THE RATIONALISM THEORY AND ITS FINITE ELEMENT ANALYSIS METHOD OF SHELL STRUCTURES

In this paper, a kind of rationalism theory of shell is established which is of different mechanic characters in tension and in compression, and the finite element numerical analysis method is also described.

SHAKEDOWN ANALYSIS OF SHELL STRUCTURES OF KINEMATIC HARDENING MATERIALS

It is of great practical importance to analyze the shakedown of shell structures under cyclic loading, especially of those made of strain hardening materials.In this paper, same further understanding of the shakedown theorem for kinematic hardening materials has been made, and it is applied to analyze the shakedown of shell structures Though the residual stress of a real stale is related to plastic strain, the time-independent residual stress field as we will show in the theorem may be unrelated to the time-independent kinematically admissible plastic strain field For the engineering application, it will lie much more convenient to point this out clearly and definitely, otherwise it will be very difficult. Also, we have proposed a new method of proving this theorem.The above theorem is applied to the shakedown analysis of a cylindrical shell with hemispherical ends. According to the elastic solution, various possible residual sfcss and plastic strain Jlelds, the shakedown analysis of the structure can be reduced to a mathematical programming problem.The results of calculation show that the shakedown load oj strain hardening materials is about 30-40% higher than that of ideal plastic materials. So it is very important to consider the hardening of materials in the shakedown analysis,for it can greatly increase the structure design capacity, and meanwhile provide ascicntific basis to improve the design of shell structures.

NONLINEAR BUCKLING ANALYSIS OF HYPERBOLIC COOLING TOWER SHELL WITH RING-STIFFENERS

This paper is concerned with a numerical solution of hyperbolic cooling tower shell, a class of full nonlinear problems in solid mechanics of considerable interest in engineering applications. In this analysis, the post-buckling analysis of cooling tower shell with discrete fixed support and under the action of wind loads and dead load is studied. The influences of ring-stiffener on instability load are also discussed. In addition, a new solution procedure for nonlinear problems which is the combination of load increment iteration with modified R-C are-length method is suggested. Finally, some conclusions having important significance for practice engineering are given.

FINITE STRIP DYNAMIC ANALYSIS OF CYLINDRICAL SHELL SANDWICH STRUCTURES

A rectangular, singly curved and finite strip element for curved sandwich dynamic analysis is developed. The convergence and speed of the method, the strip element density and the reduction of the degrees of freedom etc . are discussed through free vibration analysis of a honeycomb cylindrical shell pan-el. The results show that the frequencies and modal shapes obtained agree very well with the analytical solutions for the symmetrical honeycomb sandwich under the simply supported end conditions.

ENDOCHRONIC ANALYSIS FOR COMPRESSIVE BUCKLING OF THIN－WALLED CYLINDERS IN YIELD REGION

The longitudinal compressive buckling of long and thin-walled cylinders in yield region is analyzed with the incremental and finite forms of the endochronic constitutive equation, respectively. The relations between the critical stress σ_(cr)versus the ratio of R (the radius) versus h (the thickness of the wall) are derived. The critical stress of the thin-walled cylinders made of abuminum alloys AMГ and 1T are analyzed and compared with the experimental data and the analytical results based on traditional theory of plasticity. It is seen that. except that the σ_(cr) of the cylinders made of 1Tpredicted by the finite form of the endochronic theory seems a little more conservative than that by traditional deformation theory of plasticity, in most cases, both forms of the endochornic constitutive equation provide more satisfactory results.

Isogeometric cohesive zone model for thin shell delamination analysis based on Kirchhoff-Love shell model

We present a cohesive zone model for delamination in thin shells and composite structures.The isogeometric(IGA)thin shell model is based on Kirchhoff-Love theory.Non-Uniform Rational B-Splines(NURBS)are used to discretize the exact mid-surface of the shell geometry exploiting their C 1-continuity property which avoids rotational degrees of freedom.The fracture process zone is modeled by interface elements with a cohesive law.Two numerical examples are presented to test and validate the proposed formulation in predicting the delamination behavior of composite structures.

Time-domain analysis for vibration and sound radiation of submerged spherical shell excited by force

The vibration and sound radiation of a submerged spherical shell are studied in the time-domain by Laplace transform method, where a CW pulse force acts at the apex of the shell. The numerical results for the case of long pulse show that the different vibrational modes and the resonant or beat radiated sound are excited for different carrier-frequencies, but litle sound is radiated for some vibrational modes. For the case of short pulse the waveforms of the pulse become widened and deformed, when the pulse propagates between apexes of the shell. Then, the Doubly Asymptotic Approximations (DAA2) and Kirchhoff's Retarded Potential Formulate (KRPF)are used to solve the same problem. It is shown that the results of DAA2 and KRPF method have a good agreement with the results of Laplace transform method.

One-piece coal mine mobile refuge chamber with safety structure and less sealing risk based on FEA

In order to reduce the risk of sealing and improve the structural strength for a coal mine mobile refuge chamber,a new type of one-piece model was designed.Mechanical and mathematical calculation performed an important role.Calculated according to statics and relevant contents,the structure had the same total volume as the traditional segmented structure,but had shorter length,wider width and greater height.Those prevented the structure from stress or deformation failure.Some reinforcing ribs with enough moments of inertia were welded in the external shell.Because of the one-piece structure,this refuge chamber reduced the risk of sealing which was a serious problem of segmented structure.Impact load with 300 ms duration and0.6 MPa over-pressure was settled.Explicit nonlinear dynamic analysis program was used to simulate the response of the refuge chamber.The maximum stress and the maximum displacement were obtained.The refuge chamber including blast airtight doors could meet the rigidity requirement.Weak parts of the chamber were the front and back end shell where bigger displacement values occurred than others.Thus,the calculation indicated that the refuge chamber could meet structural safety requirements.Based on the numerical analysis,suggestions were put forward for further resistance ability improvement.Only large inclined shaft with larger wellhead was suitable for this one-piece coal mine mobile refuge chamber.

Statistical energy analysis of rotating cylindrical shell’s cutting noise

It is difficult to study the contribution to total cutting noise of each sound radiator in cutting system by means of traditional theoretical or experimental methods. In this paper, problems associated with cylindrical thin shell 's cutting noise are studied by applying Statistical Energy Analysis of Non-Conservatively Coupled Systems under Correlative Power Input. Theory and techniques for parameter evaluation, cutting system modelling and other important problems concerned are also discussed. Results show that cutting noise is mainly from the sound radiation of workpiece in cutting process, and Statistical Energy Analysis can be applied successfully to the research of large cylindrical shell 's cutting noise.