The Dynamic Characteristics Of The Crack-containing Cylindrical Shell

In engineering practice, the thin cylindrical shell structure is mainly applied in corpus structure of airplane, rocket, submarine, in common, and also used in the structure component of other mechanical engineering, chemical engineering...etc. Because of the existing various structure deflections in the actual Components, these deflections are usually expressed for the macro-cracks and perhaps the micro-cracks. The existence of the crack not only result in the stress concentrating near the crack, make structure of the rigid degree and strengths lower, and will make the dynamic characteristic of the thin shell occur change, which will affect the thin cylindrical shell's service life, on the other hand will also affect the whole safety of equipments, causing the huge safe trouble and properties loss. Therefore, it is necessary to analyze the dynamic characteristic of the thin shell implying cracks. This thesis uses experiment combine the finite element method software ANSYS together to carry on the dynamic characteristic analysis of the thin cylindrical shell with axial and circular crack in different lengths.The main works of the thesis are finished as follows:1, Introduction of the finite element method;2, Introduce the basic theories of the thin cylindrical shell with the cracks, establish geometry function,physics function and equilibrium differential function through the analysis of tiny element balance and build up basic function of the thin cylindrical shell with axial and circular cracks;3, Experimental model shape and natural frequencies of the thin cylindrical shell with axial , circular and 45°oblique cracks in different lengths are analyzed through laser holography method;4, The relation of natural frequencies and model shapes between the crack length varied is drown from calculating natural frequencies and model shapes of the thin cylindrical shell with axial or circular cracks in different lengths with the software ANSYS, i .e, the influence of dynamic characteristic on the crack lengths varied;5, Under the effect of the y-direction force, responding of displacement-the frequencies and stress - frequencies were obtained from harmonic vibration analysis of the thin cylindrical shell with axial or circular cracks in different lengths.Through the calculation in above various circumstances, the relationships of the dynamic characteristic between the varied crack's lengths are obtained. It provides the theories and related data for the research on dynamic characteristic of the thin cylindrical shell with cracks, at the same time, also provides the analytical method and way of thoughts for the dynamic characteristic analysis of the other components imply cracks.