Effect of Loading Sequence on the Fatigue Life of Notched Specimens Made From Steel and Aluminium Alloys

1991 ◽  
Vol 44 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Otto Buxbaum ◽  
Hartmut Kla¨tschke ◽  
Helge Oppermann
Keyword(s):  
Fatigue Life ◽  
Aluminium Alloys ◽  
General Relation ◽  
Statistical Parameter ◽  
Axial Loading ◽  
Fatigue Tests ◽  
Test Results ◽  
Random Loading ◽  
Test Load ◽  
Notched Specimens

A statistical parameter which can be derived from the Markov matrix has been defined in order to characterize the intermixture of random loading fluctuations. By means of this intermixture parameter, load sequences for fatigue tests can be generated closer to reality, and thus more reliable effects as well as effects resulting from loading sequences can be taken into account quantitatively in life calculations. The intermixture parameter has been calculated for 17 test load sequences. The corresponding fatigue test results obtained for notched specimens (Ki = 1.4–3.6) made from steels or aluminium alloys, either under bending or axial loading, led to a general relation between intermixture and fatigue life, being primarily influenced by the stress ratio.

Relationship Between Fatigue Life Distribution, Notch Configuration, and S-N Curve of a 2024-T4 Aluminum Alloy

1985 ◽  
Vol 107 (3) ◽  
pp. 214-220 ◽  
Author(s):  
T. Shimokawa ◽  
Y. Hamaguchi
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stress Amplitude ◽  
Fatigue Tests ◽  
Test Results ◽  
Notched Specimens ◽  
Wide Range ◽  
Life Distributions ◽  
The Relationship ◽  
Test Stress

The objective of this study is to identify the most closely related variable to the distribution of fatigue life in unnotched and three kinds of notched 2024-T4 aluminum alloy specimens. Carefully designed fatigue tests under a constant temperature and humidity condition provided fatigue life distributions over a wide range of stress amplitude. This study used about 1000 specimens. On the basis of the test results, the dependence of the scatter in fatigue life on notch configuration, the period to crack initiation, the level of stress amplitude, the median fatigue life, and the slope of the median S-N curve is investigated, and the relationship between the distributional form of fatigue life and the shape of the median S-N curve is discussed. It is concluded that the slope and shape of the median S-N curve in the vicinity of the test stress level are closely related to the scatter and distributional form of fatigue life respectively. This is common to the unnotched and three kinds of notched specimens. A variability hypothesis to correlate the median S-N curve with fatigue life distributions is examined.

Comparison of Creep-Fatigue Evaluation Methods With Notched Specimens Made of Mod.9Cr-1Mo Steel

2011 ◽  
Author(s):  
Masanori Ando ◽  
Yuichi Hirose ◽  
Takanori Karato ◽  
Sota Watanabe ◽  
Osamu Inoue ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fast Reactor ◽  
Evaluation Methods ◽  
Fatigue Tests ◽  
Test Results ◽  
Notched Specimens ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Fatigue Life Evaluation

In a component design at elevated temperature, creep-fatigue is one of the most important failure modes, and assessment of creep-fatigue life in structural discontinuity is important issue to evaluate structural integrity of the components. Therefore a lot of creep-fatigue life evaluation methods were proposed until now. To compare and assess these evaluation methods, a series of creep-fatigue tests was carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo steel, which it is a candidate material for a primary and secondary heat transport system components of JSFR (Japan Sodium-cooled Fast Reactor). Mechanical creep-fatigue tests and thermal creep-fatigue tests were performed by using conventional uni-axial push-pull fatigue test machine and thermal gradient generating system with an induction heating coil. Stress concentration levels were adjusted by varying the diameters of notch roots in the both tests. In the test, creep-fatigue lives, crack initiation and propagation processes were observed by digital micro-scope and replica method. Besides those, a series of elastic Finite Element Analysis (FEA) were carried out to predict the number of cycles to failure by several creep-fatigue life evaluation methods. Then these predictions were compared with test results. Several types of evaluation methods which are stress redistribution locus (SRL) method, simple elastic follow-up method and the methods described in JSME FR (Fast Reactor) code were applied. The applicability and conservativeness of these methods were discussed. It was appeared that SRL method gave rational prediction of creep-fatigue life with conservativeness when the factor of κ = 1.6 was applied for all the conditions tested in this study. Comparison of SRL method and simple elastic follow-up method indicated that SRL method applied factor of κ = 1.6 gave the smallest creep-fatigue life in practicable stress level. JSME FR code gave an evaluation 70∼100 times conservative lives comparing with the test results.

scholarly journals Analysis of the Correlation between the Static and Fatigue Test Results of the Interlayer Bondings of Asphalt Layers

2016 ◽  
Vol 62 (1) ◽  
pp. 83-98 ◽  
Author(s):  
A. Szydło ◽  
K. Malicki
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Asphalt Mixture ◽  
Fatigue Tests ◽  
Test Results ◽  
Static Tests ◽  
Bonding State ◽  
Road Pavement ◽  
The Future ◽  
Pavement Structure

Abstract The bonding state of the asphalt layers in a road pavement structure significantly affects its fatigue life. These bondings, therefore, require detailed tests and optimization. In this paper, the analyses of the correlation between the results of laboratory static tests and the results of fatigue tests of asphalt mixture interlayer bondings were performed. The existence of the relationships between selected parameters was confirmed. In the future, the results of these analyses may allow for assessment of interlayer bondings’ fatigue life based on the results of quick and relatively easy static tests.

High-cycle fatigue tests of pretensioned concrete beams

PCI Journal ◽  
2022 ◽  
Vol 67 (1) ◽  
Author(s):  
Jörn Remitz ◽  
Martin Empelmann
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Concrete Beams ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Design Methods ◽  
Test Results ◽  
Cycle Fatigue ◽  
Pretensioned Concrete ◽  
Current Design

Pretensioned concrete beams are widely used as bridge girders for simply supported bridges. Understanding the fatigue behavior of such beams is very important for design and construction to prevent fatigue failure. The fatigue behavior of pretensioned concrete beams is mainly influenced by the fatigue of the prestressing strands. The evaluation of previous test results from the literature indicated a reduced fatigue life in the long-life region compared with current design methods and specifications. Therefore, nine additional high-cycle fatigue tests were conducted on pretensioned concrete beams with strand stress ranges of about 100 MPa (14.5 ksi). The test results confirmed that current design methods and specifications overestimate the fatigue life of embedded strands in pretensioned concrete beams.

Study on Local Strain Field Intensity Approach for Prediction Fatigue Life of Crankshaft Based on Mechanical Mechanics

2013 ◽  
Vol 644 ◽  
pp. 251-255 ◽  
Author(s):  
Ke Bao ◽  
Qiu Fang Wang ◽  
Shu Lin Liu ◽  
Zhong Liang Wei
Keyword(s):  
Field Intensity ◽  
Strain Field ◽  
Local Strain ◽  
Fatigue Tests ◽  
Bending Moments ◽  
Test Results ◽  
Life Test ◽  
Test Load ◽  
Bending Fatigue ◽  
Crack Initiation Life

The bending fatigue limit moment and crack initiation life of 4105 crankishaft in five groups of bending moments are obtained by resonant bending fatigue tests first. Then, the static finite element calculation using sub-model is performed to get the strain distributions in every test load. The results show that in the region where stress concentrate, the strain field could be seen as plane strain state. So two dimensional strain field intensity model is selected. In order to remove the influences of size and surface conditions, the radius of strain field is determined with the strain distribution under the low-life test load. After that, the local strain field intensities under each test load are calculated with the radius of strain field. Finally, the strain-life curve of material is modified by the fatigue intensity limit of crankshaft, and the predicted life agree with the test results.

Effects of Continuous Strain Rate Changing on Environmental Fatigue for Stainless Steels in PWR Environment

2010 ◽  
Author(s):  
Yuichiro Nomura ◽  
Seiji Asada ◽  
Takao Nakamura ◽  
Masakazu Tanaka
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Water Environment ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Integral Model ◽  
Strain Rates ◽  
Test Results ◽  
Approach Method ◽  
The Difference

The strain rates in actual transients of operating plants are not constant and changing momentarily. A large number of fatigue tests under stepwise strain rate changing conditions were performed to develop a method for evaluating fatigue life under varying strain rate conditions. Based on these test results, a strain base integral model known as the named the modified rate approach method was developed and verified. However it was reported recently that in the case of sine wave fatigue tests in BWR environment, the fatigue life was two to six times longer than the fatigue life predicted by the modified rate approach method. For this paper, in order to confirm whether the same tendency is observed in PWR environment, fatigue tests of sine wave were performed of SS316 in simulated PWR water environment. As the result, the difference of fatigue life by sine wave test reported in BWR environment was not observed between experimental and predicted life in PWR environment and the modified rate approach method was applicable under continuous strain rate changing condition.

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.

scholarly journals Cyclic Tests of Smooth and Notched Specimens Subjected to Bending and Torsion Taking into Account the Effect of Mean Stress

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2141 ◽  
Author(s):  
Roland Pawliczek ◽  
Dariusz Rozumek
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Regression Equations ◽  
Allowable Stress ◽  
Cyclic Tests ◽  
Mean Values ◽  
Notched Specimens ◽  
Fatigue Characteristics

The paper contains the results of fatigue tests of smooth and notched specimens made of 10HNAP (S355J2G1W) subjected to proportional cyclic loading with use of mean values stress. The results obtained for specimens under bending, torsion and one combination of bending with torsion for four mean values have been compared. The experimental data have been collected in the tables and shown in the figures with use of various σa(τa)-N fatigue characteristics for which parameters of the regression equations have been determined. The influence of average values on the allowable stress amplitudes and amplitude of moments at the level close to the fatigue limit depending on the angle α determining loading combination and the average stress is also shown. The greatest effect of the notch on fatigue life compared to smooth specimens is observed at symmetrical loads. At unsymmetrical loads with non-zero mean stress, this effect clearly weakens or disappears.

Effect of Lubricant Viscosity on Gearing Contact Fatigue Life

2012 ◽  
Vol 190-191 ◽  
pp. 1295-1301 ◽  
Author(s):  
Xiu Mei Qi ◽  
Chuang Kuan Gao ◽  
Zeng Qiang Zhang
Keyword(s):  
Fatigue Life ◽  
Contact Fatigue ◽  
Critical Value ◽  
Fatigue Tests ◽  
Numerical Calculations ◽  
Quantitative Relation ◽  
Test Results ◽  
Contact Fatigue Life ◽  
Lubricant Viscosity ◽  
Film Lubrication

The paper considers the effect of lubricant viscosity, ν, on the contact fatigue life, N, in gearing applications. More than 40 sets of the thermal non-Newtonian EHL numerical calculations and six sets of disc fatigue tests under the conditions ranging from the mixed to full film lubrication are used. The results show that for improving gearing fatigue life it is generally useful to increase lubricant viscosity. But it is not simply the case that the higher the lubricant viscosity, the better. When lubricant viscosity, ν, is less than a critical value, νcr, a quantitative relation of is seen in the test results; When ν > νcr, however, increasing lubricant viscosity is found to reduce the fatigue life. Based on this result, the paper raises questions concerning the accuracy of the lubrication factor recommended by ISO/6336:1996.

Fatigue Life Evaluation of Vehicle Wheel Bolts under Random Loading

2005 ◽  
Vol 297-300 ◽  
pp. 1770-1775 ◽  
Author(s):  
Young Woo Choi ◽  
Byeong Wook Noh ◽  
Kyung Chun Ham ◽  
Sung In Bae
Keyword(s):  
Fatigue Life ◽  
Residual Life ◽  
Three Dimensional ◽  
Real Life ◽  
Local Stress ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Random Loading ◽  
Element Analysis ◽  
Three Dimensional Finite Element

The fatigue life of hexagon head and socket head bolts, attached to vehicle a wheel, is assessed and the estimation of the residual life of existing bolts in vehicle wheel is investigated. Field- measured load histories were applied in this test. Tensile tests and fatigue tests were performed to evaluate the effect of tightening torque and to obtain the basic experimental data. A three-dimensional finite element analysis was also performed to evaluate the local stress fields. Miner’s rule was used to predict the fatigue life of bolts. The results indicate the prediction of fatigue life of the bolts was in good agreement with the real life of vehicle wheel bolts in this test.

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