A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continua and their flexural deformations are represented by a series of admissible functions. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Application of the general formulation, illustrated through several typical MRMS configurations of practical importance, reveals complex interactions between vibrational and librational degrees of freedom, in the presence of MRMS maneuver, over a range of system parameters and initial conditions. Effectiveness of the formulation is also demonstrated through another illustrative example of the SCOLE configuration representing the Shuttle based flexible beam supporting a rigid reflector plate at its end.
An experimental investigation has been carried out to study acoustic interferences in vortex-shedding from a heated circular cylinder in a crossflow subjected to the acoustical vibrations whose direction is normal to the axis of the cylinder, and in particular, to inspect the appropriateness for the Reynolds number (Re*) used the fluid kinematic viscosity in the film temperature. The results indicate that the acoustic frequencies which produce powerful effects on vortex-shedding from the heated circular cylinder correspond to the frequencies of laminar-turbulent transition wave in a separated shear layer from an isothermal circular cylinder over the Re* range. The effects of the acoustical vibrations are similar to the effects of the acoustical vibrations directed along the axis of the cylinder on the vortex-shedding, and their vibrations bring the vortex region formed in the wake close to the cylinder surface, and increase the spanwise correlation of the wake.
Experimental approaches to free-edge delamination onset and growth are presented in combination with strain energy release rate calculations. Crossply and quasi-isotropic carbon-epoxy laminates are subjected to tension-tension and compression-compression fatigue loads and the interfaces at which delamination took place are compared with those recently predicted by the authors. The excellent correlations between analytical predictions and experimental results show the existence of loading direction effects and initial defects. Next, quasiisotropic carbon-epoxy laminates (45°/-45°/0°/90°)s with different thinckness have been tested under static tensile loads. The delamination onset strains of the laminates with and without detectable initial delaminations are measured and used to calculate the energy release rates as a function of the delamination length by a finite element method, and the length of undetectable initial defects is obtained. Finally, the static tensile test of carbon-epoxy laminates (±θ°/0°/90°)s and (0°/±θ°/90°)s where θ=25, 35, 45 with initial delaminations simulated by inserted thin films has been conducted to obtain the critical strain energy release rates. And the contribution of opening and shear mode energy release rates on the delamination onset are studied.
The rough criterion for the ground or air resonance of helicopter rotor with three or more blades, which was presented by Donham et al. in 1969, is simple and useful. The theoretical basis is however not so clear. It is the purpose of this paper to assign some theoretical reasons for the criterion. The Coleman's theory is reviewed, and then a concept of “Quasi-Resonance-Center” is defined. Then it is found that the “Resonance Region” designated by Donham et al. is the above “Quasi-Resonance-Center” and nothing but.