scholarly journals Life extension of self-healing polymers with rapidly growing fatigue cracks

2006 ◽  
Vol 4 (13) ◽  
pp. 395-403 ◽  
Author(s):  
A.S Jones ◽  
J.D Rule ◽  
J.S Moore ◽  
N.R Sottos ◽  
S.R White
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Relative Magnitude ◽  
Life Extension ◽  
Self Healing ◽  
Grubbs Catalyst ◽  
Fourfold Increase ◽  
Endurance Limits ◽  
Kinetics Of

Self-healing polymers, based on microencapsulated dicyclopentadiene and Grubbs' catalyst embedded in the polymer matrix, are capable of responding to propagating fatigue cracks by autonomic processes that lead to higher endurance limits and life extension, or even the complete arrest of the crack growth. The amount of fatigue-life extension depends on the relative magnitude of the mechanical kinetics of crack propagation and the chemical kinetics of healing. As the healing kinetics are accelerated, greater fatigue life extension is achieved. The use of wax-protected, recrystallized Grubbs' catalyst leads to a fourfold increase in the rate of polymerization of bulk dicyclopentadiene and extends the fatigue life of a polymer specimen over 30 times longer than a comparable non-healing specimen. The fatigue life of polymers under extremely fast fatigue crack growth can be extended through the incorporation of periodic rest periods, effectively training the self-healing polymeric material to achieve higher endurance limits.

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.

Fatigue crack growth behavior of rib-to-deck double-sided welded joints of orthotropic steel decks

2020 ◽  
pp. 136943322096175
Author(s):  
Yang Liu ◽  
Fanghuai Chen ◽  
Da Wang ◽  
Naiwei Lu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Growth ◽  
Welded Joints ◽  
Mixed Mode ◽  
Fatigue Cracks ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Orthotropic Steel Decks

Innovative double-sided welding is expected to improve the fatigue resistance of rib-to-deck welded joints of orthotropic steel decks (OSDs). Welding crack-like defects are the crucial issue affecting the fatigue performance of rib-to-deck double-sided welded joints. This study presents a numerical simulation of three-dimensional (3D) mixed mode fatigue crack growth behavior of rib-to-deck double-sided welded joints of OSDs. Maximum tensile stress theory and equivalent stress intensity factor (SIF) were used to simulate mixed mode fatigue cracks growth. The Paris law model was employed to predict the fatigue life. Fatigue cracks of rib-to-deck double-sided welded joints were characterized by the presence of mixed mode cracks of modes I (open), mode II (shear), and mode III (tear), which was dominated by mode I. The equivalent SIF was found to be complex at the growth stage with the maximum value at the two ends of the crack front and the minimum value at the midpoint of the crack front. The crack shape became flatter in the later phase of the crack growth. The fatigue crack surface underwent deflections during crack growth, making the final crack shape exhibiting the characteristic of a spatial curved surface. The initial crack geometry showed a significant impact on the fatigue life.

Fatigue crack growth at stress concentrators under spectrum loading

2005 ◽  
Vol 40 (2) ◽  
pp. 117-127
Author(s):  
R. V Prakash
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Growth ◽  
Surface Defects ◽  
Fatigue Cracks ◽  
Mapping Technique ◽  
Critical Dimensions ◽  
Small Cracks ◽  
Stress Raisers ◽  
Kinetics Of

Fatigue cracks initiate at stress raisers such as notches, discontinuities, and surface defects. Many of the field failures that indicate the presence of a fatigue crack at failure can be traced to crack initiation from one or more crack initiation sites and merger of cracks over a period of service. Substantial service life is spent in the growth of small cracks from an initial size of few micrometres before they coalesce and grow to critical dimensions that cause fracture. This paper summarizes research that was carried out in order to understand the kinetics of crack growth of small cracks at notches under simulated FALSTAFF service loading. This paper also presents a method used to understand crack growth kinetics in a pin-loaded lug joint through a crack-front-mapping technique.

An integrated approach to local ultrasonic monitoring of fastener hole fatigue cracks

2009 ◽  
Vol 113 (1150) ◽  
pp. 775-788 ◽  
Author(s):  
A. C. Cobb ◽  
J. E. Michaels ◽  
T. E. Michaels
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Integrated Approach ◽  
Crack Size ◽  
Recent Measurement ◽  
General Strategy ◽  
Ultrasonic Monitoring ◽  
Fastener Hole

Abstract Ultrasonic nondestructive evaluation methods are routinely used to detect and size fatigue cracks near fastener holes in aircraft structures as a part of scheduled maintenance. In contrast, statistical crack propagation models provide an estimate of the expected fatigue life assuming a known crack size and future fatigue loadings. Here an integrated approach for in situ diagnosis and prognosis of fastener hole fatigue cracks is proposed and implemented that incorporates both ultrasonic monitoring and crack growth laws. The sensing method is an ultrasonic angle beam technique, and cracks are automatically detected from the ultrasonic response. An extended Kalman filter is applied to combine ultrasonically estimated crack sizes with a crack growth law, effectively using the time history of the ultrasonic results rather than only the most recent measurement. A natural extension of this method is fatigue life prognosis. Results from fatigue tests on 7075-T651 aluminium coupons show improved crack size estimates as compared to those obtained from ultrasonic measurements alone, and also demonstrate the capability of predicting the remaining life. This approach for fatigue crack detection, sizing and prognosis is an example of a general strategy for in situ monitoring of structural damage whereby improved results are achieved from the integration of noisy measurements with imperfect crack growth models.

Methodical approach for studying kinetics of short and long fatigue cracks growth for irradiated reactor materials. Part 1. Statement of problem. The effect of the initial notch acuity on the fatigue crack rate on small-sized specimens

2019 ◽  
pp. 191-204 ◽  
Author(s):  
V. I. Smirnov ◽  
A. J. Minkin ◽  
B. Z. Margolin ◽  
V. I. Kokhonov
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Fatigue Cracks ◽  
Stress Concentration Zone ◽  
Concentration Zone ◽  
Methodical Approach ◽  
Reactor Materials ◽  
Kinetics Of

The paper considers methodical issues in the experimental research of fatigue crack growth kinetics when testing irradiated small-sized specimens. The effect of the initial notch acuity is studied on the long crack growth rate. The stress concentration zone sizes are estimated for notches of various types. A brif literature review of the main problems in the study of the growth kinetics of short fatigue cracks has been performed. The tasks of further research are formulated. 

Fatigue response of a solid state self-healing resin

2020 ◽  
pp. 096739112095509
Author(s):  
Mohd Suzeren Md Jamil ◽  
Noor Nabilah Muhamad ◽  
Wan Naqiuddin Wan Zulrushdi
Keyword(s):  
Fatigue Life ◽  
Solid State ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Healing Process ◽  
Fatigue Tests ◽  
Self Healing ◽  
Healing System ◽  
Healing Agent ◽  
Modified Epoxy

The present work verified the capability of a solid state self-healing system for retarding or arresting fatigue cracks in epoxy materials subjected to cyclic loading at room temperature. A solid state self-healing material is demonstrated using a thermosetting epoxy polymer which was modified by incorporating a linear thermoplastic polydiglycidyl ether bisphenol-A (PDGEBA) as a healing agent. The stress-controlled constant amplitude (CA) tensile fatigue behavior at stress ratio, R = 0.1 and frequency 10 Hz for both the neat and the modified epoxy was investigated. Fatigue life and residual strength degradation were continuously monitored during the fatigue tests. The modified epoxy fatigue life was shown to be increased by ∼50% after healing periods. The fatigue-healing process was proven through the surface and cross-section resin morphology analyses using microscopy optic and scanning electron microscope (SEM). On the whole, the solid state self-healing system has proven to be very effective in obstructing fatigue crack propagation, effectively improved the self-healing polymeric material to achieve higher endurance limits.

Cure kinetics of poly (5-ethylidene-2-norbornene) with 2nd generation Hoveyda-Grubbs’ catalyst for self-healing applications

Polymer ◽  
2018 ◽  
Vol 153 ◽  
pp. 1-8 ◽  
Author(s):  
Hasna Hena Zamal ◽  
David Barba ◽  
Brahim Aissa ◽  
Emile Haddad ◽  
Federico Rosei
Keyword(s):  
Cure Kinetics ◽  
Self Healing ◽  
Grubbs Catalyst ◽  
2Nd Generation ◽  
Kinetics Of

Fatigue fracture in polyethylene

1971 ◽  
Vol 325 (1560) ◽  
pp. 57-79 ◽  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Elastic Solid ◽  
Growth Characteristics ◽  
Low Density ◽  
Ductile Crack ◽  
Fatigue Data

The application of non-classical fracture mechanics to the growth of dynamic fatigue cracks in a visco-elastic solid is discussed. The ideas developed are used to characterize the results of fatigue crack growth measurements on a range of low -density polyethylenes. The results can be expressed in the form d c d N = BF n where d c d N is the growth of the crack each cycle, F is a fracture mechanics parameter and B, n are constants. Most of the materials studied reveal two distinct regions (with differing values of the constants) linked by a transition zone, and corresponding to brittle and ductile crack propagation respectively. The fatigue life of virgin specimens can be predicted from the crack growth characteristics assuming the existence of intrinsic flaws which (when the predictions are matched to actual fatigue data) are found to correspond in size to the polyethylene spherulites.

Fatigue Life Extension Procedure for Subsea Wells Based on Pressure Testing

2021 ◽  
Author(s):  
Arne Fjeldstad ◽  
Torfinn Hørte ◽  
Gudfinnur Sigurdsson ◽  
Anders Wormsen ◽  
Espen Berg ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Hot Spots ◽  
Fatigue Cracks ◽  
Load Test ◽  
Life Extension ◽  
Case Examples ◽  
Pressure Test ◽  
Number Of Cycles

Abstract This article presents a fatigue life extension procedure for subsea wells based on fracture mechanics. It makes use of the outcome of an internal pressure test to determine a safe period for drilling and completion. The pressure test is used as a load test and can only reveal deep fatigue cracks. The safe operational period is estimated as the number of cycles required to grow a fatigue crack from the largest fatigue crack that remains stable after the pressure test until it becomes unstable due to an accidental load. The procedure takes into account the probability of the presence of the fatigue crack that can be revealed by the pressure test. This is used to determine design fatigue factors for the procedure. The design fatigue factor is formulated in terms of the (S-N based) accumulated fatigue damage for historical operations. The procedure is illustrated with two case examples (fatigue hot spots) for illustrating the procedure in more detail: wellhead extension girth weld and wellhead profile. Conditions for use are given at the end of the article.

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