Citation Link: https://doi.org/10.25819/ubsi/10746
Zur Bestimmung des Kriechverhaltens martensitischer Federstähle im Niedrigtemperaturbereich
Alternate Title
Determination of the Low Temperature Creep Behavior of Martensitic Spring Steels
Publication Type
Doctoral Thesis
Author(s)
Institute
Subjects
Low Temperature Creep
Martensitic Steel
Spring Steel
DDC
620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
GHBS-Clases
Date Issued
2024
Abstract
The global transformation process, which consists of the transition from conventional drives, i.e. internal combustion engine, to battery electric vehicles, is forcing the automotive and automotive supply industries to undergo a significant change. However, the CO2 targets for 2030 cannot be achieved solely by expanding electromobility. This also requires an optimization of existing components. The reduction of CO2 emissions can be attained by reducing friction losses in the valve train. The thermal loads up to 423 K within these valve trains demand a high level of creep or relaxation resistance from the high-strength spring steels. Within the scope of this dissertation, the two existing theories for describing the creep behavior of spring steels in the low-temperature range will be verified and the creep rate-controlling mechanism of dislocation glide will be examined. For this purpose, creep tests with valve spring wires under tensile and torsional loading as well as incremental creep tests, i.e. stress-step or temperature-step tests, will be conducted. Finally, it will be reviewed whether the creep behavior of valve spring wires under biaxial loading can be predicted by the knowledge about the creep behavior of martensitic spring steels under uniaxial loading. This will be done by means of numerical methods, which enables the prediction of the creep behavior of helical compression or valve springs in future.
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Creative Commons license
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