scholarly journals Study on Short Fatigue Crack Behaviour of LZ50 Steel Under Non-Proportional Loading

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 294 ◽  
Author(s):  
Bing Yang ◽  
Zhen Liao ◽  
Shoune Xiao ◽  
Guangwu Yang ◽  
Tao Zhu ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Test Data ◽  
Short Crack ◽  
Crack Model ◽  
Short Cracks ◽  
Short Fatigue Crack ◽  
Comparison Results ◽  
Lz50 Steel

The low cycle fatigue tests using the replica technique for LZ50 steel under non-proportional cyclic loading were carried out, and eight groups of effective test data were obtained. The evolution behaviour of short cracks was studied based on the effective short cracks criterion. The results show that short cracks generally originate in the grain or along the grain boundary. At the microstructural short crack stage, the crack propagation is influenced strongly by the microstructure of the material, and the growth rate of the short crack slows down several times according to the number of obstacles encountered. At the physical short crack stage, the crack propagation breaks through the banded structure of pearlite. Thus, the dominant effective short fatigue crack is formed, and the crack growth rate increases rapidly. Based on the modified parameters of the uniaxial short crack model, an approach is presented to calculate the growth rate of short cracks under multi-axial non-proportional loadings, and the new model can consider the non-proportional factor F. The fitting results of the multi-axial microstructural obstacles model are compared with test data. The comparison results show that this model can reflect the trend of short fatigue crack propagation rate under non-proportional loadings.

scholarly journals The Effect of a Complex Stress State on Fatigue Crack Propagation and the Orientation of the Cracking Plane in VT3-1 Aeronautical Titanium Alloy

2009 ◽  
Vol 2009 (1) ◽  
pp. 116-130
Author(s):  
Dorota Kocańda ◽  
Janusz Mierzyński
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Stress State ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Complex Stress ◽  
Complex Stress State ◽  
Short Crack ◽  
Short Cracks

The Effect of a Complex Stress State on Fatigue Crack Propagation and the Orientation of the Cracking Plane in VT3-1 Aeronautical Titanium AlloyThe subject of the paper is the investigations of fatigue crack imitation and propagation in notched specimens made of the VT3-1 aeronautical russian titanium alloy under combined bending - torsion loading. The presence of short cracks was revealed at various ratios of bending to torsion. Experimental courses of short and long crack growth rates have been proved by the SEM and TEM micrographs which illustrated the changes in the mechanism of cracking in the examined specimens. The attempt was undertaken in order to explain partly brittle fracture that was observed in the range of fatigue short crack growth in the VT3-1 titanium alloy specimens. The results of the study of atmospheric hydrogen absorption capability and its ability for penetration inside the faces of nucleated and propagated microcracks in the surface layer allowed for suggestion that the cleavage mechanism of fracture found in the regime of short crack growth in the VT3-1 titanium alloy specimens was induced by hydrogen.

Short fatigue crack behavior of carbon structural steel under tension–torsion loading

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940010 ◽  
Author(s):  
B. Yang ◽  
Z. Liao ◽  
S. Dai ◽  
Y. Qin ◽  
M. Wang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Grain Boundary ◽  
Structural Steel ◽  
Short Crack ◽  
Banded Structure ◽  
Short Fatigue Crack ◽  
Carbon Structural Steel ◽  
The Rich ◽  
Life Fraction

Fatigue short crack replica tests of a carbon structural steel, i.e., LZ50 steel, were carried out under tension–torsion loading using MTS electro hydraulic servo machine. Totally eight specimens with smooth axial hourglass shape were tested. The results show that short fatigue cracks generally initiate from the ferrite grain boundary or in the ferrite grain. In the microstructural short crack (MSC) stage, the crack grows slowly, but the growth rate will decrease when the crack encounters microstructural barriers, such as the ferrite grain boundary and the rich pearlite banded structure. In the physical short crack (PSC) stage, the crack breaks through the rich pearlite banded structure and meanwhile the dominant effective short fatigue crack (DESFC) has established its dominant position. As a result, the size and the growth rate of the crack increase rapidly. Based on the fatigue failure mechanism and the safety in tail region predictions, the statistical evolution of the DESFC size and the life fraction was analyzed respectively by comparing six commonly used statistical distributions. The statistical results show that the extreme minimum value (EMV1) distribution is a good assumed distribution for both the DESFC size and the life fraction.

Morphology Evolutions of the Short Fatigue Crack Propagation of 1Cr18Ni9Ti Weld Metal

2007 ◽  
Vol 353-358 ◽  
pp. 46-49 ◽  
Author(s):  
Yong Xiang Zhao ◽  
Bing Yang ◽  
Wei Hua Zhang
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Weld Metal ◽  
Short Crack ◽  
Grain Structure ◽  
Delta Ferrite ◽  
Short Fatigue Crack ◽  
Depth Direction ◽  
Formation Zone ◽  
Columnar Grain

Surface and depth morphology evodslutions of short crack propagation of 1Cr18Ni9Ti weld metal are investigated. In accordance with the previous effective short fatigue crack (ESFC) criterion, attention is paid on the formation zone of the dominant ESFC (DESFC), which resulted finally in the specimen failure, in micro-structural short crack (MSC) regime and then, the tip zone(s) ahead of the DESFC in physical short crack (PSC) regime. Results show that in MSC regime the surface ESFCs were imitated from the distributed randomly delta ferrite bounds separated from austenite matrix. The initiated ESFCs on surface propagated perpendicularly to loading axle. But in depth direction, the initiated ESFCs grew first similarly to the surface behaviour but lately, tended to be perpendicularly to the formation direction of the material columnar grain structure. When sizes of some longer ESFCs reached around the material maximum barrier size, coalescence occurred to form a true DESFC. In PSC regime the surface DESFC grew almost perpendicularly to loading axle. But in depth direction, it grew first perpendicularly to the formation direction of the columnar grain structure and then, tended to having 45 degree angle to the loading axle. Obviously, the evolutions were strongly affected by interactions between the load and the microstructures, especially, the columnar grain structure.

scholarly journals Description of short fatigue crack propagation under low cycle fatigue regime

2016 ◽  
Vol 2 ◽  
pp. 3010-3017 ◽  
Author(s):  
Pavel Hutař ◽  
Jan Poduška ◽  
Alice Chlupová ◽  
Miroslav Šmíd ◽  
Tomáš Kruml ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Short Fatigue Crack

Effects of cementite morphology on short-fatigue-crack propagation in binary Fe–C steel

2015 ◽  
Vol 95 (7) ◽  
pp. 384-391 ◽  
Author(s):  
Zhou-Jia Xi ◽  
Motomichi Koyama ◽  
Yuichi Yoshida ◽  
Nobuyuki Yoshimura ◽  
Kohsaku Ushioda ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Short Fatigue Crack

Investigation to the Effects of Grain Misorientation on the Performance of Short Cracks

2007 ◽  
Vol 353-358 ◽  
pp. 1165-1168
Author(s):  
Yan Hai Xu ◽  
Hao Li ◽  
Li Guo
Keyword(s):  
Grain Boundary ◽  
Crack Propagation ◽  
Geometric Parameters ◽  
Short Crack ◽  
Short Cracks ◽  
Grain Orientations ◽  
Grain Misorientation

The influences of crystallographic and geometric parameters such as grain misorientation on the performance of short cracks are illustrated based on FEM in this paper. Firstly, the microstructure is simulated to account for the effects of grain misorientation on the performance of short cracks and the short cracks are initiated within the microstructure for the further investigation. The influence of grain misorientation is demonstrated by the change of neighboring grain orientations with an initiated short crack from 0° to 180°. The effects of the grain boundary on the short crack with the crack arrested or retarded are described by the crack propagation until it approached the grain boundary. The results will give more useful information such as crack arrested and retardation to the further research on the characteristics and evolution of short cracks.

Investigation of Fatigue Crack Propagation in Nickel Superalloy Using Diffraction Contrast Tomography and Phase Contrast Tomography

2014 ◽  
Vol 891-892 ◽  
pp. 923-928 ◽  
Author(s):  
Olivier M.D.M. Messé ◽  
Joel Lachambre ◽  
Andrew King ◽  
Jean Yves Buffière ◽  
Cathie M.F. Rae
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Phase Contrast ◽  
High Energy ◽  
Short Crack ◽  
X Rays ◽  
Post Mortem ◽  
Diffraction Contrast ◽  
Phase Contrast Tomography

Evaluation of superalloy component life in turbine engines requires a detailed understanding of how fatigue crack initiation and short crack propagation contribute to fatigue life. However most investigations have been carried out post-mortem and in two dimensions. New techniques are able to fully resolve cracks propagating in four dimensions (space and time), enabling characterisation of their local environments and allowing a much deeper understanding of fatigue mechanics. Nickel-based superalloys experiencing high cycle fatigue have shown a high sensitivity to microstructure during initiation and short crack propagation. Using high energy X-rays and the combination of Diffraction Contrast Tomography (DCT) and Phase Contrast Tomography (PCT), we followed a fatigue crack initiated from a Focused Ion Beam (FIB) milled notch at room temperature. Analyses have been carried out to fully characterise the crack and its environment. We tracked the evolution of the crack and interactions with the microstructure. Subsequently, post-mortem investigations have been carried out to corroborate results obtained from the tomographs and to provide more local information of fatigue crack propagation.

Prestrain Influence on Fatigue Crack Propagation in a 304L Stainless Steel

2009 ◽  
Author(s):  
Kokleang Vor ◽  
Catherine Gardin ◽  
Christine Sarrazin-Baudoux ◽  
Jean Petit ◽  
Claude Amzallag
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Crack Closure ◽  
Threshold Region ◽  
304L Stainless Steel

The scope of this study is to investigate the effect of tensile prestrain on crack growth behavior in a 304L stainless steel. Fatigue crack propagation tests were performed on single-edge notched tension (SENT) raw specimens (0% of prestrain) and on prestrained specimens (2% and 10%). On one hand, it is found that the different levels of prestrain exhibit no significant influence on crack propagation in the high range of Stress Intensity Factor (SIF), where there is no detectable crack closure. On the other hand, a clear effect of prestrain on crack growth rate can be observed in the near threshold region where closure is detected. Thus, it can be concluded that the prestrain mainly affects the crack growth rate through its influence on the crack closure.

Sign in / Sign up

Export Citation Format

Share Document