Research on Fatigue Life of Autofrettaged Thick-Walled Cylinder in Probabilistic Fracture Mechanics

2012 ◽  
Vol 249-250 ◽  
pp. 36-39 ◽  
Author(s):  
Ai Jun Chen ◽  
Zi Chu Cha ◽  
Zhi Qun Wang
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Bauschinger Effect ◽  
Fatigue Cracks ◽  
Analysis Method ◽  
Intensity Factors ◽  
Probabilistic Fracture Mechanics ◽  
Best Fit ◽  
Elliptical Cracks ◽  
Walled Cylinder

Based on the theory of probabilistic fracture mechanics and Monte Carlo simulation, reliability analysis method for fatigue life of autofrettaged thick-walled cylinder was given. The forms of fatigue cracks in bore of autofrettaged thick-walled cylinder were considered as semi-elliptical cracks. The autofrettage residual stress solution was suitable for the thick-walled cylinder made of steel with strain hardening and Bauschinger effect. The stress intensity factors of thick-walled cylinder were calculated according to weight function method. The analysis of the examples showed that lognormal distribution is the best fit for fatigue life. Finally, the fatigue life of autofrettaged thick-walled on the condition of different reliabilities and confidences were presented.

Prediction Approach for Corrosion Fatigue Life of Aircraft Structure Based on Probabilistic Fracture Mechanics

2006 ◽  
Vol 324-325 ◽  
pp. 943-946
Author(s):  
Xiao Ming Tan ◽  
Yue Liang Chen ◽  
Ping Jin
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Corrosion Fatigue ◽  
Failure Process ◽  
Short Crack ◽  
Aircraft Structure ◽  
Probabilistic Fracture Mechanics ◽  
Fracture Failure ◽  
Reliability Method ◽  
Prediction Approach

The corrosion, corrosion fatigue and fracture failure process of aircraft structure is directly concerned with combined effect of many factors, such as load, material characteristics, corrosive environment and so on. The process is very complicated, and there is typical randomness. Based on probabilistic fracture mechanics, with consideration of the limitation of the conventional probabilistic approaches for prediction of corrosion fatigue life of aircraft structure at present, and a new reliability approach under loading spectrum was proposed, in which corrosion damage and fatigue crack damage was united as a same damage parameter. Short crack and long crack growth behavior was separately discussed, and influence of short crack aspect ratio on structure life was discussed. The Advanced First-Order Reliability Method, Importance Sampling Method and iteratively advanced Second-Order Reliability Method were used to compute the fracture failure probability. The results show that the model is feasible. By sensitivity analysis of random parameter, the important parameter was obtained, which helped to monitor the structure fatigue life.

Fatigue Life Predictions of Smooth and Notched Specimens Based on Fracture Mechanics

1981 ◽  
Vol 103 (2) ◽  
pp. 91-96 ◽  
Author(s):  
M. H. El Haddad ◽  
T. H. Topper ◽  
T. N. Topper
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Propagation Model ◽  
Actual Length ◽  
Notched Specimens ◽  
Material Condition ◽  
Length Constant

An elastic plastic fracture mechanics solution for short fatigue cracks in smooth and notched specimens is presented which admits plasticity by replacing the conventional stress term with a strain term and accounts for the propagation of very short cracks by the introduction of an effective crack length which is equal to the actual length increased by length l0, the length constant l0 is characteristic of the material and material condition and is calculated from the smooth specimen endurance limit and the long crack threshold stress intensity. Crack growth results for cracks in both elastic and plastic strain fields of notched specimens when interpreted in terms of this strain based intensity factor showed excellent agreement with elastic long crack data. This intensity factor when combined with a propagation model that includes all stages of crack growth also successfully predicted the total fatigue life of the smooth and notched specimens studied here. The predicted propagation life of elliptical and circular notched specimens is in all cases within 50 percent of the actual fatigue lives.

Fracture Mechanics Consideration of Residual Stresses Introduced by Coldworking Fastener Holes

1980 ◽  
Vol 102 (1) ◽  
pp. 85-91 ◽  
Author(s):  
W. H. Cathey ◽  
A. F. Grandt
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fracture Mechanics ◽  
Test Specimen ◽  
Crack Size ◽  
Analysis Method ◽  
Constant Amplitude ◽  
Mechanics Analysis ◽  
Maximum Crack ◽  
Fatigue Crack Growth Life

Aluminum test specimens are prepared with precracked fastener holes, coldworked by means of an oversized mandrel, and then cycled to failure under constant amplitude loading. A simplified fracture mechanics analysis is performed to predict the fatigue crack growth life caused by the coldworking process. As discussed here, the analysis method is capable of obtaining reasonable estimates for the test specimen fatigue life and of determining the maximum crack size which can be “permanently” arrested by the coldworking process.

Application of Fracture Mechanics to Arch Dam Analysis

2004 ◽  
Vol 261-263 ◽  
pp. 57-62 ◽  
Author(s):  
Shui Cheng Yang ◽  
Li Song ◽  
Hong Jian Liao
Keyword(s):  
Fracture Mechanics ◽  
Three Dimensional ◽  
Arch Dam ◽  
Mixed Mode Fracture ◽  
Analysis Method ◽  
Intensity Factors ◽  
Arch Dams ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
The Stability

The authors present a procedure for the analysis of the stability and propagation of cracks in arch dams based on linear elastic fracture mechanics. A finite element method was used to calculate the stress intensity factors(KⅠ, KⅡ and KⅢ) of crack in the concrete arch dam, and fracture analysis for arch dams was carried out, which based on the criterion of three-dimensional mixed mode fracture of concrete from the experiment. The analysis method can be applied to evaluate the safety of the arch dam and improve the design for arch dam.

Fatigue Modeling of Friction-Stir-Welded (FSW) Butt-Joints for Aerospace Applications

2019 ◽  
Author(s):  
Muhammad A. Wahab ◽  
Vinay Raghuram
Keyword(s):  
Fatigue Life ◽  
Aluminum Alloys ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Fatigue Cracks ◽  
Strength Criterion ◽  
Fatigue Properties ◽  
Interface Element ◽  
Friction Stir ◽  
Stress Ratios

Abstract Among the recent research Friction-Stir-Welding (FSW) has been adopted worldwide as one of the dominant processes for welding lightweight aerospace Aluminum alloys. Al-2195 which is one of the new generation Aluminum alloys has been used in the external tank of the space shuttles. Aerospace fabricators are continuously pursuing FSW-technologies in its efforts to advance fabrication of the external tanks of the space shuttles. The future launch vehicles with reusable mandates require the structures to have excellent fatigue properties and improved fatigue lives. The butt-welded specimens of Al-2195 and Al-2219 are fatigue tested according to ASTM-E647. The effects of stress ratios, use of corrosion preventive compound (CPC), and the applications of periodic overloading on fatigue lives are investigated in this study. Scanning-electron-microscopy (SEM) is used to examine the criticality of the failure surfaces and the different modes of crack propagation that could have been initiated into the materials. It is found that fatigue life increases with the increase in stress ratio, and results show an increase in fatigue life ranging over 30% with the use of CPC, and the fatigue life increases even further with periodic overloading; whereas crack-closure phenomenon predominates the fatigue fracture. Fracture mechanics analysis and crack similitude was modified for fatigue cracks by Paris. Numerical studies using FEA has produced a model for fatigue life prediction scheme for these structures, where a novel strategy of the interface element technique with critical bonding strength criterion for formation of new fracture surfaces has been used to model fatigue crack propagation lives. The linear elastic fracture mechanics stress intensity factor is calculated using FEA and the fatigue life predictions made using this method are within 10–20% of the experimental fatigue life data obtained. This method overcomes the limitation of the traditional node-release scheme and closely matches the physics of the crack propagation.

scholarly journals Direct analysis method for probabilistic fracture mechanics

1996 ◽  
Vol 160 (3) ◽  
pp. 347-362 ◽  
Author(s):  
Hiroshi Akiba ◽  
Shinobu Yoshimura ◽  
Genki Yagawa
Keyword(s):  
Fracture Mechanics ◽  
Direct Analysis ◽  
Analysis Method ◽  
Probabilistic Fracture Mechanics

scholarly journals Fracture Mechanics and Beam Theory Analyses of Semi-Elliptical Cracks Originating in the Base of Rail

2012 ◽  
Author(s):  
David Y. Jeong ◽  
Michael E. Carolan ◽  
Hailing Yu ◽  
Benjamin Perlman ◽  
Jeffrey E. Gordon
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Stress Intensity Factors ◽  
Beam Theory ◽  
The United States ◽  
Intensity Factors ◽  
Northeast Region ◽  
Aspect Ratios ◽  
Serious Injuries ◽  
Elliptical Cracks

In May 2011, a derailment of a passenger train occurred in a tunnel in the northeast region of the United States. Fortunately, no serious injuries or fatalities resulted from this derailment. The probable cause of the derailment was determined to be a broken rail from a defect originating in the base of the rail. This internal rail base defect is characterized as having a crescent, thumbnail, or semi-elliptical shape. In addition, the formation and growth of this defect may have been exacerbated by corrosion. This paper describes engineering calculations to estimate the growth rate of this type of rail base defect. These engineering calculations are based on applying the principles of fracture mechanics and beam theory. Fracture mechanics principles are applied to determine stress intensity factors for the semi-elliptical shaped defect with different aspect ratios. Stress intensity factors are then used to estimate the growth of the defect under the accumulation of tonnage from repeated wheel passages. For this purpose, the rail is assumed to behave as a beam in bending.

Fatigue Life Reliability Analysis of Submarine Cone-Cylinder Shell

2012 ◽  
Vol 479-481 ◽  
pp. 2001-2004
Author(s):  
Zhi Yong Zhang ◽  
Tian Shu Song ◽  
Yang He
Keyword(s):  
Monte Carlo ◽  
Fatigue Life ◽  
Monte Carlo Method ◽  
Fracture Mechanics ◽  
Reliability Analysis ◽  
The Other ◽  
New Method ◽  
Probabilistic Fracture Mechanics ◽  
Two Factors

A new method is presented in the paper. The fatigue life reliability of submarine cone-cylinder shell is investigated, based on the combination between the methods of conventional Monte Carlo and classical probabilistic fracture mechanics. Firstly, Monte Carlo method is employed to obtain the reliability of given initial fatigue life. Secondly, the two induced factors M1 and M2 in the paper are estimated according to the initial fatigue life and the reliability. Thirdly, based on the two factors, the other fatigue life reliability is obtained by using classical probabilistic fracture mechanics method. Finally, numerical cases show that the proposed method is more efficient without accuracy loss for fatigue life reliability compared with Monte Carlo method. This method can also be applied to predict the fatigue life reliability of analogue structures.

scholarly journals FATIGUE LIFE ANALYSIS OF RAIL-WELDS USING LINEAR ELASTIC FRACTURE MECHANICS

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mequanent M. Alamnie ◽  
Yalelet Endalemaw
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Fatigue Cracks ◽  
High Stress ◽  
Fatigue Cracking ◽  
Linear Elastic Fracture Mechanics ◽  
Frequency Interval ◽  
Element Analysis ◽  
Linear Elastic ◽  
Elastic Fracture

The initiation and growth of fatigue cracking is mainly due to high stress concentration, heterogeneity and poor quality of weld. The detection and rectification of such weld defects are major concerns of rail network managers to reduce potential risk of rail breaks and derailments. To estimate the fatigue life of welded joints and to analyze the progress of fatigue cracks, a fracture mechanics-based analysis and fatigue models were developed using Finite Element Analysis. The initial flaw is obtained from a sample weld using ultrasonic flaw detecting machine test. Linear Elastic Fracture Mechanics (LEFM) approach based on the Paris law was applied to determine critical crack size and the number of cycles to failure using FRANC3D software. The inspection interval of rail welds before fracture (failure) was suggested based on reliability and life cycle analysis that correspond with minimum overall cost and frequency interval. It is recommended that fracture-based models in combination with reliability analyses can be a sustainable infrastructure decision-making algorithm.

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