Stress Intensity Factors for a Radially Multicracked Partially Autofrettaged Pressurized Thick-Walled Cylinder

1988 ◽  
Vol 110 (2) ◽  
pp. 147-154 ◽  
Author(s):  
M. Perl ◽  
R. Arone´
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Favorable Effect ◽  
The Finite Element Method ◽  
Intensity Factors ◽  
Slowing Down ◽  
Wide Range ◽  
Radial Cracks ◽  
Compressive Residual Stresses ◽  
Walled Cylinder

Mode I stress intensity factors for crack arrays of up to 1024 equal radial cracks originating at the inner surface of a partially autofrettaged, pressurized thick-walled cylinder are evaluated. Both stress intensity factors i.e., KIp due to the pressurization, and the negative KIA due to the compressive residual stresses, are calculated for numerous crack arrays (n = 2–1024), a wide range of nondimensional crack lengths (1/a = 0.005–0.625), and various levels of autofrettage (ε = 30, 60, 100 percent) via the finite element method. The obtained results emphasize the notable significance of the number of cracks in the array, as well as the importance of the level of autofrettage, on the stress intensity factor prevailing at the tip of these cracks. The sensitivity of the favorable effect of the overstrain in slowing down fatigue crack growth to any decrease in the level of autofreggate is also discussed.

3-D Stress Intensity Factors for Internal Cracks in an Overstrained Cylindrical Pressure Vessel—Part II: The Combined Effect of Pressure and Autofrettage

2000 ◽  
Vol 123 (1) ◽  
pp. 135-138 ◽  
Author(s):  
M. Perl ◽  
A. Nachum
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Pressure Vessel ◽  
Three Dimensional ◽  
Favorable Effect ◽  
Intensity Factors ◽  
Gun Barrel ◽  
Wide Range ◽  
The Impact ◽  
Walled Cylinder

K IA and KIP stress intensity factors (SIF) for three-dimensional semi-elliptical, surface, radial cracks prevailing in a pressurized or autofrettaged thick-walled cylinder were evaluated and discussed in Part I of this paper and in Perl et al. 1996, “Three-Dimensional Interaction Effects in an Internally Multicracked Pressurized Thick-Walled Cylinder—Part I: Radial Surface Cracks,” AMSE J. Pressure Vessel Technol. 118, pp. 357–363), respectively. These SIFs were calculated for a wide range of configurations: for cracks pertaining to large arrays of up to 180 cracks, with ellipticities of a/c=0.2, 0.5, 1, 1.5, depth ratios of a/t=0.05−0.6, and for various levels of autofrettage. In Part II of this paper, the effect of the combined SIF KIN=KIP+KIA is considered, which enables the prediction of fracture endurance, crack growth rate, and the total fatigue life for a modern gun barrel. The results reconfirm the impact autofrettage has on delaying crack initiation and propagation. This favorable effect is found to be governed by ψ=σ0/p—the ratio of the vessel’s material yield stress to its internal pressure. The higher ψ is, the more effective autofrettage becomes. While KIA and KIP reach their maximum absolute values, usually, for an array of n=2 cracks, the largest combined SIF-KIN occurs for arrays of 2–16 cracks. Finally, the similarity in the behavior of KIA and KIP along the crack front is studied as well as its relation to the respective stress fields.

The Effect of Crack Length Unevenness on Stress Intensity Factors Due to Autofrettage in Thick-Walled Cylinders

1997 ◽  
Vol 119 (3) ◽  
pp. 274-278 ◽  
Author(s):  
M. Perl ◽  
D. Alperowitz
Keyword(s):  
Stress Intensity ◽  
Crack Length ◽  
Stress Intensity Factors ◽  
Relative Length ◽  
Intensity Factors ◽  
Residual Stress Field ◽  
Interaction Range ◽  
Wide Range ◽  
Level Model ◽  
Radial Cracks

The effect of crack length unevenness on the mode I stress intensity factors (SIFs) for large uniform arrays of radial cracks of unequal depth in fully or partially autofrettaged thick-walled cylinders is investigated. The analysis is based on the previously proposed “two-crack-length level model.” Values for KIA—the SIF due to the compressive residual stress field—for various crack arrays bearing n1 = n2 = 2−512 cracks, a wide range of nondimensional crack lengths l1/a=0.01−0.1, and numerous levels of autofrettage ε = 30−100 percent are evaluated by the finite element method for a cylinder of radii ratio of b/a = 2. The interaction range for different combinations of crack arrays and crack length is then determined. The obtained results show that the unevenness in the SIFs depends on all three parameters, i.e., the number of cracks in the array, the cracks’ lengths, and the level of autofrettage, while the interaction range between adjacent cracks is determined only by the relative length of the cracks and the density of the array.

Weight Functions for an External Longitudinal Semi-Elliptical Surface Crack in a Thick-Walled Cylinder

1997 ◽  
Vol 119 (1) ◽  
pp. 74-82 ◽  
Author(s):  
A. Kiciak ◽  
G. Glinka ◽  
D. J. Burns
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Complex Stress ◽  
Weight Functions ◽  
Stress Distributions ◽  
Intensity Factors ◽  
Reference Stress ◽  
Pressurized Cylinder ◽  
Walled Cylinder

Mode I weight functions were derived for the deepest and surface points of an external radial-longitudinal semi-elliptical surface crack in a thick-walled cylinder with the ratio of the internal radius to wall thickness, Ri/t = 1.0. Coefficients of a general weight function were found using the method of two reference stress intensity factors for two independent stress distributions, and from properties of weight functions. Stress intensity factors calculated using the weight functions were compared to the finite element data for several different stress distributions and to the boundary element method results for the Lame´ hoop stress in an internally pressurized cylinder. A comparison to the ASME Pressure Vessel Code method for deriving stress intensity factors was also made. The derived weight functions enable simple calculations of stress intensity factors for complex stress distributions.

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