Fatigue Life Analyses and Tests for Thick-Wall Cylinders Including Effects of Overstrain and Axial Grooves

1995 ◽  
Vol 117 (3) ◽  
pp. 222-226 ◽  
Author(s):  
J. H. Underwood ◽  
A. P. Parker
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Good Description ◽  
Crack Size ◽  
Initial Crack ◽  
Thick Wall ◽  
Inner Diameter ◽  
Life Analysis ◽  
Fatigue Life Analysis ◽  
Laboratory Life

A fracture mechanics-based fatigue life analysis was developed for overstrained, pressurized thick-wall cylinders with one or several semi-elliptical-shaped axial grooves at the inner diameter. The fatigue life for a crack initiating at the root of the groove was calculated for various cylinder, groove, and crack configurations and for different material yielding conditions. Comparisons were made with fatigue crack growth and laboratory life results from A723 thick-wall cylinders, in which cannon firing tests were first performed to produce axial erosion grooves, followed by cyclic hydraulic pressurization to failure in the laboratory. The life analysis, with an initial crack size based on the expected preexisting defects, gave a good description of the crack growth and fatigue life of the tests for cylinders with and without grooves. General fatigue life calculations summarized important material and configurational effects on the fatigue life design of overstrained cylinders, including effects of material yield strength, cylinder diameter ratio, stress concentration factor, and initial crack size.

Analysis of Crack Growth in a 3D Voronoi Structure: A Model for Fatigue in Low Density Trabecular Bone

2002 ◽  
Vol 124 (5) ◽  
pp. 512-520 ◽  
Author(s):  
A. M. Makiyama ◽  
S. Vajjhala ◽  
L. J. Gibson
Keyword(s):  
Fatigue Life ◽  
Relative Density ◽  
Trabecular Bone ◽  
Crack Growth ◽  
Three Dimensional ◽  
Crack Size ◽  
Initial Crack ◽  
Low Density ◽  
Cycle Fatigue ◽  
Crack Growth Model

Both creep and crack growth contribute to the reduction in modulus associated with fatigue loading in bone. Here we simulate crack growth and subsequent strut failure in fatigue in an open-cell, three-dimensional Voronoi structure which is similar to that of low density, osteoporotic bone. The model indicates that sequential failure of struts leads to a precipitous drop in modulus: the failure of 1% of the struts leads to about a 10% decrease in modulus. A parametric study is performed to assess the influence of normalized stress range, relative density, initial crack size, crack shape and cell geometry on the fatigue life. The fatigue life is most sensitive to the relative density and the initial crack length. The results lead to a quantitative expression for the fatigue life associated with crack growth. Data for the fatigue life of trabecular bone are compared with the crack growth model described in this paper, as well as with a previous model for creep of a three-dimensional Voronoi structure. In our models, creep dominates the fatigue behavior in low cycle fatigue while crack growth dominates in high cycle fatigue, consistent with previous observations on cortical bone. The large scatter in the trabecular bone fatigue data make it impossible to identify a transition between creep dominated fatigue and crack growth dominated fatigue. The parametric study of the crack growth model indicates that variations in relative density among specimens, initial crack size within trabeculae and crack shape could easily produce such variability in the test results.

Fatigue Life Analysis of Al 8090 Helicopter Fuselage Panels

2007 ◽  
Vol 348-349 ◽  
pp. 637-640
Author(s):  
Marco Giglio ◽  
Andrea Manes ◽  
Massimo Fossati
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
High Stress ◽  
Experimental Tests ◽  
Life Assessment ◽  
Fatigue Crack Growth Resistance ◽  
Anisotropic Mechanical Properties ◽  
High Crack ◽  
Life Analysis ◽  
Fatigue Life Analysis

Considering the aerospace structures, the advantages of Al-Li alloys in comparison with conventional aluminium alloys comprise relatively low densities, high elastic modulus, excellent fatigue and toughness properties, and superior fatigue crack growth resistance. Unfortunately, these alloys have some disadvantages due to highly anisotropic mechanical properties and due to a very high crack growth rate for microstructurally short cracks. This could mean relatively early cracking in high stress regions such as rivet holes in helicopter fuselage panels. Consequently a more accurate approach in fatigue life analysis is requested. Considering that the 8090 T81 aluminium alloy has been widely used in an helicopter structure, in particular in the bolted connection between the stringers and the modular joint frame in the rear of the fuselage, it is extremely important to found a reliable procedure for the fatigue life assessment of the component. Thus, using the results of experimental tests made on panel specimens, a FE general model and two submodels of the critical zone (involved in fatigue damage during the tests) have been modelled in order to investigate the complex state of stress near the rivets holes. These stress values obtained have been elaborated for a fatigue assessment.

Proof-Test-Based Life Prediction of High-Toughness Pressure Vessels

1996 ◽  
Vol 118 (1) ◽  
pp. 86-94 ◽  
Author(s):  
T. L. Panontin ◽  
M. R. Hill
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Life Prediction ◽  
Crack Size ◽  
Initial Crack ◽  
Pressure Vessels ◽  
Operating Pressure ◽  
High Toughness

The paper examines the problems associated with applying proof-test-based life prediction to vessels made of high-toughness metals. Two A106 Gr B pipe specimens containing long, through-wall, circumferential flaws were tested. One failed during hydrostatic testing and the other during tension-tension cycling following a hydrostatic test. Quantitative fractography was used to verify experimentally obtained fatigue crack growth rates and a variety of LEFM and EPFM techniques were used to analyze the experimental results. The results show that: plastic collapse analysis provides accurate predictions of screened (initial) crack size when the flow stress is determined experimentally; LEFM analysis underestimates the crack size screened by the proof test and overpredicts the subsequent fatigue life of the vessel when retardation effects are small (i.e., low proof levels); and, at a high proof-test level 2.4 × operating pressure), the large retardation effect on fatigue crack growth due to the overload overwhelmed the deleterious effect on fatigue life from stable tearing during the proof test and alleviated the problem of screening only long cracks due to the high toughness of the metal.

Fatigue life analysis of shot-peened bearing steel

2012 ◽  
Vol 26 (6) ◽  
pp. 1747-1752 ◽  
Author(s):  
Sang-Jae Yoon ◽  
Jung-Hoon Park ◽  
Nak-Sam Choi
Keyword(s):  
Fatigue Life ◽  
Bearing Steel ◽  
Life Analysis ◽  
Fatigue Life Analysis
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