scholarly journals On the issue of torsion of inhomogeneous rods under the influence of external pressure

2021 ◽  
pp. 42-46
Author(s):  
Борис Гурьевич Миронов ◽  
Юрий Борисович Миронов
Keyword(s):  
Plastic Material ◽  
External Pressure ◽  
Limiting State

Работа посвящена исследованию кручения неоднородных стержней из идеального жесткопластического материала, находящихся под действием переменного внешнего давления линейно меняющегося вдоль образующей стержня. Определены основные соотношения теории кручения исследуемых стержней. Найдены характеристики основных соотношений и определены соотношения вдоль характеристик. В работе получены интегралы основных соотношений при различных условиях предельного состояния стержня. The work is devoted to the investigation of the torsion of inhomogeneous rods made of ideal hard-plastic material under the action of variable external pressure linearly varying along the generatrix rod. The basic relations of the theory of torsion of the investigated rods. The characteristics of the basic relations are found and relationships along characteristics. The integrals of the basic ratios under different conditions of the limiting state of the bar

A Global Energy Approach for Analysis of a Propagating Buckle in Submarine Pipelines

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Mingqiao Tang ◽  
Jianghong Xue ◽  
Renhuai Liu
Keyword(s):  
Steady State ◽  
Transition Zone ◽  
Plastic Material ◽  
External Pressure ◽  
Thick Wall ◽  
Yield Coefficient ◽  
Rigid Plastic ◽  
Stretching Factor ◽  
Buckle Propagation ◽  
Membrane Stretching

This paper presents a unique approach to analyze the steady-state buckle propagation phenomenon in underwater pipelines. In previous work, we restudied the buckling of a very long pipeline subjected to external pressure and found that buckling happens only over a certain length of the pipeline. In this paper, the collapse mode of the pipeline obtained in previous studies is taken as the transition zone during steady-state buckle propagation. Kinematics in the transition zone is analyzed based on von Kármán–Donnell type of nonlinearity. Assuming linear elastic rigid plastic material properties, the mechanical responses in the transition zone are examined using the deformation theory. Two parameters, the yield coefficient and the membrane stretching factor, are introduced to depict the effects of transversal bending and the membrane stretching, respectively. Analytical solution of buckle propagation pressure is derived by considering the energy conversation calculated from shell theory. It is found that the buckle propagation performance is governed by the transversal bending, including the circumferential bending and longitudinal bending. The membrane stretching is significant only for thick wall pipeline, in particular when the ratio of radius-to thickness is small than ten. The analysis is in effect by comparing the obtained solutions with the well-established predictions and the experimental results.

Investigation on Snap-Through Buckling Behavior of Dished Shells Under Uniform External Pressure

2020 ◽  
Vol 87 (12) ◽  
Author(s):  
Surya Mani Tripathi ◽  
Digendranath Swain ◽  
R. Muthukumar ◽  
S. Anup
Keyword(s):  
Numerical Study ◽  
Plastic Material ◽  
External Pressure ◽  
Image Correlation ◽  
Geometrical Parameters ◽  
Imperfection Sensitivity ◽  
Value Analysis ◽  
Uniform External Pressure ◽  
Buckling Behavior ◽  
Non Linear

Abstract Previously, the buckling behavior of several conical and spherical shells have been studied with great rigor. In this paper, snap-through buckling behavior for metallic dished shells under uniform external pressure is investigated. These shells are geometrically complex since they consist of a shallow conical frustum with a flat closed top. Such shells find many engineering applications, for instance as actuator elements in control components in cryogenic engines. Currently, no clear guidelines exist for design performance evaluation of such peculiar shells. This paper aims to establish a valid FE methodology for snap-through buckling and post-buckling analysis of such shells using abaqus in tandem with experiments. A parametric study is carried out to understand the effect of geometrical parameters and imperfection sensitivity of these shells to snap-through buckling. Moreover, experiments were carried out using 3D Digital Image Correlation (3D-DIC) for measuring whole-field deflection and strains. Numerical analysis was carried out, using generalized Eigen value analysis and non-linear analysis using a modified-Riks technique with various material models to correlate with the experimental observations. Non-linear elasto-plastic analysis with a perfectly elastic-plastic material model agrees well with the experimental observations. A comparison of experimental results with that of the numerical study indicates that material plasticity has a major effect on critical buckling pressure.

The Application of Combined Buckling Mode Imperfections on Shell Structures

2013 ◽  
Author(s):  
Sean Laird ◽  
Robert Frith
Keyword(s):  
Plastic Material ◽  
Initial Imperfection ◽  
External Pressure ◽  
Mode Shapes ◽  
Buckling Mode ◽  
Linear Elastic ◽  
Higher Order Modes ◽  
Fabrication Tolerances ◽  
Critical Buckling Pressure ◽  
Shell Geometry

This paper presents the results of a numerical investigation for applying a combination of buckling mode shapes as an initial imperfection to shell geometries under external pressure. The effect that imposed imperfections had on the critical buckling pressure was found to be dependent upon both the shell geometry and the characteristics of the imposed imperfection. Imperfections were generated via linear combinations of the linear elastic buckling mode shapes, with the fundamental mode having the greatest influence. For a number of tests, inclusion of higher order modes into the initial imperfection caused an increase in the critical buckling pressure. This behaviour was observed for both elastic and plastic material models. For the purpose of limiting the extent of the analysis, the magnitudes of imposed imperfections were maintained within the industry required fabrication tolerances and in particular, acceptable out-of-roundness. The purpose of this paper is to present the methodology and results from this imperfection investigation. Additional testing and discussion may allow a design methodology to be developed that addresses the application of initial imperfections in shells under external pressure.

Buckling Analysis of Tube for Steam Generator According to ASME B&PV Code

2014 ◽  
Author(s):  
Jungpyo Kong ◽  
Changhoon Ha ◽  
Minki Cho ◽  
Seunghoon Yeo ◽  
Tae-Jung Park
Keyword(s):  
Steam Generator ◽  
Plastic Material ◽  
External Pressure ◽  
Buckling Analysis ◽  
Dominant Factor ◽  
Elastic Instability ◽  
Element Analysis ◽  
Collapse Pressure ◽  
Elastic Plastic Material

The U-tubes installed inside the steam generator experience high temperature and pressure as a role of heat transfer. Specially, during the secondary side hydrostatic test which ensures the integrity of steam generator, the U-tube is subjected to high external pressure. The purpose of this paper is to investigate the allowable external pressure of the U-tube in steam generator. In the ASME B&PV Code Section III [1], the allowable external pressure is determined by the rules of NB-3133. Alternatively, NB-3228 analysis may be applied. In order to determining the allowable external pressure of steam generator tube, the buckling analysis is performed. The analysis consists of the collapse pressure and elastic instability pressure analyses. In this study, these pressures are determined by finite element analysis (FEA) using ANSYS computer program. The non-linear static analysis is performed with ideally elastic-plastic material properties for the collapse analysis. On the other hand, the elastic instability pressure is calculated by eigenvalue analysis in elastic range. These allowable pressures are found to be 24.1 ksi and 10.5 ksi. Therefore the lower pressure of 24.1 ksi is the allowable external pressure of tube. In addition, the results of analysis are compared with other research [6] and Det Norske Veritas (DNV) offshore standards [11]. In conclusion, the results of buckling analysis are well matched with other research [6] and standard [11]. For steam generator tubes, the collapse pressure is dominant factor in failure. Also, the collapse pressure is largely influenced by the ovality of tube.

Interaction Curves for Circular Cylindrical Shells According to the Mises or Tresca Yield Criterion

1962 ◽  
Vol 29 (2) ◽  
pp. 375-380 ◽  
Author(s):  
P. G. Hodge ◽  
Joseph Panarelli
Keyword(s):  
Cylindrical Shell ◽  
Circular Cylindrical Shell ◽  
Plastic Material ◽  
Yield Criterion ◽  
External Pressure ◽  
Shell Material ◽  
Perfectly Plastic ◽  
Axial Tensile ◽  
Circular Cylindrical Shells ◽  
Interaction Curves

A circular cylindrical shell is subjected to uniform internal or external pressure and a constant axial tensile or compressive stress. The interaction curve constituting load combinations which just cause plastic flow of a rigid/perfectly plastic material depends upon the assumed yield criterion of the shell material. Close bounds on the interaction curve are found when the material yields according to either the Tresca or Mises criterion.

scholarly journals Mechanical analysis on cement sheath integrity under asymmetric load

2021 ◽  
Author(s):  
Xiaoyu Zhang ◽  
Lei Wang ◽  
Zhenhui Bi ◽  
Yintong Guo ◽  
Chunhe Yang ◽  
...  
Keyword(s):  
High Temperature ◽  
Cyclic Loading ◽  
Stress Distribution ◽  
Negative Impact ◽  
Plastic Material ◽  
Accumulation Rate ◽  
Triaxial Compression ◽  
External Pressure ◽  
Engineering Practice ◽  
Asymmetric Stress

AbstractIn large-scale multi-section hydraulic fracturing, the stress environment of wellbore is extreme complex, often causing the unbalanced stress distribution around the wellbore. That poses great challenges to the integrity of the sheath. In this paper, firstly, triaxial compression test and triaxial cyclic test are carried out at 130 °C to study the deformation characteristics of the cement under high temperature. Then based on that, an appropriate plastic mechanics model is established. Finally, the shakedown theory is applied to analyze the model and acquires a maximum cyclic loading under asymmetric stress. The result shows that (1) the well cement, with the increase of load, shows the plastic flow characteristics and can be regarded as an ideal elastic–plastic material under high temperature. (2) During the cyclic loading and unloading process, the "hysteresis loop" becomes denser, which indicates that the accumulation rate of plastic deformation is continuously declining. The main plastic strain appears in the phase of the first loading. (3) The external pressure Pz plays a positive role in the deformation control of the sheath. With the growth of Pz, the maximum cyclic loading Pmax will also increase. (4) Asymmetric stress distribution can significantly affect the bearing capacity of the sheath. If stress difference coefficient λ = 0.3, the Pmax tends to decrease nearly by 50%. With the growth of λ, the negative influence of stress asymmetry reduces gradually. High external pressure is beneficial to reduce the negative impact of the asymmetry. With the growth of λ, the benefit tends to enhance. (5) In engineering practice, if the geology around wellhole showcases the strong asymmetry (the value of λ is large), some steps need to be adopted to reduce the stress concentration.

Trust: A National Project

2015 ◽  
pp. 138-146
Author(s):  
N. Rozinskaya ◽  
I. Rozinskiy
Keyword(s):  
Social Capital ◽  
Civil Society ◽  
Everyday Life ◽  
Western Europe ◽  
External Pressure ◽  
National Project ◽  
Low Level ◽  
General Trust

This article deals with the genesis of general trust and social capital in contemporary Russia, which faces the external pressure. The low level of general trust is noted, its economic, social and everyday life implications are considered, an explanation of Russia’s lower than in western Europe level of trust is provided. Considering society’s level of trust and social capital as externalia, the authors conclude that there is a necessity to "produce" trust intentionally. Promotion of collective charity is proposed as a mechanism of such "production". It is stressed that in order to activate the potential of trust in a society, there is a need for ideological and symbolic basis linked to its history. Russian People’s Unity Day, understood as the birthday of Russian civil society, is proposed to be used in this respect.

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

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