Fatigue Life Calculation in Conditions of Wide Spectrum Random Loadings – The Experimental Verification of a Calculation Algorithm on the Example of 41Cr4 Steel

2012 ◽  
Vol 726 ◽  
pp. 17-26
Author(s):  
Bogdan Ligaj ◽  
Grzegorz Szala
Keyword(s):  
Fatigue Life ◽  
Wide Spectrum ◽  
Loading Conditions ◽  
Test Results ◽  
Structural Elements ◽  
Random Loading ◽  
Calculation Algorithm ◽  
Fatigue Characteristic ◽  
Life Tests ◽  
Fatigue Characteristics

Precision of fatigue life calculations of structural elements in programmed loading conditions is connected with proper elaboration of loading spectrum and assumption of a proper fatigue characteristic. On the base of literature data and own research there has been elaborated an algorithm for fatigue life calculations in random loading conditions with wide spectrum. Calculations were performed with the usage of chosen mathematical models of two-parametric fatigue characteristics. Results calculated with accordance to the described procedure were validated with experimental test results of specimens made of 41Cr4 steel with a method of programmed fatigue life tests.

scholarly journals Influence of the Elastoplastic Strain on Fatigue Durability Determined with the Use of the Spectral Method

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 423 ◽  
Author(s):  
Michał Böhm ◽  
Mateusz Kowalski ◽  
Adam Niesłony
Keyword(s):  
Fatigue Life ◽  
Probability Density ◽  
Spectral Method ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Loading Conditions ◽  
Random Loading ◽  
Elastoplastic Deformations ◽  
Fatigue Life Assessment ◽  
Safe Side

The paper presents experimental static and fatigue tests results under random loading conditions for the bending of 0H18N9 steel. The experimental results were used in performing calculations, according to the theoretical assumptions of the spectral method of fatigue life assessment, including elastoplastic deformations. The presented solution extends the use of the spectral method for material fatigue life assessment, in terms of loading conditions, above Hooke’s law theorem. The work includes computational verification of the proposal to extend the applicability of the spectral method of determining fatigue life for the range of elastoplastic deformations. One of the aims of the proposed modification was to supplement the stress amplitudes used to calculate the probability density function of the power spectral density of the signal with correction, due to the plastic deformation and its use for notched elements. The authors have tested the method using four of the most popular probability density functions used in commercial software. The obtained results of comparisons between the experimental and calculation results show that the proposed algorithm, tested using the Dirlik, Benasciutti–Tovo, Lalanne, and Zhao–Baker models, does not overestimate fatigue life, which means that the calculations are on the safe side. The obtained results prove that the elastoplastic deformations can be applied within the frequency domain for fatigue life calculations.

Effects of Surface Finish and Loading Conditions on the Low Cycle Fatigue Behavior of Austenitic Stainless Steel in PWR Environment: Comparison of LCF Test Results With NUREG/CR-6909 Life Estimations

2008 ◽  
Author(s):  
Jean Alain Le Duff ◽  
Andre´ Lefranc¸ois ◽  
Jean Philippe Vernot
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Austenitic Stainless Steel ◽  
Environmental Effects ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Complex Signal ◽  
Loading Conditions ◽  
Test Results ◽  
Cycle Fatigue

During mid 2006, ANL issued a NUREG/CR-6909 [2] report that is now applicable in The US for evaluations of PWR environmental effects in the fatigue analysis of new reactor components. In order to assess the conservativeness of the application of this NUREG report, low cycle fatigue (LCF) tests were performed by AREVA NP on austenitic stainless steel specimens in a PWR environment. The selected material exhibits in an air environment a fatigue behavior consistent with the ANL reference “air” mean curve. Tests were performed for two various loading conditions: for fully reverse triangular signal (for comparison purpose with tests performed by other laboratories with same loading conditions) and complex signal, simulating strain variation for actual typical PWR thermal transients. Two surface finish conditions were tested: polished and ground. The paper presents on one side the comparison of environmental penalty factors (Fen = Nair,RT/Nwater) as observed experimentally with the ANL formulation (considering the strain integral method for complex loading), and, on the other hand, the actual fatigue life of the specimen with the fatigue life predicted through the NUREG/CR-6909 application. Low Cycle Fatigue test results obtained on austenitic stainless steel specimens in PWR environment with triangle waveforms at constant low strain rates gives Fen penalty factors close to those estimated using the ANL formulation (NUREG report 6909). On the contrary, it was observed that constant amplitude LCF test results obtained under complex signal reproducing an actual sequence of a cold and hot thermal shock exhibits significantly lower environmental effects when compared to the Fen penalty factor estimated on the basis of the ANL formulations. It appears that the application of the NUREG/CR-6909 [2] in conjunction with the Fen model proposed by ANL for austenitic stainless steel provides excessive margins whereas the current ASME approach seems sufficient to cover significant environmental effect for components.

A Study on Improvement of Fatigue Life for Woven Glass Fabric/Epoxy Laminate Composite Applied to Railway Vehicle

2010 ◽  
Vol 654-656 ◽  
pp. 2583-2586
Author(s):  
Hee Young Ko ◽  
Kwang Bok Shin ◽  
Jung Seok Kim
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Stress Ratio ◽  
Laminate Composite ◽  
Glass Fabric ◽  
Railway Vehicle ◽  
Test Results ◽  
Laminate Composites ◽  
Remarkable Improvement ◽  
Fatigue Characteristics

In this study, the fatigue characteristics and life of woven glass fabric/epoxy laminate composites applied to railway vehicle were evaluated. The fatigue test was conducted by tension-tension load with stress ratio R of 0.1 and frequency of 5Hz. The material used to fatigue test was two types of woven glass fabric/epoxy laminate composite with and without the reinforcement of carbon/epoxy ply. Also, the fatigue life of woven glass fabric/epoxy laminate composite was compared with that of aluminum 6005 used to the car-body and under-frame structures of railway vehicle. The test results showed that the failure strength and life of woven glass fabric/epoxy laminate composite with the reinforcement of three carbon/epoxy plies had a remarkable improvement in comparison with that of bare specimen without reinforcement.

scholarly journals Special Issue on Fracture and Fatigue Assessments of Structural Components

2020 ◽  
Vol 10 (18) ◽  
pp. 6327
Author(s):  
Alberto Campagnolo
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Fatigue Loading ◽  
Complex Geometries ◽  
Loading Conditions ◽  
Structural Elements ◽  
Structural Components ◽  
Special Issue ◽  
Linear Elastic ◽  
Life Predictions

This Special Issue covers the broad topic of structural integrity of components subjected to either static or fatigue loading conditions, and it is concerned with the modelling, assessment and reliability of components of any scale. Dealing with fracture and fatigue assessments of structural elements, different approaches are available in the literature. They are usually divided into three subgroups: stress-based, strain-based and energy-based criteria. Typical applications include materials exhibiting either linear-elastic or elasto-plastic behaviours, and plain and notched or cracked components subjected to static or cyclic loading conditions. In particular, the articles contained in this issue concentrate on the mechanics of fracture and fatigue in relation to structural elements from nano- to full-scale and on the applications of advanced approaches for fracture and fatigue life predictions under complex geometries or loading conditions.

Influence of the Selected Fatigue Characteristics of the Material on Calculated Fatigue Life under Variable Amplitude Loading

2011 ◽  
Vol 104 ◽  
pp. 197-205 ◽  
Author(s):  
Adam Niesłony ◽  
Andrzej Kurek
Keyword(s):  
Fatigue Life ◽  
Energy Parameter ◽  
Correct Selection ◽  
Constant Amplitude ◽  
Random Loading ◽  
Data Set ◽  
Variable Amplitude ◽  
Comparison Results ◽  
Machine Elements ◽  
Fatigue Characteristics

The algorithm of fatigue life determination for machine elements subjected to random loading uses fatigue characteristics of the material determined under constant-amplitude loading. They are usually stress or strain characteristics as well as characteristics using the energy parameter. Their correct selection influences correctness of the obtained results related to the experimental data. The paper presents analysis of convergence of the calculated fatigue lives of some constructional materials subjected to random loading under uniaxial loading state. For calculations concerning one material the same loading state was assumed and fatigue characteristics were determined on the basis of one data set obtained under constant strain amplitude tests. Calculated fatigue lives based on different fatigue characteristics were compared and their convergences were tested. It has been proved that convergences are different depending on the material. The comparison results were presented in form of graphs.

Design of welded structures working under random loading

2002 ◽  
Vol 216 (2) ◽  
pp. 191-201 ◽  
Author(s):  
R Kouta ◽  
M Gungad ◽  
D Play
Keyword(s):  
Fatigue Life ◽  
Statistical Analysis ◽  
Design Method ◽  
Test Results ◽  
Random Loading ◽  
Matrix Representations ◽  
Fatigue Lifetime ◽  
Random Loads ◽  
Number Of Cycles ◽  
Cycles To Failure

This paper presents a design method for prediciting the fatigue life of T-joint assemblies loaded by random loads, based on a statistical analysis of tests. This sduty was on the correclation between the types of loading observed in practive and test results obtained for fatigue life determination. The work follows three steps: analysis tof the statistical distributions of random loads that illustrate extremen value from Markov matrix representations; statistical analysis of lifetimes obtained when the specimens are sbumitted to random loads defined earlier; design of a set of endurance curves [stress-number of cycles to failure ( S-N) curves], called ‘random’ S-N curves. These SN curves. These S-N curves are shifted compared with that obtained under sinusoidal loading. Random S-N curve positions in the S-N plane are obtimized depending on the lifetime able to take into account the damege due to the small cycles that are often present in actual loading. The use of random S-N curves for fatigue life calculations gives results matching with theral fatigue lifetime obtained with a T-joint assembly of a bogie chassis used for railway applications. Different analyses show the robustness of the proposed approach.

Study on Weld Fatigue Evaluation Under Sour Service Environment Using Battelle Structural Stress Method

2013 ◽  
Author(s):  
Jeong K. Hong ◽  
Thomas P. Forte
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Fatigue Behavior ◽  
Structural Stress ◽  
Loading Conditions ◽  
Test Results ◽  
Knock Down ◽  
Weld Toe ◽  
Weld Fatigue ◽  
Sour Service

Risers, pipelines and flowlines for deep water applications are subject to corrosive environments. Especially, in the presence of hydrogen sulfide which makes the field sour, their fatigue performance becomes significantly degraded. In order to quantify the sour degradation effect, a knock-down factor has been introduced. This factor is defined as the fatigue life reduction relative to the in-air fatigue life. Several sets of fatigue test results in sour service environments have been published. These include strip specimens of different sizes, e.g., diameters, wall thicknesses, and arc lengths. Naturally, the knock-down factor must be based upon a statistically valid number of fatigue test results obtained from the same specimen geometry and the same loading conditions tested in air and in sour conditions. Currently, the database available in the open literature is too limited to properly define a knock-down factor. Moreover, there is a great deal of scatter within the database and each test in a sour environment is costly and time consuming. Thus, it is difficult to establish a statistically valid database upon which to base the knock-down factor. A mesh-insensitive structural stress method has been developed by Battelle researchers and has been proven to be highly effective in correlating the fatigue behavior of welded joints. In 2007, the Battelle structural stress based weld fatigue master S-N curve was included in ASME Section VIII Div. 2 because it successfully consolidated more than 800 fatigue test results for weld toe failures onto a single master S-N curve with very little scatter, regardless of specimen shape, size, loading type, and steel alloy [1–2]. A knock-down factor is derived by applying the Battelle structural stress method to the existing database for sour environment tests and by using the current in-air database as the reference condition. This approach will reduce the uncertainty in the knock-down factor because it allows a wider range of sour environment data from specimens of different sizes, types, and loading conditions to be combined, while simultaneously reducing scatter. As such, a unified knock-down factor can be determined with greater statistical validity and wider applicability for design recommendations in sour conditions.

scholarly journals Fatigue life estimation under multi-axial random loading in light poles

2015 ◽  
Vol 37 ◽  
pp. 183
Author(s):  
Kazem Reza Kashyzadeh
Keyword(s):  
Fatigue Life ◽  
Random Vibration ◽  
Equivalent Stress ◽  
Loading Conditions ◽  
Random Loading ◽  
Life Estimation ◽  
Fatigue Life Estimation ◽  
Light Pole ◽  
Variable Wind ◽  
Random Vibration Analysis

In the present paper, fatigue life of light poles under multi-axial random loading based on the variable wind direction and speed has been studied. To achieve these purposes, light pole is simulated with all loading conditions in ABAQUS Software. To consider to the three storm days as the critical loading conditions, Random vibration analysis has been performed to obtain stress histories and equivalent stress. Finally, Calculate fatigue life of light pole by using Dirlik Theory.

Evaluation of Fatigue Characteristic of a Real Waterworks Pipe

2005 ◽  
Vol 297-300 ◽  
pp. 2471-2476 ◽  
Author(s):  
Chang Sung Seok ◽  
Jae Sil Park ◽  
Hyung Ick Kim ◽  
Young Min Lee ◽  
Won Hak Cho ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Standard Specimen ◽  
Surface Condition ◽  
Fatigue Tests ◽  
Piping System ◽  
Test Results ◽  
Fatigue Characteristic ◽  
Standard Specimens ◽  
Constraint Effects ◽  
Geometrical Difference

The fatigue characteristic of a material or a structure is derived from fatigue tests of standard specimens. However, many researches have reported that test results of standard specimens are very different from those of real structures or components. One reason for this difference is the constraint effects according to the geometrical difference. Therefore, to calculate more accurate fatigue life, the constraint effect must be considered by comparing test results of standard specimens with those of real structures or components. Another reason for this difference is the surface condition. All surfaces of a standard specimen are polished to obtain similar conditions in a fatigue test. However, in a piping system, surface conditions of components are different from each other and very different from that of a standard specimen. Because fatigue life is effected by a surface condition, to evaluate the fatigue life of a piping system, fatigue tests must be conducted with a specimen extracted from a pipe with the same surface condition. The objective of this paper is to evaluate the fatigue characteristic of a real waterworks pipe by conducting fatigue tests with standard specimens and non-standard specimens of base metal and weld metal. Standard fatigue specimens and non-standard specimens were extracted from a steel pipe used in waterworks. Also, fatigue tests of pipes used in water service were carried out and then compared with those of standard specimens and non-standard specimens. From these results the relation between the S-N diagram of a specimen and that of a pipe specimen was evaluated.

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