A Study of Naturally Initiating Notch Root Fatigue Cracks Under Spectrum Loading

2009 ◽  
pp. 136-136-25 ◽  
Author(s):  
RV Prakash ◽  
R Sunder ◽  
EI Mitchenko
Keyword(s):  
Notch Root ◽  
Fatigue Cracks ◽  
Spectrum Loading

Mode II Fatigue Crack Behavior in Compact Tension Shear Specimen

2005 ◽  
Vol 297-300 ◽  
pp. 1592-1597 ◽  
Author(s):  
Sam Hong Song ◽  
Jeong Moo Lee
Keyword(s):  
Fatigue Crack ◽  
Crack Surface ◽  
Notch Root ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Load Condition ◽  
Compact Tension ◽  
Initial Crack ◽  
Shear Loading ◽  
Mode Ii

The need for research on fatigue behavior of mechanical element under mixed-mode loading has been increasing as the user environment today becomes more and more complicated. However there haven’t been enough investigations on behavior in shear loads comparing to those under tensile loading conditions. So, for this paper, we investigated the characteristics and properties of initiation and propagation behavior for fatigue crack observed for different shapes of the initial crack and magnitudes of load in the modified compact tension shear (CTS) specimen subjected to mode II load. In the low-load condition, the secondary fatigue crack was created in the notch root due to friction on the pre-crack surface grew to a main crack. In the high-load condition meanwhile, fatigue crack under shear loading propagated branching from the pre-crack tip. Influenced by the shear loading condition, fatigue crack propagation was retarded in the initial propagation region due to the decrease in crack driving force and friction on the crack surface. In both cases, however, fatigue cracks grew in tensile mode. The propagation direction of fatigue crack under mode II loading was approximately at a 70 degree angle from the initial crack, regardless of its shape and load magnitude.

Closure of part-through fatigue cracks at the notch root

1987 ◽  
Vol 9 (4) ◽  
pp. 217-222 ◽  
Author(s):  
K ANANDAN ◽  
R SUNDER
Keyword(s):  
Notch Root ◽  
Fatigue Cracks

Limits of Applicability of the Notch Failure Assessment Diagram

2018 ◽  
Author(s):  
Anthony J. Horn ◽  
Chris Aird
Keyword(s):  
Structural Integrity ◽  
Notch Root ◽  
Fatigue Cracks ◽  
Mechanical Damage ◽  
Root Radius ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Notch Root Radius ◽  
Failure Assessment ◽  
Sharp Crack

Structural integrity assessment codes such as R6 [1] and BS7910 [2] provide guidance on the assessment of flaws that are assumed to be infinitely sharp using the Failure Assessment Diagram (FAD). In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as those associated with lack of fusion, porosity or mechanical damage. Several Notch Failure Assessment Diagram (NFAD) methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. This paper uses mechanistic modelling to define the limits of applicability of the NFAD approach in terms of ρ/a, where ρ is the notch root radius and a is the notch depth. The work concludes that the NFAD can be used to assess notches with ρ/a values of up to unity.

scholarly journals Analysis on the Behavior of Nonpropagating Fatigue Cracks under Steep Stress Gradients

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Hao Wu ◽  
Qiuying Lu
Keyword(s):  
Material Properties ◽  
Notch Root ◽  
Fatigue Cracks ◽  
Stress Gradient ◽  
Local Stress ◽  
Characteristic Size ◽  
Short Crack ◽  
Stress Gradients ◽  
Applied Loading ◽  
Experimental Values

A mechanism for the formation of nonpropagating fatigue cracks ahead of a notch root is presented. The stress gradients near the elongated notch root along with the propagation of short crack and the resulting nonpropagating crack lengthsanpcare estimated. The local stress which is higher than the unnotched material fatigue limitS0initiates the crack from a notch root and local steep stress gradient as a very important element leads to the nonpropagating crack. The value ofanpcdepends on the material properties, and specimen geometry as well as applied loading. The characteristic size of the short cracka0which depends on the material properties associates with the fatigue stress concentration factorKf. The estimated values ofanpcare in fairly good agreement with the experimental values available.

scholarly journals Propagation Behavior of Long and Small Fatigue Cracks from Notch Root in Reactive-Sintered TiAl Intermetallic Compound.

2000 ◽  
Vol 49 (11) ◽  
pp. 1217-1223
Author(s):  
Hidehiko KIMURA ◽  
Yoshiaki AKINIWA ◽  
Keisuke TANAKA ◽  
Shuhei ADACHI ◽  
Haijun TENG
Keyword(s):  
Intermetallic Compound ◽  
Notch Root ◽  
Fatigue Cracks ◽  
Propagation Behavior ◽  
Tial Intermetallic Compound

scholarly journals Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Tomasz Ślęzak
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Welded Joints ◽  
Life Prediction ◽  
Notch Root ◽  
Fatigue Cracks ◽  
Strain Range ◽  
Carbon Steels ◽  
Fatigue Life Prediction ◽  
The Impact

Due to growing requirements connected with the utilization of advanced structures, nowadays the modern design processes are developed. One of the crucial issues considered in these processes is proper design of the joints against fatigue in order to fulfill a stated life of operation. In this study, the method of fatigue life prediction based on the criterion of permissible strain range in the notch root is presented. An engaged simplified model of fatigue life prediction was previously developed for mild and carbon steels. The evaluation made during the research has proven that this method can also be used for S960QL high-strength steel characterized by entirely different properties and structure. A considered theoretical model demonstrates satisfactory correlation with experimental data and safely describes the fatigue life of weldments. Furthermore, the predicted fatigue life of studied steel without welds shows great comparability with experimental data. The limit value of the strain range in the notch root was estimated. Below this value of strain, the fatigue life of welded joints is infinite, theoretically. Finally, the impact of the surface imperfections on the fatigue crack initiation was revealed. For paternal material, the origins of cracking were discovered at the places of nonmetallic scale particles. In welded joints, the fatigue cracks initiated at the whole length of the fusion line.

Effects of Interlayer Resin Bonding on Fatigue Crack Initiation/Propagation in Laminate Materials With a Surface Layer of Copper Film

2005 ◽  
Author(s):  
Akira Matsuba ◽  
Tashiyuki Torii ◽  
DongHui Ma
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Notch Root ◽  
Surface Film ◽  
Fatigue Cracks ◽  
Pure Copper ◽  
Fatigue Crack Initiation ◽  
Copper Film ◽  
Laminate Materials ◽  
Resin Bonding

As model specimens to examine the effects of interlayer resin bonding on fatigue properties in laminate materials with a surface film, pure copper films with a thickness of 100μm and 50μm were bonded with epoxy resin to steel base plates. The fatigue crack propagation from the notch root of the specimen was slower for the epoxy-bonded film than for the base specimen, because the epoxy bonding interlayer restricted crack propagation from the surface film to the inner base plate. On the epoxy-bonded film, however, many fatigue cracks initiated at multiple sites sufficiently away from the notch root, and propagated only on the surface copper film. In addition, the number of these multiple fatigue cracks, caused mostly at the site of the annealing twin boundaries, was larger on the surface copper film with a thickness of 100μm than 50μm.

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