Nonlinear Analysis of Anchored Tanks Subject to Equivalent Seismic Loading

2002 ◽  
Author(s):  
D. Redekop ◽  
P. Mirfakhraei ◽  
T. Muhammad
Keyword(s):  
Nonlinear Behavior ◽  
Seismic Loading ◽  
Material Behavior ◽  
Seismic Action ◽  
The Finite Element Method ◽  
Perfectly Plastic ◽  
Liquid Storage ◽  
Failure Loads ◽  
Elastic Perfectly Plastic ◽  
Hydrodynamic Effects

The finite element method is applied to the problem of the nonlinear behavior of anchored cylindrical liquid-storage tanks subject to horizontal seismic loading. The tank alone is modelled with assumptions of fixed conditions at the base and free conditions at the top. Geometric nonlinearity is considered and the material behavior is taken as elastic-perfectly plastic. The loading consists of a constant hydrostatic pressure to which is added an equivalent static pressure representing hydrodynamic effects arising from seismic action. The latter loading is increased until failure occurs. As an indication of the validity of the approach a comparison with a test result is given. A parametric study is then conducted. Nonlinear failure loads are calculated in each case, and these are compared with previously determined elastic buckling loads.

A General Solution for the Pressurized Elastoplastic Tube

1992 ◽  
Vol 59 (1) ◽  
pp. 20-26 ◽  
Author(s):  
David Durban ◽  
Michael Kubi
Keyword(s):  
General Solution ◽  
Finite Strain ◽  
Cylindrical Tube ◽  
Yield Function ◽  
Material Behavior ◽  
Deformation Pattern ◽  
Perfectly Plastic ◽  
Plastic Phase ◽  
Thin Walled ◽  
Elastic Perfectly Plastic

The problem of a thick-walled cylindrical tube subjected to internal pressure is investigated within the framework of continuum plasticity. Material behavior is modeled by a finite strain elastoplastic flow theory based on the Tresca yield function. The deformation pattern is restricted by the plane-strain condition but arbitrary hardening and elastic compressibility are accounted for. A general solution is given in terms of quadratures. The analysis also includes treatment of a second plastic phase, characterized by corner relations, that may develop at the inner boundary. It is shown that the interface between the two plastic regions moves initially outwards and then, beyond a certain strain level, it moves back inwards. Some useful and simple results are given for thin-walled tubes of hardening materials and for thick-walled elastic/perfectly plastic tubes.

scholarly journals Thermo-Mechanical Modeling of Distortions Promoted during Cooling of Ti-6Al-4V Part Produced by Superplastic Forming

2016 ◽  
Vol 838-839 ◽  
pp. 196-201
Author(s):  
Maxime Rollin ◽  
Vincent Velay ◽  
Luc Penazzi ◽  
Thomas Pottier ◽  
Thierry Sentenac ◽  
...  
Keyword(s):  
Finite Element ◽  
Thermal Stresses ◽  
Superplastic Forming ◽  
Model Material ◽  
Material Behavior ◽  
Mechanical Modeling ◽  
Temperature Dependent ◽  
Finite Element Software ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

In AIRBUS, most of the complex shaped titanium fairing parts of pylon and air inlets are produced by superplastic forming (SPF). These parts are cooled down after forming to ease their extraction and increase the production rate, but AIRBUS wastes a lot of time to go back over the geometric defects generated by the cooling step. This paper investigates the simulations of the SPF, cooling and clipping operations of a part on Abaqus® Finite element software. The different steps of the global process impact the final distortions. SPF impacts the thickness and the microstructure/behavior of material, cooling impacts also the microstructure/behavior of material and promotes distortions through thermal stresses and finally, clipping relaxes the residual stresses of the cut part. An elastic-viscoplastic power law is used to model material behavior during SPF and a temperature dependent elastic perfectly plastic model for the cooling and clipping operations.

Plastic Buckling of Cones Subjected to Axial Compression and External Pressure

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
J. Błachut ◽  
A. Muc ◽  
J. Ryś
Keyword(s):  
Axial Compression ◽  
Wall Thickness ◽  
True Strain ◽  
Safety Margin ◽  
External Pressure ◽  
Perfectly Plastic ◽  
Test Models ◽  
Failure Loads ◽  
Elastic Perfectly Plastic ◽  
Strain Modeling

The paper provides details about tests on six steel cones. Test models were machined from 250 mm diameter billet. All cones had substantial and integral top and bottom flanges in order to secure well defined boundary conditions. Experimental data were obtained for: (i) two cones subjected to axial compression, (ii) two cones subjected to external pressure, and (iii) the remaining two models subjected to combined action of external pressure and axial compression. Apart from axisymmetric modeling of tested cones, true geometry with true wall thickness was also used in calculations. Theoretical failure loads were obtained for: (i) elastic perfectly plastic, (ii) engineering stress–strain, and (iii) true stress–true strain modeling of steel. The latter approach coupled with measured geometry and wall thickness secured safe predictions of the collapse loads in all cases. Comparisons of experimental collapse loads with estimates given by ASME and ECCS design codes are included. It is seen here that the ASME and ECCS rules provide a safety margin of about 100% against the collapse (except 50% for axial compression in the case of the ECCS).

Mechanical and Thermodynamic Considerations of an Assemblage of Homogeneous Elastic-Plastic States

1968 ◽  
Vol 35 (3) ◽  
pp. 596-603 ◽  
Author(s):  
David Rubin
Keyword(s):  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Strain Energy ◽  
Material Behavior ◽  
Free State ◽  
Elastic Plastic ◽  
Elastic Range ◽  
Perfectly Plastic ◽  
Stress Free State ◽  
Elastic Perfectly Plastic

The mechanics and the thermodynamics of plastic deformation are considered in terms of a general assemblage or continuum of elastic, perfectly plastic elements or states. Such models not only match the external mechanical behavior of real materials structures and continua, but they also afford a simple thermodynamic definability. A consideration of the internal behavior shows that the stress-free state has the maximum elastic range. Hardening in the sense of an increasing macroscopic elastic range is accompanied by a release of stored strain energy; the stress-free state always is restorable. This behavior is appropriate for real structures and continua. However, it is precisely these continuum characteristics which make the assemblages inappropriate models of material behavior. Barriers to continuing plastic deformation are required which do exist on the microscale, but lie outside of the scope of the most complex of these thermodynamically well-defined assemblages.

Overcoming Limitations of the Conventional Strain-Life Fatigue Damage Model

1996 ◽  
Vol 118 (1) ◽  
pp. 103-108 ◽  
Author(s):  
T. E. Langlais ◽  
J. H. Vogel
Keyword(s):  
Damage Model ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Material Behavior ◽  
Perfectly Plastic ◽  
Linear Relationships ◽  
Elastic Perfectly Plastic ◽  
Plastic Components ◽  
Log Linear ◽  
Very High

The strain-based approach to fatigue life prediction usually relies on the conventional strain-life equation which correlates the elastic and plastic strain to the life. The correlation is based on separate log-linear curve fits of the elastic and plastic components of the strain data versus the life. It is well known, however, that these linear relationships may be valid only within a specific interval of stress or strain. When material behavior approaches elastic-perfectly plastic, for instance, it is not uncommon for the test data to deviate from linearity at both very high and very low strains. For such materials a separate fit of each curve is likely to give material constants significantly inconsistent with the fit of the cyclic stress-strain curve, especially if a good local fit over a restricted interval is obtained. In this work, some of the errors that arise as a result of this inconsistency are described, and recommended methods are developed for treating these errors. Numerical concerns are also addressed, and sample results are included.

scholarly journals Shakedown Analysis of “Soil-Pile Foundation-Frame” System under Seismic Action

2018 ◽  
Vol 28 (1) ◽  
pp. 100-114
Author(s):  
Piotr Alawdin ◽  
George Bulanov
Keyword(s):  
Fem Analysis ◽  
Deformation Model ◽  
Seismic Action ◽  
Elastic Halfspace ◽  
Brittle Behavior ◽  
Perfectly Plastic ◽  
Frame System ◽  
Elastic Perfectly Plastic ◽  
Pile Deformation ◽  
Shakedown Limit

Abstract In this article, the seismic shakedown FEM analysis of reinforced concrete and composite spatial frame structures on the deformable foundation, taking into account the elasticplastic and brittle behavior of structures elements, is presented. A foundation consists of group of the piles in the soil. The behavior of soil is described here using+ the elastic halfspace theory. The pile deformation model is assumed to be elastic-perfectly plastic, where the bearing capacity is determined by the results of testing the soils or the piles themselves. An example of seismic shakedown limit analysis is presented.

On the Material Modeling of the Autofrettaged Pressure Vessel Steels

2008 ◽  
Author(s):  
G. H. Farrahi ◽  
E. Hosseinian ◽  
A. Assempour
Keyword(s):  
Uniaxial Tension ◽  
High Strength Steels ◽  
High Strength ◽  
Test Methods ◽  
Material Behavior ◽  
Material Modeling ◽  
Chemical Compositions ◽  
Accurate Analysis ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

Material modeling of the high strength steels plays an important role in accurate analysis of autofrettaged tubes. Although, the loading behavior of such materials is nearly elastic-perfectly plastic, their unloading behavior due to Bauschinger effect is very complicated. DIN1.6959 steel is frequently used for construction of autofrettaged tubes in some countries such as Germany and Switzerland. In spite of similarity between chemical compositions of this steel with A723 steel, due to different material processing, two steels have unlikely behavior. In this paper material behavior of DIN1.6959 has been accurately modeled by uniaxial tension-compression test results. Both 6 mm and 12.5 mm diameter specimens were used and compared. Also various functions for modeling of autofrettaged steels were investigated and new function was introduced for accurate modeling. Moreover, two test methods, i.e. uniaxial tension-compression and torsion tests, which used for modeling of autofrettage steels, were analyzed. As well, material models of three important autofrettage steels, i.e. A723, HB7 and Din1.6959 were compared.

An efficient procedure for modelling limited plastic flow

1998 ◽  
Vol 212 (8) ◽  
pp. 731-740 ◽  
Author(s):  
P M Blomerus ◽  
D A Hills
Keyword(s):  
Plastic Material ◽  
Notch Root ◽  
Stress Raiser ◽  
Fem Analysis ◽  
The Finite Element Method ◽  
Field Boundary ◽  
Efficient Procedure ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Good Agreement

A degree of plasticity is often tolerated at stress raising features in severely loaded, nominally elastic, components. Conventionally, the methods available for analysis are the finite element method (FEM) or an approximate notch root plastic strain method. The method introduced here is based on the idea of distributing dislocations to form a perturbation on an elasticity solution to solve the problem for an elastic—perfectly plastic material in transverse plane strain. Specialized kernels are used to satisfy exactly the far field boundary conditions and those at the stress raiser, so that only the small plastic enclave of material need be discretized. The method is seen to follow the incremental nature of the problem and to take into account the stress redistribution in plasticity. The problem of a circular hole under remote tension is solved and good agreement with an FEM analysis of a similar problem is observed.

Analytical Modeling of Hydraulically Expanded Tube-To-Tubesheet Joints

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Nor Eddine Laghzale ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Contact Pressure ◽  
Analytical Model ◽  
Plastic Material ◽  
Material Behavior ◽  
Initial Contact ◽  
Expansion Process ◽  
Element Analysis ◽  
Elastoplastic Behavior ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

The loss of the initial tightness during service is one of the major causes of failure of tube-to-tubesheet joints. The initial residual contact pressure and its variation during the lifetime of the joint are among the parameters to blame. A reliable assessment of the initial contact pressure value requires accurate and rigorous modeling of the elastoplastic behavior of the tube and the tubesheet during the expansion process. This paper deals with the development of a new analytical model used to accurately predict the residual contact pressure resulting from a hydraulic expansion process. The analytical model is based on the elastic perfectly plastic material behavior of the tube and the tubesheet and the interaction between these two elements of the expanded joint. The model results have been compared and validated with those of the more accurate finite element analysis models. Additional comparisons have been made with existing methods.

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