Shakedown analysis for complex loading using superposition

2002 ◽  
Vol 37 (5) ◽  
pp. 399-412 ◽  
Author(s):  
M Muscat ◽  
R Hamilton ◽  
J. T Boyle
Keyword(s):  
Finite Element ◽  
Complex Loading ◽  
Design Criteria ◽  
Cyclic Loads ◽  
Linear Superposition ◽  
Element Analysis ◽  
Shakedown Analysis ◽  
Mechanical Loads ◽  
Square Plate ◽  
Elastic Shakedown

Bounding techniques for calculating shakedown loads are of great importance as design criteria since these eliminate the need for performing full cyclic loading programs either numerically or experimentally. The classical Melan theorem provides a way to recognize whether or not elastic shakedown occurs under a specified loading. Polizzotto extended Melan's theorem to the case where a combination of steady and cyclic loads are acting on the structure. The purpose of this paper is to present a finite element method, based on Polizzotto's theorem, to estimate elastic shakedown for a structure subjected to loads resulting from a combination of steady and cyclic mechanical loads. This method, called non-linear superposition, is then applied to investigate the shakedown behaviour of a biaxially loaded square plate with a central hole. Results obtained for the plate with a hole problem are compared with those available in the literature and are verified by means of cyclic elastoplastic finite element analysis.

Elastic Shakedown in Pressure Vessel Components Under Non-Proportional Loading

2002 ◽  
Author(s):  
Martin Muscat ◽  
Robert Hamilton
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Pressure Vessel ◽  
Proportional Loading ◽  
Linear Superposition ◽  
Element Analysis ◽  
Mechanical Loads ◽  
Bound Theorem ◽  
Square Plate ◽  
Elastic Shakedown

Bounding techniques for calculating shakedown loads are of great importance in design since this eliminates the need for performing full elasto-plastic cyclic loading analyses. The classical Melan’s lower bound theorem is widely used for calculating shakedown loads of pressure vessel components under proportional loading. Polizzotto extended the Melan’s theorem to the case of non-proportional loading acting on a structure. This paper presents a finite element method, based on Polizzotto’s theorem, to estimate the elastic shakedown load for a structure subjected to a combination of steady and cyclic mechanical loads. This method, called non-linear superposition, is then applied to investigate the shakedown behaviour of a pressure vessel component — a nozzle/cylinder intersection and that of a biaxially loaded square plate with a central hole. Results obtained for both problems are compared with those available in the literature and are verified by means of cyclic elasto-plastic finite element analysis.

Elastic-Shakedown Analysis of Axisymmetric Nozzles

2003 ◽  
Vol 125 (4) ◽  
pp. 365-370 ◽  
Author(s):  
Martin Muscat ◽  
Donald Mackenzie
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Lower Bound ◽  
Pressure Vessel ◽  
Element Analysis ◽  
Shakedown Analysis ◽  
Elastic Plastic ◽  
Section Viii ◽  
Elastic Shakedown ◽  
Division 2

An investigation of the shakedown behavior of axisymmetric nozzles under internal pressure is presented. The analysis is based on elastic-plastic finite element analysis and Melan’s lower bound shakedown theorem. Calculated shakedown pressures are compared with values from the literature and with the ASME Boiler and Pressure Vessel Code Section VIII Division 2 primary plus secondary stress limits. Results obtained by the lower bound method are also verified by cyclic elastic-plastic finite element analysis.

A Non-Cyclic Method for Plastic Shakedown Analysis

2003 ◽  
Author(s):  
W. Reinhardt
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Computing Time ◽  
Strain Accumulation ◽  
Analysis Method ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Cyclic Phenomenon ◽  
Elastic Shakedown ◽  
Plastic Shakedown

Shakedown is a cyclic phenomenon, and for its analysis it seems natural to employ a cyclic analysis method. Two problems are associated when this direct approach is used in finite element analysis. Firstly, the analysis typically needs to be stabilized over several cycles, and the analysis of each individual cycle may need a considerable amount of computing time. Secondly, even in cases where a stable cycle is known to exist, the finite element analysis can show a small continuing amount of strain accumulation. For elastic shakedown, non-cyclic analysis methods that use Melan’s theorem have been proposed. The present paper extends non-cyclic lower bound methods to the analysis of plastic shakedown. The proposed method is demonstrated with several example problems.

scholarly journals Finite Element Analysis to the Effect of Thermo-Mechanical Loads on Stress Distribution in Buried Polyethylene Gas Pipes Jointed by Electrofusion Sockets, Repaired by PE Patches

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2818 ◽  
Author(s):  
Reza Khademi-Zahedi ◽  
Pouyan Alimouri
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Temperature Drop ◽  
Traffic Load ◽  
Seasonal Temperature ◽  
Thermal Loads ◽  
Stress Concentrations ◽  
Present Contribution ◽  
Element Analysis ◽  
Mechanical Loads

Polyethylene (PE) gas pipes can be jointed together by electrofusion PE fittings, which have sockets that are fused onto the pipe. Additionally, electrofused PE patches can be used to repair defected pipes. When these pipelines are buried under the ground, they can experience sever local stresses due to the presence of pipe joints, which is superimposed on the other effects including the soil-structure interaction, traffic load, soil’s column weight, a uniform internal pressure, and thermal loads imposed by daily and/or seasonal temperature changes. The present contribution includes two cases. At first, stress variations in buried polyethylene gas pipe and its socket due to the aforementioned loading condition is estimated using finite element. The pipe is assumed to be made of PE80 material and its jointing socket material is PE100. Afterward, the effects of aforementioned thermo-mechanical loads on the stress distribution in patch repaired buried pipes are well investigated. The soil physical properties and the underground polyethylene pipe installation method are based on the American association of state highway and transportation officials and American society for testing and material standards. The computer simulation and analysis of stresses are performed through the finite element package of ANSYS Software. Stress concentrations can be observed in both components due to the presence of the socket or the repair patch. According to the results, the electrofusion sockets can be used for joining PE gas pipes even in hot climate areas. The maximum values of these stresses happen to be in the pipe. Also, the PE100 socket is more sensitive to a temperature drop. Additionally, all four studied patch arrangements show significant reinforcing effects on the defected section of the buried PE gas pipe to withstand applied loads. Meanwhile, the defected buried medium density polyethylene (MDPE) gas pipe and its saddle fused patch can resist the imposed mechanical and thermal loads of +22 °C temperature increase.

Probing the Instability of a Cluster of Slip Bonds Upon Cyclic Loads With a Coupled Finite Element Analysis and Monte Carlo Method

2014 ◽  
Vol 81 (11) ◽  
Author(s):  
Xiaofeng Chen ◽  
Bin Chen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Failure Modes ◽  
Underlying Mechanism ◽  
Cyclic Stretch ◽  
Cyclic Loads ◽  
Element Analysis ◽  
The Stability

Cells are subjected to cyclic loads under physiological conditions, which regulate cellular structures and functions. Recently, it was demonstrated that cells on substrates reoriented nearly perpendicular to the stretch direction in response to uni-axial cyclic stretches. Though various theories were proposed to explain this observation, the underlying mechanism, especially at the molecular level, is still elusive. To provide insights into this intriguing observation, we employ a coupled finite element analysis (FEA) and Monte Carlo method to investigate the stability of a cluster of slip bonds upon cyclic loads. Our simulation results indicate that the cluster can become unstable upon cyclic loads and there exist two characteristic failure modes: gradual sliding with a relatively long lifetime versus catastrophic failure with a relatively short lifetime. We also find that the lifetime of the bond cluster, in many cases, decreases with increasing stretch amplitude and also decreases with increasing cyclic frequency, which appears to saturate at high cyclic frequencies. These results are consistent with the experimental reports. This work suggests the possible role of slip bonds in cellular reorientation upon cyclic stretch.

Finite Element Based Automated Analysis for Determining Ratchet, Shakedown and Elastic Limits

2011 ◽  
Author(s):  
Jeries Abou-Hanna ◽  
Michael Paluszkiewicz
Keyword(s):  
Finite Element ◽  
Cyclic Load ◽  
Complex Geometry ◽  
Limit Load ◽  
Automated Analysis ◽  
Numerical Approach ◽  
Material Behavior ◽  
Element Analysis ◽  
Daunting Task ◽  
Elastic Shakedown

In order to determine the ratchet and shakedown limit curves for even a simple component, such as a tube under a constant pressure load and cyclic thermal load, can be a daunting task when using conventional analysis methods (elasto-plastic cyclic finite element analysis) that require repeated iterative simulations to determine the state of the structure, elastic, shakedown, plastic or ratchet. In some cases, the process is further complicated by the difficulty in interpreting results of the cyclic loading to determine in which regime the structure is. Earlier work by Abou-Hanna and McGreevy was able to demonstrate limit load analysis of a structure whose yield strength is modified based on cyclic load, provided the ratchet limit [1]. The method, called Anisotropic Load Dependent Yield Modification (LDYM), was implemented by using a user subroutine with ABAQUS, a general commercial finite element code. The approach adopted provided ratchet limits for only one individual cyclic load value. The work presented here describes a process for analyzing the structure and determining the elastic, shakedown and ratchet boundaries all in one finite element simulation using only one analysis step. The approach manipulates the structure material behavior that enables the resetting of the material characteristics to their original values in order to be able to analyze the structure for different sets of cyclic and primary load combinations. The process was verified using problems available in the literature, such as the Bree tube and Ponter’s Holed Plate. Additionally, a tubular T-joint was used as an example of the effectiveness of the process for a three dimensional complex geometry. The tubular T-joint results are verified against baseline data from the iterative elastic-plastic simulations used to determine the elastic, shakedown, and ratchet limits. The work presented highlights the advantages and limitations of this numerical approach which requires little interaction with the analyst.

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