A Parametric Study of Fatigue Crack Growth Behavior in Adhesively Bonded Metallic Structures

1978 ◽  
Vol 100 (1) ◽  
pp. 46-51 ◽  
Author(s):  
M. M. Ratwani
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stress Intensity Factors ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Intensity Factors ◽  
Adhesively Bonded

Problems of adherend cracks inadhesively bonded structures are considered in this paper. Two different methods of analysis, namely the finite element method and the integral equation approach, are used to obtain the stress intensity factors, which are compared with those obtained experimentally. The results of fatigue crack growth tests on two-ply, adhesively bonded panels with a width of 300 mm and 150 mm, a crack at a hole, and a cracked plate with a bonded stiffener are discussed. Fatigue crack growth behavior predictions based on the analytical stress intensity factors are correlated with those obtained from experiments for a variety of test geometries. The influence of adhesive type, adhesive thickness, and stiffener thickness on crack growth behavior are discussed for the case of a cracked plate with a bonded stiffener.

Experimental Technique for Elevated Temperature Mode I Fatigue Crack Growth Testing of Ni-Base Metal Foils

2006 ◽  
Vol 129 (4) ◽  
pp. 594-602 ◽  
Author(s):  
L. Liu ◽  
J. W. Holmes
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Constant Amplitude ◽  
Stress Intensity Range ◽  
Metallic Foils

Details are provided for an experimental approach to study the tensile fatigue crack growth behavior of very thin metallic foils. The technique utilizes a center-notched specimen and a hemispherical bearing alignment system to minimize bending strains. To illustrate the technique, the constant amplitude fatigue crack growth behavior of a Ni-base superalloy foil was studied at temperatures from 20°C to 760°C. The constant amplitude fatigue tests were performed at a frequency of 2Hz and stress ratio of 0.2. The crack growth rate versus stress intensity range data followed a Paris relation with a stress intensity range exponent m between 5 and 6; this exponent is significantly higher than what is commonly observed for thicker materials and indicates very rapid fatigue crack propagation rates can occur in thin metallic foils.

scholarly journals Effect of Heat-Treatment Upon the Fatigue-Crack Growth Behavior of Alloy 718 Weldments—Part II: Microscopic Behavior

1985 ◽  
Vol 107 (1) ◽  
pp. 41-47 ◽  
Author(s):  
W. J. Mills ◽  
L. A. James
Keyword(s):  
Heat Treatment ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Alloy 718 ◽  
Fatigue Crack Growth Behavior ◽  
Heat Treated

The microstructural features that influenced the fatigue-crack growth behavior of as-welded, conventional heat-treated, and modified heat-treated Alloy 718 GTA weldments were studied. Electron fractographic examination revealed that operative fatigue mechanisms were dependent on microstructure, temperature and stress intensity factor. All specimens exhibited three basic fracture surface morphologies at temperatures up to 538°C: crystallographic faceting at low stress intensity range (ΔK) levels, striation formation at intermediate values, and dimples coupled with striations in the highest ΔK regime. At 649°C, extensive amounts of intergranular cracking were observed. Laves and δ particles in the conventional heat-treated material nucleated microvoids ahead of the advancing crack front and caused an overall acceleration in crack growth rates at intermediate and high ΔK levels. The modified heat treatment removed many of these particles from the weld zone, thereby improving its fatigue resistance. The dramatically improved fatigue properties exhibited by the as-welded material were attributed to compressive residual stresses introduced by the welding process.

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