Karl Heinz Lang - Academia.edu (original) (raw)
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Papers by Karl Heinz Lang
Procedia Engineering, 2010
To increase the fatigue limit of high-strength steels which typically fail from non-metallic incl... more To increase the fatigue limit of high-strength steels which typically fail from non-metallic inclusions it is necessary to modify the inclusions and/or the surrounding matrix. The goal must be a higher threshold for crack initiation and/or crack propagation. One possibility to reach this goal is to execute a thermal or thermomechanical treatment (TT and TMT). The present work discusses a series of such treatments that were applied to classical bainitic materials states. The different treatments consisted of shortened isothermal bainitic transformations as well as cyclic loading, either with constant or stepwise increasing load amplitude, which were applied at increased temperature in the range of dynamic strain ageing. The lifetime behaviour of the different material states was determined in bending fatigue tests. In order to describe and compare the different treatments it was necessary to evaluate the stress intensity factors arising at the critical inclusions. The results for cyclic loading yielding a lifetime of 10 7 cycles turned out to be in good agreement with the predictions using the stress intensity factor developed by Murakami. To consider different numbers of cycles to failure this calculation method was successfully extended and a modified stress intensity factor was defined. The same method was also used to test and evaluate specimens with artificial flaws. These showed the same behaviour as the specimens which failed from natural non-metallic inclusions.
MTZ - Motortechnische Zeitschrift, 2008
In den letzten Jahren hat die Steigerung der Motoreneffizienz und der spezifischen Leistung zu pr... more In den letzten Jahren hat die Steigerung der Motoreneffizienz und der spezifischen Leistung zu progressiv höheren Belastungen der inneren Komponenten von Verbrennungsmotoren geführt. Besonders das Downsizing von Ottound Dieselmotoren hat die thermomechanische Belastung zu einem kritischen Aspekt in der Auslegung neuer Motoren gemacht. Die Haltbarkeitsabschätzung derart belasteter Komponenten ist hier sowohl durch Anforderungen an die Zuverlässigkeit als auch an die Wirtschaftlichkeit zunehmend gefordert. Die im Antriebsstrangbereich bei BMW entwickelte Methodik zur Betriebsfestigkeitsbewertung erfolgte mit dem Schwerpunkt auf dem Mechanismus der thermomechanischen Ermüdung TMF (Thermo-Mechanical Fatigue). ENTWICKLUNG MTZ 03I2008 Jahrgang 69 206 Finite Elemente Bild 6: Beschreibung der Lebensdauer in TMF-und LCF-Versuchen mit einem ΔJ-Parameter Download des Beitrags unter www.ATZonline.de Read the English e-magazine.
Procedia Engineering, 2010
To increase the fatigue limit of high-strength steels which typically fail from non-metallic incl... more To increase the fatigue limit of high-strength steels which typically fail from non-metallic inclusions it is necessary to modify the inclusions and/or the surrounding matrix. The goal must be a higher threshold for crack initiation and/or crack propagation. One possibility to reach this goal is to execute a thermal or thermomechanical treatment (TT and TMT). The present work discusses a series of such treatments that were applied to classical bainitic materials states. The different treatments consisted of shortened isothermal bainitic transformations as well as cyclic loading, either with constant or stepwise increasing load amplitude, which were applied at increased temperature in the range of dynamic strain ageing. The lifetime behaviour of the different material states was determined in bending fatigue tests. In order to describe and compare the different treatments it was necessary to evaluate the stress intensity factors arising at the critical inclusions. The results for cyclic loading yielding a lifetime of 10 7 cycles turned out to be in good agreement with the predictions using the stress intensity factor developed by Murakami. To consider different numbers of cycles to failure this calculation method was successfully extended and a modified stress intensity factor was defined. The same method was also used to test and evaluate specimens with artificial flaws. These showed the same behaviour as the specimens which failed from natural non-metallic inclusions.
MTZ - Motortechnische Zeitschrift, 2008
In den letzten Jahren hat die Steigerung der Motoreneffizienz und der spezifischen Leistung zu pr... more In den letzten Jahren hat die Steigerung der Motoreneffizienz und der spezifischen Leistung zu progressiv höheren Belastungen der inneren Komponenten von Verbrennungsmotoren geführt. Besonders das Downsizing von Ottound Dieselmotoren hat die thermomechanische Belastung zu einem kritischen Aspekt in der Auslegung neuer Motoren gemacht. Die Haltbarkeitsabschätzung derart belasteter Komponenten ist hier sowohl durch Anforderungen an die Zuverlässigkeit als auch an die Wirtschaftlichkeit zunehmend gefordert. Die im Antriebsstrangbereich bei BMW entwickelte Methodik zur Betriebsfestigkeitsbewertung erfolgte mit dem Schwerpunkt auf dem Mechanismus der thermomechanischen Ermüdung TMF (Thermo-Mechanical Fatigue). ENTWICKLUNG MTZ 03I2008 Jahrgang 69 206 Finite Elemente Bild 6: Beschreibung der Lebensdauer in TMF-und LCF-Versuchen mit einem ΔJ-Parameter Download des Beitrags unter www.ATZonline.de Read the English e-magazine.