PROBABILISTIC SPECIMEN PROPERTY-FATIGUE LIFE MAPPING AND P-S-N CURVE FITTING

2013 ◽  
Vol 20 (05) ◽  
pp. 1350020
Author(s):  
LIYANG XIE ◽  
JIANZHONG LIU ◽  
NINGXIANG WU ◽  
WENXUE QIAN
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Stress Level ◽  
Curve Fitting ◽  
Cyclic Stress ◽  
Small Sample ◽  
Test Method ◽  
Life Distribution ◽  
Stress Levels ◽  
Curve Fitting Method

Fitting P-S-N curve with small-size sample of fatigue test data is significant in engineering applications. Although several small sample-based P-S-N curve fitting methods have been developed, complexity in mathematics and/or the unrealistic assumption of the methods hinder their application seriously. Based on the principle of probabilistically mapping from the probability distribution of specimen property to that of fatigue life of the specimen, this paper presents a new, easy to apply P-S-N curve fitting method. By collecting the life distribution information dispersed in several small-size samples of fatigue lives tested under different cyclic stress levels, a large-size sample of equivalent fatigue life data can be built based on the mapping mechanism as well as the uniqueness of the relationship between fatigue life standard deviation and cyclic stress level. The basic viewpoint is that the fatigue lives tested at any cyclic stress levels can be equivalently converted to an arbitrary baseline stress level according to the life distribution–stress relationship, and this principle can be applied to determine the P-S-N curves with a limited number of test data. Test results illustrate that the P-S-N curves obtained by such methods with 30, 24 or 20 samples, respectively, are close to those obtained by the conventional test method with 60 or 40 samples.

A Probabilistic Fatigue Damage Model for Describing the Entire Set of Fatigue Test Data of the Same Material

2019 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Test ◽  
Fatigue Damage ◽  
Test Data ◽  
Stress Level ◽  
Damage Model ◽  
Fatigue Tests ◽  
Small Sample ◽  
Test Machine ◽  
Stress Levels ◽  
D Model

Abstract One typical widely-accepted approach for describing the fatigue test data is the P-S-N curve approach. However, the P-S-N curve approach has some issues such as: (1) If there are only a few fatigue test data at a fatigue test stress level, the P-S-N curve approach is not valid due to the small sample size; (2) When the total number of fatigue tests under different stress levels might be larger such as more than 30 even though the number of fatigue tests at the same stress level is small, the P-S-N curve cannot be used to analyze such set of fatigue data; (3) It is difficult to calculate the reliability of a component under a cyclic stress level when the probabilistic distribution function under this stress level is not available in the P-S-N curves. The author has proposed the K-D probabilistic fatigue damage model (K-D model) to overcome those issues. The 6061-T6 10-gauge sheet-type flat fatigue specimen was designed, manufactured, and tested on the Instron 8081 fatigue test machine to verify this K-D model. The fatigue tests were under five different cyclic axial loadings with a total of 195 tests. In this paper, the fatigue test data will be analyzed by the P-S-N curve approach and the K-D model. The systematic comparisons between the P-S-N curve approach and the K-D model have approved and verified that the K-D model can be used to analyze and to describe the fatigue test data under all different fatigue stress levels and can be used to calculate the reliability of a component under any type of cyclic fatigue loading.

Design Allowable for Durability Analysis of Advanced Composites

2010 ◽  
Vol 160-162 ◽  
pp. 395-400
Author(s):  
Xue Ling Fan ◽  
Wen Jun Qin
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Composite Structures ◽  
Small Sample ◽  
Test Method ◽  
Test Statistic ◽  
Significance Level ◽  
Advanced Composites ◽  
Durability Analysis ◽  
Standard Design

An allowable design method is presented, along with its experimental validation, to obtain engineering-standard design allowable for fatigue life evaluation of advanced composites. A small sample test method for stress/life curves was established to overcome these issues based on the regression analysis theory. Statistically-based design values, such as the B-basis value, the Anderson-Darling test statistic and the observed significance level, were obtained depends on the characteristics of the composite material test data. For evaluation of the fatigue life of advanced composites, the S-N curve-fitting parameters are obtained using the linear heteroscedastic regression method based on experimental data. Another advantage of this method is that all the test data at different stress levels can be analyzed coinstantaneously, which greatly saved the experimental efforts and specimen for confidential statistical results. Finally, an experimental test program has been conducted on typical laminate composites to generate statistically meaningful data for durability design. The numerical results show that the proposed method can be used as a guide to obtaining design allowable for durability analysis of advanced composite structures.

Fatigue Characteristics of Open-End Thick-Walled Cylinders Under Cyclic Internal Pressure

1963 ◽  
Vol 85 (4) ◽  
pp. 555-565 ◽  
Author(s):  
T. E. Davidson ◽  
R. Eisenstadt ◽  
A. N. Reiner
Keyword(s):  
Fatigue Crack ◽  
Internal Pressure ◽  
Stress Level ◽  
Cyclic Stress ◽  
Diameter Ratio ◽  
Tensile Fatigue ◽  
Stress Levels ◽  
Fatigue Characteristics ◽  
Using Data ◽  
Rate Of Improvement

Thick-walled cylinder fatigue data due to cyclic internal pressure for open-end cylinders in the range of 103 to 105 cycles to failure and having a diameter ratio of 1.4 to 2.0 at a nominal yield strength of 160,000 pounds per square inch is presented. Discussed and also presented are the effects of autofrettage on the fatigue characteristics of thick-walled cylinders. Autofrettage substantially enhances fatigue characteristics at stress levels below the corresponding overstrain pressure, the degree of improvement increasing the decreasing stress levels. The rate of improvement in fatigue characteristics increases significantly with diameter ratio in autofrettaged cylinders up to a diameter ratio of 1.8–2.0 and to a much smaller degree in the nonautofrettaged condition. The rate of improvement of fatigue characteristics above 2.0 is the same for both the autofrettaged and nonautofrettaged cases. It is shown that thermal treatment of 675 F for 6 hours after autofrettage does not affect fatigue characteristics and that there is a correlation between the cyclic-stress level and the area and depth of the fatigue crack to the point of ductile rupture. The depth of the fatigue crack decreases with increasing cyclic-stress level. A means for using data from a unidirectional tensile fatigue test to predict the fatigue characteristics of thick-walled cylinders is discussed.

scholarly journals A Small Sample Prediction Method for Engineering p-S-N Curve

2018 ◽  
Vol 36 (5) ◽  
pp. 831-838 ◽  
Author(s):  
Xiaoran Liu ◽  
Qin Sun ◽  
Ke Liang
Keyword(s):  
Fatigue Life ◽  
Aluminium Alloy ◽  
Stress Level ◽  
Bayesian Method ◽  
Polynomial Chaos ◽  
Least Squares Method ◽  
Prediction Method ◽  
Optimization Method ◽  
Small Sample ◽  
The Relationship

Based on Non-intrusive Polynomial Chaos method, a small sample prediction method for engineering p-S-N curve that has a medium fatigue life is proposed. Parameters in Basquin model are calculated through optimization method based on small sample of observed fatigue life. We establish NIPC polynomials and obtain big sample parameters, obtaining probabilistic properties of parameters with the big sample EDF method. Then the relationship between statistics and stress level are fitted with least squares method. Some new samples are introduced to improve the accuracy of the method. The statistics are updated by Bayesian method. Samples parameters under any stress level are obtained to calculate corresponding fatigue life. Probabilistic properties of fatigue life are predicted, and the p-S-N curve is established. Test observations of aluminium alloy T-2024 are all located in the interval of 95% quantile, showing that the method can effectively predict probabilistic properties of medium fatigue life.

The Reliability of a Component Under Multiple Cyclic Stress Levels With Distributed Cyclic Numbers

2016 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Fatigue Life ◽  
Probabilistic Models ◽  
Random Variable ◽  
Fatigue Loading ◽  
Cyclic Stress ◽  
Initial Crack ◽  
Stress Levels ◽  
Single Constant ◽  
Unsolved Issue ◽  
Loading Spectrum

Fatigue damage is initiated through some “defects” on the surfaces of and/or inside the component and induced by the fatigue cyclic loadings. These “defects” are randomly scattered in components, and one of these “defects” will be randomly “activated” and finally developed to become the initial crack which causes the final fatigue failure. Therefore, the fatigue strength is inherently a random variable and should be treated by probabilistic models such as typical P-S-N curves. The fatigue cyclic loading could be presented or described in any form. But the fatigue loading spectrum can generally be grouped as and described by these five models: (1) a single constant cyclic stress (loading) with a given cyclic number, (2) a single constant cyclic stress with a distributed cyclic number, (3) a distributed cyclic stress (loading) at a given fatigue life (cyclic number), (4) multiple constant cyclic stress levels with given cyclic numbers, and (5) multiple constant cyclic stress levels with distributed cyclic numbers. The approaches for determining the reliability of components under fatigue loading spectrum of the models 1∼4 are available in literature and books. But few articles and books have addressed an approach for determining the reliability of components under the fatigue loading spectrum of the model 5. This paper will propose two approaches for addressing this unsolved issue. Two examples will be presented to implement the proposed approaches with detailed procedures.

Interfacial properties and fatigue behavior of carbon fiber epoxy laminate composites

2013 ◽  
Vol 33 (2) ◽  
pp. 173-179 ◽  
Author(s):  
Hsien-Tang Chiu ◽  
Yung-Lung Liu ◽  
Kuo-Chuan Liang ◽  
Peir-An Tsai
Keyword(s):  
Fatigue Life ◽  
Carbon Fiber ◽  
Fatigue Fracture ◽  
Stress Level ◽  
Fatigue Behavior ◽  
Cyclic Stress ◽  
Matrix Cracking ◽  
Stacking Sequence ◽  
Carbon Fiber Laminate ◽  
Carbon Fiber Epoxy

Abstract The study elucidated the relationship between the stacking sequence and physical properties, by investigating mechanical properties, fatigue life and the morphology, after fatigue fracture of carbon fiber/epoxy composites. The results show that the unidirectional carbon fiber laminate has the maximum tensile stress. Moreover, the laminate with ±45° plies can improve the tensile strain. The fatigue life of all specimens was shorter than 103 cycles under high cyclic stress level, and longer than 106 cycles under low cyclic stress level. Laminates with [908]s stacking sequence had the shortest fatigue life under high and low cyclic stress, while the unidirectional carbon fiber laminate had the highest fatigue life. A number of fatigue damage models, including delaminating, matrix cracking and fiber failure, have been identified by scanning electron microscopy (SEM). The SEM micrographs showed that the morphology on the cross section, after fatigue fracture, was significantly correlated to the stacking sequence.

scholarly journals Study on the Influence of Different Prophase Stress Levels on the Fatigue Damage Characteristics of Granite

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Tianzuo Wang ◽  
Mengya Xue ◽  
Peng Sha ◽  
Fei Xue ◽  
Linxiang Wang
Keyword(s):  
Fatigue Damage ◽  
Stress Level ◽  
Development Trend ◽  
Cyclic Stress ◽  
Tangent Modulus ◽  
Dissipated Energy ◽  
Upper Limit ◽  
Stress Levels ◽  
Number Of Cycles ◽  
The Development Trend

In order to reveal the influence of prophase stress levels on the fatigue damage characteristics of granite, uniaxial fatigue tests of granite with different prophase stress levels were carried out on the basis of the MTS 815.04 rock mechanics test system. The results show that, under the same number of cycles, the failure degree increases with the increase of the prophase stress level. Under the low upper limit of cyclic stress, the tangent modulus and dissipated energy increase significantly with the increase of prophase stress level at the early stage of the cycle loading, while the increasing trend is not obvious with the increase of prophase stress level at the late stage. Under the high upper limit of cyclic stress, the tangent modulus and dissipated energy are less affected by the prophase stress level. The development trend of elastic release energy is not obvious with the increase of prophase stress level, which is less affected by the number of cycles. From the damage parameters defined by dissipative energy, under the low upper limit of cyclic stress, the initial damage is less affected by the prophase stress level. With the increase of the number of cycles, the influence of the prophase stress level on the development trend of the damage variable increases gradually. And the development trend of damage variables shows “C-shaped” damage.

Study on the Life Distribution and Reliability of Roller Based Linear Bearing

2007 ◽  
Author(s):  
Shigeo Shimizu ◽  
Hirokazu Shimoda ◽  
Katsuji Tosha
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Dynamic Load ◽  
Distribution Functions ◽  
Load Rating ◽  
Life Test ◽  
Life Distribution ◽  
Dynamic Load Rating ◽  
Log Normal ◽  
Log Normal Distribution

A study on the life distribution and reliability for roller guides with cage is carried out with a total number of 90 test samples in two lots (Ns = 38 and 52), and fatigue life distribution functions, such as two and three parameters Weibull distribution, and log-normal distribution are used for analyzing the test data. The basic dynamic load rating formula standardized by ISO in 2004 is also compared with the life test data in relation to the effect of crowning on both ends of the carriage raceway. Weibull slope, compatibility of distribution functions and λbm factor are also examined.

A New Model for Fatigue Life Distribution of Concrete

2007 ◽  
Vol 348-349 ◽  
pp. 201-204 ◽  
Author(s):  
Dong Fu Zhao ◽  
Qui Ying Chang ◽  
Jian Hui Yang ◽  
Yu Pu Song
Keyword(s):  
Fatigue Life ◽  
Test Data ◽  
Fuzzy Optimization ◽  
Fatigue Loading ◽  
Static Strength ◽  
Multiaxial Fatigue ◽  
Life Distribution ◽  
New Model ◽  
Kolmogorov Smirnov ◽  
Smirnov Test

Based on the S-N relationship and statistical property of concrete static strength, a function of fatigue life of concrete,1 (a − blog N) , is found to follow the normal distribution. Thus a new probabilistic model of fatigue life distribution of concrete is presented in this paper. The model connects statistical properties of static strength and fatigue life of concrete together in theory, so it is of clear physical meaning. An experiment was conducted. The experiment was a part of the project of The State Natural Science Foundation—Failure Criterion of Plain Concrete Under Multiaxial Fatigue Loading. 2 χ -test and Kolmogorov-Smirnov test are employed to test the proposed model. Fuzzy optimization is used to compare the model with lognormal distribution. 2 χ -test, Kolmogorov-Smirnov test and fuzzy optimization are also conducted for test data from references. The results show that the new model is more flexible to fit test data.

scholarly journals A Survey of Accelerated Vibratory Fatigue Test Method of Aero-Engine Compressor Blading

1985 ◽  
Author(s):  
Tie-Ying Wu ◽  
Qi-Xin Lu
Keyword(s):  
Fatigue Test ◽  
Statistical Methods ◽  
Test Data ◽  
T Test ◽  
Test Method ◽  
Life Distribution ◽  
F Test ◽  
Aero Engine ◽  
Engine Compressor

In this paper, a new accelerated fatigue test (AFT) method based on Miner’s Law is advanced, which is used for vibratory fatigue test of aero-engine compressor blading. By using this method, a sample life distribution can be obtained and it saves time about 50–60%. This approach is validated by experiments and the test data are compared by two statistical methods — namely, F-test and t-test.

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