Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


toledo1198808409.pdf (7.85 MB)

ETD Abstract Container

Abstract Header

Anisotropy and Sulfide Inclusion Effects on Tensile Properties and Fatigue Behavior of Steels

Cyril, Nisha S
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1198808409

Abstract Details

2007, Master of Science in Mechanical Engineering, University of Toledo, Mechanical Engineering.
During metal forming processes such as rolling and forging, deformable sulfide inclusions become elongated. Such elongated inclusions can have considerable adverse effects on mechanical properties, if the inclusions are not aligned with the loading direction. The objectives of this study were to evaluate and compare fatigue, monotonic tensile and CVN impact behavior of SAE 4140 steel with high (0.077%S), low (0.012% S) and ultra low (0.004% S) sulfur contents at two hardness levels approximately 43 HRC and 52 HRC). The longitudinally oriented samples at 40 HRC, where sulfide inclusions were oriented along the loading direction, did not exhibit any significant sensitivity of tensile or fatigue properties to the sulfur content. For the transversely oriented samples, however, the tensile ductility and the impact toughness of the high sulfur material was very low at either hardness level while the yield strength of the materials did not differ significantly with the sulfur content at either hardness level. Based on strain-life curves at 52 HRC, there was about a factor of 8 difference in fatigue life in the low cycle fatigue regime and more than an order of magnitude difference in the high cycle regime between the high S and the low S transverse materials. This difference was about a factor of 30 in the low cycle regime and about two orders of magnitude in the high cycle regime between the high S and the ultra low S materials. At 43 HRC, there was about a factor of 40 difference in short life and about one order of magnitude difference at long life between the high S and the ultra low S materials in the transverse direction. At 43 HRC, for which case longitudinal direction data were also available, little difference was noted between the low S, the ultra low S and the longitudinal materials. At 52 HRC, the high S material had a 27% lower fatigue limit than the ultra low S material under transverse loading. At 43 HRC, this reduction was 18%. SEM inspection of failed fatigue test specimens revealed that the fracture surfaces of the high S material were very rough and jagged, indicating several cracks originating from MnS inclusions at either hardness level. For the higher amplitude strain-controlled fatigue tests at both hardness levels, surface cracks that did not result in failure were found for all transverse materials indicating that the cracks initiated very early in the fatigue life. The ratios of predicted fatigue limit values using the parea parameter model proposed by Murakami et al based on inclusion inspection, to the experimental values, ranged between 0.84 and 1.29. The variations of the fatigue and tensile properties were plotted against the sulfur content and relations were obtained for the fatigue constants as functions of sulfur. The relations for the fatigue strength and ductility coefficients and exponents were expressed as functions of sulfur in the Roessle-Fatemi equation which is used to predict the strain-life curve of a steel based on only the hardness, in order to incorporate the effects of sulfur under transverse loading.
Ali Fatemi (Advisor)
233 p.
Engineering, Mechanical
Fatigue; Anisotropy; steels

Recommended Citations

Citations

  • Cyril, N. S. (2007). Anisotropy and Sulfide Inclusion Effects on Tensile Properties and Fatigue Behavior of Steels [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1198808409

    APA Style (7th edition)

  • Cyril, Nisha. Anisotropy and Sulfide Inclusion Effects on Tensile Properties and Fatigue Behavior of Steels. 2007. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1198808409.

    MLA Style (8th edition)

  • Cyril, Nisha. "Anisotropy and Sulfide Inclusion Effects on Tensile Properties and Fatigue Behavior of Steels." Master's thesis, University of Toledo, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1198808409

    Chicago Manual of Style (17th edition)

toledo1198808409
1,792
© 2007, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.