[en] The fiber-wound composite cylindrical shell has the characteristics of simple structure, high specific strength, high specific rigidity, strong design and high bearing capacity, and is widely used in pressure vessels, aviation, aerospace and military industries. At present, the cylindrical shell we use usually consists of a small angle layer and a circumferential layer, after the small angle layer is wound and formed on the core mold, it needs to be de molded into the initial test piece, and then subjected to large tension secondary winding forming, improper design is likely to cause entanglement instability problems. In this paper, the Ritz method theory is used to derive the stability equation of the small-angle layer shell, and the critical instability pressure and the prestressing force are obtained, then the initial test piece lay-up structure is given in combination with the actual winding process, and the material parameters and cylindrical shell are also carried out, the influence of wall thickness factors on critical instability pressure. This study provides theoretical support for the rational design of fiber-wound composite cylindrical shells. (authors)

[en] The carbon fiber composite cylindrical shell are composed of spiral winding layer and hoop winding layer, for researching the spiral winding layer stiffness degradation rule of the carbon fiber cylindrical composite shell with rotating load, based on the thin-shell theory, the analytical expressions for the model frequency of the cylinder are derived by creating the differential equations for the shell and then per 50 s^-1 velocity increased test is designed to getting frequency change rule after test by experimented, at last the results of spiral winding layer stiffness degradation rule is obtained by theoretically analysis agrees with the frequency change rule, and the others material parameters have no change. We should take stiffness degradation into account when designing the carbon fiber cylindrical composite shell with rotating load. (authors)

[en] Composite is widely used owing to its excellent stiffness and strength performance. For rotating machine, in order to satisfy with structural stiffness and strength, the composite cylindrical shell is usually composed of spiral wingding layer and hoop winding layer, it gives rise to mechanical anisotropic which is different from that of metallic material, so that the difficulty of the structural design optimization is highly increased. Based on the thin-shell theory, the expressions of multilayer composite cylindrical layer stress are derived, and the effects of some factors such as the material parameters, layering system, winding angle, thickness of cylinder are studied. The results obtained can be applied in optimization design on the composite cylindrical shell of rotating machine. (authors)

[en] Bellows is an important connected part of flexible rotor. One of the important performance parameter of bellows is bending stiffness. It is difficult to measure bending angle because expansion joint of bellows is small and deformation is tiny under load. So it is essential to study the measuring method of bending stiffness of bellows for good test. Three measuring methods of bending stiffness of bellows are method of axial loading, method of the horizontal support and method of static vibrational excitation. It is concluded that the method of axial loading is fit for measuring bending stiffness of bellows in flexible rotor by studying. (authors)

[en] In this paper, based on the equivalent simulation method, the equation of bending for the composite cylindrical shell that under the rotating state with the coupling of tension and bend (shear) is founded by the theory of plates and shells. It is considered that the bending of composite cylindrical shell brought by the coupling of tension and bend (shear) is so wee that the effect of the coupling of tension and bend (shear) could be ignored when designing the laminate structure of composite cylindrical. (authors)

[en] The U-shaped bellows need not only lower bending stiffness, but also upper strength as flexible connected part in some machine. It is difficult to gain both performances by normal designing, so it is essential to study the relation of performance to structure and assembly of the bellows. The paper systematically researches on influence of bellows parameters, structure and assembly on performance of the bellows by using finite element method. In bellows parameters, the paper chooses height, width, thickness and radius of bellows. In assembly of bellows, it chooses assembly position and magnitude of interference. The paper has obtained rules of influence on performance of bellows by studying all these factors. It can offer theoretical direction for structure design and assembly of bellows. (authors)

[en] For the composite material cylindrical shell material properties test, usually using the material properties of the laminate test method, that is, in the composite cylindrical shell on the specimen for performance for performance testing, this method will destroy the integrity of the structure, so that fiber discontinuity, the greater the impact of the boundary effect, so that the test results deviation from the true value. In order to make the measured results as close as possible, the method of increasing the width of the sample is usually adopted, the increase of the sample width will increase the difficulty of the test, the increase of the sample width will also need to consider the influence of the curvature of the cylindrical shell itself. In order to solve the above problems, this paper designs the special equipment to rotate the composite cylindrical shell at high speed, and uses the special test equipment to measure the of the cylindrical shell in the axial and radial directions, and combined with the theoretical calculation, the mechanical properties of the fibre-wound cylindrical shell composite can be obtained. Compared with the traditional method, the method has the advantages of accurate test date, convenient sample preparation, no damage of the test pieces, and small external factors. (authors)

[en] Creep of a structure which runs for a long time is must be considered, and creep performance of material is also an important mechanical property. Usually, creep limit or creep-rupture strength is used as an index to judge the creep performance of material, but both of them do not apply to the rotor whose stress changes over time. A new and available creep performance index must be established to judge the rotor's reliability. The creep model is transformed into another form, and all models are mapped to a Cartesian coordinate system, so each point in the coordinate plane will present a creep model. Then all models will be calculated whose creep strain equal to design allowed value by finite element analysis. All these models will map into a straight line, and it will be used to determine the material creep performance. (authors)

[en] The disk rotor is one of the commonly used structure in mechanical system. The intensity design is based on 'ASME Rule for constructing of pressure vessel'. The rotor's hole in the center area with maximum stress meet such plastic strength criterion P_L ≤ 1.5 S_m. But in recent years a large number of engineering practice shows that the stress intensity criterion of pressure vessel is not suitable for the structure design of the disk rotor. Based on the elastic-plastic mechanics combined with FET, the stress distribution and the elastic and plastic limit speed of the rotating disk are calculated in the paper. Through the disk rotor's strength experiments the probability of the optimization of the criteria P_L ≤ 1.5 S_m is discussed. It is suggested that the yield area ratio can be used to judge strength failure of rotating disks. In the way, the structure strength design method of high-speed rotating disk is improved. (authors)

[en] High performance aramid fiber is a high strength, high modulus, low density and good wear resistance of high-tech fiber, has been widely used in aviation, aerospace, military and other fields. But aramid fiber is a high molecular organic synthetic materials, under the long time stress there may be viscoelastic deformation, namely creep occurs, once the creep larger, is bound to affect the stability of fiber composite structure size and performance may eventually lead to structural parts failure. Therefore, considered from the point of view of engineering application, the aramid fiber to carry out study on creep properties is very necessary, the aramid fiber impregnated yarn creep properties under long term high were tested and analyzed by the suspension manual measurement method, the result show that aramid fiber in high load with high ability anti creep, 10 months creep deformation is less than 0.1% and with the extension of time, the creep basically unchanged. The influence of creep properties on the structure of aramid fiber can not be considered in practical application. (authors)