Room temperature low cycle fatigue (LCF) and fracture behaviour of a medium carbon V-bearing microalloyed steel has been studied. The experimentally determined LCF life is compared with the life predicted by the 'modified universal slopes' equation. Cyclic stress response showed softening at lower plastic strain amplitudes (≤0.3%) and hardening at higher plastic strain amplitudes (>0.3%). The possible reasons for the above behaviour are discussed. An analysis of the fracture surfaces revealed a mixed mode of fracture that involved different fracture mechanisms. Cracks did not initiate at the inclusions. Copyright © 1997 Elsevier Science Ltd. All rights reserved.

V. Subramanya Sarma

Department of Metallurgical and Materials Engineering

Fatigue of materials

FRACTURE MECHANICS

Inclusions

Strain hardening

Stress analysis

CYCLIC STRESSES

LOW CYCLE FATIGUE (LCF)

MEDIUM CARBON MICROALLOYED STEEL

Plastic strain

Carbon steel

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IIT Madras

Low cycle fatigue behaviour of a medium carbon microalloyed steel

International Journal of Fatigue

Experimental determination of strain-fatigue life curve is expensive considering the time and effort involved. Several empirical relations based on monotonic tensile properties and/or hardness is available for estimating strain-fatigue life properties. Existing criteria to evaluate the accuracy of these empirical relations are limited by the data points in the strain-fatigue life curve. A new criterion based on the prediction errors of fatigue constants is proposed to overcome the limitation. Around eight prediction methods are evaluated for two hundred twenty-six steel grades from literature using the existing and the proposed criteria. It is observed that the conclusions from the new criterion are more reliable than the existing criteria. © 2010 Elsevier Ltd. All rights reserved.

Weighted error criterion to evaluate strain-fatigue life prediction methods

The cyclic stress-strain behaviour of two microalloyed steels with different microstructures has been characterised at room temperature under strain controlled low cycle fatigue. The cyclic stress-strain curve in the double logarithmic plot shows a linear relation for both steels. A transition of the cyclic stress-strain curve from softening to hardening with increasing strain amplitude has been observed with respect to the corresponding tensile curve. The strain amplitude for the onset of cyclic softening to hardening transition has been found to be dependent on grain size. The strain lifetime behaviour, estimated from modified universal slopes equation, shows similar trends as Nb or V bearing microalloyed steels. The cyclic characteristics of the two microalloyed steels have been compared with corresponding predeformed state carried out under stress controlled conditions. While, cyclic saturation was observed in case where the extent of predeformation was within the Lüders strain, cyclic softening occurred when it exceeded the Lüders strain. It has been attempted to provide a mechanistic understanding of the differences in the cyclic behaviour of the two steels owing to the microstructure and predeformation. © 2009 Institute of Materials, Minerals and Mining.

Materials Science and Technology

Cyclic stress-strain characteristics of two microalloyed steels

The surfaces of specimens of AISI 304LN stainless steel were given different levels of finish by means of electropolishing and mechanical polishing with emery papers of different grit sizes. They were subjected to total strain-controlled low-cycle fatigue (LCF) deformation at room temperature. The cyclic stress response and the strain-life plots were recorded. As opposed to the mechanically polished specimens, the electropolished specimens displayed secondary hardening in the later stages of deformation even at low strain amplitudes. This behaviour could be attributed to increased martensite formation in the latter case because of the enhanced life. The effect of electropolishing in enhancing the LCF life was more pronounced at the lower strain amplitudes. © 1995.

Journal	Data powered by TypesetInternational Journal of Fatigue
Publisher	Data powered by TypesetElsevier Ltd
ISSN	01421123
Open Access	No