Comparison of Different Approaches for Fatigue Damage Accumulation in Steel Risers

2011 ◽  
Author(s):  
Fernanda C. M. Takafuji ◽  
Clo´vis A. Martins
Keyword(s):  
Fatigue Life ◽  
Dynamic Analysis ◽  
Fatigue Damage ◽  
Time Domain ◽  
Damage Accumulation ◽  
Maximum Stress ◽  
Fatigue Analysis ◽  
Fatigue Damage Accumulation ◽  
Stress Point ◽  
Offshore Industry

Fatigue is one of the main concerns of the offshore industry nowadays, since the failure of equipments could put not only the environment but also some people’s lives in danger. As described in DNV-RP-C203 and in DNV-RP-F204, the aim of fatigue analysis is to verify if a certain structure — in this case, a riser — will be able to operate adequately during a desired period of time, as well as to obtain information to program inspections. In a riser, the efforts vary along its length and also around its circumference. If one considers the stress around the circumference, the maximum stress point may change. To be realistic, one approach is to calculate the stress and fatigue life around the circumference. To be more conservative and also simplify the calculation, one could consider that the maximum stress always occurs at the same point. The purpose of this paper is to compare the fatigue life obtained with both approaches in order to verify the differences between them and verify how conservative that simplification can be. To perform the task, a steel riser is considered and the dynamic analysis is executed in time domain using Orcaflex 9.4. The fatigue is analyzed through the S-N Curve approach and the Miner’s rule is used to accumulate the damage.

scholarly journals Fatigue Damage Accumulation Modeling of Metals Alloys under High Amplitude Loading at Elevated Temperatures

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1030 ◽  
Author(s):  
Jarosław Szusta ◽  
Andrzej Seweryn
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
High Amplitude ◽  
Metal Alloys ◽  
Damage State ◽  
State Variable ◽  
Fatigue Damage Accumulation

This article presents an approach related to the modeling of the fatigue life of constructional metal alloys working under elevated temperature conditions and in the high-amplitude load range. The article reviews the fatigue damage accumulation criteria that makes it possible to determine the number of loading cycles until damage occurs. Results of experimental tests conducted on various technical metal alloys made it possible to develop a fatigue damage accumulation model for the LCF (Low Cycle Fatigue) range. In modeling, the material’s damage state variable was defined, and the damage accumulation law was formulated incrementally so as to enable the analysis of the influence of loading history on the material’s fatigue life. In the proposed model, the increment of the damage state variable was made dependent on the increment of plastic strain, on the tensile stress value in the sample, and also on the actual value of the damage state variable. The model was verified on the basis of data obtained from experiments in the field of uniaxial and multiaxial loads. Samples made of EN AW 2024T3 aluminum alloy were used for this purpose.

Fatigue Damage Accumulation Prediction for Combined Sine and Random Stresses

1988 ◽  
Vol 31 (3) ◽  
pp. 53-63
Author(s):  
Ronald Lambert
Keyword(s):  
Fatigue Life ◽  
Closed Form ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Structural Elements ◽  
Numerical Examples ◽  
Stress Situation ◽  
Fatigue Damage Accumulation ◽  
Special Cases ◽  
Parameters Of Interest

Simple closed-form expressions have been derived to predict fatigue life, damage accumulation, and other fatigue parameters of interest for structural elements with combined sinusoidal (sine) and narrowband Gaussian random stresses. These equations are expressed in common engineering terms. The sine and random only stress situations are special cases of the more general combined sine/random stress situation. They also have application for establishing vibration workmanship screens. Numerical examples are also included.

Model of fatigue damage in strain-rate-sensitive composite materials

2003 ◽  
Vol 18 (1) ◽  
pp. 77-80 ◽  
Author(s):  
Sanboh Lee ◽  
Tinh Nguyen ◽  
Tze-jer Chuang
Keyword(s):  
Composite Materials ◽  
Strain Rate ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Maximum Stress ◽  
Paris Law ◽  
Damage Rate ◽  
Fatigue Damage Accumulation ◽  
Damage Accumulation Model ◽  
Extent Of Damage

A fatigue damage accumulation model based on the Paris law is proposed for strain-rate-sensitive polymer composite materials. A pre-exponent factor c2/f and strain-rate-sensitive exponent n are introduced. Numerical analysis of the model was performed using experimental data obtained in the literature. Both factors were found to enhance fatigue damage accumulation. The analysis also revealed that the extent of damage increases with decreasing frequency and that the damage rate is more sensitive to the applied maximum stress than to the stiffness of the material.

scholarly journals NUMERICALLY MODELING FATIGUE LIFE OF STRUCTURAL ELEMENTS UNDER THERMAL CYCLIC LOADING

2020 ◽  
Vol 82 (2) ◽  
pp. 168-188
Author(s):  
I.A. Volkov ◽  
L.A. Igumnov ◽  
D.N. Shishulin ◽  
V.A. Eremeev
Keyword(s):  
Plastic Deformation ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Strength Criterion ◽  
Cyclic Fatigue ◽  
Defining Relations ◽  
Damage Degree ◽  
Fatigue Damage Accumulation ◽  
Main Effects

The paper considers processes of fatigue life of materials and structures in the exploitation conditions characterized by multiparametric nonstationary thermal-mechanical effects In the framework of mechanics of damaged media, a mathematical model is developed that describes processes of thermal-plastic deformation and fatigue damage accumulation in materials with degradation according to low- and high-cycle fatigue mechanisms (accounting for their interaction). The model consists of three interconnected parts: relations determining cyclic thermal-plastic behavior of a material, accounting for its dependence on the failure process; equations describing kinetics of fatigue damage accumulation; a strength criterion of the damaged material. The version of the defining relations of thermal plasticity is based on the notion of the yield surface and the principle of orthogonality of the plastic strain rate vector to the yield surface at the loading point and reflects the main effects of the process of cyclic plastic deformation of the material for arbitrarily complex trajectories of combined thermal-mechanical loading. The version of kinetic equations of fatigue damage accumulation is based on introducing a scalar parameter of damage degree and on energy-based principles, and takes into account the main effects of the nucleation, growth and merging of microdefects under arbitrarily complex loading regimes. A generalized form of an evolutionary equation of fatigue damage accumulation in low-cycle and high-cycle fatigue regions is introduced. The condition when the damage degree reaches its critical value is taken as the strength criterion of the damaged material. To assess the reliability and the scope of applicability of the developed defining relations of mechanics of damaged media, processes of thermal-plastic deformation and fatigue damage accumulation have been numerically analyzed, and the numerical results obtained have been compared with the data of full-scale experiments for a particular applied problem. The effect of the dropping frequency of a distillate on thermal cyclic fatigue life of the material of a heated surface of a tube has been numerically analyzed. The computational results for the fatigue damage accumulation processes under thermal pulsed loading are compared with experimental data. It is shown that the developed model describes both qualitatively and, accurately enough for engineering purposes, quantitatively the experimental data and can be effectively used for evaluating thermal-cyclic fatigue life of structures working in the conditions of multiaxial non-proportional regimes of combined thermal-mechanical loading.

scholarly journals Numerical Study on Vibration Response and Fatigue Damage of Axial Compressor Blade Considering Aerodynamic Excitation

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1835
Author(s):  
Xi Fu ◽  
Chao Ma ◽  
Jiewei Lin ◽  
Junhong Zhang
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Equivalent Stress ◽  
Axial Compressor ◽  
Compressor Blade ◽  
Torsional Shear ◽  
Fatigue Damage Accumulation ◽  
Fatigue Model

Axial compressor blades with a deformed initial torsion angle caused by aerodynamic excitation resonated at the working speed and changed the rule of fatigue damage accumulation. The fatigue life of a blade has a prediction error, even causing serious flight accidents if the effect of torque causing damage deterioration of the blade fatigue life is neglected. Therefore, in this paper, a uniaxial non-linear fatigue damage model was modified using the equivalent stress with torsional shear stress, and the proposed fatigue model including the torsional moment was used to study the compressor blade fatigue life. Then, the blade numerical simulation model was established to calculate the vibration characteristics under complex loads of airflow excitation and a rotating centrifugal force. Finally, the blade fatigue life under actual working conditions was predicted using the modified fatigue model. The results show that the interaction between centrifugal and aerodynamic loads affects the natural frequency, as the frequencies in modes dominated by bending deformation decreased whereas those dominated by torsional deformation increased. Furthermore, the blade root of the suction surface showed stress concentration, but there is an obvious difference of stress distribution and amplitude between the normal stress and the equivalent stress including torsional shear stress. The additional consideration of the torsional shear stress decreased the predicted fatigue life by 4.5%. The damage accumulation rate changes with the loading cycle, and it accelerates fast for the last 25% of the cycle, when the blade fracture may occur at any time. Thus, the aerodynamic excitation increased the safety factor of blade fatigue life prediction.

In situ and experimental analysis of longitudinal load on carbody fatigue life using nonlinear damage accumulation

2021 ◽  
pp. 105678952110460
Author(s):  
Sunil Kumar Sharma ◽  
Rakesh Chandmal Sharma ◽  
Jaesun Lee
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Dynamic Stress ◽  
Fatigue Analysis ◽  
Analysis Method ◽  
Accumulation Model ◽  
Longitudinal Load ◽  
Damage Accumulation Model

In this paper, a multi-disciplinary analysis method is proposed for evaluating the fatigue life of railway vehicle car body structure under random dynamic loads. Firstly, the hybrid fatigue analysis method was used with Multi-Body System simulation and finite element method for evaluating the carbody structure dynamic stress histories. The dynamics stress is calculated from the longitudinal load using longitudinal train dynamics. Secondly, the nonlinear damage accumulation model was used in fatigue analysis, and carbody structure fatigue life and fatigue damage were predicted. The mathematical model simulations are compared with results produced experimentally, showing good agreement. Finally, the mode is determined after the finite element model is established. To achieve the dynamic stress at each node, the modal response is used as excitation. The carbody damage was obtained by combining dynamics stress with the NMCCMF damage accumulation model. As a result, the effect of longitudinal load on carbody fatigue damage is investigated. The longitudinal load contributes significantly to the fatigue damage of the carbody.

Contact fatigue life prediction of rolling bearing considering machined surface integrity

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Li Cui ◽  
Yin Su
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Fatigue Failure ◽  
Surface Integrity ◽  
Damage Accumulation ◽  
Rolling Bearing ◽  
Content Type ◽  
Accumulation Model ◽  
Fatigue Damage Accumulation ◽  
Damage Accumulation Model

Purpose Rolling bearings often cause engineering accidents due to early fatigue failure. The study of early fatigue failure mechanism and fatigue life prediction does not consider the integrity of the bearing surface. The purpose of this paper is to find new rolling contact fatigue (RCF) life model of rolling bearing. Design/methodology/approach An elastic-plastic finite element (FE) fatigue damage accumulation model based on continuous damage mechanics is established. Surface roughness, surface residual stress and surface hardness of bearing rollers are considered. The fatigue damage and cumulative plastic strain during RCF process are obtained. Mechanism of early fatigue failure of the bearing is studied. RCF life of the bearing under different surface roughness, hardness and residual stress is predicted. Findings To obtain a more accurate calculation result of bearing fatigue life, the bearing surface integrity parameters should be considered and the elastic-plastic FE fatigue damage accumulation model should be used. There exist the optimal surface parameters corresponding to the maximum RCF life. Originality/value The elastic-plastic FE fatigue damage accumulation model can be used to obtain the optimized surface integrity parameters in the design stage of bearing and is helpful for promote the development of RCF theory of rolling bearing.

scholarly journals Multiscale Damage Evolution Analysis of Aluminum Alloy Based on Defect Visualization

2019 ◽  
Vol 9 (23) ◽  
pp. 5251 ◽  
Author(s):  
Yuquan Bao ◽  
Yali Yang ◽  
Hao Chen ◽  
Yongfang Li ◽  
Jie Shen ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Evolution Model ◽  
Micro Computed Tomography ◽  
Fatigue Damage Accumulation ◽  
Macro Scale ◽  
Computed Tomography Scanning ◽  
Damage Data

The evaluation of fatigue life through the mechanism of fatigue damage accumulation is still a challenging task in engineering structure failure analysis. A multiscale fatigue damage evolution model was proposed for describing both the mesoscopic voids propagation in the mesoscopic-scale and fatigue damage evolution process, reflecting the progressive degradation of metal components in the macro-scale. An effective method of defect classification was used to implement 3D reconstruction technology based on the MCT (micro-computed tomography) scanning damage data with ABAQUS subroutine. The effectiveness was validated through the comparison with the experimental data of fatigue damage accumulation. Our results indicated that the multiscale fatigue damage evolution model built a bridge between mesoscopic damage and macroscopic fracture, which not only used the damage variable in the macro-scale to characterize the mesoscopic damage evolution indirectly but also understood macroscopic material degradation behavior from mesoscale with sufficient precision. Furthermore, the multiscale fatigue damage evolution model could offer a new reasonable explanation of the effect of load sequence on fatigue life, and also could predict the fatigue life based on damage data by nondestructive testing techniques.

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