Thick-walled micropolar cylinder in a state of plane strain

This paper deals with the important boundary value problem of a thick-walled micropolar cylinder loaded with an internal pressure. Use is made of a finite element model to study the influence of the micropolar characteristics on the stresses and displacements in the cylinder.     

Earthquake response of nonlinear plates

The finite amplitude vibration of a plate subjected to earthquake support motion is considered. Several bounds on the maximum responses of the plate are established which are based on the knowledge of the response spectra of the seismic motion. The stochastic models of the earthquake ground motion is then briefly discussed. The single mode of vibration of the plate is then considered and a perturbation series expansion is developed for the vibration amplitude. Mean square responses of the plate are then calculated for both stationary as well as nonstationary seismic excitations. It is observed that the variance of the deflection field of the nonlinear plate is less than that of the corresponding linear one. The reliability of design is also considered and the probability of no barrier crossing is briefly discussed.     

Design of 90 Degree Bending Alpha Magnet

<正>The beam distribution will be distorted as shown in Fig.1,when it is bended a big angle by the regular bending magnet.The distribution curve at the bending direction is not the Gaussian as its original.This distortion can not be cured by the latter optic,and it will bring the bad effect for the beam transportation and operation.If the alpha magnet is instead of the regular bending magnet,     

Bending and twisting of pipe with creep

An exact analysis is presented for the creep deformation of a pipe under the action of combined bending and twisting moments. Dimensionless interaction curves and charts which relate the variables, bending moment, angle change rate, twisting moment, and twist rate per unit length are also provided for engineering practice convenience. The constitutive relationship of the pipe is assumed to obey Prandtl-Nadai creep law.     

核电厂管道弯曲工艺

目前,在核电管道安装中大量使用了弯管,这些弯管不仅改善了流体的力学性能,同时也减少了管道上的焊口数量,提高了管线运行的可靠性;弯管可根据技术要求采用冷弯或热弯工艺,每种工艺又各有几种方法,弯管的加工一般都在车间进行,生产环境和精度上有可靠地保证,是工厂化管道生产的发展趋势,而合理地选取弯曲工艺和方法是保证弯管质量的关键,目前工艺管道弯曲半径普遍都在3倍公称直径以上,管径愈大,弯曲半径也愈大,工艺操作难度愈大,所以在选材、弯制、检查、处理等环节上必须严格执行标准;随着弯管在核电、化工等领域的普遍应用,弯管的加工工艺水平还在不断的提升。     

Bending diamonds by femtosecond laser ablation

We present a new method based on femtosecond laser ablation for the fabrication of statically bent diamond crystals. Using this method, curvature radii of 1 m can easily be achieved, and the curvature obtained is very uniform. Since diamond is extremely tolerant to high radiation doses, partly due to its densely packed lattice, such bent crystals are optimal solutions for crystal-based collimation and/or extraction. Furthermore, using interlaced ablation on both sides, the technique opens for the possibility of constructing a crystalline undulator based on the best material known, to approach the enormous beam densities required for lasing operation of such a device.     

Thermal bending of thick rectangular plates

An analysis with a shear deformation capability for the thermal bending of thick rectangular plates is presented. Formulation of the problem, with appropriate thermal terms incorporated and applicable to the bending of moderately thick plates, has been carried out by using Reissner's plate bending theory. Representative plate bending problems have been considered for illustrating the procedure. Numerical results obtained indicate that thick plate solutions to thermal problems deviate from those of the classical theory in practically the same manner as with mechanical loading cases.     

Ductile fracture of cracked steel plates

A simple relationship between loading for crack initiation, or onset of ductile tear, and crack length is presented for center-cracked plates of mild steel. Formulation of the nonlinear boundary-value problem is based on incremental theory of plasticity for Prandtl-Reuss materials. Quasi-static solutions corresponding to a series of incremental loading conditions are obtained by the mothod of finite elements. Tests conducted on plates of two types of mild steel agree with numerical results.     

Bending failure by flattening of circumferentially cracked pipes

The bending failure by cross-section flattening of circumferentially cracked pipes has been studied. Flattening may be described by four plastic hinges and is caused by the vertical component of the axially directed bending stresses. An analytical expression for the failure moment of a material subject to strain hardening is given.     

Hydraulic Performance of Small Bending Radius Helical Coil-Pipe

Helical steam generator or helical heat exchanger is extensively used in high-temperature gas cooling reactor, fast breeder reactor, pressurized water reactor using in ship propulsion and areas of electro-power, chemical industry and petroleum industry. The purpose of this paper is to research the hydraulic performance of small bending radius helical coil-pipe used in HTR-10. Research for hydraulic performance of small bending radius helical pipe was carried out on the HTR-10 steam generator experimental facility. Based on the experimental results, it was confirmed that for helical pipe the critical Reynolds number (Re) is much greater than in a straight pipe and is a function of De. Formulas for Re of single-phase flow structure transition, friction coefficient of single-phase flow, and two-phase flow friction factor are obtained. Experience formulas of small bending radius helical pipe are recommended for design and research.     

Flow-induced plastic collapse of stacked fuel plates

Flow-induced plastic collapse of stacked fuel plate assemblies was first noted in experimental nuclear reactors such as the Oak Ridge National Laboratory High Flux Reactor Assembly and the Engineering Test Reactor (ETR). The ETR assembly is a stack of 19 thin flat rectangular fuel plates separated by narrow channels through which a coolant flows to remove the heat generated by the nuclear fission of the fuel within the plates. The uranium alloyed plates have been noted to buckle laterally and plastically collapse at the system design coolant flow rate of 10.7 m/s, thus restricting the coolant flow through adjacent channels. In this paper a methodology and criterion are developed for predicting the plastic collapse of ETR fuel plates. The criterion is compared to some experimental results and the Miller critical velocity theory.     

Laminar flow induced deflections of stacked plates

Some research and power reactors such as the Engineering Test Reactor (ETR), the Materials Test Reactor (MTR) and the Shippingport Reactor have core designs which consist of parallel, flat or curved plate fuel assemblies. The fuel is contained in the thin plates which are separated by narrow channels through which coolant flows to remove heat generated within the plates. Since the plates are flexible, the coolant flowing through the channels causes the plates to deflect. At high coolant velocities large deflections have been observed causing the plates to deform plastically leading to structural failure or plate collapse. This work examines a single plate bounded by two channels and determines the static plate deflection as a function of plate, channel and flow parameters. The deflection is due to differences in pressure and flow velocity in the channels bounding the plate and also due to different channel dimensions caused by tolerance effects. The classical thin plate equations are used with a nonlinear hydrodynamic loading function expressing the external fluid forces on the plate surfaces.     

Thermal analysis of plates with circular inclusions

A least square boundary point matching method is employed to determine the temperature distributions and deformations of rectangular plates with circular elastic inclusions. Solutions for two problems have been obtained. The first problem is concerned with the determination of the temperature distribution in a finite rectangular plate having a circular inclusion and subjected to prescribed temperature distribution and thermal conditions along the edges. The plate is heated uniformly through the thickness. The second problem is concerned with the deflection and moment distribution in the same plate model with simply supported edges and prescribed temperature variation across the thickness but no temperature variation over the plate surface. Numerical results are presented.     

Digital enhancement and analysis of TEM plates

The techniques of digital image analysis and enhancement have been applied to TEM micrographs. Digitized micrographs of irradiated A1 and Mo containing cavities were enhanced by applying digital unsharp masking and thresholding techniques. These techniques produce enhanced images that allow for more effective analysis of image features using conventional analysis methods as well as computer methods. For the Mo data, a template-matching algorithm was applied to thresholded data and a computer-generated void histogram was obtained. The computer analysis gives results that are in agreement with conventional analysis of the same data. It is concluded that computer methods for cavity/void analysis can be successfully developed.     

X射线螺旋波带片制备技术

本文将电子束曝光和X射线曝光技术相结合以制造X射线波段螺旋波带片。用电子束曝光和微电镀技术在镂空薄膜上制备母波带片X射线掩模版,用X射线曝光和微电镀技术小批量复制螺旋波带片。研制成可用于1.24nm波长的螺旋波带片,其最外环宽度为200nm,金吸收体厚度为700nm,占空比合理,侧壁陡直,结构优良。     

Hybrid method for vibration analysis of rectangular plates

This paper presents a semi-analytical approach for the dynamic analysis of rectangular plates. The mathematical model is developed using a hybrid combination of the finite element method and Sanders’ shell theory. The in-plane, membrane displacement components are modelled by bilinear polynomials and the out-of-plane, normal to mid-surface displacement component is modelled by an exponential function that represents a general form of the exact solution of the equations of motion. The displacement functions are obtained by exact solution of the equilibrium equations of the rectangular plates. The mass and stiffness matrices are then determined by exact analytical integration to establish the plate's dynamic equations. The effect of various geometrical parameters and boundary conditions on the dynamic responses of the rectangular plates has been explored in this work. The results are in satisfactory agreement with those of experiments and other theories.     

Three dimensional analysis of thermally loaded thick plates

A mixed three dimensional formulation is presented for the analysis of thermally loaded thick plates. The method developed follows the guidelines furnished by the Vlasov-Iyengar technique applicable to the analysis of mechanically loaded thick plates, in which the three dimensional governing equations are derived from the elasticity equations by using a MacLaurin series approach. The expressions for the components of displacement, stress, and heat flux as well as the temperature are obtained in a series form in terms of the linear partial differential operators operating on a set of initial functions, which are the solutions to the governing equations. The procedure to be followed in arriving at the solution is illustrated by solving the problem of the thermal bending of a clamped-supported thick square plate; it is found that the present solution deviates significantly from those of the lower order theories for large values of the thickness ratio.     

Behavior of viscoplastic circular plates under Gaussian impulse

The dynamic plastic behavior of viscoplastic circular plates subjected to impulse loading is presented. The impulse is assumed to impart a transverse axisymmetric velocity with a spatial Gaussian distribution. The combined influence of membrane forces, bending moments and strain-rate sensitivity is considered in predicting the deformation. Numerical results are presented to show this influence on the rate of growth of plastic regimes, the deflection configuration and the total time of response. It is concluded that the spatial distribution of impulse has a considerable effect on the deformation response of the plate, and relatively small effect on the total time of response; furthermore, the simple bending theory is inadequate to reliably predict the response.