to the XB-70 program, touching on alloy applications to solve specific design problems, and describing fabrication processes and sequences. A brief discussion of a space booster application, a sine wave welded crossbeam, is included. The discussion is concluded by the description of new titanium applications as diffusion bonded structure and as composite materials.

Emphasis on a new line of titanium mill products has been generated by programs such as SST and C5A. Also affecting these new products is the emphasis on fracture toughness and salt water toughness. These new products include close tolerance continuously rolled alloy sheet, large plate, and long extrusions.

Plasma arc welding produces butt-type joints satisfactorily in titanium as thick as 5/16 of an inch and in three common welding positions. The Keyholing technique accomplishes this in one pass. Without a filler wire addition this results in weld bead reinforcement that has slight undercutting at the weld edges. Undercutting could be prevented by filler wire addition or corrected by a second ‘wash’ pass. Much higher depth-to-width weld bead ratios and much higher welding rates can be achieved by plasma instead of by conventional welding methods. Tooling for plasma arc welding requires a deeper under-bead gap and wider holddown clearance than for conventional welding methods. Joint evaluation revealed excellent results. X-ray quality was defect-free (“water-clear”). Joint strength approximated 100% for mill-annealed material. Joint ductility was also high relative to parent material. This was established by Elongation and by Bend Radii determinations relative to parent material.

The design and fabrication of an experimental titanium crossbeam is described in this paper. The purpose of the program was to develop advanced manufacturing technology applicable to the production of large titanium alloy structures. Specific areas of the full-size cross beam design were established as test specimens and were fabricated early in the program to assure a usable manufacturing process. The designs, tools, equipment, and processes utilized in the fabrication process are discussed. The 8Al-1Mo-1V titanium alloy used to fabricate the modified full-size crossbeams is weldable and is capable of production utilization to provide advanced structural development hardware.

Development of integrally heated draw dies and insulated die cases with a capability for accepting interchangeable die inserts greatly reduced problems of producing severely formed sheet titanium alloy airframe parts. Parts which were previously made in a multiple series of ambient temperature performing operations, followed by hot sizing, are now produced in less time than formerly required for hot sizing alone. High scrappage rates formerly encountered were reduced to the point of being negligible. Although stainless steel draw dies are expensive, their cost is still less than the combined costs of preforming tools and matched hot sizing tooling.