218 Prakt. Met. Sonderband 52 (2018)
simulation model (FE) of the microstructure was created. The targeted microhardness
measurements delivered load-indentation depth results, which were used for determination
of local stress-strain-curves for FE simulations. The aim of this study was to develop an
effective method of material’s characterization in order to provide reliable data for FE
simulations of anisotropic materials on the micro scale. Especially, segregation regions in
steels are known as prone to build inhomogeneity and deviations from regular
microstructure e.g. hydrogen-flakes which may promote crack propagation under
mechanical loading. The role of martensite in these regions and its influence on enhanced
heterogeneity of stress and strain distributions in connection with elevated risk of crack
initiation and crack growth there [4] need in-depth investigations. The further development
of the FE models and parameter studies taking into account different crack configurations (me
in the microstructure are in progress. This contribution presents an additional tool to
fracture mechanics methods through extension of the length scale to micro scale on which i”
effects leading to crack initiation may occur. =
4. SUMMARY
» Characterization of complex microstructures with a combination of different fs
experimental methods (optical microscopy + SEM + EBSD + IQ + KAM +EDX) was PL
performed in this work. tr
+ Determination of local material's properties from instrumented microhardness HEE
measurements (Vickers) was carried out.
» The local stress-strain-curves were used as input data for FE simulations.
Simulated stress and strain partitioning among the microstructural
phases/constituents can help to clarify and to predict damage mechanisms active in
this material under mechanical loading.
* The influence of the microstructure on the stress and strain distributions can be he
studied in more sophisticated models containing realistic crack configuration known '
for instance from ultrasonic measurements. F
Analysis of possible micro-mechanisms that can be active in regions with high Ü
stress and strain-gradients leading to development of high tensile stresses which Ro
are crucial for crack growth and detrimental for material integrity. VE
lz
Können
REFERENCES jenen
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16. für
