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G. Jaeger

Bio: G. Jaeger is an academic researcher from Leibniz Association. The author has contributed to research in topics: Fatigue limit & Tempering. The author has an hindex of 1, co-authored 1 publications receiving 43 citations.

Papers
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TL;DR: In this paper, a mutiphase microstructure was developed in a V-bearing medium carbon microalloyed (MA) steel through a two-step cooling process that was followed by an annealing treatment.
Abstract: To improve toughness and fatigue strength, a mutiphase (ferrite (F)–bainite (B)–martensite (M)) microstructure was developed in a V-bearing medium carbon microalloyed (MA) steel through a two-step cooling process that was followed by an annealing (two-step cooling and annealing (TSCA)) treatment In the present paper, the high cycle fatigue (HCF) response determined in terms of the endurance limit, long crack fatigue threshold (ΔKth), crack closure and fatigue crack growth rate (FCGR) in a material that has a multiphase microstructure is presented and compared with those of the same material with a ferrite–pearlite (F–P) and a tempered martensite (T–M) microstructure obtained by air-cooling (AC) and quenching and tempering (Q&T), respectively Long crack fatigue threshold (ΔKth) and crack closure were evaluated using a dynamic compliance (DYNACOMP) measurement technique The fatigue limit of the F–B–M and the T–M microstructures (∼400 MPa) was greater than that of the F–P microstructure (∼340 MPa) At load ratios less than 05, the threshold for long crack growth was lower for the F–B–M microstructure compared with that of the F–P microstructure This is attributed to the reduced roughness-induced crack closure (RICC) contribution to the threshold in the former multiphase microstructure A quantitative analysis of the near-threshold fracture surfaces validated the above conclusion Fatigue crack growth rate in the Paris regime was found to be independent of the microstructure but dependent on the load ratio

51 citations


Cited by
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TL;DR: In this article, the authors analyzed the fatigue behavior of 22MnB5 press hardened steels cut by laser and shearing with two different clearance values and compared them with a high drawing quality mild steel and a dual phase steel with a tensile strength of 1000MPa, DP1000.

70 citations

Journal ArticleDOI
TL;DR: In this paper, the role of microstructure types in fatigue crack growth behaviors in ferrite-pearlite steel and ferrite bainite steel was investigated using in-situ scanning electron microscopy (SEM) and fatigue fractography analysis.
Abstract: The roles of microstructure types in fatigue crack growth behaviors in ferrite–pearlite steel and ferrite–bainite steel were investigated. The ferrite–bainite dual-phase microstructure was obtained by intermediate heat treatment, conducted on ferrite–pearlite hot-rolled low carbon steel. This paper presents the results from investigation using constant stress-controlled fatigue tests with in-situ scanning electron microscopy (SEM), fatigue crack growth (FCG) rate tests, and fatigue fractography analysis. Microscopy images arrested by in-situ SEM showed that the fatigue crack propagation in F–P steel could become unstable more ealier compared with that in F–B steel. The fatigue cracks in ferrite–pearlite were more tortuous and could propagate more freely than that in ferrite–bainite microstructures. However, frequent crack branching were observed in ferrite–bainite steel and it indicated that the second hard bainite phase effectively retarded the crack propagation. The variation of FCG rate ( da / dN ) with stress intensity factor range (Δ K ) for F–P and F–B steels was discussed within the Paris region. It was shown that FCG rate of F–P steel was higher than that of F–B steel. Moreover, the fatigue fracture surface analysis proved that grain boundaries could also play a role in the resistance of crack propagation.

59 citations

Journal ArticleDOI
TL;DR: In this paper, the role of microstructure on the fatigue behavior of pearlitic steels with different degrees of cold drawing was investigated, focusing on the region II (Paris) of the fatigue behaviour, measuring the constants (C and m) for the different degree of drawing.

54 citations

Journal ArticleDOI
TL;DR: In this article, a correlation between the microstructure and mechanical properties of 42CrMo4 steel, with two different microstructures, was concerned with a correlation of the micro-structure with mechanical properties.
Abstract: This study is concerned with a correlation between the microstructure and mechanical properties of 42CrMo4 steel, with two different microstructures. Quench tempering and step quenching heat treatments produced tempered martensite and ferrite–bainite–martensite (FBM) microstructures, respectively. Tensile test results indicated a yield-drop effect in FBM microstructure with ferritic matrix. This was attributed to dislocation generation in ferrite phase during bainitic and martensitic transformations. Fractographic investigations indicated transgranular cleavage and microvoid in FBM and tempered martensite microstructures, respectively. This can be attributed to high density of interphase boundary in FBM microstructure and carbide formation in tempered martensite microstructure.

47 citations

Journal ArticleDOI
TL;DR: In this article, the effect of V up to 0.45% on the high-cycle fatigue properties of medium-carbon microalloyed (MA) steel 37MnSiVS, for the development of new crackable MA forging steel with excellent fatigue properties was investigated.

47 citations