Strain rate sensitivity behavior of a structural steel during low-cycle fatigue investigated using indentation

Nguyen, Ngoc-Vinh; Pham, Thai‐Hoan; Kim, Seung-Eock

doi:10.1016/j.msea.2018.12.025

Cited by 28 publications

(23 citation statements)

References 47 publications

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“…The transition from the maximum to minimum and vice versa in the axial and shear strains is almost instantaneous. A recent study on structural steel, [17], has shown that yield strength and strain hardening exponent increases with increasing the strain rate. Also, increasing the strain amplitudes cause decrease of the strain rate sensitivity.…”

Section: Resultsmentioning

confidence: 99%

New research findings on non-proportional low cycle fatigue

Cernescu

Pullin

2019

MATEC Web Conf.

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One of the challenges regarding multiaxial fatigue damage predictions is non-proportional loading. Relevant studies have shown that these multiaxial loadings cause significant additional hardening and reduction in durability due to non-proportionality. Fatigue life predictions due to non-proportional loadings are based on an equivalent nonproportional strain range that considers a material constant related to additional hardening and a non-proportionality factor. In this paper an analysis of the non-proportional factor for three multiaxial loadings forming a square in γ/√3 -ε coordinates is carried out. One of the observations revealed by this analysis is the sensitivity of the non-proportional factor to variable shear strain rate.1

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Section: Resultsmentioning

confidence: 99%

New research findings on non-proportional low cycle fatigue

Cernescu

Pullin

2019

MATEC Web Conf.

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“…The geometry of the fatigue specimens is divided into three segments as follows: a clamping section, a transition section, and an effective length section. Further details of the fatigue specimens and the fatigue machine can be found out elsewhere [21]. It should be noted that the specimen preparation complies with the ASTM standard [35].…”

Section: Methodsmentioning

confidence: 99%

“…The experimental results showed the excellent LCF properties, in which the number of cycles was less than 100 when the strain amplitude was more than 3%, while the number of cycles was larger than 100 with smaller strain amplitudes. Recently, Nguyen et al [21] investigated the strain rate sensitivity behavior of structural steel subjected to the cyclic loading using the depth-sensing instrumented technique. However, the strain amplitude-dependent behavior of hardness and indentation size effect of SS400 structural steel has not been well investigated so far.…”

Section: Introductionmentioning

confidence: 99%

Characterization of strain amplitude-dependent behavior of hardness and indentation size effect of SS400 structural steel

Vinh

Anh

Thang

2020

STCE

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In this paper, the continuous stiffness measurement (CSM) indentation is employed to investigate fatigue mechanical properties of structural steel under cyclic loading. For this purpose, several representative analytical approaches were introduced to estimate the basic mechanical properties including Young’s modulus and indentation hardness from the characteristics of the loading/unloading curves. Several experiments including CSM nanoindentation, low-cycle fatigue experiment for four strain amplitude levels, optical microscope (OM), and transmission electron microscopy (TEM) examinations were conducted to observe the variation characteristics of mechanical properties at the microscale and their micro-mechanisms. The microstructural evolution of the specimens deformed by the low-cycle fatigue was observed using the OM and TEM examinations. The standard nanoindentation experiments were then performed at different strain rate levels to characterize the influences of strain rate indentation on hardness of the material. The micro-mechanisms established based on the microstructural evolution and strain gradient plasticity theory were introduced to be responsible for the variation of indentation hardness under cyclic loading. Finally, the indentation size effect (ISE) phenomenon in SS400 structural steel was investigated and explained through the strain gradient plasticity theory regarding geometrically necessary dislocations underneath the indenter tip. The experimental results can be used for practical designs as well as for understanding the fatigue behavior of SS400 structural steel. Keywords: cyclic loading; fatigue; nanoindentation; indentation size effect; strain rate sensitivity; structural steel.

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“…For a material with microscale grain size, the dislocation-based activities could be the dominant mechanism during inelastic deformation in such low values of m. Therefore, the dislocation and HAGB densities could play an important role in the varied values of m. It was widely accepted that the increased m could be contributed by lower dislocation density. 14 The dislocations of the FGHAZ region for as-welded and CF-tested specimens were observed by transmission electron microscope (TEM), as show in Figure 12A,B, respectively. It could be observed that the dislocation density was clearly decreased after CF test, from which the dislocation density was supposed to be reduced.…”

Section: Strain Rate Sensitivitymentioning

confidence: 99%

“…13 Nguyen et al investigated the SRS of SM490 steel under prior fatigue loading by nanoindentation and found that the lower dislocation density resulted in the higher value of SRS after fatigue test. 14 Due to the ultra-high displacement sensitivity and high shear-compressive stress beneath nanoindentation, the occurrence of creep deformation was widely observed even for the materials with high-melting point at room temperature. 8,9 In the authors' previous research, the varied creep resistances of the HAZ regions in the as-welded SA508 Gr3 steel welded joints were studied at the microscale by nanoindentation.…”

Section: Introductionmentioning

confidence: 99%

On the microstructural evolution and room‐temperature creep behaviour of 9%Cr steel weld joint under prior creep–fatigue interaction

Song

Qin

Chen

et al. 2020

Fatigue Fract Eng Mat Struct

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The high‐temperature creep–fatigue (CF) interaction on the service damage of P92 welded joint was uncovered based on the evolution of local creep behaviour by nanoindentation. The creep resistance and high‐angle grain boundary (HAGB) distributions of the different regions of welded joint were investigated for the specimens under individual creep (stress relaxation [RS]), fatigue and CF loadings interrupted at lifetime fractions of 10%, 20%, 30%, 60% and 100%. According to structure evolution including the changes of HAGB and dislocation densities during high‐temperature deformation, the local variation mechanism of creep behaviour at different microstructural zones was systematically discussed.

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Strain rate sensitivity behavior of a structural steel during low-cycle fatigue investigated using indentation

Cited by 28 publications

References 47 publications

New research findings on non-proportional low cycle fatigue

New research findings on non-proportional low cycle fatigue

Characterization of strain amplitude-dependent behavior of hardness and indentation size effect of SS400 structural steel

On the microstructural evolution and room‐temperature creep behaviour of 9%Cr steel weld joint under prior creep–fatigue interaction

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