In this report, the gust responses of a threedimensional elastic wing are investigated theoretically and experimentally, where the two kinds of gust, sinusoidal gust and random gust, are treated. It is assumed here that the deformation of an elastic wing is generated by bending moment and torsional moment which act on a wing independently. First, for the responses to the sinusoidal gust, the modes of deformation are calculated applying the modes of natural oscillation of a cantilever beam. The results of calculation agree well with the experimental values. Next, the frequency transfer functions of deformations by bending moment and torsional moment are obtained for the random gust responses. In this case, the phase difference of the gust along the wing span is taken into consideration. The calculated results agree well with the experimental results.
Water impact accelerations of axially symmetric bodies are analyzed considering the flexibility of the bottom surfaces. The bottom surfaces considered are spherical shells. Four equations are derived to express this phenomenon. These are the equation of the motion of the bodies during water impact, the equation of the area of the bodies in the undisturbed water surface, the equations which give the pressure distribution on the bottom surfaces, and the vibrational equation of the spher- ical shells. These four equations are solved numerically and the results are shown in graphical forms. The water pressure on the spherical shells is given by adding the pressure due to the velocity change and the expanding area of the body in the undisturbed water surface and the pressure due to the vibrational motion of the shells. The equation expressing the hydroelastic interaction between the vibrational motion and the water is derived by applying the method to write the velocity potential Φ on one side of an infinite plane (z=0) in terms of the value of Φ at points of this plane11). The maximum accelerations calculated considering the interaction are much larger than the values obtained considering the bottom surface as rigid or neglecting the interaction. The analytical results including the hydroelastic interaction also show that the period observed in the acceleration curves is much longer than the free-vibrational period of the bottom surfaces.
The experimental results on the water impact accelerations of axially symmetric bodies are presented in this paper. The bottom surfaces of the models were the flexible spherical shells made of PMMA and expected to have much interaction with the fluid. Three types of the models, whose bottom thicknesses were 4.0mm (S-6), 2.5 mm (S-7), and 1.8mm (S-8), were used and these bottoms had the same radius of curvature. A model (S-5) made of acetal copolymer whose bottom was thick was also used to compare with these three models. The bottom of this model could be considered very rigid and to have little interaction with the fluid. The experimental results on the water impact accelerations were compared with the author's analysis. The analysis explained qualitatively the experimental phenomena very well.
Using the seamless specimen made of PMMA sheet by a vacuum-forming process at elevated temperature, an experimental investigation on tne buckling of imperfect truncated conical shells under axial compression is carried out. The imperfection implies here that the thickness of specimen is uniform in the circumferential direction and varies nearly linearly along its generating line. It is shown that the empirical formula given by WEINGARTEN et al. can be used conservatively in the design of imperfect truncated conical shells mentioned above representing their thickness by the mean value, and the initiation and propagation of buckling deformation are discussed. too.