Microscale based prediction of matrix crack initiation in UD composite plies subjected to multiaxial fatigue for all stress ratios and load levels

2017 ◽  
Vol 142 ◽  
pp. 124-138 ◽  
Author(s):  
R.D.B. Sevenois ◽  
D. Garoz ◽  
F.A. Gilabert ◽  
S.W.F. Spronk ◽  
W. Van Paepegem
Keyword(s):  
Crack Initiation ◽  
Matrix Crack ◽  
Multiaxial Fatigue ◽  
Stress Ratios

scholarly journals Application of Life-Dependent Material Parameters to Fatigue Life Prediction under Multiaxial and Non-Zero Mean Loading

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1587 ◽  
Author(s):  
Krzysztof Kluger ◽  
Aleksander Karolczuk ◽  
Szymon Derda
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Fatigue Loading ◽  
Mean Value ◽  
Multiaxial Fatigue ◽  
Fatigue Life Prediction ◽  
Test Results ◽  
Material Parameters ◽  
Fixed Material ◽  
Stress Ratios

This study presents the life-dependent material parameters concept as applied to several well-known fatigue models for the purpose of life prediction under multiaxial and non-zero mean loading. The necessity of replacing the fixed material parameters with life-dependent parameters is demonstrated. The aim of the research here is verification of the life-dependent material parameters concept when applied to multiaxial fatigue loading with non-zero mean stress. The verification is performed with new experimental fatigue test results on a 7075-T651 aluminium alloy and S355 steel subjected to multiaxial cyclic bending and torsion loading under stress ratios equal to R = −0.5 and 0.0, respectively. The received results exhibit the significant effect of the non-zero mean value of shear stress on the fatigue life of S355 steel. The prediction of fatigue life was improved when using the life-dependent material parameters compared to the fixed material parameters.

scholarly journals A fatigue crack initiation and growth life estimation method in single-bolted connections

2019 ◽  
Vol 54 (2) ◽  
pp. 79-94 ◽  
Author(s):  
Arash P Jirandehi ◽  
TN Chakherlou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Estimation Accuracy ◽  
Life Estimation ◽  
Lower Error ◽  
Fatigue Life Estimation

Fatigue life estimation accuracy of mechanical parts and assemblies has always been the source of concern in different industries. The main contribution of this article lies in a study on the accuracy of different multiaxial fatigue criteria, proposing and investigating the accuracy of four optimized fatigue crack initiation life estimation methods—volume, weighted volume, surface and point, thereby improving the multiaxial fatigue life estimation accuracy. In order to achieve the goal, the fatigue lives of bolt clamped specimens, previously tested under defined experimental conditions, were estimated during fatigue crack initiation and fatigue crack growth and then summed together. In the fatigue crack initiation part, a code was written and used in the MATLAB software environment based on critical plane approach and the different multiaxial fatigue criteria. Besides the AFGROW software was utilized to estimate the crack growth share of fatigue life. Experimental and numerical results showed to be in agreement. Furthermore, detailed study and comparison of the results with the available experimental data showed that a combination of Smith–Watson–Topper approach and volume method results in lower error values, while a combination of Fatemi–Socie criterion and surface or point method presents estimated lives with lower error values. In addition, the numerical proposed procedure resulted in a good prediction of the location of fatigue crack initiation.

VHCF Behavior and Word Hardening of a Ferritic-Martensitic Steel at High Mean Stresses

2015 ◽  
Vol 664 ◽  
pp. 246-254 ◽  
Author(s):  
Tilmann Beck ◽  
Stephan A. Kovacs ◽  
Fabian Ritz
Keyword(s):  
Crack Initiation ◽  
Fatigue Testing ◽  
Turbine Blades ◽  
Cyclic Creep ◽  
Cyclic Hardening ◽  
Testing System ◽  
Fine Grained ◽  
Ultrasonic Fatigue ◽  
Stress Ratios ◽  
Mean Stresses

Low-pressure steam turbine blades undergo VHCF-loadings induced by inhomogenous flow behind the vanes resulting in excitation frequencies of ≈ 2 kHz for rotational speeds of 50 Hz and a typical number of stator vanes of ≈ 60. The VHCF loading is superimposed by considerable mean stresses caused by centrifugal forces. In the present study, the VHCF-behavior of the ferritic-martensitic turbine blade steel X10CrNiMoV12-2-2 is investigated using an ultrasonic fatigue testing system up to cycle numbers of 5∙109 at stress ratios from R = -1 up to 0.7, i.e. up to very high mean stresses. Generally, crack initiation changes from the surface to internal inclusions at fatigue lives around 4∙107. The transition between fatigue failure and run-outs is shifted to higher lifetime with increasing R, and fine grained areas (FGAs) at the crack initiation sites only occur at R < -0.1. However, the fracture mechanics approach proposed by Murakami consistently describes the lifetime behavior for all load ratios over 4 decades of lifetime. At R up from 0.5 considerable cyclic creep occurs, even for lifetimes above 108 cycles, resulting in cyclic hardening which was proved by microhardness measurements at longitudinal sections. This effect at least partially explains the high maximum stresses close to the tensile strength of the material occurring in the VHCF regime at load ratios ≥ 0.5.

Fatigue Crack Initiation and Mechanism of GH4133B Superalloy Used in Turbine Disk of Aero-Engine

2014 ◽  
Vol 602-603 ◽  
pp. 665-670
Author(s):  
Rong Guo Zhao ◽  
Jun Fei Li ◽  
Yong Zhou Jiang ◽  
Xi Yan Luo ◽  
Wei Li ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Phase Particle ◽  
Source Region ◽  
Fatigue Crack Initiation ◽  
Compact Tension ◽  
Second Phase ◽  
Stress Ratios ◽  
Crack Initiation Life ◽  
Surface Morphologies

The fatigue crack initiation life at various stress ratios for GH4133B superalloy specimen with different circular notch radios are studied at ambient temperature and atmospheric pressure utilizing the fracture mechanics method. It is shown that a controlling parameter ΔKI/ρ0.5 can be adopted to characterize the fatigue crack initiation life, and the effect of notch radius on fatigue crack initiation life increases with increasing control parameter, while the fatigue crack initiation life firstly increases and then decreases with increasing stress ratio. The fatigue fracture surfaces of circular notched compact tension specimens of GH4133B superalloy for fatigue crack initiation tests at various stress ratios are investigated using a scanning electron microscopy, and the fracture surface morphologies in the fatigue source region are analyzed. It is found that the separation between carbide inclusion on the surface or subsurface and matrix, or the separation between nickel-rich second phase particle and matrix, or the interaction between persistent slip bands and inclusion, mainly results in the fatigue crack initiation.

Crack Initiation Under Low-Cycle Multiaxial Fatigue in Type 316L Stainless Steel

1983 ◽  
Vol 105 (2) ◽  
pp. 138-143 ◽  
Author(s):  
B. Jacquelin ◽  
F. Hourlier ◽  
A. Pineau
Keyword(s):  
Stainless Steel ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Stage I ◽  
Type B ◽  
Strain Behavior ◽  
Number Of Cycles

Low-cycle fatigue tests corresponding to fatigue life range between 103 and 105 cycles were carried out at room temperature on one heat of 316 L austenitic stainless steel. These tests included: (i) reversed tension-compression, (ii) reversed tension-compression with a superimposed steady torque, (iii) pulsated tension-compression with a stress ratio (Rσ) such that −0.5<Rσ<0, (iv) reversed and pulsated tension-compression with a superimposed steady internal pressure. In tests (ii), the torsional ratcheting effect was measured. SEM observations were used to determine the number of cycles corresponding to Stage I crack initiation and the orientation of Stage I microcracks. It was observed that the in-depth growing Type B shear microcracks were most damaging. A simple criterion is proposed Ni=No(Δγp B)α•(σnB)β where Ni is the number of cycles to crack initiation, Δγp B is the range of plastic shear strain on Type B planes, σnB is the maximum normal stress acting on these planes, No,α and β are parameters adjusted from the Manson-Coffin law and reversed cyclic stress-strain behavior.

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