. The Bell System technical journal . step is to find a value of db such that a graph of P/db vs Xo/dbwill fall slightly above the curve ko = 30(0) in Fig. ; db must be greaterthan 2 inches, since that displacement was obtained in the a trial take db = inches and test it at one point, say the experi-mental point P = 300 lbs., x^ = | in. Then P/db = 133 and Xo/db = The point (, 133) falls below the curve ko = 30(0) in Fig. try db = inches. In this case, for the point P = 386 BELL SYSTEM TECHNICAL JOURNAL 300, .T2 = I, we find P/db =
. The Bell System technical journal . step is to find a value of db such that a graph of P/db vs Xo/dbwill fall slightly above the curve ko = 30(0) in Fig. ; db must be greaterthan 2 inches, since that displacement was obtained in the a trial take db = inches and test it at one point, say the experi-mental point P = 300 lbs., x^ = | in. Then P/db = 133 and Xo/db = The point (, 133) falls below the curve ko = 30(0) in Fig. try db = inches. In this case, for the point P = 386 BELL SYSTEM TECHNICAL JOURNAL 300, .T2 = I, we find P/db = 120, = .35. This falls slightly above theko — 30(0) curve as required. The whole experimental curve is thenplotted to the coordinates vs .V2 and is found to fit as closely asnecessary. Hence the parameters are adopted as ^0 = 305, db = We can now calculate the maximum acceleration that the tube willreceive in, say, a three-foot drop test. First calculate, from equations (1)and (2), 2hW2 ^ /2 X 36 X ^ ^ 31. 2hko _ , / - ^N ^^^^^^^^^^ _ .. Then db/do = Entering Fig. 4 with this value we find G,n/Go = the maximum acceleration is: Grn = X = 57g. Finally, entering Fig. 5 with db/do = we find d,n/db = Hence themaximum displacement is dm = X = inches. This indicatesthat the load-displacement test was carried far enough to cover the rangeup to a three-foot drop. It may be observed that the results obtained, by treating the same dataas Class B or Class C cushioning, agree within a few per cent. This isbecause, in the example chosen, both B and C curves can be made to fit theexperimental load-displacement curve. Consequences of x\brupt Bottoming (Class D)It is useful to examine cushioning systems that can bottom more abruptlythan Class C cushioning. Abrupt bottoming is possible, for example, in atension spring package lacking a snubbing device. An estimate of theincrease in acceleration can be made by s
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