Numerical study of the stress-strain state of the thermal insulating sections of a column of steam delivery pipes

A procedure is suggested for a numerical study of the axisymmetrical thermoelastoplastic stresss-train state of sections of a column of steam delivery pipes based on modelling a section of a shell of rotation with a proportionally reduced number of corrugations and lengths of cylindrical sections. The procedure is developed within the scope of the KirchhoffLove hypothesis on the basis of equations of the theory of simple loading processes taking their history into account. The procedure is substantiated by comparing calculated results for the stressstrain state of sections with eight and four corrugations.Translated from Problemy Prochnosti, No. 5, pp. 18–23, May, 1992.     

Determination of the limiting stress-strain state of helically corrugated pipes

An approximate procedure for calculating the limiting stress-strain state (SSS) of helically corrugated pipes that operate under an axial force is developed. The calculation reduces to determination of the elastoplastic SSS of a shell of revolution with a circular corrugation, which is under axial and torsional loads. The problem is solved using the geometrically nonlinear theory of shells in a quadratic approximation based on Kirchhoff-Love hypotheses, and relationships of the theory of deformation with respect to low-curvature trajectories. The SSS of a self-compensating helically corrugated pipe is investigated, the limiting axial load estimated, and good correspondence between the results obtained and experimental data indicated on the basis of the procedure that we developed.Translated from Problemy Prochnosti, No. 7, pp. 48–53, July, 1993.     

Investigation of the stress-strain state of a particleboard in the process of hot pressing

We propose a physicomathematical model for the evaluation of the temperature, humidity, and pressure of an air-vapor mixture and use this model to determine the stresses and strains formed in the process of pressing of a particleboard under the action of variable pressure. The adequacy of the results of numerical realization of the model to the experimental data is demonstrated. The influence of the principal thermal parameters on the stresses and strains is analyzed for different stages of pressing. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 1, pp. 43–48, January–February, 2007.     

Simulation and analysis of the emergency relief process of HTGR steam generator

研究了高温气冷堆( HTGR)蒸汽发生器事故排放过程的动态特性.把事故排放过程分为水排放和蒸汽排放两个阶段,对两个阶段分别建立了集总参数模型.在典型事故排放工况下,计算了蒸汽发生器排放温度、排放压力、排放比焓和排放流量随时间的变化.计算结果表明,事故排放系统可在6.175s内将HTGR蒸汽发生器二回路压力降低到一回路的压力水平,在事故排放结束时,蒸汽发生器仍然处于水排放阶段.计算得到的蒸汽发生器排放比焓和排放流量随时间变化的曲线为今后事故排放系统的排放罐内流动和传热的数值模拟提供了输入条件.     

In-service defects in the heat-exchange tubes of steam generators at nuclear power plants

We consider specific features of the in-service defects in the heat-exchange tubes of steam generators at nuclear power plants with VVéR (water-moderated water-cooled power reactor) power-generating units. The existence of correlation between the character of defects and the mechanism of their formation under the operating conditions is established. It is shown that the process of formation of defects is connected both with the intercrystalline and intracrystalline mechanisms of cracking detected in different sections of the tubes. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 4, pp. 109–113, July–August, 2008.     

Composite nozzle dam in the steam generator of a nuclear reactor

The period of normal shutdown and maintenance for a nuclear power plant can be remarkably shortened when the examination and maintenance of the tubes of a steam generator are simultaneously carried out with refueling. The nozzle dam in a steam generator is a closure to block the flow of coolant from the inlet-outlet nozzles in a steam generator. Recently, the installation and removal operations of the nozzle dam were attempted using a robot rather than the manual operation because of the radioactive hazard. For the operation using the robot the weight of the dam must be reduced because the robot's payload for assembling operations is usually small.

In this work, a lighter nozzle dam was designed and manufactured using a carbon-epoxy composite, a glass-epoxy fabric composite, an aluminium plate and honeycomb. The carbon-epoxy composite was used for the main structural material and the honeycomb was used to increase the bending stiffness, while the aluminium plate and the glass-epoxy fabric composite were used to reduce the stress concentration around bolt holes. Also, the variation in mechanical properties of composites with respect to radiation emission was investigated.

In order to verify the structural integrity of the nozzle dam installed on the nozzle ring with bolts, the stress analyses of the nozzle dam under hydrostatic pressure were performed using commercial finite-element software and the pressure test was performed. The stiffness of the composite nozzle dam was measured and compared to that obtained by finite-element analysis.     

Heat exchange in a flat solar collector with heat pipes and honeycombed fill

A flat solar collector with honeycombed fill and a system of heat pipes has been developed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 4, pp. 546–552, October, 1987.     

Investigation of the stress-strain state of building elements containing a filler

The stressstrain state of building elements, in the form of parts of the Taurus, sphere, cone, and ellipsoid, with a filler is investigated. The filler is assumed to be isotropic. Relations describing the behavior of building elements containing a filler are presented. A building element is subjected to a uniform transverse pressure. Curves of deflection and membrane and flexural stresses in different sections of building elements in the form of parts of a sphere, cone, or ellipsoid are presented. The effect of stresses, shape of a building element, and the curvature of an element on the magnitude of the deflections is analyzed. Deflections and stresses in filled sections of building elements is smaller than unfilled building elements.Translated from Problemy Prochnosti, No. 4, pp. 72–78, April, 1993.     

Computer analysis of the three-dimensional flow and heat transfer in a steam generator

A calculation procedure is described for the class of flows in which the flow domain contains numerous dispersed solid objects such as tubes or rods. The central idea is to treat the solid objects as distributed resistances to flow and heat transfer. The calculation procedure is illustrated by an application to a steam generator of a nuclear power plant. The three-dimensional flow field and the enthalpy distribution are calculated. Since details of the thermal-hydraulic behaviour of the steam generator can thus be inexpensively predicted, the procedure can be useful to designers.     

Analytic evaluation of the stress-strain state of a pipeline elastically bent in the ground

We construct a mathematical model of three-dimensional bending with tension and torsion of a prestressed curvilinear pipeline in an elastic compliant soil with longitudinal and torsional frictiontype reactions. The model has the form of a system of 12 ordinary linear differential equations. It takes into account large initial displacements of the pipeline and the action of temperature and pressure linearly distributed along the axis of the pipe. The analytic solution of the problem obtained in elementary functions is of significant practical interest for the inspection and design-basis strength analyses of underground, surface, and above-ground pipelines. Scientific and Engineering Center of Materials-Science Support of the Production and Certification of Equipment of Nuclear Power Plants at the Institute for Problems of Strength of the National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 2, pp. 151 – 160, March – April, 1998.     

Calculation of the stress-strain state of orthotropic bodies under a bending load

A method is developed for determining the components of the stress tensor and displacement vector in a bent thick orthotropic slab. The solution is obtained in the form of double exponential-trigonometric series. The unknown parameters of the problem are determined by minimizing the functional of potential energy with allowance for boundary conditions on the surface of the slab.     

Effect of thermal cycling on the stress-strain state of a rotating disk

The effect of repeated thermal cycling on the stress-strain state of a rotating disk is investigated. It is demonstrated that repeated temperature cycling in a given regime nearly doubles the deformation of the rotating disk. This suggests the probability of a major influence of thermal cycling on the deformed state of the rotating disk.Translated From Problemy Prochnosti, No. 1, pp. 57–62, January, 1991.