Evaluation of Fatigue Crack Propagation Behavior Crossing Interface in Cladded Plates

2017 ◽  
Author(s):  
Masaki Nagai ◽  
Kiminori Murai ◽  
Toshio Nagashima ◽  
Naoki Miura
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Base Metal ◽  
Fatigue Crack Propagation ◽  
Dissimilar Materials ◽  
Low Alloy Steel ◽  
Fatigue Crack Propagation Behavior ◽  
Propagation Behavior ◽  
Crack Propagation Behavior ◽  
Reactor Pressure

In nuclear power plants, inner surface of reactor pressure vessel, which is made of low-alloy steel, is cladded by austenitic stainless steel to improve corrosion resistance of vessel. In an evaluation of fatigue crack propagation behavior at J-welding portions of bottom mounted instrumentation in reactor pressure vessel, crack propagation crossing dissimilar materials interface between base metal of low-alloy steel and stainless steel cladding is assumed. Fatigue crack growth rate of the cladding is predicted to be captured by that of the base metal because thickness of the cladding is very thin compared that of the base metal. In this study, fatigue crack propagation analyses of cladded plates under cyclic loading were performed using XFEM, which can model crack independently of finite elements, as a preliminary study for crack propagation analyses considering dissimilar materials interface.

Fatigue Crack Propagation Behavior Near Fusion Line between SA508 Steel and Ni-Based Buttering Metal

2007 ◽  
Vol 353-358 ◽  
pp. 154-157 ◽  
Author(s):  
Ho Jin Lee ◽  
Maan Won Kim ◽  
Bong Sang Lee
Keyword(s):  
Fatigue Crack ◽  
Yield Strength ◽  
Crack Propagation ◽  
Base Metal ◽  
Fatigue Crack Propagation ◽  
Filler Metal ◽  
Fusion Line ◽  
Fatigue Crack Propagation Behavior ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

Fatigue crack propagation behavior near the fusion line between SA508 ferritic steel and Ni-based buttering metal was studied to assess the integrity of dissimilar metal welded zone in reactor pressure vessels. Ni-based filler metal has been used as a buttering or filler metal to weld the ferritic steel to the Ni-alloy or austenitic stainless steel. The J integral value and stress field at the crack tip in a simulated small-CT welded specimen model was calculated by using the commercial FE calculation code to anticipate the effect of the yield strength differences between dissimilar metals. If the Ni-based buttering metal has lower yield strength, which means the decrease of material constraint by the weld metal, the J integral value of the crack tip in the base metal near the fusion line was calculated higher than that of the base metal. The fatigue crack propagation behavior near the fusion line was measured by using the small-CT welded specimens of 5 mm thickness. The relationships between da/dN and )K were measured in the base metal and the HAZ near fusion line. The yield strength of the weld metal including microstructure at the joint can be considered more effective than the material constraint on explaining the behavior of fatigue crack propagation near the fusion line.

Effect of Biaxial Static Loads on Fatigue Crack Propagation Behavior under Cyclic Tensile and Torsional Loading

2006 ◽  
Vol 321-323 ◽  
pp. 720-723
Author(s):  
Yong Hak Huh ◽  
Philip Park ◽  
Dong Jin Kim ◽  
Jun Hyub Park
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Growth Rates ◽  
Biaxial Loading ◽  
Torsional Loading ◽  
Static Loads ◽  
Fatigue Crack Propagation Behavior ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

Fatigue crack propagation behavior under cyclic tensile or torsional loading with biaxial static loads has been investigated. Two different biaxial loading systems, i.e. cyclic tensile loading with static torsional load and cyclic torsional loading with static tensile load, were employed to thin-walled tubular specimens. The crack propagation was measured by two crack gages mounted near the notch and crack opening level was measured by unloading compliance method. The directions of the fatigue crack propagated under respective biaxial loading conditions were examined and the growth rates were evaluated by using several cyclic parameters, including equivalent stress intensity factor range, Keff, crack tip opening displacement range, CTD, minimum strain energy density factor range, Smin. Furthermore, the growth rates were evaluated by effective cyclic parameters considering crack closure. It was found that the biaxial static stress superimposed on the cyclic tensile or torsional loading tests has no influence on the propagation directions of the cracks. Furthermore, it was shown that the fatigue crack growth rates under biaixial faigue loading were well expressed by using the cyclic fatigue parameters, Keq,eff, CTDeff, Smin,eff considering crack closure effect.

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