Approximate method for the analysis of components undergoing ratchetting and failure

1998 ◽  
Vol 33 (1) ◽  
pp. 55-65 ◽  
Author(s):  
J Lin ◽  
F P E Dunne ◽  
D R Hayhurst
Keyword(s):  
Approximate Method ◽  
Mechanical Loading ◽  
Thermal Loading ◽  
Cyclic Plasticity ◽  
Processing Unit ◽  
Computationally Efficient ◽  
Element Analysis ◽  
Cyclic Thermal Loading ◽  
Central Processing ◽  
Practical Design

An approximate method has been presented for the design analysis of engineering components subjected to combined cyclic thermal and mechanical loading. The method is based on the discretization of components using multibar modelling which enables the effects of stress redistribution to be included as creep and cyclic plasticity damage evolves. Cycle jumping methods have also been presented which extend previous methods to handle problems in which incremental plastic straining (ratchetting) occurs. Cycle jumping leads to considerable reductions in computer CPU (central processing unit) resources, and this has been shown for a range of loading conditions. The cycle jumping technique has been utilized to analyse the ratchetting behaviour of a multibar structure selected to model geometrical and thermomechanical effects typically encountered in practical design situations. The method has been used to predict the behaviour of a component when subjected to cyclic thermal loading, and the results compared with those obtained from detailed finite element analysis. The method is also used to analyse the same component when subjected to constant mechanical loading, in addition to cyclic thermal loading leading to ratchetting. The important features of the two analyses are then compared. In this way, the multibar modelling is shown to enable the computationally efficient analysis of engineering components.

scholarly journals Shakedown of a Thick Cylinder With a Radial Crosshole

2006 ◽  
Author(s):  
Duncan Camilleri ◽  
Donald Mackenzie ◽  
Robert Hamilton
Keyword(s):  
Thermal Loading ◽  
Constant Pressure ◽  
Element Analysis ◽  
Cyclic Thermal Loading ◽  
Interaction Diagram ◽  
Thin Cylinder ◽  
Structural Discontinuity ◽  
Thick Cylinder ◽  
Elastic Shakedown ◽  
Plastic Shakedown

The shakedown behaviour of a thin cylinder subject to constant pressure and cyclic thermal loading is described by the well known Bree diagram. In this paper, the shakedown and ratchetting behaviour of a thin cylinder, a thick cylinder and a thick cylinder with a radial crosshole is investigated by inelastic finite element analysis. Load interaction diagrams identifying regions of elastic shakedown, plastic shakedown and ratchetting are presented. The interaction diagrams for the plain cylinders are shown to be similar to the Bree Diagram. Incorporating the radial crossbore in the thick cylinder significantly reduces the plastic shakedown boundary on the interaction diagram but does not significantly affect the ratchet boundary. The radial crosshole can therefore be regarded as a local structural discontinuity and neglected when determining the maximum shakedown or (primary plus secondary stress) load in Design by Analysis.

Computation of Ratchet Limits for Structures Subjected to Cyclic Loading and Temperature

2002 ◽  
Author(s):  
A. R. S. Ponter ◽  
H. Chen ◽  
M. Habibullah
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Mechanical Loading ◽  
Limit Theorems ◽  
Thermal Loading ◽  
Loading History ◽  
Cyclic Thermal Loading ◽  
Elastic Plastic ◽  
Plastic Structure ◽  
Shakedown Limit

The paper discusses methods of evaluating the ratchet limit for an elastic/plastic structure subjected to cyclic thermal and mechanical loading. A recently developed minimization theorems by Ponter and Chen [2] provides a generalization of the shakedown limit theorems for histories of load in excess of shakedown. This allows the development of programming methods that locate the ratchet boundary in excess of shakedown. Examples of applications are provided including the performance of a cracked body subjected to cyclic thermal loading. Finally, the theory is used to discuss Kalnins’ [4] proposal that short cut finite element solutions may be used to assess whether a particular loading history lies within a ratchet limit.

Large Scale Finite Element Analysis Via Assembly-Free Deflated Conjugate Gradient

2014 ◽  
Vol 14 (4) ◽  
Author(s):  
Praveen Yadav ◽  
Krishnan Suresh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Conjugate Gradient ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Solid Mechanics ◽  
Processing Unit ◽  
Element Analysis ◽  
Central Processing ◽  
Computational Bottleneck

Large-scale finite element analysis (FEA) with millions of degrees of freedom (DOF) is becoming commonplace in solid mechanics. The primary computational bottleneck in such problems is the solution of large linear systems of equations. In this paper, we propose an assembly-free version of the deflated conjugate gradient (DCG) for solving such equations, where neither the stiffness matrix nor the deflation matrix is assembled. While assembly-free FEA is a well-known concept, the novelty pursued in this paper is the use of assembly-free deflation. The resulting implementation is particularly well suited for large-scale problems and can be easily ported to multicore central processing unit (CPU) and graphics-programmable unit (GPU) architectures. For demonstration, we show that one can solve a 50 × 106 degree of freedom system on a single GPU card, equipped with 3 GB of memory. The second contribution is an extension of the “rigid-body agglomeration” concept used in DCG to a “curvature-sensitive agglomeration.” The latter exploits classic plate and beam theories for efficient deflation of highly ill-conditioned problems arising from thin structures.

scholarly journals Examining Photolysis Rates with a Prototype Online Photolysis Module in CMAQ

2007 ◽  
Vol 46 (8) ◽  
pp. 1252-1256 ◽  
Author(s):  
Francis S. Binkowski ◽  
Saravanan Arunachalam ◽  
Zachariah Adelman ◽  
Joseph P. Pinto
Keyword(s):  
Nitrogen Dioxide ◽  
Cross Sections ◽  
Lookup Table ◽  
Processing Unit ◽  
Computationally Efficient ◽  
Time Step ◽  
Central Processing ◽  
Online Module ◽  
Table Method ◽  
Photolysis Rates

Abstract A prototype online photolysis module has been developed for the Community Multiscale Air Quality (CMAQ) modeling system. The module calculates actinic fluxes and photolysis rates (j values) at every vertical level in each of seven wavelength intervals from 291 to 850 nm, as well as the total surface irradiance and aerosol optical depth within each interval. The module incorporates updated opacity at each time step, based on changes in local ozone, nitrogen dioxide, and particle concentrations. The module is computationally efficient and requires less than 5% more central processing unit time than using the existing CMAQ “lookup” table method for calculating j values. The main focus of the work presented here is to describe the new online module as well as to highlight the differences between the effective cross sections from the lookup-table method currently being used and the updated effective cross sections from the new online approach. Comparisons of the vertical profiles for the photolysis rates for nitrogen dioxide (NO2) and ozone (O3) from the new online module with those using the effective cross sections from a standard CMAQ simulation show increases in the rates of both NO2 and O3 photolysis.

An FEA Investigation Into Ratchetting Induced Purely by Cyclic Thermal Loading

2014 ◽  
Author(s):  
Conor S. Campbell ◽  
Donald Mackenzie
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Thermal Loading ◽  
Plastic Material ◽  
Lead Author ◽  
Element Analysis ◽  
Linear Temperature ◽  
Cyclic Thermal Loading ◽  
Elastic Plastic ◽  
Model Structures

A detailed finite element investigation of the cyclic elastic-plastic response of three model structures subject to thermal and mechanical loading is presented within the context of ASME B&PV Code Section VIII Division 2 design requirements. The model structures are a thin tube subject to constant internal pressure and a cyclic through-thickness linear temperature gradient (the Bree problem), a three bar system subject to cyclic thermal loading only and an intermediate thickness tube subject to internal pressure and an axially moving cyclic temperature wave. Incremental elastic-plastic finite element analysis assuming an elastic-perfectly-plastic material model and small deformation theory is performed for each model structure and ratchet and shakedown boundaries determined by application of a bisection method. Results are compared with ASME VIII ratcheting assessment procedures. The results show that in the Bree problem ratcheting does not occur under thermal loading alone, as expected, however for the two other sample structures it is shown that ratchetting can occur under thermal loading for structures subject to specific deformation constraints. The lead author is an MS level student at the University of Strathclyde.

The Incremental Strain Growth of Elastic-Plastic Bodies Subjected to High Levels of Cyclic Thermal Loading

1984 ◽  
Vol 51 (3) ◽  
pp. 470-474 ◽  
Author(s):  
A. R. S. Ponter ◽  
A. C. F. Cocks
Keyword(s):  
Mechanical Loading ◽  
Yield Surface ◽  
Thermal Loading ◽  
Local Curvature ◽  
Cyclic Thermal Loading ◽  
Elastic Plastic ◽  
Plastic Shakedown ◽  
Incremental Strain

A linearized method of analysis proposed in an accompanying paper [1] is used to obtain the ratchet rate for two types of thermal loading problems where parts of the structure experience reversed plastic straining. For structures that can shakedown plasticially it is found that for a given increment of load beyond the plastic shakedown boundary, the rate of ratchet increases with increasing level of thermal loading. When a structure is unable to shakedown plastically it ratchets at low mechanical loading as the result of a localized mechanism that involves some reversed plasticity. It is shown that the ratchet rate in such situations can be substantial but its value is very dependent on the local curvature of the yield and not the accuracy of the yield surface itself.

A Deflated Assembly Free Approach to Large-Scale Implicit Structural Dynamics

2015 ◽  
Vol 10 (6) ◽  
Author(s):  
Amir M. Mirzendehdel ◽  
Krishnan Suresh
Keyword(s):  
Structural Dynamics ◽  
Large Scale ◽  
Processing Unit ◽  
Element Analysis ◽  
Central Processing ◽  
Bottle Neck ◽  
Gpu Architectures ◽  
Many Core ◽  
Matrix Free ◽  
Fast Inversion

The primary computational bottle-neck in implicit structural dynamics is the repeated inversion of the underlying stiffness matrix. In this paper, a fast inversion technique is proposed by merging four distinct but complementary concepts: (1) voxelization with adaptive local refinement, (2) assembly-free (a.k.a. matrix-free or element-by-element) finite element analysis (FEA), (3) assembly-free deflated conjugate gradient (AF-DCG), and (4) multicore parallelization. In particular, we apply these concepts to the well-known Newmark-beta method, and the resulting AF-DCG is well-suited for large-scale problems. It can be easily ported to many-core central processing unit (CPU) and multicore graphics-programmable unit (GPU) architectures, as demonstrated through numerical experiments.

Continuum damage based constitutive equations for copper under high temperature creep and cyclic plasticity

1992 ◽  
Vol 437 (1901) ◽  
pp. 545-566 ◽  
Keyword(s):  
Constitutive Equations ◽  
Damage Evolution ◽  
Thermal Loading ◽  
Evolution Equations ◽  
Experimental Results ◽  
Cyclic Plasticity ◽  
Nominal Composition ◽  
Cyclic Thermal Loading ◽  
Temperature Range ◽  
Good Agreement

Viscoplastic constitutive equations without damage for cast copper have been developed for cyclic mechanical and cyclic thermal loading over the temperature range 20-500 °C (nominal composition: 99.99 % Cu, 0.005 % O 2 , B.S. 10355-1037). Model predictions have been compared with experimental cyclic plasticity tests. Good agreement has been achieved. Creep and cyclic plasticity damage evolution equations have been developed. The effect of cyclic hardening on creep damage evolution has been modelled by introducing an internal variable to represent the state of material hardening. A creep cyclic plasticity interaction law has been proposed, and with the creep and cyclic plasticity damage evolution equations, has been combined with the viscoplastic constitutive equations to establish a unified material model for copper over the temperature range 20-500 °C. Predictions of lifetime and deformation history have been made for uni-axial test specimens subject to strain-controlled cyclic plasticity and ratchetting. Good agreement has been obtained with experimental results. The model has been validated for mechanical loading by predicting the response of uni-axial test specimens to strain-controlled cyclic plasticity with strain hold periods, and to combined strain-controlled cyclic plasticity tests with strain holds and ratchetting. The predictions compare well with experimental results. The model has been validated for cyclic thermal loading by predicting the response of uni-axial test specimens subjected to thermal loading cycles. Good comparisons have been achieved with experimental results.

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