Shakedown Bounds of Structures Using Linear and Nonlinear Methods

2008 ◽  
Author(s):  
Dan Vlaicu
Keyword(s):  
Material Properties ◽  
Plastic Material ◽  
Nonlinear Material ◽  
Upper And Lower Bounds ◽  
The Finite Element Method ◽  
Periodic Loading ◽  
Elastic Plastic Material ◽  
Compensation Approach ◽  
Elastic Shakedown ◽  
Loaded Structure

For a cyclically loaded structure made of elastic-plastic material it is considered elastic shakedown if plastic straining occurs in the first few cycles and the sequent response is wholly elastic. In this paper the finite element method is used to develop upper and lower bounds limits for the elastic shakedown of structures under periodic loading conditions. Linear methods using elastic compensation approach and the residual stress method derived from Melan’s theorem are used to generate the lower bound limit for the shakedown load while the upper bound is found through a method derived from Koiter’s theorem. Furthermore the results are compared with cycle-by-cycle method based on nonlinear material properties.

Shakedown Analysis of Nuclear Components Using Linear and Nonlinear Methods

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Dan Vlaicu
Keyword(s):  
Lower Bound ◽  
Plastic Material ◽  
Nonlinear Material ◽  
The Finite Element Method ◽  
Shakedown Analysis ◽  
Periodic Loading ◽  
Elastic Plastic Material ◽  
Compensation Approach ◽  
Elastic Shakedown ◽  
Loaded Structure

A cyclically loaded structure made of elastic-plastic material is considered as an elastic shakedown if plastic straining occurs in the first few cycles and the sequent response is wholly elastic. In this paper, the finite element method is used to develop upper and lower bound limits for the elastic shakedown of structures under periodic loading conditions. Linear methods using elastic compensation approach and the residual stress method derived from Melan’s theorem are used to generate the lower bound limit for the shakedown load, while the upper bound is found through a method derived from Koiter’s theorem. Furthermore, the results are compared with cycle-by-cycle method based on nonlinear material properties.

Structural Integrity Research for Reactor Pressure Vessel Under In-Vessel Retention of a Core Melt

2016 ◽  
Author(s):  
Yongjian Gao ◽  
Yinbiao He ◽  
Ming Cao ◽  
Yuebing Li ◽  
Shiyi Bao ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Material Properties ◽  
Power Plants ◽  
Structural Integrity ◽  
Plastic Material ◽  
Plastic Region ◽  
Reactor Pressure Vessel ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Reactor Pressure

In-Vessel Retention (IVR) is one of the most important severe accident mitigation strategies of the third generation passive Nuclear Power Plants (NPP). It is intended to demonstrate that in the case of a core melt, the structural integrity of the Reactor Pressure Vessel (RPV) is assured such that there is no leakage of radioactive debris from the RPV. This paper studied the IVR issue using Finite Element Analyses (FEA). Firstly, the tension and creep testing for the SA-508 Gr.3 Cl.1 material in the temperature range of 25°C to 1000°C were performed. Secondly, a FEA model of the RPV lower head was built. Based on the assumption of ideally elastic-plastic material properties derived from the tension testing data, limit analyses were performed under both the thermal and the thermal plus pressure loading conditions where the load bearing capacity was investigated by tracking the propagation of plastic region as a function of pressure increment. Finally, the ideal elastic-plastic material properties incorporating the creep effect are developed from the 100hr isochronous stress-strain curves, limit analyses are carried out as the second step above. The allowable pressures at 0 hr and 100 hr are obtained. This research provides an alternative approach for the structural integrity evaluation for RPV under IVR condition.

Experiment and Elastic-Plastic Modelling of the IPN160 Beam

2015 ◽  
Vol 769 ◽  
pp. 331-335
Author(s):  
Jakub Vasek ◽  
Oldrich Sucharda
Keyword(s):  
Computational Models ◽  
Plastic Material ◽  
Numerical Models ◽  
Steel Structure ◽  
Material Model ◽  
Nonlinear Material ◽  
Software Application ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Isoparametric Finite Elements

The paper compares the numerical models of and experiments with a beam. The purpose is to evaluate the nonlinear material model of a steel structure. The steel is modelled as an ideal elastic-plastic material. The FEM and eight-node isoparametric finite elements are considered in the analysis. The 3D calculations use different material constants and several approaches are being tested in order to create the computational models. The calculations are performed in the software application developed by our university.

Hole-Drilling Method for Residual Stress Measurement - Consideration of Elastic-Plastic Material Properties

2013 ◽  
Vol 768-769 ◽  
pp. 174-181 ◽  
Author(s):  
David von Mirbach
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Yield Stress ◽  
Material Properties ◽  
Plastic Material ◽  
Hole Drilling ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
Elastic Plastic Material ◽  
Ring Core

Two commonly used mechanical methods for the determination of residual stresses are the hole-drilling method and the ring-core method, which can be regarded as semi-destructive. The most restricting limitation for the general applicability of both methods, according to the current state of science and technology, is the fact that the scope for relatively low residual stress under 60% of the yield stress is limited.This is a result of the notch effect of the hole or ring core, which leads to a plastification around and on the bottom of the hole and ring shaped groove already at stresses well below the yield stress of the material. The elastic evaluation of the resulting plastic strains leads consequently to an overestimation of the delineated residual stresses. In this paper the influence of elastic-plastic material properties no the specific calibration function for the hole-drilling method using the differential method is studied, and the method of adaptive calibration functions is presented.

Stress and Buckling of Internally Pressurized, Elastic-Plastic Torispherical Vessel Heads—Comparisons of Test and Theory

1977 ◽  
Vol 99 (1) ◽  
pp. 39-53 ◽  
Author(s):  
D. Bushnell ◽  
G. D. Galletly
Keyword(s):  
Mild Steel ◽  
Large Deflection ◽  
Plastic Material ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Test Results ◽  
Elastic Plastic ◽  
State Of Stress ◽  
Elastic Plastic Material ◽  
Good Agreement

Several aluminum and mild steel torispherical heads were tested by Galletly and by Kirk and Gill and subsequently analyzed by Bushnell with use of the BOSOR5 computer program. The thinnest specimens buckled at pressures for which part of the toroidal knuckle was stressed well beyond the yield point. The analysis includes large deflection effects, nonlinear material behavior, and meridional variation of the thickness. The calculated strains in the thicker specimens agree reasonably well with the test results, but the calculated prebuckling strains in the thinnest specimens are generally greater than the values measured in the torodial knuckle after the onset of plastic flow. Reasonably good agreement between test and theory is obtained for the buckling pressures of aluminum specimens, but the calculated buckling pressures for mild steel specimens are much lower than the observed values, a discrepancy that is attributed to circumferentially varying thickness and possible inability of the analytical model of the elastic-plastic material to predict accurately the state of stress in the toroidal knuckle where loading is nonproportional once yielding has occurred.

Elastic-Plastic Analysis of Stresses and Initiation of Cracks in a Ceramic Coating Under Indentation by an Elastic Sphere

1998 ◽  
Vol 120 (3) ◽  
pp. 463-469 ◽  
Author(s):  
K. Hayashi ◽  
F. Yuan
Keyword(s):  
Ceramic Coating ◽  
Plastic Material ◽  
Circumferential Stress ◽  
Material Behavior ◽  
Elastic Sphere ◽  
The Finite Element Method ◽  
Elastic Plastic ◽  
Formation Of Cracks ◽  
Elastic Plastic Material ◽  
Radial Cracks

The elastic-plastic contact problem of a ceramic coating on a half-space indented by an elastic sphere is solved by the use of the finite element method under a variety of conditions. An elastic-plastic material behavior with isotropic strain hardening was employed. Results for stresses, during loading and after unloading, on the surface and along the axis of symmetry are presented and formation of cracks is discussed in detail, emphasizing the influence of the thickness of coating. It is shown that the circumferential stress on the surface of the coating is highly tensile so that radial cracks are induced for a sharp indenter. But, for a blunt indenter, the radial stress is tensile and is always larger than the circumferential stress, leading to the formation of circumferential cracks. It is also shown that, in the case of a sharp indenter, radial cracks can be induced during unloading.

Analysis of the spherical indentation cycle for elastic–perfectly plastic solids

2004 ◽  
Vol 19 (12) ◽  
pp. 3641-3653 ◽  
Author(s):  
L. Kogut ◽  
K. Komvopoulos
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Elastic Modulus ◽  
Yield Strength ◽  
Material Properties ◽  
Deformation Behavior ◽  
Plastic Material ◽  
Elastic Plastic ◽  
Loading And Unloading ◽  
Elastic Plastic Material

A finite element analysis of frictionless indentation of an elastic–plastic half-space by a rigid sphere is presented and the deformation behavior during loading and unloading is examined in terms of the interference and elastic–plastic material properties. The analysis yields dimensionless constitutive relationships for the normal load, contact area, and mean contact pressure during loading for a wide range of material properties and interference ranging from the inception of yielding to the initiation of fully plastic deformation. The boundaries between elastic, elastic–plastic, and fully plastic deformation regimes are determined in terms of the interference, mean contact pressure, and reduced elastic modulus-to-yield strength ratio. Relationships for the hardness and associated interference versus elastic–plastic material properties and truncated contact radius are introduced, and the shape of the plastic zone and maximum equivalent plastic strain are interpreted in light of finite element results. The unloading response is examined to evaluate the validity of basic assumptions in traditional indentation approaches used to measure the hardness and reduced elastic modulus of materials. It is shown that knowledge of the deformation behavior under both loading and unloading conditions is essential for accurate determination of the true hardness and reduced elastic modulus. An iterative approach for determining the reduced elastic modulus, yield strength, and hardness from indentation experiments and finite element solutions is proposed as an alternative to the traditional method.

Structural Integrity Evaluation for the Analysis of Corroded Pipelines With Multiple Corrosion Defects

2006 ◽  
Author(s):  
Alejandro Andueza ◽  
Thiago Pontual
Keyword(s):  
Structural Integrity ◽  
Plastic Material ◽  
Material Model ◽  
Model Generation ◽  
The Finite Element Method ◽  
Failure Pressure ◽  
Linear Elastic ◽  
Asme Code ◽  
Corrosion Defects ◽  
Elastic Plastic Material

The structural integrity evaluation of corroded pipelines is very important for the management of systems that are in operation in order to help managers in the important decision of repairing the line. The required models for the analysis of corroded pipelines with multiple corrosion defects are in many cases a hard task to be generated. This paper presents a new methodology for the generation of full 3D hex meshes for the analysis using the Finite Element Method. The algorithm, developed specifically for the analysis of corroded pipelines, makes the task of model generation with multiple corrosion defects easier and faster. Examples with one and two corrosion defects are presented using a linear-elastic material model and the corresponding results compared to the criteria established by ASME code sec. VIII div. 2. The same models are analyzed using ideal elastic-plastic material model in order to determine the minimum failure pressure for the corroded pipes. The numerical failure pressures obtained are also compared to the values obtained from DNV RP-F101 method for single defects and experimental results. Finally, a new repairing methodology that allows the continuous operation of the pipeline in a safer way is presented. This methodology can help managers in the undertaking of scheduling a full repair of the pipeline in a much more flexible way.

Characterization of Elastic-plastic Material Properties for IMC Layer of ENEPIG by Using Reverse Algorithm

2010 ◽  
Author(s):  
Jong-Min Kim ◽  
Hyun-Boo Lee ◽  
Yoon-Suk Chang ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
...  
Keyword(s):  
Material Properties ◽  
Plastic Material ◽  
Elastic Plastic ◽  
Elastic Plastic Material
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