Elastic-Plastic Analysis of Thick-Walled Pressure Vessels With Sharp Discontinuities

1971 ◽  
Vol 93 (4) ◽  
pp. 1016-1020 ◽  
Author(s):  
P. K. Larsen ◽  
E. P. Popov
Keyword(s):  
Pressure Vessels ◽  
Layered System ◽  
Axially Symmetric ◽  
Shells Of Revolution ◽  
Elastic Plastic ◽  
Solid Of Revolution ◽  
Plastic Analysis ◽  
Isoparametric Finite Elements ◽  
Thick Shells ◽  
Flow Theory Of Plasticity

Application of special isoparametric finite elements is presented for the elastic-plastic analysis of shells of revolution. General isoparametric elements are selected which, in the form of a layered system, are capable of representing a solid of revolution. The customary Kirchhoff-Love hypothesis is not invoked and solutions therefore apply both to thin and thick shells of revolution. Sharp discontinuities in geometry, circumferential ribs and/or grooves, as well as cellular walls may be studied. A special feature is the development of an element permitting sliding at the element interfaces with or without friction. The illustrative examples include a pressure vessel with a circumferential crack in the wall thickness, and a circular plate consisting of two disks which can slide along their interface. The solutions are limited to axially symmetric problems. Flow theory of plasticity is used in the inelastic regions.

Elastic-Plastic Behaviour of Flush Nozzles in Spherical Pressure Vessels

1967 ◽  
Vol 9 (3) ◽  
pp. 182-189 ◽  
Author(s):  
P. V. Marcal ◽  
C. E. Turner
Keyword(s):  
Computer Program ◽  
Shell Theory ◽  
Pressure Vessels ◽  
Finite Width ◽  
Test Results ◽  
Shells Of Revolution ◽  
Elastic Plastic ◽  
Plastic Behaviour ◽  
Plastic Analysis ◽  
Spherical Pressure

A computer program for the elasto-plastic analysis of axially symmetrical shells of revolution has been modified to allow interaction loads at nozzle junctions to be distributed over bands of finite width, rather than the conventional concentrated lines of loading at the intersection of the shell centre-lines. Comparison with previously published test results for displacements, yield and collapse loads of flush nozzles shows that this modification greatly improves the predictions from those of conventional shell theory so that realistic behaviour of nozzle junctions can be forecast.

Computational Aspect of Nonlinear Fracture Mechanics Application

2015 ◽  
Author(s):  
Igor Orynyak ◽  
Andrii Oryniak
Keyword(s):  
Residual Stress ◽  
Fracture Mechanics ◽  
Thermal Stresses ◽  
Crack Tip ◽  
Pressure Vessels ◽  
Point Of View ◽  
Computational Aspect ◽  
J Integral ◽  
Elastic Plastic ◽  
Plastic Analysis

The development of powerful commercial computer programs made the concept of J-integral as computational parameter of fracture mechanics to be a very attractive one. It is equivalent to SIF in linear case, it converges in numerical calculation and the same results are obtained by different codes (programs). Besides, it is widely thought that elastic-plastic analysis gives bigger values than elastic SIF ones what is good from regulatory point of view. Such stand was reflected in the recommended by IAEA TECDOC 1627 (February 2010) devoted to pressurized thermal shock analysis of reactor pressure vessels, where the embedded crack in FEM mesh, elastic-plastic analysis with simultaneous determination of J-integral was stated as the best option of analysis. But at that time all the most widely used software were not able to treat the residual stresses, the thermal stresses in case of two different materials. Such a contradiction between requirements and the possibilities made a lot of problems for honest contractors especially in countries where the regulator had no own experience in calculation and completely relied on the authority of international documents. This means that at that time the said recommendations were harmful. The main reason of such a situation was the absence of the carefully elaborated examples. Now the capabilities and accuracy of such software are increasing. Nevertheless, some principal ambiguities and divergences of computations results in various J-integral contours around the crack tip still exist. They are exhibited when the large plastic zone emerges at the crack tip. Other problem is influence of the history of loading and the specification of the time of crack insertion in the mesh including the time of emergence of residual stress. This paper is invitation for discussion of the accuracy and restriction of computational J-integral. With this aim the detailed analysis of some simplified 2D examples of calculation of elastic -plastic J-integral for surface crack with accounting for residual stress, thermal stress and inner pressure are performed and commented. The attainment of consensus among the engineering society for treating the outcome results is the prerequisite for practical application of computational elastic plastic J-integral.

Approximate Elastic-Plastic Analysis of Intersecting Equal Diameter Cylindrical Shells

1981 ◽  
Vol 103 (1) ◽  
pp. 111-115
Author(s):  
D. P. Updike
Keyword(s):  
Plastic Material ◽  
Cylindrical Shells ◽  
Yield Condition ◽  
Pressure Vessels ◽  
Ductile Materials ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Plastic Analysis ◽  
Elastic Perfectly Plastic ◽  
Von Mises

Design of connections of pipes and pressure vessels on the basis of a calculated maximum elastic stress often proves to be too conservative in the case of ductile materials. Elastic-plastic analysis by the finite element method proves to be too costly. This paper presents an alternative method which reduces the calculations to those of a rotationally symmetric shell subjected to axisymmetric loading. Using this approach approximate elastic-plastic deformations on the meridian passing through the crotch of a tee branch connection of cylindrical shells of equal diameter and thickness are determined. The method is limited to cases of the normal intersection of very thin shells of identical diameter, thickness, and material and to internal pressure loading. Numerical results for the intersection of two shells of R/t equal to 100 are given for an elastic-perfectly plastic material satisfying the von Mises yield condition.

Shakedown and Fatigue Evaluations of Overlay Cladding on Reactor Pressure Vessels

2011 ◽  
Author(s):  
Seiji Asada ◽  
Harutaka Suzuki ◽  
Toshiya Saruwatari
Keyword(s):  
Stress Distribution ◽  
Base Metal ◽  
Design Methodology ◽  
Evaluation Method ◽  
Pressure Vessels ◽  
Stress Evaluation ◽  
Alternative Design ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Reactor Pressure

Overlay cladding is classified to non-pressure boundary. Not only the ASME Boiler & Pressure Vessels Code Section III [1] but also the JSME Design and Construction Code [2] prescribe that no structural strength shall be attributed to cladding and the presence of the cladding shall be considered with respect to both the thermal analysis and the stress analysis. This means the codes do not require stress evaluation for overlay cladding itself. If overlay cladding has a fatigue crack, the crack may grow and extend to the base metal. Thus overlay cladding may give an influence on the integrity of base metal in the pressure boundary. The thermal expansion of stainless steel cladding is different from that of base metal made of low alloy steel, and this difference causes discontinuity of stress distribution between the cladding and the base metal. It is questionable that a stress evaluation line is set on such stress distribution including discontinuity between the cladding and the base metal. An evaluation method based on elastic-plastic analysis is preferable to evaluate such portion. ASME B&PV Sec.III and Sec.VIII, Div. 2 [3] have plastic analysis provisions. Also the JSME D&C Code issued a code case on alternative design methodology by using elastic-plastic finite element analysis for Class 1 vessels [4, 5]. In this paper, shakedown, fatigue and environmental fatigue evaluations are performed for the overlay cladding of direct vessel injection nozzle of Reactor Pressure Vessel by using the JSME Code Case on the alternative design methodology.

Elastic-Plastic Analysis of Functionally Graded Spherical Pressure Vessels Using Strain Gradient Plasticity

2017 ◽  
Vol 09 (08) ◽  
pp. 1750118 ◽  
Author(s):  
Hassan Shokrollahi
Keyword(s):  
Internal Pressure ◽  
Strain Gradient ◽  
Plastic Region ◽  
Pressure Vessels ◽  
Functionally Graded ◽  
Strain Gradient Plasticity ◽  
Gradient Plasticity ◽  
Elastic Plastic ◽  
Plastic Analysis ◽  
Spherical Pressure

In this paper, formulation of elastic-plastic analysis of functionally graded (FG) spherical pressure vessels under internal pressure based on strain gradient plasticity is presented. The material properties are assumed to vary in a power law manner in the radial direction. A linear hardening rule for the material behavior in the plastic region is assumed. After deriving the governing differential equations, a closed form solution is obtained. At the first step, the obtained results were validated against other available results in the literature. Then the effects of changing the inner radius from a few micro-meters to one meter, FG power index and strain gradient coefficient on stress and plastic region size are studied based on classical and strain gradient theories. Also, the effect of internal pressure on the size of plastic region is studied.

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