. eae yee eae’, Be a le Oe fe Male He . Pa 8 Me te - whe at aha tot at ete tate ver a me . et a we et ee ee Oe eee . ee te arene .* ete ww, , ones 6.4 FUSELAGE BENDING portion, but differ in tiis region from the Shot 9 curve. The peak posi- tive value is reached at approximately the same time, 0.18 sec, on all three shots; however, the Shot 9 curve swings negative earlier and reaches a considerably higher negative value. The response curve for Shot 9 is also more regular, having no secondary peaks in the first posi~ tive swing. Tne differences noted above are not unexpected if it is assumed that the fuselage vending stresses, at least initially, are primarily a function of the leads on the horizontel stabilizers. It was noted in paragraph 6.3 that after the first positive peak the horizontal stabinezative bending moment was ootained. ww. lizer Lending moment for Mike and King remained positive for a longer time than it did in Shot 9, and, further, in Shot 9 a considerably higher . os the curves for Mike and King are quite similar, especially in the early «eae. oie PL J " ho . . t ae! The aft fuselage bending moment measurements obtained at station 1040 on the B-36 aircfaft for the three shots are shown as superimposed time-history curves in Fig, 6.3. From the figure it can ce seen that The duration of the first positive swing of the stabilizer in Shot 9 was sufficiently short so that it was approximately in phase with the fuselage, thus helping to produce the large negative fuselage bending moment observed. The longer duration of the upload on the stabilizers during Mike and King shot retarded the downtending of the fuselage causing relatively lower negative bending moments. It is therefore concluded that the observed deviation repre~ ‘ sents no reason to cuestion the validity of the curves presented. 6.5 ACCELERATION The acceleration measurements made on the three different shots were not very similar, except for the undesirable high frecuency oscillations characteristic of impact loading. These high freauency oscillations are caused by the vibration of the particular structural member to ‘which the accelerometer is attached. The desired measurement is the net acceleration of this member, i.e., the over-all reaction of the aircraft at the accelerometer locaticn. If the reaction of the member is such that the net vertical acceleration is considerable in comparison to the virrational acceleration, it is possible to obtain the desired acceleration uy sraphically averaging the original curve. If the relative magni~ tude of the undesired oscillaticns is too great, the averaging procedure In Mike Shot the oscillations were of such 4 magnitude and frequency as to render the initial position of the traces unreadable, after the spurious oscillations diminished, the traces vecame readable and ylelded good data, The blast input on King Shot was too Low to provide acceleration data of value equivalent to Mike Shot, From an over-all standpoint, Shot 9 provided the best acceleration me.surements ocotained. The readable portion of the Mike acceleration data show that the nose, tail, end center of cravity accelerations were roughly in phase 0.4 eec after shock errivel, Gince in ‘‘ike Shot the blast wave struck the tail Lefore the wines, one could expect a nitching motion to result. If this did oceur (acceleration 7ita ere unavailable), the motion damped eee eee ° e e 9 ® ettosthhgey 9 pw is imrossible or at vest questionable.