Factors determining the torsional fatigue strength in bainitic steels with banded microstructures

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2024-11-17 DOI:10.1016/j.ijfatigue.2024.108714

Soma Yoshimura , Kentaro Wada , Sungcheol Park , Hisao Matsunaga

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Abstract

This study aimed to identify the microstructural factors governing the torsional fatigue strength of bainitic steels. Torsional fatigue tests were performed on two bainitic steels with banded microstructures comprised of soft and hard layers. The soft layers were coarse-grained with low Vickers hardness (HV), while the hard layers were fine-grained with high HV. Both materials possessed similar average HV values but differing band morphologies: a coarse band (CB) with HV = 329 and a fine band (FB) with HV = 314. Interestingly, the FB exhibited a 30 % higher fatigue strength than the CB. Through microscopic observations and finite element analysis, it was established that different fatigue strengths could be attributed to the particular width and array of the bands. The reticular band array in the FB steel raises crack initiation resistance due to the constraint of cyclic plastic deformation. In addition, the narrower spacing of hard layers can impede crack propagation when the extension mode transitions from shear mode to Mode I. In contrast, the columnar array and wider spacing of the bands in the CB steel are likely to provide weaker resistance to crack initiation and propagation, resulting in an inferior fatigue strength.

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决定带状微结构贝氏体钢扭转疲劳强度的因素

本研究旨在确定影响贝氏体钢扭转疲劳强度的微观结构因素。对两种贝氏体钢进行了扭转疲劳试验，这两种钢的微观结构由软层和硬层组成，呈带状。软层为粗颗粒，维氏硬度（HV）较低，而硬层为细颗粒，维氏硬度较高。两种材料的平均维氏硬度值相似，但条带形态不同：粗条带（CB）的维氏硬度值为 329，细条带（FB）的维氏硬度值为 314。有趣的是，FB 的疲劳强度比 CB 高 30%。通过显微镜观察和有限元分析，可以确定不同的疲劳强度可归因于条带的特定宽度和阵列。由于循环塑性变形的限制，FB 钢中的网状带阵列提高了抗裂纹萌生的能力。此外，当延伸模式从剪切模式过渡到模式 I 时，较窄的硬层间距会阻碍裂纹扩展。相比之下，CB 钢中的柱状阵列和较宽的带间距可能会削弱裂纹萌发和扩展的阻力，从而导致疲劳强度降低。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

International Journal of Fatigue 工程技术-材料科学：综合

CiteScore

10.70

自引率

21.70%

发文量

619

审稿时长

58 days

期刊介绍： Typical subjects discussed in International Journal of Fatigue address: Novel fatigue testing and characterization methods (new kinds of fatigue tests, critical evaluation of existing methods, in situ measurement of fatigue degradation, non-contact field measurements) Multiaxial fatigue and complex loading effects of materials and structures, exploring state-of-the-art concepts in degradation under cyclic loading Fatigue in the very high cycle regime, including failure mode transitions from surface to subsurface, effects of surface treatment, processing, and loading conditions Modeling (including degradation processes and related driving forces, multiscale/multi-resolution methods, computational hierarchical and concurrent methods for coupled component and material responses, novel methods for notch root analysis, fracture mechanics, damage mechanics, crack growth kinetics, life prediction and durability, and prediction of stochastic fatigue behavior reflecting microstructure and service conditions) Models for early stages of fatigue crack formation and growth that explicitly consider microstructure and relevant materials science aspects Understanding the influence or manufacturing and processing route on fatigue degradation, and embedding this understanding in more predictive schemes for mitigation and design against fatigue Prognosis and damage state awareness (including sensors, monitoring, methodology, interactive control, accelerated methods, data interpretation) Applications of technologies associated with fatigue and their implications for structural integrity and reliability. This includes issues related to design, operation and maintenance, i.e., life cycle engineering Smart materials and structures that can sense and mitigate fatigue degradation Fatigue of devices and structures at small scales, including effects of process route and surfaces/interfaces.