Numerical lower bound shakedown analysis of engineering structures

2011 ◽  
Vol 200 (41-44) ◽  
pp. 2828-2839 ◽  
Author(s):  
Jaan-Willem Simon ◽  
Dieter Weichert
Keyword(s):  
Lower Bound ◽  
Engineering Structures ◽  
Shakedown Analysis

Shakedown Analysis Combined With the Problem of Heat Conduction

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Jaan-Willem Simon ◽  
Min Chen ◽  
Dieter Weichert
Keyword(s):  
Heat Conduction ◽  
Lower Bound ◽  
Heat Exchangers ◽  
Thermal Loading ◽  
Heat Conduction Problem ◽  
Simplified Model ◽  
Interior Point Algorithm ◽  
Tube Sheet ◽  
Engineering Structures ◽  
Shakedown Analysis

This paper deals with the computation of shakedown loads of engineering structures subjected to varying loads. In particular, we focus on thermal loading and the resulting heat conduction problem in combination with shakedown analysis. The analysis is based on the lower bound shakedown theorem by Melan. The calculation is carried out by use of an interior-point algorithm. Emphasis is placed on the presentation of theoretical derivations, whereas numerical aspects are out of scope. The methodology is illustrated by application to a simplified model of a tube sheet in heat exchangers.

A numerical method of lower bound dynamic shakedown analysis for 3D structures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guichen Zhang ◽  
Heng Peng ◽  
Hongtao Zhang ◽  
Juzhen Tang ◽  
Yinghua Liu
Keyword(s):  
Lower Bound ◽  
Stress Field ◽  
Iterative Algorithm ◽  
Dynamic Load ◽  
Closed Loop ◽  
The Self ◽  
Engineering Structures ◽  
Shakedown Analysis ◽  
Equilibrium Stress ◽  
Content Type

PurposeThe safety assessment of engineering structures under repeated variable dynamic loads such as seismic and wind loads can be considered as a dynamic shakedown problem. This paper aims to extend the stress compensation method (SCM) to perform lower bound dynamic shakedown analysis of engineering structures and a double-closed-loop iterative algorithm is proposed to solve the shakedown load.Design/methodology/approachThe construction of the dynamic load vertexes is carried out to represent the loading domain of a structure under both dynamic and quasi-static load. The SCM is extended to perform lower bound dynamic shakedown analysis of engineering structures, which constructs the self-equilibrium stress field by a series of direct iteration computations. The self-equilibrium stress field is not only related to the amplitude of the repeated variable load but also related to its frequency. A novel double-closed-loop iterative algorithm is presented to calculate the dynamic shakedown load multiplier. The inner-loop iteration is to construct the self-equilibrated residual stress field based on the certain shakedown load multiplier. The outer-loop iteration is to update the dynamic shakedown load multiplier. With different combinations of dynamic load vertexes, a dynamic shakedown load domain could be obtained.FindingsThree-dimensional examples are presented to verify the applicability and accuracy of the SCM in dynamic shakedown analysis. The example of cantilever beam under harmonic dynamic load with different frequency shows the validity of the dynamic load vertex construction method. The shakedown domain of the elbow structure varies with the frequency under the dynamic approach. When the frequency is around the resonance frequency of the structure, the area of shakedown domain would be significantly reduced.Research limitations/implicationsIn this study, the dynamical response of structure is treated as perfect elastoplastic. The current analysis does not account for effects such as large deformation, stochastic external load and nonlinear vibration conditions which will inevitably be encountered and affect the load capacity.Originality/valueThis study provides a direct method for the dynamical shakedown analysis of engineering structures under repeated variable dynamic load.

Recent Advances in Lower Bound Shakedown Analysis

2009 ◽  
Author(s):  
Dieter Weichert ◽  
Abdelkader Hachemi
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Process Engineering ◽  
Operating Conditions ◽  
Structural Elements ◽  
Shakedown Analysis ◽  
Material Models ◽  
Practical Engineering ◽  
Safe Operating ◽  
New Algorithms

The special interest in lower bound shakedown analysis is that it provides, at least in principle, safe operating conditions for sensitive structures or structural elements under fluctuating thermo-mechanical loading as to be found in power- and process engineering. In this paper achievements obtained over the last years to introduce more sophisticated material models into the framework of shakedown analysis are developed. Also new algorithms will be presented that allow using the addressed numerical methods as post-processor for commercial finite element codes. Examples from practical engineering will illustrate the potential of the methodology.

A lower bound formulation for shakedown analysis

2004 ◽  
pp. 303-307
Author(s):  
A Lyamin ◽  
S Sloan ◽  
K Krabbenhoft ◽  
M Hjiaj
Keyword(s):  
Lower Bound ◽  
Shakedown Analysis

On the Constraint-Based Failure Assessment of Surface Cracks in T-Plate Welded Joints

2003 ◽  
Author(s):  
X. Wang ◽  
R. Bell ◽  
S. B. Lambert
Keyword(s):  
Lower Bound ◽  
Welded Joints ◽  
Structural Integrity ◽  
Constraint Effect ◽  
Engineering Structures ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Recent Developments ◽  
Failure Predictions ◽  
Crack Tip Constraint

The loss of crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. However, conventional failure assessment schemes (CEGB-R6, BS-7910) use lower bound toughness obtained from highly constrained test specimens. Cracks in many real engineering structures are not highly constrained, which makes failure predictions using conventional failure assessment schemes based on lower bound fracture toughness values overly pessimistic. Excessive pessimism in the structural assessment can lead to unwarranted repair or decommissioning of structures, and thus cause unneeded cost and inconvenience. Recent developments on constraint-based fracture mechanics have enabled the practical assessment of defective components including the constraint effect. For example, the recent revision of R6 and the newly developed structural integrity assessment procedures for European industry (SINTAP) have suggested a framework for failure assessments including the constraint effect. In this paper, the constraint-based failure assessment of surface cracked T-plate welded joints under tension load is presented. Different issues including the constraint-based failure assessment diagrams, the treatment of combining primary and the secondary loads, and the calculation of stress intensity factors, limit loads and constraint parameters for surface cracked T-plate joints are discussed. It is demonstrated that when the lower constraint effect is properly accounted for, the maximum allowable tensile stress level increases substantially.

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