Fatigue Crack Growth of Thin Wall Magnesium AZ91 Alloy Cast

2013 ◽  
Vol 592-593 ◽  
pp. 749-752
Author(s):  
Tomasz Brynk ◽  
Barbara Romelczyk ◽  
Anna Jastrzębska ◽  
Katarzyna Nowak ◽  
Zbigniew Pakiela
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Image Correlation ◽  
Az91 Alloy ◽  
Uniaxial Tensile ◽  
Thin Wall ◽  
Magnesium Az91 Alloy ◽  
Alloy Cast

The paper presents the results of fatigue crack growth rate tests performed in magnesium AZ91 alloy cast of different wall thicknesses. Due to the limited size of investigated cast the tests were carried on mini-samples of 4x4x1 mm gauge section dimensions. The samples were cut from the 5, 10 and 30 mm thick walls. The optical displacement measurement technique, namely Digital Image Correlation, and inverse method were applied for determination of the stress intensity factors and the crack tip coordinates during tests. There were also performed uniaxial tensile tests in mini-samples for the determination of the mechanical properties changes related to different cast thicknesses. The relation between the microstructure and the results of mechanical tests was discussed.

Numerical Determination of Paris Law Constants for Carbon Steel Using a Two-Scale Model

2022 ◽  
pp. 1-15
Author(s):  
M. Mlikota
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Scale Model ◽  
Numerical Determination ◽  
Paris Law

For most engineering alloys, the long fatigue crack growth under a certain stress level can be described by the Paris law. The law provides a correlation between the fatigue crack growth rate (FCGR or da/dN), the range of stress intensity factor (ΔK), and the material constants C and m. A well-established test procedure is typically used to determine the Paris law constants C and m, considering standard specimens, notched and pre-cracked. Definition of all the details necessary to obtain feasible and comparable Paris law constants are covered by standards. However, these cost-expensive tests can be replaced by appropriate numerical calculations. In this respect, this paper deals with the numerical determination of Paris law constants for carbon steel using a two-scale model. A micro-model containing the microstructure of a material is generated using the Finite Element Method (FEM) to calculate the fatigue crack growth rate at a crack tip. The model is based on the Tanaka-Mura equation. On the other side, a macro-model serves for the calculation of the stress intensity factor. The analysis yields a relationship between the crack growth rates and the stress intensity factors for defined crack lengths which is then used to determine the Paris law constants.

A uniaxial tensile behavior based fatigue crack growth model

2020 ◽  
Vol 131 ◽  
pp. 105324 ◽  
Author(s):  
S.C. Wu ◽  
C.H. Li ◽  
Y. Luo ◽  
H.O. Zhang ◽  
G.Z. Kang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Model ◽  
Tensile Behavior ◽  
Uniaxial Tensile ◽  
Behavior Based ◽  
Crack Growth Model

scholarly journals Characterization and Quantitative Analysis of Crack Precursor Size for Rubber Composites

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3442 ◽  
Author(s):  
Hao Guo ◽  
Fanzhu Li ◽  
Shipeng Wen ◽  
Haibo Yang ◽  
Liqun Zhang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Failure ◽  
Theoretical Formula ◽  
Uniaxial Tensile ◽  
Rubber Composites ◽  
Economic Output ◽  
Average Size ◽  
Crack Growth Model

In the field of engineering, the annual economic loss caused by material fatigue failure reaches 4% of the total economic output. The deep understanding of rubber fatigue failure can help develop and prepare rubber composites with high durability. The crack precursor sizes within the rubber composites are vital for the material mechanical and fatigue properties. In this study, we adopted three different characterization methods to analyze crack precursor sizes and their distribution. First, based on the theoretical formula of fracture mechanics, the size of the crack precursor was deduced from 180 μm to 500 μm by the uniaxial tensile experiment combined with tear test (nicked angle tear, planar tear and trouser tear). Second, by combining the uniaxial fatigue test of dumbbell specimen with the fatigue crack growth rate test, the average size of the crack precursor was calculated as 3.3 μm based on the Thomas fatigue crack growth model. Third, the average size of the crack precursor was 3.6 μm obtained by scanning electron microscope. Through theoretical calculations and experimental tests, the size and distribution of the crack precursors of rubber composites were systematically presented. This work can provide theoretical guidance for the improvement of fatigue performance of rubber composites.

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