scholarly journals Effects of Machining Induced Residual Shear and Normal Stresses on Fatigue Life and Stress Intensity Factor of Inconel 718

2019 ◽  
Vol 9 (22) ◽  
pp. 4750
Author(s):  
Yang Hua ◽  
Zhanqiang Liu
Keyword(s):  
Experimental Data ◽  
Stress Intensity Factor ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Inconel 718 ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Shear Stresses ◽  
Normal Stresses

Residual shear stresses and normal stresses induced by machining affect the fatigue performance of components. Thus, residual shear and normal stresses should be considered simultaneously when evaluating the influence of residual stress on fatigue performance. In the present paper, the influences of residual shear and normal stresses on the fatigue life and stress intensity factor (SIF) of turned Inconel 718 were investigated. Firstly, the cos α measurement method was utilized to calculate the residual shear stress and residual normal stress of turned Inconel 718. Then, the combined effects of residual shear and normal stresses on fatigue life were evaluated through uniaxial tension–tension fatigue tests. Thirdly, a prediction model for the SIF was proposed by taking the residual shear and normal stresses into account. Finally, the predicted SIF was validated by the published experimental data from the literature. The predicted results of the proposed model generally agreed well with the available experimental data.

A Fatigue Study of C-130 Aircraft Skin Using the Stop Drill Technique

2012 ◽  
Vol 730-732 ◽  
pp. 685-690
Author(s):  
José A.S. Cardoso ◽  
Virgínia Infante ◽  
Bruno A.S. Serrano
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Intensity Factor ◽  
Fatigue Tests ◽  
Drilling Technique ◽  
Drill Diameter ◽  
Aircraft Skin ◽  
Reducing Stress

The stop-drilling technique is a simple and economic way to delay crack propagationby drilling a hole on the crack tip and reducing stress concentration. This paper presents thepropagation of cracks and investigates how the increasing of the stop-drill diameter improvescrack initiation life in specimens of 2024-T3 aluminium alloy of C-130 aircraft skin. A numericalmethod was applied to simulate an automatic crack propagation by interacting ANSYSr andMATLABr, and several experimental fatigue tests were done to support the computationalresults. A Morrow equation was used to predict the fatigue life of the stop-drill. Good agreementof stress intensity factor along crack length was obtained between numerical and experimentalresults. All results show that fatigue life increases when the stop-drill diameter is larger. Whencompared to the 2mm diameter stop-drill, the experimental results show an improvement of189% and 464% to 4mm and 6mm diameter stop-drill fatigue life, and the numerical results of333% and 952%, respectively.

scholarly journals Effect of Pre-Corrosion Pits on Residual Fatigue Life for 42CrMo Steel

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2130 ◽  
Author(s):  
Dezheng Liu ◽  
Yan Li ◽  
Xiangdong Xie ◽  
Jing Zhao
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Research Work ◽  
Residual Fatigue Life ◽  
42Crmo Steel ◽  
Regression Formula ◽  
Residual Fatigue ◽  
Corrosion Pits

The effect of pre-corrosion pits on residual fatigue life for the 42CrMo steel (American grade: AISI 4140) is investigated using the accelerated pre-corrosion specimen in the saline environment. Different pre-corroded times are used for the specimens, and fatigue tests with different loads are then carried out on specimens. The pre-corrosion fatigue life is studied, and the fatigue fracture surfaces are examined by a surface profiler and a scanning electron microscope (SEM) to identify the crack nucleation sites and to determine the size and geometry of corrosion pits. Moreover, the stress intensity factor varying with corrosion pits in different size parameters is analyzed based on finite element (FE) software ABAQUS to derive the regression formula of the stress intensity factor. Subsequently, by integrating the regression formula with the Paris formula, the residual fatigue life is predicted and compared with experimental results, and the relationship of the stress intensity factor, pit depth, and residual fatigue life are given under different corrosion degrees. The fatigue life predicted by the coupled formula agrees well with experiment results. It is observed from the SEM images that higher stress amplitude and longer pre-corroded time can significantly decrease the residual fatigue life of the steel. Additionally, the research work has brought about the discovery that the rate of crack extension accelerates when the crack length increases. The research in this paper also demonstrates that the corrosion pit size can be used as a damage index to assess the residual fatigue life.

Fatigue Damage Analysis on Crack Growth and Fatigue Life of Welded Bridge Members with Initial Crack

2006 ◽  
Vol 324-325 ◽  
pp. 251-254 ◽  
Author(s):  
Tai Quan Zhou ◽  
Tommy Hung Tin Chan ◽  
Yuan Hua
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Initial Crack ◽  
Traffic Loading

The behavior of crack growth with a view to fatigue damage accumulation on the tip of cracks is discussed. Fatigue life of welded components with initial crack in bridges under traffic loading is investigated. The study is presented in two parts. Firstly, a new model of fatigue crack growth for welded bridge member under traffic loading is presented. And the calculate method of the stress intensity factor necessary for evaluation of the fatigue life of welded bridge members with cracks is discussed. Based on the concept of continuum damage accumulated on the tip of fatigue cracks, the fatigue damage law suitable for steel bridge member under traffic loading is modified to consider the crack growth. The proposed fatigue crack growth can describe the relationship between the cracking count rate and the effective stress intensity factor. The proposed fatigue crack growth model is then applied to calculate the crack growth and the fatigue life of two types of welded components with fatigue experimental results. The stress intensity factors are modified by the factor of geometric shape for the welded components in order to reflect the influence of the welding type and geometry on the stress intensity factor. The calculated and measured fatigue lives are generally in good agreement, at some of the initial conditions of cracking, for a welded component widely used in steel bridges.

An Infinite Plate Weakened by Periodic Cracks

2002 ◽  
Vol 69 (4) ◽  
pp. 552-555 ◽  
Author(s):  
Y. Z. Chen ◽  
K. Y. Lee
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Eigenfunction Expansion ◽  
Infinite Plate ◽  
Elastic Response ◽  
Shear Stresses ◽  
Orthotropic Medium ◽  
T Stress ◽  
Periodic Cracks

An infinite plate weakened by doubly distributing cracks is studied in this paper. Two loading cases, the remote tension and the remote shear stresses, are assumed. Analysis is performed for a cracked cell cut from the infinite plate. It is found that the eigenfunction expansion variational method is efficient to solve the problem. The stress intensity factor, the T-stress, and the elastic response are evaluated. The cracked plate can be equivalent to an orthotropic medium without cracks. The equivalent elastic constants are presented.

scholarly journals An Analytical Model for the Identification of the Threshold of Stress Intensity Factor Range for Crack Growth

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Marzio Grasso ◽  
Antonio De Iorio ◽  
Yigeng Xu ◽  
George Haritos ◽  
M. Mohin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Analytical Model ◽  
Analytical Techniques ◽  
Stress Intensity Factor Range ◽  
Maximum Deviation ◽  
Experimental Identification

The value of the stress intensity factor (SIF) range thresholdΔKthfor fatigue crack growth (FCG) depends highly on its experimental identification. The identification and application ofΔKthare not well established as its determination depends on various factors including experimental, numerical, or analytical techniques used. A new analytical model which can fit the raw FCG experimental data is proposed. The analytical model proposed is suitable to fit with high accuracy the experimental data and is capable of estimating the threshold SIF range. The comparison between the threshold SIF range identified with the model proposed and those found in the literature is also discussed.ΔKthidentified is found to be quite accurate and consistent when compared to the literature with a maximum deviation of 5.61%. The accuracy with which the analytical model is able to fit the raw data is also briefly discussed.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2019 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

Abstract This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

Fracture Mechanics Fatigue Evaluation of a Flowline Clamp Connector Using Finite Element Modeling of a Crack

2018 ◽  
Author(s):  
Curtis Sifford ◽  
Ali Shirani
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Element Analysis

This paper presents the application of the rules from ASME Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code for a fracture mechanics evaluation to determine the damage tolerance and fatigue life of a flowline clamp connector. The guidelines from API 579-1 / ASME FFS-1 Fitness-For-Service for the stress analysis of a crack-like flaw have been considered for this assessment. The crack tip is modeled using a refined mesh around the crack tip that is referred to as a focused mesh approach in API 579-1 / ASME FFS-1. The driving force method is used as an alternative to the failure assessment diagram method to account for the influence of crack tip plasticity. The J integral is determined using elastic-plastic finite element analysis and converted to an equivalent stress intensity factor to be compared to the fracture toughness of the material. The fatigue life is calculated using the Paris Law equation and the stress intensity factor calculated from the finite element analysis. The allowable number of design cycles is determined using the safety factors required from Division 3 of the ASME Pressure Vessel Code.

scholarly journals Ultrasonic and Conventional Fatigue Endurance of Aeronautical Aluminum Alloy 7075-T6, with Artificial and Induced Pre-Corrosion

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1033
Author(s):  
Ishvari F. Zuñiga Tello ◽  
Marijana Milković ◽  
Gonzalo M. Domínguez Almaraz ◽  
Nenad Gubeljak
Keyword(s):  
Stress Intensity Factor ◽  
Aluminum Alloy ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Initiation ◽  
Transverse Direction ◽  
Fatigue Tests ◽  
Testing Specimen ◽  
Ultrasonic Fatigue ◽  
Fatigue Endurance

Ultrasonic and conventional fatigue tests were carried out on the AISI-SAE AA7075-T6 aluminum alloy, in order to evaluate the effect of artificial and induced pre-corrosion. Artificial pre-corrosion was obtained by two hemispherical pitting holes of 500-μm diameter at the specimen neck section, machined following the longitudinal or transverse direction of the testing specimen. Induced pre-corrosion was achieved using the international standard ESA ECSS-Q-ST-70-37C of the European Space Agency. Specimens were tested under ultrasonic fatigue technique at frequency of 20 kHz and under conventional fatigue at frequency of 20 Hz. The two applied load ratios were: R = −1 in ultrasonic fatigue tests and R = 0.1 in conventional fatigue tests. The main results were the effects of artificial and induced pre-corrosion on the fatigue endurance, together with the surface roughness modification after the conventional fatigue tests. Crack initiation and propagation were analyzed and numeric models were constructed to investigate the stress concentration associated with pre-corrosion pits, together with the evaluation of the stress intensity factor in mode I from crack initiation to fracture. Finally, the stress intensity factor range threshold ΔKTH was obtained for the base material and specimens with two hemispherical pits in transverse direction.

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