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Research Papers: Materials and Fabrication

# A Preliminary Assessment of the $Ke$ Factor Proposed in the EN13445 Standard for Fatigue Analysis of Unwelded Material

[+] Author and Article Information
Hélder F. Pereira

UCVE, IDMEC-Pólo FEUP, Rua Dr. Roberto Frias, 4200-465 Porto, Portugalhfpereira@portugalmail.pt

Abílio M. De Jesus

Department of Engineering, University of Trás-os-Montes and Alto Douro, Quinta de Prados, 5001-801 Vila Real, Portugalajesus@utad.pt

Alfredo S. Ribeiro

Department of Engineering, University of Trás-os-Montes and Alto Douro, Quinta de Prados, 5001-801 Vila Real, Portugalaribeiro@utad.pt

António A. Fernandes

Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugalaaf@fe.up.pt

J. Pressure Vessel Technol 131(1), 011405 (Dec 01, 2008) (9 pages) doi:10.1115/1.3027455 History: Received August 07, 2006; Revised January 12, 2008; Published December 01, 2008

## Abstract

This paper presents an investigation about the plasticity correction factor, $Ke$, proposed in the Part 3-Clause 18 of the EN13445 standard, for correction of the elastic stress ranges exceeding twice the yield stress, resulting from mechanical loading. The plasticity correction factors are analyzed using a calculation strategy based on a comparison between results from linear elastic and elastoplastic analyses. Several materials, elastoplastic models, and geometries are considered in the study. The performed analyses revealed, for an important number of the situations, an underestimation of the $Ke$ factor when calculated according to the standard procedures. A greater emphasis should be dedicated in the standard to the elastoplastic analysis, since the fatigue resistance data presented in the standard are strain-life type data, overcoming the need for the plasticity correction factor. The elastoplastic analysis should be the preferred approach for evaluation of the strains/stresses for fatigue analysis.

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Copyright © 2009 by American Society of Mechanical Engineers
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## Figures

Figure 8

Typical total εxx strain distributions (generic steel 1 with bilinear plasticity model)

Figure 1

Assessment procedure for Ke factor

Figure 2

Best fit of the plasticity models response to the Ramberg–Osgood relation for the generic steel 1

Figure 3

Best fit of the plasticity models response to the Ramberg–Osgood relation for the generic steel 2

Figure 4

Best fit of the plasticity models response to the Ramberg–Osgood relation for the generic steel 3

Figure 5

Geometry of the tested structural details (dimensions in mm)

Figure 6

Finite element meshes of the structural details with 5mm and 20mm plate thicknesses

Figure 7

Typical stress linearization (σ∞=150MPa, t=5mm)

Figure 13

Deviations from standardized Ke and calculated using a multilinear model, for generic steel 2

Figure 9

Deviations from standardized Ke and calculated using the bilinear model, for generic steel 1

Figure 10

Deviations from standardized Ke and calculated using the multilinear model, for generic steel 1

Figure 11

Deviations from standardized Ke and calculated using the Chaboche model, for generic steel 1

Figure 12

Deviations from standardized Ke and calculated using a bilinear model, for generic steel 2

Figure 14

Deviations from standardized Ke and calculated using the Chaboche model, for generic steel 2

Figure 15

Deviations from standardized Ke and calculated using a bilinear model, for generic steel 3

Figure 16

Deviations from standardized Ke and calculated using a multilinear model, for generic steel 3

Figure 17

Deviations from standardized Ke and calculated using the Chaboche model, for generic steel 3

Figure 18

Prediction of Ke values for generic steel 1

Figure 19

Prediction of Ke values for generic steel 2

Figure 20

Prediction of Ke values for generic steel 3

## Errata

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