A Simulation Method of Establishing Fatigue Life Distribution

1976 ◽  
Vol 98 (1) ◽  
pp. 183-188 ◽  
Author(s):  
H. A. Elmaraghy ◽  
J. N. Siddall
Keyword(s):  
Fatigue Life ◽  
Material Properties ◽  
Digital Simulation ◽  
Simulation Method ◽  
Fatigue Tests ◽  
Design Tool ◽  
Statistical Characteristics ◽  
Life Distribution ◽  
Parametric Studies ◽  
Life Distributions

This paper presents a Monte Carlo simulation method for fatigue failure, by which the randomness of two material properties as well as that of the applied load can be incorporated into a stochastic model using an appropriate failure criterion to predict the statistical characteristics of fatigue life under constant and random amplitude cyclic loading conditions. In this technique, both the endurance limit Se and the fatigue strength coefficient Sf′ are treated as stochastic variables. The combined effect of the randomness of Se, Sf′, and the applied stress on the statistical characteristics of fatigue lives is predicted analytically using digital simulation of fatique tests. The life distributions and their statistical characteristics are found to be in good agreement with those obtained from analyzing the experimental results, indicating that the proposed technique and the underlying assumptions and hypotheses are adequate. The suggested method is believed to be an effective, fast, and easy-to-use design tool which is suitable for use on electronic computers. It is ideal for parametric studies compared with the costly and time-consuming laboratory fatigue tests. Minimum experimental data are needed as a basis for the analysis. New results are presented which show the effect of the randomness of the loads and material properties on the randomness of fatigue life distribution.

Fatigue Reliability Functions in Semilogarithmic Coordinates

1991 ◽  
Author(s):  
Vladimir A. Avakov
Keyword(s):  
Fatigue Life ◽  
Coordinate System ◽  
Strength Distribution ◽  
Fatigue Reliability ◽  
Life Distribution ◽  
Similar Transformation ◽  
Asymptotic Type ◽  
Life Distributions ◽  
Strength Distributions

Abstract In the previous publication [2], the transformation between fatigue life and strength distribution was established using double-logarithmic coordinate system (lnN-lnS). Here, a similar transformation is established using a semi logarithmic (lnN-S) coordinate system. With the aid of the developed orthogonal relations, lognormal, Weibull and three-parameter logweibull life distributions have been transformed into normal, asymptotic type 1 of smallest value, and three-parameter Weibull strength distributions, respectively. This procedure may be applied to other types of fatigue life distribution.

The Montecarlo Method in Application of Fatigue Life Reliability Analysis

2013 ◽  
Vol 395-396 ◽  
pp. 822-825 ◽  
Author(s):  
Yue Yang ◽  
Jia Ping Yao ◽  
Xiu Jin Yang ◽  
Zhi Bo Yang
Keyword(s):  
Fatigue Life ◽  
Integration Method ◽  
Simulation Method ◽  
Crack Size ◽  
Numerical Integration Method ◽  
Life Distribution ◽  
Deterministic Method ◽  
Montecarlo Simulation ◽  
Montecarlo Method ◽  
Fatigue Crack Propagation Life

Based on the probability theory, combined with the deterministic method for estimating the fatigue fracture mechanics, the formula was deduced to calculate the fatigue crack propagation life of examples components. The uncertainty and randomness of main assessment parameters were considered:initial crack size, practical working load,fracture toughness, mechanical intensity and coefficients. Since there are not many data, Weibull distribution was adopted to denote the life distribution of equipment approximately. A computer program was developed by using numerical integration method, and the fatigue life under given reliability and credit degree was solved. Analysis result shows that MonteCarlo simulation method can reflect objectively the uncertainty of assessment parameters and overcome the shortcomings of certainty assessment methods.

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.

Fatigue Reliability Functions in Semilogarithmic Coordinates

1991 ◽  
Vol 113 (3) ◽  
pp. 352-358 ◽  
Author(s):  
V. A. Avakov
Keyword(s):  
Fatigue Life ◽  
Coordinate System ◽  
Strength Distribution ◽  
Fatigue Reliability ◽  
Life Distribution ◽  
Similar Transformation ◽  
Asymptotic Type ◽  
Life Distributions ◽  
Straight Lines

In the previous publication [2], the transformation between fatigue life and strength distribution was established using double-logarithmic coordinate system (InN-InS). Here, a similar transformation is established using a semilogarithmic (InN-S) coordinate system. It is assumed that the set of S = Sj (N/Qj) (j = 1,2,...,p) relations, plotted in the InN-S coordinates, becomes a family of parallel straight lines. With the aid of the developed orthogonal relations, lognormal, Weibull and three-parameter logweibull life distributions have been transformed into normal, asymptotic type 1 of smallest value, and three-parameter Weibull strength distributions, respectively. This procedure may be applied to other types of fatigue life distribution.

scholarly journals Fatigue Life Testing of Locally Additive Manufactured AlSilOMg Test Specimens

R&D Journal ◽  
2021 ◽  
Vol 37 ◽  
Author(s):  
N. Agenbag ◽  
C. McDuling
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Additive Manufacturing ◽  
Surface Finish ◽  
Material Properties ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Surface Finishing ◽  
Test Results ◽  
Static Testing

ABSTRACT In order for additive manufacturing to become a viable manufacturing methodfor aerospace engineering, it is required that exhaustive static and fatigue testing be performed. The testing is required in order to describe material properties in a statistical manner. Fatigue tests were performed on standard additive manufactured ASTM E466 test specimens in order to obtain the low (1000 cycles) to high cycle (1E6 cycles) behaviour of AlSi10Mg. The specimens were manufactured using non-heat treated, but stress relieved specimens. Specimens were printed in three build directions, namely the XY (parallel with build plate), 45 degree and vertical direction as measured with respect to the build baseplate. The three different directions were chosen to investigate the sensitivity of the material properties to the build direction. The specimens were stress relieved on the baseplate. Static testing was also performed on specimens according to ASTM E8/E8M. The specimens were produced to have a surface finish representative of standard deburring techniques used in the aerospace industry. The surface roughness on the specimens were measured. The scatter in test data as a result of the surface finish on material properties is quantified. It is a requirement to quantify the effect of the surface roughness on fatigue failure allowable values since a machined type finish (less than 3.2 micrometer) is not always practically possible to achieve with additive manufactured structures. This is because the organic shapes produced with additive manufacturing makes some surfaces inaccessible to normal surface finishing techniques. Furthermore, some internal structures such as lattice structures are completely inaccessible to surface finishing techniques such as polishing or lapping. In addition to the surface roughness the roundness of the test section was also measured using inspection equipment. This was required since the industrial deburring techniques did not yield a completely concentric test section as a lathe operation would produce. Once again this is representative of an additive manufactured structure. The fatigue tests were performed at an R-ratio of 0.1. The test results were used to produce Wöhler or S-N curves for the material in all three material directions. The scatter was quantified using industry accepted methods. The results were compared with fatigue test results from literature of specimens produced with a lathe in order to compare a practical industrial surface finish on an additive manufactured component with a machined surface finish. It was found that the build support structures of the additive manufacturing process causes stress concentrations in the fatigue test specimens. This leads to a reduction in fatigue life and an increase in the scatter of the results. Additional keywords: Additive manufacturing, fatigue testing, static testing, aluminium, AlSi10Mg.

Fatigue Behavior and Deformation of Aluminum and Steel HVOF Sprayed with WC-Co Coatings

1997 ◽  
Author(s):  
A. Ibrahim ◽  
C.C. Berndt
Keyword(s):  
Fatigue Life ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Element Model ◽  
Fatigue Tests ◽  
Dimensional Finite Element ◽  
Life Distributions ◽  
Three Dimensional Finite Element ◽  
Good Agreement

Abstract The effect of WC-Co coating on the high cycle fatigue (HCF) behavior of SAE 12L14 steel and 2024-T4 aluminum was investigated. The fatigue tests were performed at room temperature and 370°C. The fatigue life distributions of specimens in the polished, grit blasted, peened, and coated conditions are presented as a function of the probability of failure. HVOF sprayed WC-Co coating has influenced the fatigue life of aluminum and steel. Factors contributing to this influence, which include grit blasting, elastic modulus, and residual stress, are discussed. A three-dimensional finite-element model (FEM) of the coated specimen was used to calculate the stress distribution across the coating and the substrate. The results of the analytical model are in good agreement with fatigue lives observed experimentally.

A Study on Fatigue Life Distribution of Butt-Welded Joints

1985 ◽  
Vol 107 (4) ◽  
pp. 338-342 ◽  
Author(s):  
T. Sakai ◽  
T. Kikuchi ◽  
T. Tanaka ◽  
K. Fujitani
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Welded Joints ◽  
Welded Joint ◽  
Statistical Test ◽  
Fatigue Tests ◽  
Distribution Characteristics ◽  
Life Distribution ◽  
Crack Initiation Life ◽  
Definition Of

To examine the statistical fatigue life properties of welded joints, fatigue tests were performed on a number of butt-welded specimens, in parallel with similar tests conducted on small specimens spliced from larger butt-welded plates. Based on a statistical test, it was concluded that the distribution characteristics of crack initiation life for the butt-welded joint were successfully evaluated by the results for the spliced specimens for a certain definition of the crack initiation. The definition of crack initiation was based on a fracture mechanics similitute approach.

scholarly journals P-S-N Curve Description of Laser Metal Deposition Ti-6.5Al-2Zr-1Mo-1V Titanium Alloy after Duplex Annealing

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 418
Author(s):  
Tianshuai Wang ◽  
Xiaofan He ◽  
Xiaobo Wang ◽  
Yuhai Li
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Estimation Method ◽  
Likelihood Estimation ◽  
Fatigue Tests ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Life Distribution ◽  
Likelihood Functions ◽  
Distribution Parameters

Fatigue tests were conducted on standard smooth laser metal deposition (LMD) Ti-6.5Al-2Zr-1Mo-1V titanium alloy specimens under three constant-amplitude stresses. The mixed failure behaviors and the influence of internal pores on the fatigue life were discussed in detail. The double-peak characteristics of the fatigue life distribution have been observed, and a bimodal lognormal distribution (BLG) with five variables can be used to describe the fatigue life variation. A parameter estimation method based on the maximum likelihood estimation (MLE) method was proposed to estimate the BLG distribution parameters, and the Newton–Raphson algorithm was used to solve the nonlinear equations derived from the likelihood functions. A P-S-N curve description of LMD titanium alloy was established based on the BLG and verified by fatigue life data obtained from a fatigue test.

A Fatigue Test to Assess the Deformation Behavior of Dental Implants

2010 ◽  
Author(s):  
Choongryeong Lee ◽  
Hyun-Yong Jeong
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Fatigue Life ◽  
Dental Implants ◽  
Fatigue Test ◽  
Material Properties ◽  
Deformation Behavior ◽  
Fatigue Tests ◽  
Test Method ◽  
Test Results

A purpose of this paper is to analyze the effects of material properties and design of a jig on fatigue test results of dental implants. An implant fatigue test method is specified in ISO14801 [1], but it is not described well about the fatigue test jig. The jig of ISO14801 has to firmly hold the fixture, and the elastic modulus of the jig should be more than 3 GPa. These requirements are not sufficient enough to represent the dental implant in the jawbone because the fixture is osseointegrated in the jawbone that is made up with the cortical bone and cancellous bone. In this paper three different materials were used for the jig, and two different fixation methods to hold the fixture were examined in several FE (Finite Element) simulations and fatigue tests. From the simulation and test results, the effects of material properties and design of the jig were evaluated in the light of fatigue life of dental implants.

Minimal distributions in a stochastic partial ordering and bounds for Gaussian processes

1983 ◽  
Vol 20 (03) ◽  
pp. 529-536
Author(s):  
W. J. R. Eplett
Keyword(s):  
Gaussian Process ◽  
Gaussian Processes ◽  
Partial Ordering ◽  
Boundary Crossing ◽  
Conditional Probabilities ◽  
Life Distribution ◽  
Life Distributions ◽  
Bounded Below ◽  
Crossing Probabilities

A natural requirement to impose upon the life distribution of a component is that after inspection at some randomly chosen time to check whether it is still functioning, its life distribution from the time of checking should be bounded below by some specified distribution which may be defined by external considerations. Furthermore, the life distribution should ideally be minimal in the partial ordering obtained from the conditional probabilities. We prove that these specifications provide an apparently new characterization of the DFRA class of life distributions with a corresponding result for IFRA distributions. These results may be transferred, using Slepian's lemma, to obtain bounds for the boundary crossing probabilities of a stationary Gaussian process.

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