Influence of Microstructure and Specimen Size on Cleavage Fracture Below and At General Yield

Dünnewald-Arfmann, H.; Twickler, M.; Twickler, R.; Dahl, Winfried

doi:10.1016/b978-0-08-034804-9.50168-6

Cited by 2 publications

(1 citation statement)

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“…But it seems to us more reasonable to explain, together with other authors, the temperature dependent rJ; -values by the lower yield stress [12;20]. The temperature dependence of rJ; was also found for line-pipe steels with bainitic microstructures in [21]. Cleavage fracture is of statistical matter.…”

Section: Discussionmentioning

confidence: 63%

Temperature dependence of the microscopic cleavage fracture stress

Jüde-Esser¹,

Grimpe²,

Dahl³

1995

Steel Research

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The microscopic cleavage fracture stress aj which could be responsible for dramatic failure is commonly seen as a temperature independent material property. But a dependence on temperature was found in several former investigations. In this work new studies on cleavage fracture with low carbon steel C 10 were performed. The stress aj = a~r was determined with double-edge notched tensile (DENT) specimens at different temperatures and various crosshead speeds. In addition tests were made with four-point bend specimens (SENB4) according to Griffiths and Owen. A significant influence of temperature on the microscopic cleavage fracture stress was found.The explanation for this result is seen in terms of the thermal activation of dislocation movement, which is needed to produce the critical conditions for fracture. As temperature independence is proposed from the "Local Approach" a check up of this procedure is given and limitations of the "Weakest Link-model" are shown. Temperaturabhangigkeit der mikroskopischen Spaltbruchspannung. FOr das katastrophale Versagen eines Bauteils kann das Erreichen der mikroskopische Spaltbruchspannung aj verantwortlich sein. Aligemein wird diese kritische Spannung als unabhanqiq von Temperatur und Belastungsgeschwindigkeit angesehen. Eigene Untersuchungen hatten jedoch eine Abhanqigkeit von der Temperatur festgestellt. Daher wurden am Stahl C 10 Doppelkerbzugversuche (DENT) Ober einen weiten Temperatur-und Dehngeschwindigkeitsbereich und erqanzend Versuche an Vierpunktbiegeproben (SENB4) durchgefOhrt und mit Hilfe von FE-Rechnungen die mikroskopische Spaltbruchspannung aj = a~ax ermittelt. Die Untersuchungen ergaben eine deutliche Temperaturabhanqlqkelt von ot . Diese Temperaturabhangigkeit wird mit der thermisch aktivierten Versetzungsbewegung begrOndet, die notwendig ist, um die kritischen Bedingungen fOr Spaltbruch herzustellen. Da aus dem "Local Approach" eine Ternperaturunabhanqlqkelt gefolgert wird, wird dessen Aussaqefahlqkelt OberprOft. Die Grenzen des "Weakest Link-Modells" werden aufgezeigt.

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Section: Discussionmentioning

confidence: 63%