scholarly journals Multiaxial Fatigue Spectrum Editing by Using Combined Wavelet Analysis and Stress Invariant Approach

2018 ◽  
Vol 165 ◽  
pp. 16009
Author(s):  
Anahita Imanian ◽  
Kelvin Leung ◽  
Nagaraja Iyyer
Keyword(s):  
Fatigue Damage ◽  
Fatigue Testing ◽  
Fatigue Crack Initiation ◽  
Statistical Parameter ◽  
Multiaxial Fatigue ◽  
Loading Path ◽  
Plane Stress Condition ◽  
Structural Fatigue ◽  
Wavelet Transform Analysis ◽  
Parameter Values

The practicalities of structural fatigue testing limit the fidelity of the cyclic load history that can be applied to a test structure. Testing is, therefore, a compromise between fatigue damage fidelity and test economy. A new methodology is proposed for multiaxial loading spectrum editing to extract cycles that contribute negligible damage during fatigue crack initiation. The method is based on projection by projection (PbP) technique and wavelet transform analysis (WTA) procedure. In this approach, the cycles with negligible contribution to damage in every decoupled projected loading path (i.e. obtained from PbP approach) are extracted using the WTA procedure. Each extracted segment is then replaced with an equivalent cycle that produces the same amount of damage. The effectiveness of the edited spectrums is evaluated by the degree of fatigue damage retention as the original damage and preservation of statistical parameter values. As a case study, the proposed approach has been applied to the numerically produced random bending-torsion fatigue spectrum in plane-stress condition. The result shows an average of 75% reduction of the original spectrums with retention of 90% of the original spectrums’ damage values.

OS2117 Multiaxial Fatigue Damage Evaluation of Ti-6Al-4V Based on Loading Path

2012 ◽  
Vol 2012 (0) ◽  
pp. _OS2117-1_-_OS2117-3_
Author(s):  
Masahiro TAKANASHI ◽  
Hiroshi NAKAMURA ◽  
Min WU ◽  
Takamoto ITOH
Keyword(s):  
Fatigue Damage ◽  
Multiaxial Fatigue ◽  
Loading Path ◽  
Damage Evaluation

Prediction of Fatigue Initiation Life of 16MnR Notched Components

2007 ◽  
Author(s):  
Baoxiang Qiu ◽  
Zengliang Gao ◽  
Xiaogui Wang ◽  
Yanyao Jiang
Keyword(s):  
Fatigue Damage ◽  
Fatigue Crack Initiation ◽  
Material Point ◽  
Multiaxial Fatigue ◽  
Cyclic Plasticity ◽  
Pure Torsion ◽  
Damage Criterion ◽  
Loading Cycle ◽  
Fatigue Initiation ◽  
Critical Damage

Fatigue initiation life of smooth and notched rod 16MnR specimens subjected to fully reversed uniaxial tension-compression and pure torsion cyclic loading was studied by a multiaxial fatigue damage criterion. A robust cyclic plasticity model was implemented into ABAQUS via a user-material subroutine UMAT. In virtue of the axisymmetry of geometry and loading, an axisymmetric model was facilitated to get the cyclic elasto-plastic stress-strain relationship. The accumulated fatigue damage of each material point in different material plane was then obtained by Jiang’s fatigue damage criterion. From the results of fatigue damage analysis we know that the maximum stabilized damage per loading cycle was at the root of the notch, where the material point firstly reaches the critical damage value. Fatigue crack initiation life is defined as the ratio of the critical damage to the maximum fatigue damage per loading cycle. Uniaxial and pure torsion fatigue experiments for the smooth rod specimens, sharp and blunt notched rod specimens were also conducted. Good agreement was achieved by comparing the predicted fatigue initiation life with the experiment results.

Shattered Rim Failure Analysis in Railroad Wheels

2006 ◽  
Author(s):  
Yongming Liu ◽  
Brant Stratman ◽  
Liming Liu ◽  
Sankaran Mahadevan
Keyword(s):  
Fatigue Damage ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Railroad Wheel ◽  
Fatigue Reliability ◽  
Numerical Predictions ◽  
Fatigue Damage Accumulation ◽  
Stochastic Loading ◽  
Railroad Wheels ◽  
Fatigue Failures

A general methodology for fatigue reliability degradation of railroad wheels is proposed in this paper. Both fatigue crack initiation and crack propagation life are included in the proposed methodology using previously developed multiaxial fatigue models by the authors. A response surface method in conjunction with design of experiments is used to develop a closed form approximation of the fatigue damage accumulation with respect to the input random variables. The total fatigue life of railroad wheels under stochastic loading is simulated, accounting for the spatial and temporal randomness of the fatigue damage. The field observations of railroad wheel fatigue failures are compared with the numerical predictions using the proposed methodology.

Issues With Multiaxial Fatigue Assessment in the ASME Boiler and Pressure Vessel Code

2018 ◽  
Author(s):  
Marco Antonio Meggiolaro ◽  
Jaime Tupiassú Pinho de Castro ◽  
Hao Wu
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Critical Point ◽  
Fatigue Damage ◽  
Pressure Vessel ◽  
Fatigue Crack Initiation ◽  
Multiaxial Fatigue ◽  
Fatigue Assessment ◽  
Damage Models ◽  
Principal Directions

This work analyzes the applicability of the ASME Boiler and Pressure Vessel Code procedures to calculate fatigue crack initiation under multiaxial stresses and/or strains, in particular when caused by non-proportional loads that lead the principal directions at the critical point to vary with time, e.g. due to out-of-phase bending and torsion loads induced by independent sources. Classic uniaxial fatigue damage models are usually inappropriate for analyzing multiaxial loads, since they can generate highly inaccurate predictions. Moreover, it is shown that the ASME procedures can lead to non-conservative results for non-proportional load histories.

Modeling Multiaxial Fatigue Damage Using Polar Equations

2017 ◽  
Author(s):  
Jafar Albinmousa ◽  
Syed Haris Iftikhar ◽  
Mustafa Al-Samkhan
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Closed Form Solution ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Loading Path ◽  
Shear Stresses ◽  
Critical Plane ◽  
Stress Strain ◽  
Loading Paths

It is estimated that more than 70% of failures in engineering components are associated with fatigue loading. Therefore, fatigue is a major design tool for mechanical components. These components are usually subjected to multiaxial cyclic loading. In fact, multiaxial state is very common as tension specimen is under triaxial strain state even though its stress state is uniaxial. There are three approaches to modeling fatigue damage: stress, strain and energy. Critical plane concept is established based on the fact that fatigue cracks initiate at specific plane(s), therefore, multiaxial fatigue damage parameter is evaluated at these plane(s). Critical plane fatigue models such as Fatemi-Socie is among the popular strain-based models. Because it was shown to provide estimation mostly within two factors of life for different materials and different multiaxial loading conditions. This paper presents a new method for analyzing critical plane damage parameters. Using plane stress-strain transformation, maximum values of normal and shear stresses and strains from hysteresis loops are obtained at 360 planes. Plotting these values on polar diagrams shows that multiaxial cyclic responses represent polar curves that can successfully be fitted with definitive known polar equations. In principle, this means that both critical plane and fatigue damage can be determined analytically for a given loading path. However, fitting constants must first be determined. A systematic analysis is performed on different experimental data that were obtained by testing two extruded magnesium alloys at proportional and 90° out of phase loading paths. A closed-form solution for Fatemi-Socie damage parameter is presented for these two loading paths.

Plastic Slip and Early Stage of Fatigue Damage in Polycrystals: Comparison between Experiments and Crystal Plasticity Finite Elements Simulations

2014 ◽  
Vol 891-892 ◽  
pp. 1711-1716 ◽  
Author(s):  
Loic Signor ◽  
Emmanuel Lacoste ◽  
Patrick Villechaise ◽  
Thomas Ghidossi ◽  
Stephan Courtin
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Crystal Plasticity ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Plastic Slip

For conventional materials with solid solution, fatigue damage is often related to microplasticity and is largely sensitive to microstructure at different scales concerning dislocations, grains and textures. The present study focuses on slip bands activity and fatigue crack initiation with special attention on the influence of the size, the morphology and the crystal orientation of grains and their neighbours. The local configurations which favour - or prevent - crack initiation are not completely identified. In this work, the identification and the analysis of several crack initiation sites are performed using Scanning Electron Microscopy and Electron Back-Scattered Diffraction. Crystal plasticity finite elements simulation is employed to evaluate local microplasticity at the scale of the grains. One of the originality of this work is the creation of 3D meshes of polycrystalline aggregates corresponding to zones where fatigue cracks have been observed. 3D data obtained by serial-sectioning are used to reconstruct actual microstructure. The role of the plastic slip activity as a driving force for fatigue crack initiation is discussed according to the comparison between experimental observations and simulations. The approach is applied to 316L type austenitic stainless steels under low-cycle fatigue loading.

Modeling of Fatigue Crack Propagation

2004 ◽  
Vol 126 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Yanyao Jiang ◽  
Miaolin Feng
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Cyclic Plasticity ◽  
R Ratio

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

Crack mode and life of Ti-6Al-4V under multiaxial low cycle fatigue

2015 ◽  
Author(s):  
Takamoto Itoh ◽  
Masao Sakane ◽  
Takahiro Morishita ◽  
Hiroshi Nakamura ◽  
Masahiro Takanashi
Keyword(s):  
Hollow Cylinder ◽  
Stress Ratio ◽  
Biaxial Loading ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Testing Machine ◽  
Multiaxial Fatigue ◽  
Cycle Fatigue ◽  
Loading Test ◽  
Failure Life

This paper studies multiaxial low cycle fatigue crack mode and failure life of Ti-6Al-4V. Stress controlled fatigue tests were carried out using a hollow cylinder specimen under multiaxial loadings of ?=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. ? is a principal stress ratio and is defined as ?=sigmaII/sigmaI, where sigmaI and sigmaII are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at ?=0 is a uniaxial loading test and that at ?=1 an equi-biaxial loading test. A testing machine employed is a newly developed multiaxial fatigue testing machine which can apply push-pull and reversed torsion loadings with inner pressure onto the hollow cylinder specimen. Based on the obtained results, this study discusses evaluation of the biaxial low cycle fatigue life and crack mode. Failure life is reduced with increasing ? induced by cyclic ratcheting. The crack mode is affected by the surface condition of cut-machining and the failure life depends on the crack mode in the multiaxial loading largely.

scholarly journals Fatigue Strength Analysis and Fatigue Damage Evaluation of Roller Chain

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 847 ◽  
Author(s):  
Ryoichi Saito ◽  
Nao-Aki Noda ◽  
Yoshikazu Sano ◽  
Jian Song ◽  
Takeru Minami ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Fatigue Crack Initiation ◽  
Strength Analysis ◽  
The Finite Element Method ◽  
Roller Chain ◽  
Press Fitting ◽  
The Press ◽  
Static Tensile

This paper deals with the roller chain commonly used for transmission of mechanical power on many kinds of industrial machinery, including conveyors, cars, motorcycles, bicycles, and so forth. It consists of a series of four components called a pin, a bush, a plate, and a roller, which are driven by a sprocket. To clarify the fatigue damage, in this paper, the finite element method (FEM) is applied to those components under three different types of states, that is, the press-fitting state, the static tensile state, and the sprocket-engaging state. By comparing those states, the stress amplitude and the average stress of each component are calculated and plotted on the fatigue limit diagram. The effect of the plastic zone on the fatigue strength is also discussed. The results show that the fatigue crack initiation may start around the middle inner surface of the bush. As am example, the FEM results show that the fatigue crack of the inner plate may start from a certain point at the hole edge. The results agree with the actual fractured position in roller chains used in industry.

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