A brief study of delayed fracture in a seam-welded titanium panel is summarized in this memorandum. Examination of the fracture surface with electron microscopy showed that the material cleaved, failing in a brittle manner. Although the nature of the embrittlement was not clearly defined, titanium hydride phase was suspected as a prime contributor to failure. Even though the hydrogen content of the titanium was only 65 ppm, hydride embrittlement was thought to have occurred from precipitation of hydride platelets on crystal planes oriented normal to welding stresses. Other work, briefly discussed in the memorandum, has confirmed that hydride platelets in titanium can be oriented by stress and that tensile ductility of Zircaloy (which behaves similarly with respect to hydrogen, to titanium) depends upon hydride orientation. Stress-relief annealing of welded titanium structures is recommended wherever possible to minimize embrittlement by stress-oriented hydrides. (Author).

This memorandum supplements and augments information presented in DMIC Memorandum 178 (AD-422 463). In the present report, Neuber's stress equations are rewritten entirely in rectangular coordinates. In addition, numerical results have been extended to include the stress distribution around an indefinitely sharp crack. It is also shown that the stress function used in a British work for an indefinitely sharp crack yielded identical numerical results, even though the stress function was of a different type than that employed by Neuber. The Von Mises relation was chosen to delineate the area around a crack in which plastic flow is occurring. The numerical tables in this memorandum give values for the function of plane stress as well as one possible interpretation of plane strain. Values of the hydrostatic stress variant are also given for both plane stress and plane strain. (Author).

A review of machining damage effects in beryllium was made. Surface damage is caused by twinning and microcracking as a result of various machining operations. Twinning is a result of surface working while microcracks initiate at intersections of twins and grain boundaries, at twin-matrix interfaces, at impurity particles, and in heavily twinned regions. These phenomena may be due to residual stresses in wrought products as well as machining parameters such as tool type, feed, and speed and depth of cut. The loss of mechanical properties due to machining damage is reviewed. Also presented is a study of surface damage actually encountered with machining of the shingles for the Gemini spacecraft.

The memorandum summarizes the available information on the compatibility of liquid rocket propellants with prominent materials of construction. Fuels and oxidizers of current interest are discussed. The corrosion data which are presented will apply to storing, handling, and control equipment outside of missiles and to missile components excluding combustion chamber. The compatibility of materials with reaction products in combustion chambers, nozzles, etc., is not considered. Included in the summary are data for many nonmetallic materials. The memorandum is subdivided into sections according to the propellant. Each material of construction is rated for a given medium as belonging to one of four classes, based primarily upon corrosion resistance. Consideration also is given to such factors as catalytic decomposition and sensitivity to impact.