A Method for Multiaxial Fatigue Reliability Analysis Based on Mixed Weibull Distribution

2013 ◽  
Author(s):  
Dan Ling ◽  
Hong-Zhong Huang ◽  
Song Wang ◽  
Chuan-hao Wu ◽  
Shun-peng Zhu ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Weibull Distribution ◽  
Normal Stress ◽  
Strain Range ◽  
Multiaxial Fatigue ◽  
Stress And Strain ◽  
Fatigue Reliability ◽  
Critical Plane ◽  
Element Analysis ◽  
Maximum Normal Stress

The fatigue life of mechanical element is a random variable in nature following some kind of statistical distribution. In this paper, a method for reliability life prediction considering life randomness is proposed. Firstly, the Smith-Watson-Topper (SWT) model is used to describe the relationship of the maximum normal stress and strain range on the critical plane. Secondly, the maximum normal stress and strain range on the critical plane are calculated by finite element analysis. Thirdly, fatigue life samples are generated using Monte Carlo simulation method, and the mixed Weibull distribution is used to model the distribution of fatigue life of turbine discs. Finally, the proposed method is validated by comparing the prediction results from the proposed method, the observed cumulative failure probability based on median rank, and the standard two-parameter Weibull distribution.

Fatigue Life Predictions for Thermally Loaded Solder Joints Using a Volume-Weighted Averaging Technique

1997 ◽  
Vol 119 (4) ◽  
pp. 228-235 ◽  
Author(s):  
H. U. Akay ◽  
N. H. Paydar ◽  
A. Bilgic
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Strain Energy ◽  
Solder Joints ◽  
Strain Range ◽  
Inelastic Strain ◽  
Weighted Averaging ◽  
Stress And Strain ◽  
Element Analysis ◽  
Averaging Technique

Fatigue lives of thermally loaded solder joints are predicted using the finite element method. An appropriate constitutive relation to model the time-dependent inelastic deformation of the near-eutectic solder is implemented into a commercial finite element code, and the stress-strain responses of different electronic assemblies under the applied temperature cycles are calculated. The finite element analysis results are coupled with a newly developed approach for fatigue life predictions by using a volume-weighted averaging technique instead of an approach based on the maximum stress and strain locations in the solder joint. Volume-weighted average stress and strain results of three electronic assemblies are related to the corresponding experimental fatigue data through least-squares curve-fitting analyses for determination of the empirical coefficients of two fatigue life prediction criteria. The coefficients thus determined predict the mean cycles-to-failure value of the solder joints. Among the two prediction criteria, the strain range criterion uses the inelastic shear strain range and the total strain energy criterion uses the total inelastic strain energy calculated over a stabilized loading cycle. The obtained coefficients of the two fatigue criteria are applied to the finite element analysis results of two additional cases obtained from the literature. Good predictions are achieved using the total strain energy criterion, however, the strain range criterion underestimated the fatigue life. It is concluded that the strain information alone is not sufficient to model the fatigue behavior but a combination of stress and strain information is required, as in the case of total inelastic strain energy. The superiority of the volume-weighted averaging technique over the maximum stress and strain location approach is discussed.

Critical plane–based multiaxial fatigue life prediction of turbine disk alloys by refining normal stress sensitivity

2018 ◽  
Vol 53 (8) ◽  
pp. 719-729 ◽  
Author(s):  
Shen Xu ◽  
Shun-Peng Zhu ◽  
Yong-Zhen Hao ◽  
Ding Liao
Keyword(s):  
Fatigue Life ◽  
Normal Stress ◽  
Life Prediction ◽  
Stress Sensitivity ◽  
Damage Parameter ◽  
Turbine Disk ◽  
Multiaxial Fatigue ◽  
Critical Plane ◽  
Additional Material ◽  
Proposed Model

For engineering components subjected to complex multiaxial loadings, critical plane approaches like Fatemi–Socie criterion have been commonly utilized for life prediction of these components. Within the Fatemi–Socie criterion, the normal stress sensitivity parameter k is usually fitted from additional experimental data, which introduces inconvenience for practice especially under limited testing data conditions. In this regard, a simple critical plane–based damage parameter is put forward with no additional material constants, which attempts to provide a robust method for multiaxial fatigue analysis of turbine disk alloys. Using experimental datasets of TC4 and GH4169 alloys under different loadings, the proposed model provides better correlations with fatigue life of the two alloys than the models of Smith–Watson–Topper and Wang–Brown.

scholarly journals Multiaxial high-cycle fatigue modelling for random loading

2019 ◽  
Vol 300 ◽  
pp. 12005
Author(s):  
Haoyang Wei ◽  
Jie Chen ◽  
Patricio Carrion ◽  
Anahita Imanian ◽  
Nima Shamsaei ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Normal Stress ◽  
Life Prediction ◽  
Equivalent Stress ◽  
Multiaxial Fatigue ◽  
Fatigue Life Prediction ◽  
Load Spectrum ◽  
Critical Plane ◽  
Random Loading ◽  
Random Load

In this paper, a multiaxial fatigue life prediction model is proposed under general multiaxial random loadings. First, a brief review for existing multiaxial fatigue models is given and special focus is on the LiuMahadevan critical plane concept, which can be applied to both brittle and ductile materials. Next, new model development based on the Liu-Mahadevan critical plane concept for random loading is presented. The key concept is to use two-steps to identify the critical plane: identify the maximum damage plane due to normal stress and calculate the critical plane orientation with respect to the maximum damage plane due to normal stress. Multiaxial rain-flow cycle counting method with mean stress correction is used to estimate the damage on the critical plane. Equivalent stress transformation is proposed to convert the multiaxial random load spectrum to an equivalent constant amplitude spectrum. The equivalent stress is used for fatigue life prediction. Following this, experimental design and testing is performed for Al 7075-T6 under various different random uniaxial and multiaxial spectrums. The developed model is validated with both literature and in-house testing data. Very good agreement is observed for the investigated material. Finally, conclusion and future work is given based on the proposed study.

A computational approach based on a multiaxial fatigue criterion combining phase transformation and shakedown response for the fatigue life assessment of Nitinol stents

2018 ◽  
Vol 29 (19) ◽  
pp. 3710-3724 ◽  
Author(s):  
Giulia Scalet ◽  
Costantino Menna ◽  
Andrei Constantinescu ◽  
Ferdinando Auricchio
Keyword(s):  
Phase Transformation ◽  
Fatigue Life ◽  
Computational Design ◽  
Phase Evolution ◽  
Multiaxial Fatigue ◽  
Life Assessment ◽  
Patient Specific ◽  
Element Analysis ◽  
Nitinol Stents ◽  
Fatigue Criterion

Self-expanding stents made of Nitinol, a Nickel–Titanium shape memory alloy, are used in standard medical implants for the treatment of cardiovascular diseases. Despite the increasing success, clinical studies have reported stent failure after the deployment in the human body, thus undermining patient’s safety and life. This study aims to fill the gap of reliable assessment of the fatigue life of Nitinol stents. We propose a global computational design method for preclinical validation of Nitinol stents, which can be extended to patient-specific computations. The proposed methodology is composed of a mechanical finite element analysis and a fatigue analysis. The latter analysis is based on a novel multiaxial fatigue criterion of the Dang Van type, combining the shakedown response of the stent and the complexity of phase transformation taking place within the material. The method is implemented in the case of a carotid artery stent. The implant configuration as well as the applied cyclic loading are shown to affect material phase evolution as well as stent lifetime. The comparison with the results obtained by applying a strain-based constant-life diagram approach allows to critically discuss both fatigue criteria and to provide useful recommendations about their applicability.

scholarly journals Multiaxial Fatigue Life Calculation Model for Engineering Components in Rolling-Sliding Contact

2018 ◽  
Vol 188 ◽  
pp. 02016
Author(s):  
Robert Basan ◽  
Tea Marohnić
Keyword(s):  
Fatigue Life ◽  
Complex Geometry ◽  
Calculation Model ◽  
Multiaxial Fatigue ◽  
Sliding Contact ◽  
Engineering Practice ◽  
Critical Plane ◽  
Principal Axes ◽  
Critical Plane Approach ◽  
Crack Initiation Criterion

Number of important engineering components and elements such as gears, rollers, bearings operate in conditions of rolling-sliding contact loading. Determination of fatigue lives of such components and elements is very important for engineering practice but remains quite chalenging task due to complex states of stress and strain in the material in the vicinity of contact (multiaxiality, non-proportionality, rotation of principal axes, mean compressive stress) as well as complex contact conditions such as loading amplitude, complex geometry of bodies in contact, type of lubrication, value of coefficient of friction, etc. Proposed fatigue life calculation model for cases of rolling-sliding contact is based on critical plane approach in the form of Fatemi-Socie crack initiation criterion. Developed model was implemented in the case of gears teeth flanks in mesh and compared with results and fatigue lives of gears reported in literature. Good agreement was determined confirming validity of developed model. Further advantage of presented approach and developed model is obtained information on critical location(s) and critical plane(s) orientation which can subsequently be used for estimation of crack shapes in initial phases of their growth and later damage type into which they can be expected to develop.

Multiaxial Low Cycle Fatigue Life Prediction at 300 °C Using Equivalent Strain Appoach

2011 ◽  
Vol 361-363 ◽  
pp. 1669-1672
Author(s):  
Wen Xiao Zhang ◽  
Guo Dong Gao ◽  
Guang Yu Mu
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Cyclic Fatigue ◽  
Equivalent Strain ◽  
Multiaxial Fatigue ◽  
Fatigue Life Prediction ◽  
Cycle Fatigue

The low cycle fatigue behavior was experimentally studied with the 3-dimension notched LD8 aluminum alloy specimens at 300°C. The 3- dimension stress-strain responses of specimens were calculated by means of the program ADINA. The multiaxial fatigue life prediction was carried out according to von Mises’s equivalent theory. The results from the prediction showed that the equivalent strain range can be served as the valid mechanics for predicting multiaxial high temperature and low cyclic fatigue life.

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