Fatigue Damage Prediction for Combined Random and Static Mean Stresses

1993 ◽  
Vol 36 (3) ◽  
pp. 25-32
Author(s):  
Ronald Lambert
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Narrow Band ◽  
Stress Rupture ◽  
Structural Elements ◽  
Damage Prediction ◽  
Static Tensile ◽  
Analytical Expressions ◽  
Static Tensile Stress ◽  
Mean Stresses

Closed form analytical expressions have been derived and are proposed for use to predict accumulated fatigue damage and fatigue life of structural elements subjected to a combination of fully reversed narrow-band Gaussian random and static mean stresses. Such mean stresses can significantly alter fatigue life. The proposed method of combining random alternating and mean stresses shows excellent agreement with published experimental data for a steel alloy. Reasonable agreement is maintained, surprisingly, even for static tensile stress values up to near the material's yield stress where the failure mode shifts from that of typical brittle fatigue to that of stress rupture (i.c.,creep). Numerical examples are provided to illustratc the application.

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.

scholarly journals A Theoretical Approach to Predict the Fatigue Life of Flexible Pipes

2012 ◽  
Vol 2012 ◽  
pp. 1-29 ◽  
Author(s):  
José Renato M. de Sousa ◽  
Fernando J. M. de Sousa ◽  
Marcos Q. de Siqueira ◽  
Luís V. S. Sagrilo ◽  
Carlos Alberto D. de Lemos
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Cross Section ◽  
Time Domain ◽  
Theoretical Approach ◽  
Flexible Pipe ◽  
Stress Effects ◽  
Flexible Pipes ◽  
Counting Methods ◽  
Mean Stresses

This paper focuses on a theoretical approach to access the fatigue life of flexible pipes. This methodology employs functions that convert forces and moments obtained in time-domain global analyses into stresses in their tensile armors. The stresses are then processed by well-known cycle counting methods, andS-Ncurves are used to evaluate the fatigue damage at several points in the pipe’s cross-section. Finally, Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers, the effect of the annulus conditions, the importance of evaluating the fatigue life in various points of the pipe’s cross-section, and the effect of mean stresses. The results obtained suggest that the friction between layers and the annulus conditions strongly influences the fatigue life of flexible pipes. Moreover, mean stress effects are also significant, and at least half of the wires in each analyzed section of the pipe must be considered in a typical fatigue analysis.

Fretting-Fatigue Damage-Factor Determination

1965 ◽  
Vol 87 (3) ◽  
pp. 298-302 ◽  
Author(s):  
J. A. Collins
Keyword(s):  
Fatigue Damage ◽  
Normal Force ◽  
Experimental Tests ◽  
Fretting Fatigue ◽  
Damage Factor ◽  
Sliding Motion ◽  
Static Tensile ◽  
Tentative Explanation ◽  
Solid Bodies ◽  
Static Tensile Stress

Small-amplitude cyclic sliding motion at the interface between two solid bodies pressed together by a normal force initiates microcracks which propagate and cause premature fatigue failure. This action is defined to be fretting-fatigue. A quantitative evaluation of fretting-fatigue damage would be of great value to the mechanical engineering designer. It is proposed that a fretting-fatigue damage-factor could be developed to provide a quantitative index to fretting-fatigue damage. The damage-factor proposed is a function of eight basic fretting-fatigue parameters. Experimental tests were conducted to establish quantitative values for the fretting-fatigue damage-factor for a few specific sets of fretting-fatigue conditions. An unexpected trend in the value of the fretting-fatigue damage-factor was observed for the case of static stress in the specimen during fretting. With a static tensile stress in the specimen during fretting, the fretting-fatigue damage, as measured by reduction in fatigue limit, was very slight, while with a static compressive stress in the specimen during fretting, the fretting-fatigue damage was very great. A tentative explanation is presented.

Fatigue Life Assessment of Aluminium Alloy 6061 Specimen Using Signal Analysis Approach for Automotive Components

2012 ◽  
Vol 165 ◽  
pp. 26-30
Author(s):  
N.A. Azmir ◽  
Shahrum Abdullah ◽  
Mahfodzah M. Padzi
Keyword(s):  
Fatigue Life ◽  
Aluminium Alloy ◽  
Fatigue Damage ◽  
Structural Engineering ◽  
Manufacturing Industry ◽  
Dynamic Responses ◽  
Life Assessment ◽  
Fatigue Assessment ◽  
Damage Prediction ◽  
Data Editing

This paper is aimed to investigate the fatigue assessment of aluminium alloy 6061specimen, one of the widely used aluminium alloys in the production of mechanical components. The alloy possesses the ability of critical failure caused by fatigue when they are subjected to dynamic responses in automotive-type components. The specimens were prepared according to the ASTM E606 and ASTM E1820 standards which were then subjected to two types of cyclic loading amplitude modes namely constant amplitude and random amplitude. The effort is initiated by implementing fatigue data editing approach for random amplitude signal, the conventional method, the finite element method (FEM) and fatigue assessment determination through the statistical method of root mean square (r.m.s) and kurtosis. The input and edited signal acquired will be analyzed for the prediction of the fatigue damage based on the strain model approaches, i.e. Coffin-Manson, Morrow and SWT. From the results obtained, both edited and non-edited signals load display the same amount of fatigue damage to consequently decrease the analysis duration. In addition, the FEM was found to be the best approach for estimating the fatigue life. This research has finally revealed that the higher cyclic load amplitude will only diminish the fatigue life of a specimen. Furthermore, this fatigue assessment study will look forward to improve structural engineering development in monitoring components and consequently access the damage prediction variable which could later be implemented to the manufacturing industry.

scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

A Multi-Level Low Cycle Fatigue Damage Model for Forging Die Material

2006 ◽  
Vol 514-516 ◽  
pp. 804-809
Author(s):  
S. Gao ◽  
Ewald Werner
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Die Material ◽  
Multi Level ◽  
Loading Sequence ◽  
Forging Die

The forging die material, a high strength steel designated W513 is considered in this paper. A fatigue damage model, based on thermodynamics and continuum damage mechanics, is constructed in which both the previous damage and the loading sequence are considered. The unknown material parameters in the model are identified from low cycle fatigue tests. Damage evolution under multi-level fatigue loading is investigated. The results show that the fatigue life is closely related to the loading sequence. The fatigue life of the materials with low fatigue loading first followed by high fatigue loading is longer than that for the reversed loading sequence.

Hybrid Fatigue Analysis Method for Railway Carbody Structure

2008 ◽  
Vol 44-46 ◽  
pp. 733-738 ◽  
Author(s):  
Bing Rong Miao ◽  
Wei Hua Zhang ◽  
Shou Ne Xiao ◽  
Ding Chang Jin ◽  
Yong Xiang Zhao
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Hybrid Method ◽  
Dynamic Stress ◽  
Stress Test ◽  
Fatigue Analysis ◽  
Railway Vehicle ◽  
Analysis Method ◽  
Structure Dynamic ◽  
Multi Body

Railway vehicle structure fatigue life consumption monitoring can be used to determine fatigue damage by directly or indirectly monitoring the loads placed on critical vehicle components susceptible to failure from fatigue damage. The sample locomotive carbody structure was used for this study. Firstly, the hybrid fatigue analysis method was used with Multi-Body System (MBS) simulation and Finite Element Method (FEM) for evaluating the carbody structure dynamic stress histories. Secondly, the standard fatigue time domain method was used in fatigue analysis software FE-FATIGUE and MATLAB WAFO (Wave Analysis for Fatigue and Oceanography) tools. And carbody structure fatigue life and fatigue damage were predicted. Finally, and carbody structure dynamic stress experimental data was taken from this locomotive running between Kunming-Weishe for this analysis. The data was used to validate the simulation results based on hybrid method. The analysis results show that the hybrid method prediction error is approximately 30.7%. It also illustrates that the fatigue life and durability of the locomotive can be predicted with this hybrid method. The results of this study can be modified to be representative of the railway vehicle dynamic stress test.

Evaluating the Coupledness of the Aerodynamics and Hydrodynamics on the Estimation of Fatigue Damage Equivalent Load for a Floating Offshore Wind Platform

2018 ◽  
Author(s):  
Samuel Kanner ◽  
Bingbin Yu
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Environmental Conditions ◽  
Offshore Wind ◽  
Coupled Analysis ◽  
Offshore Wind Turbine ◽  
Wave Conditions ◽  
Equivalent Load ◽  
The Waves

In this research, the estimation of the fatigue life of a semi-submersible floating offshore wind platform is considered. In order to accurately estimate the fatigue life of a platform, coupled aerodynamic-hydrodynamic simulations are performed to obtain dynamic stress values. The simulations are performed at a multitude of representative environmental states, or “bins,” which can mimic the conditions the structure may endure at a given site, per ABS Floating Offshore Wind Turbine Installation guidelines. To accurately represent the variety of wind and wave conditions, the number of environmental states can be of the order of 103. Unlike other offshore structures, both the wind and wave conditions must be accounted for, which are generally considered independent parameters, drastically increasing the number of states. The stress timeseries from these simulations can be used to estimate the damage at a particular location on the structure by using commonly accepted methods, such as the rainflow counting algorithm. The damage due to either the winds or the waves can be estimated by using a frequency decomposition of the stress timeseries. In this paper, a similar decoupled approach is used to attempt to recover the damages induced from these coupled simulations. Although it is well-known that a coupled, aero-hydro analysis is necessary in order to accurately simulate the nonlinear rigid-body motions of the platform, it is less clear if the same statement could be made about the fatigue properties of the platform. In one approach, the fatigue damage equivalent load is calculated independently from both scatter diagrams of the waves and a rose diagram of the wind. De-coupled simulations are performed to estimate the response at an all-encompassing range of environmental conditions. A database of responses based on these environmental conditions is constructed. The likelihood of occurrence at a case-study site is used to compare the damage equivalent from the coupled simulations. The OC5 platform in the Borssele wind farm zone is used as a case-study and the damage equivalent load from the de-coupled methods are compared to those from the coupled analysis in order to assess these methodologies.

Effect of Surface Machining on the Fatigue Life of Low Alloy Steel for Hydrogen Pressure Vessels

2007 ◽  
Author(s):  
Yoru Wada ◽  
Ryoji Ishigaki ◽  
Yasuhiko Tanaka ◽  
Tadao Iwadate ◽  
Keizo Ohnishi
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Pressure Vessels ◽  
Hydrogen Gas ◽  
Annealed Specimen ◽  
Surface Machining ◽  
Hydrogen Fatigue ◽  
Effect Of Surface

The effect of surface machining on fatigue life in high pressure hydrogen gas was investigated. The test was conducted under the elastic range under 45MPa gaseous hydrogen environment by the ground specimen which were machined so that the surface roughness to be Rmax = 19μm(Mark: 19s), 26μm(26s) and 93μm(93s) and by the polished specimen which are prepared so that the surface roughness to be Rmax = 1μm(1s), 3.6μm(3.6s) and 10μm(10s). The hydrogen fatigue life of ground specimens was considerably reduced with increasing surface roughness as compared to the fatigue life in air at the same surface condition. On the other hand, for the annealed conditions of the ground specimen, the reduction by hydrogen effect was fairly small. The residual stress for the ground specimen at the surface rises sharply in tension while the residual stress for the annealed specimen was nearly equal to zero. We have shown that the hydrogen fatigue damage can be evaluated by obtaining the information about residual stress on surface, stress concentration by maximum surface roughness and the threshold stress intensity SH above which hydrogen fatigue damage occurs.

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