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Roll-welding attachment for robot simple, inexpensive device incorporating modified commercial resistance-welding gun. Modified welding gun easily attaches to end effector of robot. Robot applies welding force and moves electrode wheel along prescribed path. Resistance-welding current starts and stops automatically according to force exerted against workpiece. Used to apply brazing foil to workpiece.
A simulation of a Boeing 727 aircraft during acceleration on the runway is used to determine the effect of windshear on stopping distance. Windshears of various magnitudes, durations, and onset times are simulated to assess the aircraft performance during an aborted takeoff on five different runway surfaces. A windshear detection system, active during the takeoff roll and similar to the Honeywell Windshear Detection System is simulated to provide a discrete system to activate aircraft braking upon shear detection. The results of the simulation indicate that several factors effect the distance required to stop the aircraft. Notable among these are gross weight, takeoff flap position, runway characteristics, and pilot reaction time. Of the windshear parameters of duration, onset and magnitude, magnitude appears to have the most significant effect.
The results of a two year study of the mechanisms of spall failure in the HPOTP bearings are described. The objective was to build a foundation for detailed analyses of the contact life in terms of: cyclic plasticity, contact mechanics, spall nucleation, and spall growth. Since the laboratory rolling contact testing is carried out in the 3 ball/rod contact fatigue testing machine, the analysis of the contacts and contact lives produced in this machine received attention. The results from the experimentally observed growth lives are compared with calculated predictions derived from the fracture mechanics calculations.
Roller element bearings provide the primary mechanical interface between rotating and nonrotating components in the high performance turbomachinery of the Space Shuttle Main Engine (SSME). Knowledge of bearing behavior under various loading and environmental conditions is essential to predicting and understanding the overall behavior of turbopumps, including rotordynamic stability, critical speeds and bearing life. The objective is to develop mathematical models and computer programs to describe the mechanical behavior of ball and cylinder roller bearings under the loading and environmental conditions encountered in the SSME and future high performance rocket engines. This includes characteristics such as nonlinear load/motion relationships, stiffness and damping, rolling element loads for life prediction, and roller and cage stability.
The uniform geometrical theory of diffraction (UTD) concept is used to predict the scattered fields in the target zones of compact-range blended rolled-edge reflectors. Since the necessary diffraction coefficients are not known in a closed form, a numerical method to calculate the diffraction coefficients is described. In the numerical method, the problem is reduced to two dimensions, and physical optics line integration is used to compute the diffraction coefficients. Thus, the method is computationally efficient. The method is used to analyze two compact-range reflectors. The results obtained using the numerical UTD show good agreement with the scattered fields obtained using a corrected physical optics surface integration.
The present paper describes a transient translating elastoplastic thermomechanical finite element model to study two-dimensional frictional rolling contact. Frictional two-dimensional contact is simulated by repeatedly translating a nonuniform thermomechanical distribution across the surface of an elastoplastic half space. The half space is represented by a two-dimensional finite element mesh with appropriate boundaries. Calculations are for an elastic-perfectly plastic material and the selected thermophysical properties are assumed to be temperature independent. The paper presents temperature variations, stress and plastic strain distributions and deformations. Residual tensile stresses are observed. The magnitude and depth of these stresses depends on (1) the temperature gradients and (2) the magnitudes of the normal and tangential tractions.
A lumped parameter model of a single-stage rotor system is developed which includes a new mathematical model for precision rolling element bearings to clarify this issue quantitatively and qualitatively. A comprehensive bearing stiffness matrix of dimension six is proposed which clearly demonstrates the coupling between the rotating shaft and casing motion. An eigensolution and the forced harmonic solution are obtained numerically. The natural frequencies predicted are found to be in excellent agreement with a finite element model.
Hand-operated rolling spotwelder stitch-welds foil faster and more consistently than single-spotwelding gun without damaging it. Internal spring reacts against roller frame, exerting force on welding wheel when rollers contact workpiece.
Compact robotic wrist-joint assembly includes two motor subassemblies providing two concentric output rotations about axis of wrist: outer output flange on front face of assembly rotated to, and held at, any predetermined roll angle within range of plus or minus 180 degrees, and inner output flange concentric with outer output flange capable of unlimited rotation relative to outer flange. Each motor subassembly includes concentric rotor and stator and harmonic drive.
Robotic gripper using rolling-friction fingers closes in on object with interface designed to mate with rollers somewhat misaligned initially, aligns object with respect to itself, then holds object securely in uniquely determined position and orientation. Operation of gripper causes minimal wear and burring of gripper and object. Exerts minimal friction forces on object when grasping and releasing. Releases object easily and reliably even when side forces and torques are between itself and object.
Robotic gripper includes split-rail drive assembly that moves two gripping fingers toward or away from each other. Gripping fingers equipped with rollers mating with recesses and seating ramps on specially designed object. Similar in design and operation, to those described in "Rolling-Friction Robotic Gripper" (GSC-13261). Present gripper includes rotary tool operating on mechanism in gripped object.
A rolling joint is provided for obtaining slewing maneuvers for various apparatus including space structures, space vehicles, robotic manipulators, and simulators. Two noncircular cylinders, namely a drive and a driven cylinder, are provided in driving contact with one another. This contact is maintained by two pairs of generally S-shaped bands, each pair forming a generally 8-shaped coupling tightly about the circumferential periphery of the noncircular drive and driven cylinders. A stationarily fixed arm extends between and is rotatably journalled with a drive axle and a spindle axle respectively extending through selected rotational points of the drive cylinder and of the driven cylinder. The noncircular cylinders are profiled to obtain the desired varying gear ratio. The novelty of the present invention resides in using specifically profiled noncircular cylinders to obtain a desired varying gear ratio.
In response to the failure of a conical section of the Insat C satellite during certification testing, the use of beryllium for payload structures, particularly in sheet product form, is being reevaluated. A test program was initiated to study the tensile, shear, and out-of-plane failure modes of beryllium cross-rolled sheet and to apply data to the development of an appropriate failure criterion. Tensile test results indicated that sanding the surface of beryllium sheet has no significant effect on yield strength but can produce a profound reduction in ultimate strength and results obtained by finite element analysis. Critical examination of these test results may contribute to the modification of a JSC policy for the use of beryllium in orbiter and payload structures.
Ailerons described in references 1, 2, and 3, are summarized in the form of empirical equations which relate the aileron dimensions and displacements to the rolling, yawing, and hinge moments for pitch angles of 0 and 12 degrees, corresponding to angles of attack of the wings of 4 and 16 degrees, respectively.
Results are presented of a wind-tunnel investigation to determine influence of the fuselage and tail on static stability and rotary derivatives in roll of a model having 45 degrees sweptback wing and tail surfaces. The wing alone and the model without the horizontal tail showed marginal longitudinal stability near maximum lift. The longitudinal stability of the complete model was satisfactory. The vertical tail produced larger increments of rate of change of lateral-force and yawing-moment coefficients with wing-tip helix angle than the fuselage or the horizontal tail.
Damping-in-roll coefficients for a series of triangular plan-form wings and two rectangular plan-form wings have been obtained from supersonic-tunnel tests. The wings were mounted on a body of revolution and tested at Mach numbers of 1.62 and 1.92.
A simple method for calculating the characteristics of the Dutch roll motion of an airplane is obtained by arranging the lateral equations of motion in such form and order that an iterative process is quickly convergent.
An investigation of the rolling effectiveness at transonic and supersonic speeds of partial-span ailerons on a 42.7 degree sweptback wing having symmetrical circular-arc airfoil sections of 10-percent thickness ratio normal to the wing quarter-chord line has been made by means of rocket-propelled test vehicles. The results are compared with results of a supersonic wind-tunnel test at Mach number 1.9.