hot peening is a surface treatment used to increase the fatigue strength of metallic components, for example gears, and it is of great interest to be able to model and simulate the effect of this treatment in order to save time and money. An important parameter that has to be considered when modeling the peening situation is the strain rate dependence of the target material. In this work the strain rate dependence of SS2506 case hardened gear steel was investigated experimentally by making single impacts with spherical carbide balls on test plates of the steel and measuring depth, diameter and material pile-up of the formed indents. The results were then used to verify an FE-model for single impacts, which includes a model for strain rate dependence. The aim was to find the model, with corresponding material parameters, that represents the strain rate dependence the best. As a complement, experiments and simulations were also performed on an Almen strip (SAE 1070 cold rolled spring steel) to compare with the results of the SS2506 steel. Single impacts were also made with shot peening media used in the industry on the SS2506 test plates, in order to see how these indents differ from the ones made with spherical carbide balls. No strain rate dependence model was found that fit the experimental results for the SS2506 steel, while for the Almen plate, the Johnson-Cook model showed to fit the experimental results the best. The reason for this behavior of the SS2506 steel could be the transformation of retained austenite in the steel. The impacts made with shot peening media on the SS2506 steel showed that the roughness of the media has a great influence on the shape of the indents.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-141667 |
| Date | January 2013 |
| Creators | Ekström, Karin |
| Publisher | KTH, Materialvetenskap |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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