,~ study was made of t he creep behavior in tensio n at 300 0 700 0 900 0 and 1 200 0 F of initi, !I y annealed high-purity nickeL Discontinuous flow was dbsel' v~d in ~ach of' the three stages of creep, and . it was affected by ~e mperatu~'e, s train rate, and prior-strain hi stor y. Th e phenomenon of s tram aglllg was especially promlll ent at 300 0 F as manifested by t he attainment of an appreciable creep life in specimens stressed in excess of the te ns ile streno-th at this temperatur~. The experimentall'esults are analyzed in terms of t he past and prese~ t theories of deformat IOn of metals. Stralll hardenlllg, recovery, and t he initiation , propagation , and types of fractures obtamed dunng creep are further evaluated by means of true-stress-truestrain and hardness data obtained at room temperature and by metallographic examination of the fractured specimens.

Short-time tensile tests were m ade at temperatures ranging from 75 0 to 1,700 0 F on high-purity nickel, copper, a 70-percent-nickel-30-percent-copper alloy, and a 70-percenteopper-3 0-percent-nickel alloy. The high-purity component metals and the two alloys were investigated in the initial conditions, as annealed for a uniform grain size, a nd as colddrawn 40-percent reduction in area. The results were affected m a rkedly by variations in the nickel content, temperature, and degree of cold-working. However, the effects of colddrawing at room temperature were obliterated at temp eratures above that of recrystallization.The effects of cold-drawing the 30 % -Ni-70 % -Cu a lloy differe nt amounts a nd of variatio ns in g rain size of the copper on the ten sile properties are evaluated. R es uHs on the tensil e properties of the same annealed materials at low temperat u res are included for completeness.

T ension tests were made at temperatures rangin g from -320° to 1,500° F on highpurit y nickel in t he annealed condition . Exception s to t he usual trend ex hibited by metals of decreasing strength and increasin g ductili ty with increasin g test temperature were observed and disc ussed . Stra in ag in g occlIJ'I'ed in specimens tested in the tempe rature ran ge of about 80° to 300° F, bu t recrystalli zation and recovery predominated in specimens fractured at ] ,200° and 1,500° F.

All of the fuel tested in this program changed in octane rating as the pressure of the altitude chamber was decreased. In general, the fuels that were the most sensitive to altitude changes were those with the high9s.t se nsitivity to engil~e severity, as defined by the dIffer ences between thClr Motor Method and Researc~l Method rati!lgs. ~his is to be expected, as the hJgh er compreSSIOn ratIOs used at lower chamber pressures. increase the engine severity by raising the compr eSSIOn temperatures.It has been shown that decreased inlet temperature and decreased speed shift altitude ratings by the Motor Method toward their sea-level values, but at different rates for various fu els. Although th e effects of spark advance on this method were not investigated, a change in this factor might prove advantageous. Larger carburetor venturis have proved useful, and permit ratings to be maintained at about their ea-Ievel values up to altitudes to 3,000 to 4 000 ft. It is possible that the Motor Method rating~ are capable of being equalized throughout the altitude range by usc of a suitable combina tion of changed conditions.The Research Method, on the other hand do cs not lend itself well to modifications of this' type. fhe spark advanc.e is already nearly the optimum, mlet temperature lS at about the minimum that will assure adequate vaporization of the fuel the volumetric efficiency is improved very little by use of a larger venturi, and the engine speed is already very low.It appears, therefore, that the surest way of making the engine severity equal to that a t sea level, regardless of the altitude, is to sup ercharge the inlet and thro~t~e the exhau~t, thereby simulating sea-level conclttIOns. For thls purpose, a small single-sta,ge centrifugal compressor would probably suffice. The ail' would enter the blower through a standard humidity-controll ing ice towel', and thence through the s tandard air h eater to a pressurized carburetor. It is possible that an after-cooler may also be necessary to k eep the inlet temperature below 125 0 F in the R esearch Method at the lower chamber pressures..This investigation was carri ed out in cooperation wlth the Octane Correlation Advisory Committee of the Division of R efining of the American Petroleum Institute. Members of this committee arc: Bruno R. Siegel, chairman, Frank C. Burk, Carl E. Habermann, J . E. Taylor; associate members are Harold M. Trimble, H. R. Stacey , John M. Snell, Afton D. Puckett, and Hudson W. K ellogg. Appreciation is expressed to the committee members for planning th e scope of the work and their expert advice in car~'ying it o~t. Cred.it is also due th e following for thCJ.r work ltl operatmg the engines and alti tude eqll1pment: IV. C. Lacey, Myron C. Wolfe, Jame Creep tests we; e made at l10 0 , 250 0 , and. 300 0 F on a.nn~aled oxyge n-free high-conductIvIty copper .. lhe rate of 10adll1g to the ultImate had a slgn Ifl cant eff ect on t h e amount of plastic ext e nsIOn and t hereby affected the creep behavior. The strain rate durin g the so-calle...

A comprehensive study was made of the effec ts of notc h geometry on the mec hanical behavior of a duplex-annealed titanium-8 aluminum-1 molybdenum-1 vanadium all oy within th e te mperature range 75 to 1200 of (297 to 921 O K). Yi eld strength , tensile strength , and true stress at fracture increased with increase in notc h depth and decrease in notch angle and te mperature. The maximum strength (tensile and yield) properties were obtained for the cylindrical specim ens having a root radiu s of O.OI -inch. Gen erally , th e increase in tensile propertie s was ac co mpani e d by a decrease in red uc tion of area values . The mi cros tru ctures and the initiation and propagation of fra cture of the spec imens were affected by th e notch geo metry and test temperature.