Development of Structural Steel With Superior Resistance Against Fatigue Crack Growth

2003 ◽  
Author(s):  
Noboru Konda ◽  
Kazushige Arimochi ◽  
Kazuhiro Hirota ◽  
Eiichi Watanabe ◽  
Masuo Tada ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Structural Steel ◽  
Crack Growth ◽  
Sea Water ◽  
Fatigue Crack Initiation ◽  
Life Extension ◽  
Fatigue Properties ◽  
Fatigue Crack Growth Resistance ◽  
Crack Problems

The fatigue crack problems that broke out at the end of the twentieth century were fatigue crack properties in hull structures. This motivated research on a lot of technologies against fatigue fracture. It was clarified that the detection of fatigue crack initiation in complex welded structures like hulls is quite difficult, and that the crack length at recognition is mostly long compared to mechanical parts. From these research results, not only stress reduction at critical areas by improvement in design but also newly developed materials with excellent resistance to fatigue crack growth has been desirable for structural integrity. The newly developed structural steel, in which fatigue crack growth resistance is controlled by microstructures, will be introduced in this report. Various fatigue properties of the base steel plates in air and in synthetic sea water are compared. And the fatigue life extension effects by FCA is observed in fatigue tests of welded joints and welded structural models.

Development of Structural Steel With Superior Resistance Against Fatigue Crack Growth: Part II

2004 ◽  
Author(s):  
Noboru Konda ◽  
Kazushige Arimochi ◽  
Kazuhiro Hirota ◽  
Eiichi Watanabe ◽  
Masuo Tada ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Structural Steel ◽  
Crack Growth ◽  
Sea Water ◽  
Fatigue Crack Initiation ◽  
Life Extension ◽  
Fatigue Properties ◽  
Fatigue Crack Growth Resistance ◽  
Crack Problems

The fatigue crack problems that broke out at the end of the twentieth century were fatigue crack properties in hull structures. This motivated research on a lot of technologies against fatigue fracture. It was clarified that the detection of fatigue crack initiation in complex welded structures like hulls is quite difficult, and that the crack length at recognition is mostly long compared to mechanical parts. From these research results, not only stress reduction at critical areas by improvement in design but also newly developed materials with excellent resistance to fatigue crack growth has been desirable for structural integrity. The newly developed structural steel, in which fatigue crack growth resistance is controlled by microstructures, will be introduced in this report. Various fatigue properties of the base steel plates in air and in synthetic sea water are compared. And the fatigue life extension effects by FCA is observed in fatigue tests of welded joints and welded structural models.

scholarly journals Mechanical and Fatigue Properties of Diamond Reinforced Cu and Al Metal Matrix Composites Prepared by Cold Spray

2021 ◽  
Author(s):  
O. Kovarik ◽  
J. Cizek ◽  
S. Yin ◽  
R. Lupoi ◽  
M. Janovska ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Cold Spray ◽  
Pure Metal ◽  
Crack Growth Resistance ◽  
Fatigue Properties ◽  
Matrix Composites ◽  
Fatigue Crack Growth Resistance

Abstract Diamond-reinforced composites prepared by cold spray are emerging materials simultaneously featuring outstanding thermal conductivity and wear resistance. Their mechanical and fatigue properties relevant to perspective engineering applications were investigated using miniature bending specimens. Cold sprayed specimens with two different mass concentrations of diamond 20% and 50% in two metallic matrices (Al – lighter than diamond; Cu – heavier than diamond) were compared with the respective pure metal deposits. These pure metal coatings showed rather limited ductility. The diamond addition slightly improved ductility and fracture toughness of the Cu-based composites; having a small effect also on the fatigue crack growth resistance. In case of the Al composites; the ductility as well as fatigue crack growth resistance and fracture toughness have improved significantly. The static and fatigue failure mechanisms were fractographically analyzed and related to the microstructure of the coatings; observing that particle decohesion is the primary failure mechanism for both static and fatigue fracture.

Effects of Prestrain on Fracture Toughness and Fatigue-Crack Growth of Line Pipe Steels

2001 ◽  
Vol 123 (3) ◽  
pp. 355-361 ◽  
Author(s):  
Naoto Hagiwara ◽  
Tomoki Masuda ◽  
Noritake Oguchi
Keyword(s):  
Fatigue Crack ◽  
Transition Temperature ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Fatigue Properties ◽  
Uniaxial Tensile ◽  
Pipe Steels ◽  
Line Pipe ◽  
Brittle Transition

Crack-tip-opening displacement (CTOD) and fatigue-crack growth tests were conducted for several line pipe steels with uniaxial tensile or compressive prestrain, εpr. Critical CTOD decreased with increasing |εpr|. The reduction of critical CTOD due to prestrain was dependent on the ductile-brittle transition temperature of the steels without prestrain. A few percent of εpr induced the ductile-brittle transition for the steels with a higher transition temperature. The compressive εpr had larger effects on both reduction of critical CTOD and strain induced ductile-brittle transition than the tensile εpr. Only the high compressive εpr accelerated both fatigue crack initiation and growth, and no obvious effect of the tensile εpr on the fatigue properties was observed.

scholarly journals Near-threshold fatigue crack growth in bulk metallic glass composites

2009 ◽  
Vol 24 (12) ◽  
pp. 3611-3619 ◽  
Author(s):  
Kombaiah Boopathy ◽  
Douglas C. Hofmann ◽  
William L. Johnson ◽  
Upadrasta Ramamurty
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Volume Fraction ◽  
Fatigue Crack Initiation ◽  
Stress Intensity Factor Range ◽  
Crack Growth Behavior ◽  
Major Drawback ◽  
Fatigue Crack Growth Resistance ◽  
Near Threshold

A major drawback in using bulk metallic glasses (BMGs) as structural materials is their extremely poor fatigue performance. One way to alleviate this problem is through the composite route, in which second phases are introduced into the glass to arrest crack growth. In this paper, the fatigue crack growth behavior of in situ reinforced BMGs with crystalline dendrites, which are tailored to impart significant ductility and toughness to the BMG, was investigated. Three composites, all with equal volume fraction of dendrite phases, were examined to assess the influence of chemical composition on the near-threshold fatigue crack growth characteristics. While the ductility is enhanced at the cost of yield strength vis-à-vis that of the fully amorphous BMG, the threshold stress intensity factor range for fatigue crack initiation in composites was found to be enhanced by more than 100%. Crack blunting and trapping by the dendritic phases and constraining of the shear bands within the interdendritic regions are the micromechanisms responsible for this enhanced fatigue crack growth resistance.

scholarly journals Effect of Bond-Line Thickness on Fatigue Crack Growth of Structural Acrylic Adhesive Joints

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1723
Author(s):  
Yu Sekiguchi ◽  
Chiaki Sato
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Adhesive Bond ◽  
Bond Line ◽  
Loading Conditions ◽  
Fatigue Crack Growth Resistance ◽  
Line Thickness ◽  
Bond Line Thickness

With an increasing demand for adhesives, the durability of joints has become highly important. The fatigue resistance of adhesives has been investigated mainly for epoxies, but in recent years many other resins have been adopted for structural adhesives. Therefore, understanding the fatigue characteristics of these resins is also important. In this study, the cyclic fatigue behavior of a two-part acrylic-based adhesive used for structural bonding was investigated using a fracture-mechanics approach. Fatigue tests for mode I loading were conducted under displacement control using double cantilever beam specimens with varying bond-line thicknesses. When the fatigue crack growth rate per cycle, da/dN, reached 10−5 mm/cycle, the fatigue toughness reduced to 1/10 of the critical fracture energy. In addition, significant changes in the characteristics of fatigue crack growth were observed varying the bond-line thickness and loading conditions. However, the predominance of the adhesive thickness on the fatigue crack growth resistance was confirmed regardless of the initial loading conditions. The thicker the adhesive bond line, the greater the fatigue toughness.

Modeling of Fatigue Crack Propagation

2004 ◽  
Vol 126 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Yanyao Jiang ◽  
Miaolin Feng
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Fatigue Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Cyclic Plasticity ◽  
R Ratio

Fatigue crack propagation was modeled by using the cyclic plasticity material properties and fatigue constants for crack initiation. The cyclic elastic-plastic stress-strain field near the crack tip was analyzed using the finite element method with the implementation of a robust cyclic plasticity theory. An incremental multiaxial fatigue criterion was employed to determine the fatigue damage. A straightforward method was developed to determine the fatigue crack growth rate. Crack propagation behavior of a material was obtained without any additional assumptions or fitting. Benchmark Mode I fatigue crack growth experiments were conducted using 1070 steel at room temperature. The approach developed was able to quantitatively capture all the important fatigue crack propagation behaviors including the overload and the R-ratio effects on crack propagation and threshold. The models provide a new perspective for the R-ratio effects. The results support the notion that the fatigue crack initiation and propagation behaviors are governed by the same fatigue damage mechanisms. Crack growth can be treated as a process of continuous crack nucleation.

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