Estimation of Weibull Parameters for Composite Material Strength and Fatigue Life Data

2009 ◽  
pp. 291-291-21 ◽  
Author(s):  
R Talreja
Keyword(s):  
Composite Material ◽  
Fatigue Life ◽  
Material Strength ◽  
Weibull Parameters ◽  
Life Data

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

scholarly journals Bayesian estimation of the lethargy coefficient for probabilistic fatigue life model

2017 ◽  
Vol 5 (2) ◽  
pp. 191-197 ◽  
Author(s):  
Jaehyeok Doh ◽  
Jongsoo Lee
Keyword(s):  
Fatigue Life ◽  
Sampling Method ◽  
Bayesian Updating ◽  
Unknown Parameters ◽  
Life Data ◽  
Mcmc Sampling ◽  
Fatigue Model ◽  
Relative Stress ◽  
Life Model ◽  
Static Tensile

Abstract In this study, a model for probabilistic fatigue life that is based on the Zhurkov model is suggested using stochastically and statistically estimated lethargy coefficients. The fatigue life model was derived using the Zhurkov life model, and it was deterministically validated using real fatigue life data as a reference. For this process, firstly, a lethargy coefficient that is related to the failure of materials must be obtained with rupture time and stress from a quasi-static tensile test. These experiments are performed using HS40R steel. However, the lethargy coefficient has discrepancies due to the inherent uncertainty and the variation of material properties in the experiments. The Bayesian approach was employed for estimating the lethargy coefficient of the fatigue life model using the Markov Chain Monte Carlo (MCMC) sampling method and considering its uncertainties. Once the samples are obtained, one can proceed to the posterior predictive inference of the fatigue life. This life model was shown to be reasonable when compared with experimental fatigue life data. As a result, predicted fatigue life was observed to significantly decrease in accordance with increasing relative stress conditions. Highlights Zhurkov fatigue life model is deterministically validated with experiments. Prediction of the S-N curve using Zhurkov fatigue model and lethargy coefficients. Lethargy coefficients of Zhurkov fatigue model are estimated by Bayesian updating. Bayesian updating is useful for quantifying the uncertainty of unknown parameters.

Capturing uncertainty in fatigue life data

2015 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
Ravi C. Penmetsa ◽  
Raymond R. Hill ◽  
Darryl K. Ahner ◽  
Brent D. Russell
Keyword(s):  
Fatigue Life ◽  
Life Data

Study on Transient Response Analysis and Fatigue Life Evaluation of Water Pump Volute Casing under Impact Load

2012 ◽  
Vol 155-156 ◽  
pp. 550-554
Author(s):  
Min Li ◽  
Zeng Hui Yin ◽  
Kui Shi ◽  
Jian Xin Liu ◽  
Hui Yong Du
Keyword(s):  
Fatigue Life ◽  
Impact Load ◽  
Flaw Detection ◽  
Bench Test ◽  
Response Analysis ◽  
Material Strength ◽  
Water Pump ◽  
Life Evaluation ◽  
Curve Method ◽  
Fatigue Life Evaluation

A water pump volute casing was found leak after 359 hours in a 500-hour-durability bench test. The flatness of big surface, flaw detection and material strength of the pump volute casing were tested, the failure reason was identified and the structure was optimized. The fatigue life of the optimization pump volute casing was simulated by applying S-N curve method, and the optimization structure was also identified successfully by experiments.

Effect of Water Absorption on Strength of the Aeronautical Composite Material Fiberdux HTA/6376

2009 ◽  
Vol 417-418 ◽  
pp. 457-460 ◽  
Author(s):  
S.G. Pantelakis ◽  
C.V. Katsiropoulos ◽  
K.I. Tserpes ◽  
Therese Felgeyrolles
Keyword(s):  
Tensile Strength ◽  
Composite Material ◽  
Fatigue Life ◽  
Water Absorption ◽  
Damage Model ◽  
Fatigue Tests ◽  
Progressive Damage ◽  
Saturation Point ◽  
Effect Of Water ◽  
Progressive Damage Model

The effect of water absorption on tensile strength and fatigue life of the Fiberdux HTA/6376 composite laminated material was experimentally and numerically investigated. For the investigation, a quasi-isotropic and a cross-ply layup were considered. Tensile and fatigue tests were carried out with dry and wet specimens subjected to water absorption up to the water uptake saturation point. Fractographic analyses of fracture surfaces were conducted to detect the type of accumulated damage. To describe the mechanical behavior of the material a FE-based progressive damage model was developed. Material properties used in the model are those of the saturated material evaluated experimentally. Convergent results reveal an appreciable degradation in the ultimate tensile strength and fatigue life of the composite material owing to water absorption.

Lower Tail Estimation of Fatigue Life

2019 ◽  
Author(s):  
D. Gary Harlow
Keyword(s):  
Fatigue Life ◽  
Extreme Value ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Tail Behavior ◽  
Confidence Bounds ◽  
Lower Tail ◽  
Life Data ◽  
Order Of Magnitude ◽  
Value Estimation

Abstract Uncertainty in the prediction of lower tail fatigue life behavior is a combination of many causes, some of which are aleatoric and some of which are systemic. The error cannot be entirely eliminated or quantified due to microstructural variability, manufacturing processing, approximate scientific modeling, and experimental inconsistencies. The effect of uncertainty is exacerbated for extreme value estimation for fatigue life distributions because by necessity those events are rare. In addition, typically, there is a sparsity of data in the region of smaller stress levels in stress–life testing where the lives are considerably longer, extending to giga cycles for some applications. Furthermore, there is often over an order of magnitude difference in the fatigue lives in that region of the stress–life graph. Consequently, extreme value estimation is problematic using traditional analyses. Thus, uncertainty must be statistically characterized and appropriately managed. The primary purpose of this paper is to propose an empirically based methodology for estimating the lower tail behavior of fatigue life cumulative distribution functions, given the applied stress. The methodology incorporates available fatigue life data using a statistical transformation to estimate lower tail behavior at much smaller probabilities than can be estimated by traditional approaches. To assess the validity of the proposed methodology confidence bounds will be estimated for the stress–life data. The development of the methodology and its subsequent validation will be illustrated using extensive fatigue life data for 2024–T4 aluminum alloy specimens readily available in the open literature.

scholarly journals Numerical Evaluation of Structural Safety for Aged Onshore Wind Foundation to Extend Service Life

2020 ◽  
Vol 10 (13) ◽  
pp. 4561
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Sung-Hoon Song ◽  
Jeongsoo Kim
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Safety Evaluation ◽  
Life Extension ◽  
Structural Safety ◽  
Material Strength ◽  
Design Strength ◽  
Onshore Wind ◽  
Service Period ◽  
Service Life Extension

In this paper, for the case of “service life extension” with the same capacity for wind turbines, a structural safety evaluation was carried out to determine whether to extend the service life of the aged foundation. As a result of this study, it was found that the aged foundation satisfies the structural safety of material strength, ultimate strength, fatigue life, and serviceability up to the present. Although the in-service period has been over 16 years, it has been shown that the material properties of concrete have exceeded the design strength, and no significant material deterioration has occurred. Also, structural safety could be evaluated more realistically based on actual concrete properties. In particular, it has been shown that it has a fatigue life of 40 years or more, so service life can be extended. It is expected that the methodology used in this paper will be useful not only for structural safety evaluation of the foundation in service, but also for decision-making for extending the service life. Furthermore, a more technical approach should be explored by many researchers in the future.

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