C. Morita

Fundamental vibration of rotating cantilever blades with pre-twist

Abstract A non-linear strain–displacement relationship of a pre-twisted conical shell on the general shell theory is utilized, and a method for vibration of a rotating cantilever conical shell with pre-twist is developed by the principle of virtual work and the Rayleigh–Ritz method. Firstly, deformation and stress resultants caused by rotation are analyzed. Secondly, an equilibrium of energy for vibration of a pre-twisted conical shell having the conditions achieved in the first process is given and then an eigenfrequency equation of a rotating cantilever conical shell with pre-twisted is formulated. The effects of parameters such as an angular velocity, a radius of a hub, a setting angle, a twist angle, a subtended angle and a tapered ratio of cross-section on the fundamental vibration are investigated.

Vibration of twisted laminated composite conical shells

Abstract A methodology for free vibration of a laminated composite conical shell with twist is proposed, in which a strain–displacement relationship of a twisted conical shell is given by considering the Green strain tensor on the general thin shell theory, the principle of virtual work is utilized, and the governing equation is formulated by the Rayleigh–Ritz procedure with algebraic polynomials in two elements as admissible displacement functions. The convergence, the accuracy and the validity of the methodology are verified by comparisons. As a result of the vibration frequencies and mode shapes, the effects of the laminated constructional and the geometric parameters, such as the number of laminae, the fiber orientation angles, the twist angle, the subtended angle and the taper ratio, on the vibration characteristics are studied by the present methodology.

Vibration analysis of rotating twisted and open conical shells

Abstract Based on a non-linear strain–displacement relationship of a non-rotating twisted and open conical shell on thin shell theory, a numerical method for free vibration of a rotating twisted and open conical shell is presented by the energy method, where the effect of rotation is considered as initial deformation and initial stress resultants which are obtained by the principle of virtual work for steady deformation due to rotation, then an energy equilibrium of equation for vibration of a twisted and open conical shell with the initial conditions is also given by the principle of virtual work. In the two numerical processes, the Rayleigh–Ritz procedure is used and the two in-plane and a transverse displacement functions are assumed to be algebraic polynomials in two elements. The effects of characteristic parameters with respect to rotation and geometry such as an angular velocity and a radius of rotating disc, a setting angle, a twist angle, curvature and a tapered ratio of cross-section on vibration performance of rotating twisted and open conical shells are studied by the present method.

Vibration analysis of twisted conical shells with tapered thickness

Abstract Considering twisted conical shells with tapered thickness, a numerical method for analyzing free vibration is developed, where an exact strain–displacement relationship of twisted conical shells is derived based on the shell theory, the equation of energy equilibrium for free vibration is formulated by the principle of virtual work, and the governing equation is obtained by the Rayleigh–Ritz procedure. The convergent property is investigated in view of the assumed displacement functions, and the comparison between the present and the available previous results for several typical conical shells is carried out in order to demonstrate the practicability and the accuracy. The effects of the tapered thickness in two directions, the twist angle, the subtended angle and the taper ratio of cross-section on the vibration behavior are discussed through the frequencies and corresponding mode shapes.

Buckling of Thin-walled Cylinder Shell Specimens with Cut-out Imperfections

In this paper, effects of imperfections on the buckling behaviours of aluminium thin-walled cylindrical shells under compression are investigated by experimental and numerical methods. The imperfections are produced by one or two circular cut-out on the shell surface. Recently, a lot of numerical analysis have been carried out by using cylindrical shell with imperfections. However, there are a few experimental substantiations. Furthermore, the combined effect of two circular cut-out on the buckling load of cylindrical shell is not treated from experiment point of view. In this experiment, Digital Image Correlation Method (DICM) was used to obtained 3D displacement and strain data of the specimens during the test. Numerical simulations are also calculated. In this study, the difference between them and the effects of parameter on the buckling load of specimens are also discussed. It is shown that the experimental and finite element (FE) analytical results combine well. Moreover, the effects of imperfections found to be sensitive to the buckling load of specimens.