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Research Papers: Materials and Fabrication

# Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading

[+] Author and Article Information
Hélder F.S.G Pereira

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

Abílio M. P. De Jesus

Department of Engineering, Mechanical 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, Mechanical 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(2), 021407 (Jan 21, 2009) (9 pages) doi:10.1115/1.3066774 History: Received August 06, 2007; Revised February 21, 2008; Published January 21, 2009

## Abstract

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren–Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope stress-life curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as nonconservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two-block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely, $R=0$, $R=0.15$, and $R=0.3$. Also, constant amplitude fatigue data are generated for the investigated structural component. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels, and stress ratios. In particular, a clear load sequence effect is verified for the two-block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is nonlinear. This suggests an important effect of the stress ratio on fatigue damage accumulation.

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

Figure 1

Illustration of the nonlinear damage evolution and load sequential effects for two-block loading

Figure 2

Geometry of the specimens (dimensions in millimeters)

Figure 3

S-N curves for the structural component (stress amplitude versus cycles to failure)

Figure 4

S-N curves for the structural component (maximum stress versus cycles to failure)

Figure 5

Comparison between constant and block loading data. H-L and L-H sequences defined by 280 MPa and 400 MPa stress ranges (R=0).

Figure 6

Comparison between constant and block loading data. H-L and L-H sequences defined by 280 MPa and 330 MPa stress ranges (R=0).

Figure 7

Comparison between constant and block loading data. H-L and L-H sequences defined by 280.5 MPa and 340 MPa stress ranges (R=0.15).

Figure 8

Comparison between constant and block loading data. H-L and L-H sequences defined by 245 MPa and 280 MPa stress ranges (R=0.3).

Figure 9

Fatigue data for two-block loading defined by 280 MPa and 400 MPa stress ranges (R=0)

Figure 10

Fatigue data for two-block loading defined by 280 MPa and 330 MPa stress ranges (R=0)

Figure 11

Fatigue data for two-block loading defined by 280.5 MPa and 340 MPa stress ranges (R=0.15)

Figure 12

Fatigue data for two-block loading defined by 245 MPa and 280 MPa stress ranges (R=0.3)

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