Free body diagrams of arm segments show what forces are involved in planar motions. To represent equilibrium D'Alembert's principle is applied in graphical vector diagrams. From these diagrams are derived equations for determining joint force and torque reactions to weight and inertia. The equations make it clear that accelerations and physical constants are needed. A graphical vector acceleration diagram shows how linear accelerations can be determined from angular accelerations, derived in turn by finite differences from displacement time data. Experimental methods of determining kinematic data and constants are described. The analysis rationale is then used to establish an algorithm for programmed computation by digital computer. The output information is presented in a sample set of curves for one of the several types of motions treated.
An important use of shock spectra is to make estimates of the maximum responses of linearly modeled multidegree-of-freedom structures to shock excitations. In this paper a lower-bound estimate to complement a well known upper bound on such a maximum response is proposed and examined. The conditions under which the estimate is a lower bound are delineated. The set of bounds is applied to an examination of the performance of two maximum response estimators in current use, the root-mean-square, and one which is a function of the root-mean-square and dominant mode. The results of an empirical study show that the estimators do not perform well except when the bounds are close together.
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AbstractThe behavior of pressure fluctuations measured on the airframe of a prototype high lift jet transport (YC-14) is presented. Efforts to characterize the data in terms of a modest number of parameters, and, resulting prediction procedures are described. Comparisons with near field engine exhaust noise of a conventional jet ,transport (Boeing 747) are presented. The results suggest that the same two exhaust noise sources are important for both aircraft types. The results also suggest a consistent frequency sensitivity a s well a s level sensitivity to airplane velocity. The frequency result appears to be new. -AFFDL ALT C ' . mb DH NASA Ni s SFP STOL TBL USB V G S VA,VA,P ' j Vmm vo 8 p,,, Nomenclature = Air Force Dynamcs Laboratory = Airplane altitude = Sonic velocity at nozzle throat = Sonic velocity of ambient air = Nozzle hydraulic diameter = National Aeronautics & Space Administration = Engine fan speed = Downstream distance of field point = Surface fluctuating pressures = Short takeoff and landing I Turbulent boundary layer = Upper surface blowing = Vortex generators = Airplane velocity * Jet velocity, ideally expanded = Jet exhaust mixed velocity = Reference velocity (250 MeterdSec.) = Distance between point of closest approach of flow stream to field point and field point = Jet exhaust mixed density P O Or, USB 8 , 8' = Reference density (sea-level ambient air) = USB flap angle = Thrust flow turning angle = Flow idealization ribbon angle
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