Schallemission als Mittel zur Beobachtung von Rißbeginn und Rißfortschritt bei Kaltrissen in geschweißten niedrig legierten hochfesten Stählen / Acoustic emission for observation of cold crack-initiation and -propagation in low alloyed high strength steels / Emission acoustique pour observer initialisation et progress des fissures en des aciers soudes faillement allie a resistance elevee

1980 ◽  
Vol 22 (9) ◽  
pp. 361-364
Author(s):  
N. Prinz ◽  
E. Neumann ◽  
W. Florian ◽  
V. Neumann ◽  
R. Thiel
2007 ◽  
Vol 353-358 ◽  
pp. 1185-1190 ◽  
Author(s):  
Yan Ping Zeng ◽  
Hong Mei Fan ◽  
Xi Shu Wang ◽  
Xi Shan Xie

Specially designed SEM in-situ tensile and fatigue tests have been conducted to trace the entire process of crack initiation and propagation till fracture in an ultra-high strength steel MA250. TiN is a typical inclusion and its average size is in the range of 8~10μm in MA250 steel. The micro-mechanism of the effect of TiN inclusion on crack initiation and propagation at tensile and fatigue tests both have been studied in detail. Experimental results show the harmful effect of TiN on tensile and fatigue properties both. This work is helpful to establish the practical life prediction model for the characteristic inclusion parameters in ultra-high strength steel components. It also enlightens us to eliminate TiN in the further development of ultra-high strength steels.


2019 ◽  
Vol 9 (21) ◽  
pp. 4590 ◽  
Author(s):  
Markus J. Ottersböck ◽  
Martin Leitner ◽  
Michael Stoschka ◽  
Wilhelm Maurer

The division of the total fatigue life into different stages such as crack initiation and propagation is an important issue in regard to an improved fatigue assessment especially for high-strength welded joints. The transition between these stages is fluent, whereas the threshold between the two phases is referred to as technical crack initiation. This work presents a procedure to track crack initiation and propagation during fatigue tests of ultra high-strength steel welded joints. The method utilizes digital image correlation to calculate a distortion field of the specimens’ surface enabling the identification and measurement of cracks along the weld toe arising during the fatigue test. Hence, technical crack initiation of each specimen can be derived. An evaluation for ten ultra high-strength steel butt joints reveals, that for this superior strength steel grade more than 50% of fatigue life is spent up to a crack depth of 0.5 mm, which can be defined as initial crack. Furthermore, a notch-stress based fatigue assessment of these specimens considering the actual weld topography and crack initiation and propagation phase is performed. The results point out that two phase models considering both phases enable an increased accuracy of service life assessment.


2011 ◽  
Vol 80-81 ◽  
pp. 148-152 ◽  
Author(s):  
M.F.M. Yusof ◽  
C.K.E. Nizwan ◽  
Nordin Jamaludin ◽  
S. Abdullah

This paper present Acoustic Emission (AE) generated during fatigue mechanism of API5LX70 steel which was widely use as gas pipeline materials. Fully reverse (R=-1) constant amplitude fatigue test were done with four different stress amplitudes which were 437.5MPa, 406.25Mpa, 390.6MPa and 359.4MPa respectively. An observation from those tests shows that AE Count gives a significant value during cyclic softening and bauschinger effect. Crack initiation indicated by rapid increase of AE count values at positive peak stress and followed by high AE count values around zero stress which indicate crack closure phenomena. Among all four tests, it was show that AE activity from fatigue test with amplitude of 359.4MPa can be significantly divided into 3 region which correspond to crack incubation stage, microplastic and slip plane formation stage and crack initiation and propagation stage. Further analysis was done by separating AE signals from those 3 regions into 6 different groups. Ten AE signatures from each group were selected to calculate AE RMS and AE kurtosis. Analyses on AE RMS which correspond to overall energy of the signal were useful to indicate the microplastic and slip plane formation stage and crack initiation and propagation stage while AE kurtosis was useful in indicating crack stage including initiation, propagation and closure stage.


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