Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth

This work presents an in-depth study of the low-cycle fatigue behaviour of ferritic-pearlitic HSLA-420 high-strength steel sheets, with emphasis on the influence of loading direction on fatigue life and damage mechanisms. Plastic strain-controlled fatigue tests were conducted along the rolling (RD)...

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Main Authors: María Cecilia Marinelli, Felipe Díaz, Raúl Bolmaro
Format: Article
Language:English
Published: Gruppo Italiano Frattura 2025-08-01
Series:Fracture and Structural Integrity
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Online Access:https://www.fracturae.com/index.php/fis/article/view/5568
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author María Cecilia Marinelli
Felipe Díaz
Raúl Bolmaro
author_facet María Cecilia Marinelli
Felipe Díaz
Raúl Bolmaro
author_sort María Cecilia Marinelli
collection DOAJ
description This work presents an in-depth study of the low-cycle fatigue behaviour of ferritic-pearlitic HSLA-420 high-strength steel sheets, with emphasis on the influence of loading direction on fatigue life and damage mechanisms. Plastic strain-controlled fatigue tests were conducted along the rolling (RD), transverse (TD), and diagonal (DD) directions. Despite the nearly isotropic tensile response associated with weak crystallographic texture and similar microstructural characteristics, fatigue life varied depending on the loading orientation. RD specimens showed the highest fatigue life, nearly doubling TD at low strain and remaining over 25% at high strain. DD behaved similarly to RD at low strain but approached TD at higher strain levels.  The Coffin–Manson relationship was linear in RD, while TD and DD showed bilinear trends with a slope change at Δεp/2 = 1 × 10⁻³. Transmission electron microscopy revealed that dislocation structure evolution during cycling was direction-dependent. In RD, intragranular slip bands within ferrite grains dominated and acted as primary crack initiation sites. In contrast, TD and DD exhibited subgrain structures near grain boundaries, promoting strain localization and intergranular crack nucleation. At higher strain amplitudes, compact subgrains reinforced by cementite particles favored intergranular crack propagation in TD and DD samples, contributing to reduced fatigue life.
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spelling doaj-art-d96dae9b86d84e5d96fa0733f5f868c52025-08-20T06:51:11ZengGruppo Italiano FratturaFracture and Structural Integrity1971-89932025-08-011974Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growthMaría Cecilia Marinelli0https://orcid.org/0000-0003-3032-9918Felipe Díaz1https://orcid.org/0000-0003-4998-5536Raúl Bolmaro2https://orcid.org/0000-0002-8218-6958Instituto de Física Rosario – CONICET, Universidad Nacional de Rosario, Bv. 27 de febrero 210 bis, 2000 Rosario, ArgentinaDepartamento de Ingeniería Electromecánica, Universidad Tecnológica Nacional-Facultad Regional Rafaela-CONICET, Acuña 49, Rafaela, Santa Fe, Argentina Instituto de Física Rosario – CONICET, Universidad Nacional de Rosario, Bv. 27 de Febrero 210 bis, 2000 Rosario, Argentina This work presents an in-depth study of the low-cycle fatigue behaviour of ferritic-pearlitic HSLA-420 high-strength steel sheets, with emphasis on the influence of loading direction on fatigue life and damage mechanisms. Plastic strain-controlled fatigue tests were conducted along the rolling (RD), transverse (TD), and diagonal (DD) directions. Despite the nearly isotropic tensile response associated with weak crystallographic texture and similar microstructural characteristics, fatigue life varied depending on the loading orientation. RD specimens showed the highest fatigue life, nearly doubling TD at low strain and remaining over 25% at high strain. DD behaved similarly to RD at low strain but approached TD at higher strain levels.  The Coffin–Manson relationship was linear in RD, while TD and DD showed bilinear trends with a slope change at Δεp/2 = 1 × 10⁻³. Transmission electron microscopy revealed that dislocation structure evolution during cycling was direction-dependent. In RD, intragranular slip bands within ferrite grains dominated and acted as primary crack initiation sites. In contrast, TD and DD exhibited subgrain structures near grain boundaries, promoting strain localization and intergranular crack nucleation. At higher strain amplitudes, compact subgrains reinforced by cementite particles favored intergranular crack propagation in TD and DD samples, contributing to reduced fatigue life. https://www.fracturae.com/index.php/fis/article/view/5568Multiaxial low cycle fatigueMechanical propertiesHSLA steel sheetDislocation structuresMicrocraks
spellingShingle María Cecilia Marinelli
Felipe Díaz
Raúl Bolmaro
Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth
Fracture and Structural Integrity
Multiaxial low cycle fatigue
Mechanical properties
HSLA steel sheet
Dislocation structures
Microcraks
title Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth
title_full Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth
title_fullStr Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth
title_full_unstemmed Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth
title_short Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initiation and growth
title_sort fatigue behaviour of high strength low alloy steel sheets influence of loading direction and microstructure on microcrack initiation and growth
topic Multiaxial low cycle fatigue
Mechanical properties
HSLA steel sheet
Dislocation structures
Microcraks
url https://www.fracturae.com/index.php/fis/article/view/5568
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AT felipediaz fatiguebehaviourofhighstrengthlowalloysteelsheetsinfluenceofloadingdirectionandmicrostructureonmicrocrackinitiationandgrowth
AT raulbolmaro fatiguebehaviourofhighstrengthlowalloysteelsheetsinfluenceofloadingdirectionandmicrostructureonmicrocrackinitiationandgrowth