Dresden 2006 – scientific programme

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MM: Metall- und Materialphysik

MM 43: Diffusion III

MM 43.1: Talk

Friday, March 31, 2006, 12:30–12:45, IFW B

Imaging of defect structure in fatigued carbon steel C45E — •Patrick Eich, Matz Haaks, and Karl Maier — Helmholtz Institut für Strahlen- und Kernphysik, Rheinische Friedrich-Wilhelms-Universität Bonn, Nußallee 14-16,D-53115 Bonn, Germany

Nowadays all used construction parts have a finite lifetime under alternate conditions. Hence, a precise damage prediction would be very useful. The observation of the microscopic process of fatigue in a metal is a condition for a reliable damage prediction. Physically, the reason for fatigue is the accumulation of lattice defects, like dislocations, vacancies and vacancy clusters. The increase of the defect concentration due to alternate load fatigue can be observed by positron annihilation spectroscopy. The deformation state at higher load cycle numbers can be estimated from the defect concentration in the early stages of fatigue. [1] Even if a homogeneous stress field is applied, heterogeneous structures in the defect concentration are formed during fatigue. These structures can be imaged using the fine focus positron beam of the Bonn Positron Microprobe. Samples of the carbon steel C45E were tested with alternate load fatigue. At different stages the defect density was examined with a spatial resolution in the micrometer range. [1] M. Haaks, K. Maier in V. Jentsch et al. *extreme events*, Springer 2005, in press