PSI - Issue 68

T. Korschinsky et al. / Procedia Structural Integrity 68 (2025) 1196–1202 Korschinsky et al. / Structural Integrity Procedia 00 (2025) 000–000

1202

7

3.4. Comparison of the Chaboche combined hardening model and the DD3M When comparing the simulated hysteresis loops in Figure 6, the improvement of the DD3M over the Chaboche combined hardening model becomes evident. Especially the better match of the location of the reversal points promises to be an improved basis for fatigue life estimations, since the x- and y- values of these points are exactly the stress and strain values, /01 = ( 0 + / ) and 0,3 , that are used to calculate the damage parameter according to (Smith, et al., 1970). 456 = 6( 0 + / ) ∙ 0,3 ∙ (3) In (Korschinsky, et al., 2024) a graphic illustration of the improvement in fatigue life evaluation is given for both the unnotched as well as the notched specimens as well as additional information on the transferability. 4. Conclusion and further investigation 4.1 Conclusion The study presented in this paper started with the experimental investigation on the cyclic transient material behavior and showed the inadequacies of the Chaboche combined hardening model when dealing with materials that do not have a stabilizing behavior. A solution for these shortcomings was presented with the Damage-dependent Modified Material Model: The DD3M describes the transient softening behavior significantly more precisely by simulating each cycle with an individual kinematic parameter set. The result is a hysteresis loop with a better match to the experimental data and is the basis for big improvements in fatigue life evaluation. 4.2 Further investigation At the current status, the DD3M is relatively elaborate due to the calibration and the code that needs to run within the FE-system. A further development of the DD3M towards an easier application would certainly help using the models benefits to solve actual engineering problems in industry. To use the DD3M beyond the academic application, further investigations on the boundaries and the universality of the DD3M need to take place. When it comes to the transferability of the model to notched specimens or parts, further attention is needed. While implementing the micro supporting effect on top of the elastic-plastic calculations, the physical correctness of the approach should be checked and understood in more detail. References Korschinsky, T., Möller, B., Kiel, M., Hecht, M., 2024: Analysis of the Anisotropic Cyclic Material Behavior of EN AW-1050A H24 derived from strain-contolled testing using clip-on extensometer and an optical system. Crystals 14 8, 686. Kiel, M., Möller, B., 2024: Berücksichtigung der WAAM-gefertigten Oberfläche bei der Betriebsfestigkeitsbewertung. WerkstattsTechnik , submitted . Stahlinstitut, 2006: SEP1240. Prüf- und Dokumentationsrichtlinie für die experimentelle Ermittlung mechanischer Kennwerte von Feinblechen aus Stahl für die CAE-Berechnung. Basquin, O. H., 1910: The exponential law of endurance tests. Proc. ASTM 10 2, 625–630. Coffin, L. F., 1954: A study of the effects of cyclic thermal stresses on a ductile metal. Transactions of the American Society of Mechanical Engineers , 931–950. Manson, S. S., 1965: Fatigue: a complex subject - some simple approximations. Experimental mechanics 7 5, 193–226. Morrow, J. D., 1965: Cyclic plastic strain energy and fatigue of metals. Internal friction, damping, and cyclic plasticity, ASTM International 378, 45–87. Ramberg, W.; Osgood, W. R., 1943: Description of stress-strain curves by three parameters. NACA Technical Note 902, 23–41. Chaboche J.L., 1986: Time-Independent Constitutive Theories For Cyclic Plasticity. International Journal of Plasticity 2.2, 149-188. Smith, K. N.; Watson, P.; Topper, T. H., 1970: A Stress-Strain Function for the Fatigue of Metals. Journal of matierals 5 4, 767–778. Korschinsky, T.; Möller, B.; Kiel, M., 2024: Dehnungsbasierte Lebensdauerabschätzung von Aluminiumwerkstoffen für Zellverbinder. WerkstattsTechnik , submitted .