Collapse Of Shell Research Articles

Capillaria hepatica: Relation of structure and composition of egg shell to antigen release

Clean, nonembryonated Capillaria hepatica eggs recovered from infected liver tissue by physical methods as well as eggs obtained after passage through the mouse gastrointestinal tract were examined with the electron microscope. In eggs collected by physical methods the outer membrane showed defects where it was lacking at various points or disrupted. The pillars of the outer shell were frequently broken or fractured resulting in virtual collapse or separation of the outer shell from the inner shell. No shell matrix was observed in any eggs examined. Even more dramatic effects were observed in eggs recovered following passage through the mouse gastrointestinal tract. Clean, nonembryonated eggs collected by physical methods were suspended at 5 C in phosphate-buffered saline. A large amount of protein was released initially into the medium; the amount released then fell to a low level at which it remained for several weeks. Gel diffusion tests with concentrated protein supernatant and C. hepatica egg-derived antigen were compared using appropriate antisera. Bands of identity were present in both; however, egg antigen contained other proteins not present in egg supernatant. These studies indicate that during physical collection of C. hepatica eggs, sufficient damage occurs to allow for the release of materials into host tissue during experimental egg granuloma formation. An hypothesis is presented concerning the viability of C. hepatica eggs in host liver tissue following host cellular response and the possible modes of action which trigger development of eggs after release from infected liver.

Collapse of Long Cylindrical Shells under Combined Bending and Pressure Loads

The nonlinear collapse behavior of long cylindrical shell structures subject to a bending load only or combined bending and uniform normal pressure loads is studied using the STAGS computer code. Two modes of nonlinear collapse are investigated to determine maximum strength. One mode of collapse is described by circumferential flattening of the cylinder cross section, while the other mode is represented by axial wrinkling in the region of maximum compression. Results compare favorably with available published data for cylinders loaded by pure bending, and results are presented for combined loads which have not been previously reported. The collapse loads obtained in this study show that current design criteria are conservative except for a narrow range of length-to-radius ratios and pressures.

On some general variational principles for creep with applications to thin shells

A constitutive relation for a viscous material subject to small strains but finite rotations is postulated and associated variational theorems are formulated. These are similar to the principle of minimum of potential energy and the Hellinger-Reissner theorem of an elastic solid. The derivation of strain-displacement relations for thin shells subject to small strains but moderately large rotations are given. On this basis a mixed variational principle for thin viscous shells is developed. For the problem of creep collapse of long cylindrical shells under external pressure it is demonstrated that the mixed variational principle may be advantageous compared to other variational theorems. A comparison with the creep collapse theory of Hoff et al. is given.

Critical Velocity for Collapse of a Shell of Circular Cross Section Without Buckling

Many practical devices involve high-speed collapse of shells of circular cross section, In all of the devices the stability of the collapse motion is of interest and in some it is essential for successful operation. In this paper, the buckling motion of shells of circular cross section during high-speed collapse is analyzed and critical collapse velocities are determined for which the growth of initial nonuniformities by buckling during collapse is 10 and 100.

Formation of artificial top component from brome mosaic virus at high salt concentrations

In both 1.5 M NaCl and 1 M CaCl 2, brome mosaic virus (BMV) particles are unaffected at low pH but are degraded above a well defined pH value. The degradation into protein subunits and RNA occurs in two steps in both NaCl and CaCl 2. First, the RNA is released without collapse of the protein shell: the products obtained are RNA and artificial top component (ATC); in a second step, the ATC formed undergoes degradation into protein subunits upon further pH rise. The main difference between the action of 1 M CaCl 2 and 1.5 M NaCl is that, with CaCl 2, no intermediates of degradation were found between virus and ATC, while in NaCl, some particles underwent progressive degradation, yielding intermediate forms together with reassociation products and contaminated protein subunits.

Effect of time-varying external pressure on creep collapse of a cylindrical shell.

Effect of time-varying external pressure on creep collapse of a cylindrical shell.

Analysis of the Collapse of Cylindrical Shells Using High-Speed Photography

The primary load-carrying member in many structures, particularly in the aerospace industry, is the Cylindrical shell. In the design of these shells, buckling load calculations play a major role in determining the load-carrying capacity of the structure under compressive loading. To perform an analysis experimentally, high-speed framing photography is used. A combined theoretical and experimental program was undertaken to investigate the behavior of photoelastic cylindrical shells of circular and elliptical cross-section subjected to static and dynamic axial loading. By recording the change in the photoelastic isoclinic patterns (which characterize the collapse modes of the cylinders) at framing rates up to 5000 pictures/s using a 16mm Hycam camera, a comparbon of these patterns with theory was possible. Theoretical and experimental results clearly demonstrate the variation in collapse modes of cylinders as a function of their cross-section, shape imperfections and rate of axial loading.

Creep Buckling of Thin-Walled Circular Cylindrical Shells Subject to Radial Pressure and Thermal Gradients

A method of calculating the creep deflections and predicting the creep collapse of a thin-walled circular cylindrical shell, subject to uniform external radial pressure and arbitrary temperature gradients, is shown. This method may also be applied to investigate the behavior of a shell subject to time-dependent temperature gradients and deformations due to other inelastic causes. The set of simultaneous differential equations of equilibrium in terms of creep, thermal, and other inelastic strains is presented. Applications of this method to long cylindrical shells are illustrated by two numerical examples.

Gravitational instability and collapse of charged fluid shells

A solution of Einstein’s field equations is derived, representing a thin spherical shell of charged fluid, falling in a spherically symmetric field due to mass and charge at its centre. No restrictions are placed on the equation of state. By integrating the equations of motion, the law of conservation of total energy is obtained, and used to study the equilibrium states of the system, and their stability against collapse. It is found, under reasonable assumptions, that for a given equation of state and a given entropy, there is a maximum equilibrium mass, and that instability sets in at a critical radius which is always larger (very much larger, for a shell of highly relativistic fluid) than the upper Nordstrom gravitational radius. For uncharged bodies, these results completely parallel, and serve as a simple illustration of, the results of the much more complicated analyses needed for fluid balls.

Collapse of Thick Spherical Shells by External Pressure

Collapse of Thick Spherical Shells by External Pressure

Creep buckling of a cylindrical shell under non-uniform external loads

A method of analysis is presented for circular cylindrical shells under non-uniform external loads. The equations are valid for moderately large displacements and take secondary creep into account. Thermal effects and initial imperfections are included.As the general equations are non-linear, an iterative method is used in the numerical analysis. The nonlinear terms are at a certain iteration considered as known, generally determined by the previous iteration. They may thus be regarded as pseudo loads which are added to the actual external load terms. The variables of the thus linearized differential equations are expanded in Fourier series with respect to the circumferential coordinate. As a result, a series of sets of ordinary differential equations is obtained, one set for each Fourier index. These sets of equations are solved by use of a finite difference method. For each load or time step the equations are repeatedly solved until convergence is obtained.A computer program was developed and was verified by comparison with known solutions for elastic buckling of shells. The theoretical behavior of a cylinder under creep is demonstrated for a number of different loading conditions, in particular the response is studied of an imperfect shell under uniform loads. In the case of external pressure, the critical time was found to be extremely sensitive to the imperfection shape. For a short cylinder under axial compression the presence of initial imperfections was shown to shorten the creep life substantially in comparison with the critical time corresponding to axisymmetrical collapse of the perfect shell.

Charged shells in general relativity and their gravitational collapse

The boundary conditions for the gravitational and electromagnetic fields on charged shells are formulated. The shells are characterized in geometrical terms and the boundary conditions are manifestly covariant. The formalism is applied to the study of the gravitational collapse of homogeneous charged spherical shells. The law of conservation of energy, obtained by integrating the equations of motion of the shell and interpreted in full analogy with the special theory of relativity, is the starting point in analyzing the equilibrium states and the motion of the shells. It is concluded that no charge, however high it may be, can stop the gravitational collapse of the shell below the upper Nordstrom radius.

Buckling of a Long Fiber-Wound Cylindrical Shell Due to Stresses Caused by Windings

The collapse of a cylindrical shell due to tight fiber windings is investigated theoretically and experimentally. Buckling in the infinitesimal sense of Euler appears to be possible, if the fibers are not bonded well to the shell. Perhaps more significant than the Euler critical load is a dangerous snap-through condition that may develop.

Bodily Collapse of Ring-Stiffened Circular Cylinders Subjected to External Pressure

Recent experimental works in our country on the bodily collapse of ring-stiffened circular cylindrical shells subjected to hydrostatic external pressure are almost concerned with welded and so initially deformed models in order to apply the results directly to the design of submarine hulls.But the results can not satisfactorily be explained by the analyses which makes use of exsisting theories, hereby the method of analysis which accommodates to such imperfect models seems to be needed very much.This report deals with a method for estimating the collapse pressure which relates to material strength and initial out-of-roundness as parameters. This method is based on the consideration that, when ring-stiffeners have some initial out-of-roundnesses and the model is loaded by uniform pressure, the stiffeners contract gradually while being bent in a certain circumferential mode, and finally when at least three plastic hinges occur at the adjacent positions on them, the stiffeners collapse locally and immediately after that a total model collapses generally. Some experimental results are refered to ascertain this method.

Creep collapse of cylindrical shells

This paper develops a theory for the collapse of cylindrical shells under steady-state creep and under external radial pressure and high temperature (300 to 500 F.). The boundary conditions assumed for the cylinders approximate the “simply supported” and “fixed-end” conditions and the theory takes into account the initial deviation from circularity of the cylinder cross section. The paper thus represents an extension of the investigation described in (5) in which cylinders with “free” ends were considered. The theoretical predictions of collapse time ( t er ) are compared with experimental results on aluminum alloy (6061-T6) cylinders and show reasonably good agreement.

Collapse of Ring-stiffened Thin Cylindrical Shell under External Pressure

Collapse of ring-stiffened thin cylindrical shell under external pressure can be divided into two kinds, one “Shell Collapse”, the other “Bodily Collapse”.The “Bodily Collapse” was named and proposed by Tokugawa as the originator in this study of the world, but subsequently it is called “General Collapse” in the United States. As for “Shell Collapse”, researches were made by both Tokugawa and Windenburg, and are sufficiently practical in respect of Mild Steel. But, since High Tension Steel with superior weldability came out in public sales, we carried out experiments to obtain its characteristic qualities.Regarding “Bodily Collapse” there are two Theories in Elasticity, one by Tokugawa, the other by Kendrick, but they have not been put into actual use yet. Formulae, either by Levy or by Lame, which are now adopted in actual designs, show considerable discrepancies, as far as their definite length are concerned, when compared with the experimental results. Therefore, we aimed at putting Tokugawa's Theory of Elasticity into actual design, this time.Now, let us take : ψ=PK·D/2S (1+σYF/σYS·F/l'S) ·σYS, B=σYS· (1+σYE/σYS·F/l'S) /E· (D/L) (S/D) 1.5· (I/l'S3/12) 3/4considering, ψ is “Mean Pressure Factor” and B is “Bodily Factor”. The relation of ψ and B is shown in Fig 9.When calculating moment of inertia of stiffener, the effective breadth can be adopted with three (3) S in case of inner stiffener, and one (1) S in case of outer stiffener.If ±10% of tolerance is permitted, Fig 9 may be used in the actual design as they are, regardless whether they are Mild Steel or High Tension Steel.

Axi-Symmetric Collapsing of Circular Cylindrical Shells of Submarines

Collapsing of circular cylindrical shells under external pressure has been investigated in relation to the strength of pressure hulls of a submarine. Cylindrical shells collapse by causing shell yielding when they are reinforced closely by circular frames. This phenomenon takes place suddenly with a loud noise, and it seems therefore to be a sort of buckling accompanied by large plastic deformations. If shells are made literally in a circular form, the collapsing pattern will be axially symmetric ; hence, such collapsing shoild be called axi-symmetric collapsing rather than shell yielding.Axi-symmetric collapsing was investigated by Sanden-Giinther and Trilling. Their theories are based on an assumption that shells will collapse as soon as the stress condition reaches a certain state. The behaviors of shells are different from those expected by these theories, and there follows even a marked discrepancy between experiments and the theory of Sanden-Gunther.In this paper a rational theory is developed on the basis of the theories of plasticity and buckling ; the validity of this theory was confirmed by experiments. When the sectional area of frames is comparatively small, collapsing occurs over three frame spaces, and when large enough, between two consecutive frames. In respective cases, the pressure factor for axi-symmetric 'collapsing is given by (22) and by (20) or (21).

Limit Analysis of Simply Supported Circular Shell Roofs

Plastic collapse of a partial circle cylindrical shell simply supported at each end with the longitudinal edges free is investigated for the case of uniform radial loading. The principles of Limit Analysis applicable to a plastic-rigid structure are utilized to develop upper and lower bounds for the collapse pressure parameter, P. Bounds are obtained for a wide range in shell shape parameters with the deviation between the mean of the bounds and either bound varying between 2 and 25 per cent.

Minimum Weight Design of Cylindrical Shells

Abstract The theory of collapse and minimum weight design of cylindrical shells by Onat and Prager is applied in this paper to the development of a method for designing the variable wall thickness of a cylindrical shell under axial loading and arbitrary pressures to give maximum economy of material. The design is such that the shell does not fail plastically in the sense used in limit analysis. It will be assumed that the shell is supported at the ends by inextensible rings so that the circumferential strain rates vanish there.

The plastic collapse of cylindrical shells under axially symmetrical loading

The plastic collapse of cylindrical shells under axially symmetrical loading