Macroscopic Crack Growth

2019 ◽  
pp. 258-299
Keyword(s):  
Crack Growth ◽  
Macroscopic Crack

Fractographic analysis of fatigue crack growth in lightweight integral stiffened panels

2010 ◽  
Vol 1 (3) ◽  
pp. 233-258 ◽  
Author(s):  
Pedro M.G.P. Moreira ◽  
Paulo M.S.T. de Castro
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Testing ◽  
Content Type ◽  
Stiffened Panels ◽  
Friction Stir ◽  
Final Fracture ◽  
Striation Spacing ◽  
Macroscopic Crack

PurposeThe purpose of this paper is to complement available macroscopic fatigue crack growth measurements in flat stiffened panels with scanning electron microscopy (SEM) measurements of striation spacing.Design/methodology/approachThe paper's approach is fatigue testing of two‐stiffener flat panels manufactured using three different processes, with a central initial crack perpendicular to the stiffeners and load, in order to identify striation spacing during crack growth up to final fracture, using SEM.FindingsAn increase of striation spacing as cracks grow was quantified. Although when cracks approach the stiffeners the stress intensity factor decreases, there is no clear decrease of striation spacing in that region. Striation spacing is roughly similar to macroscopic crack‐propagation rate da/dN measured in the panels testing. This observation is no longer valid once the stiffeners are reached; this stage is characterized by fast acceleration of the cracking process until final complete rupture is verified, and macroscopic crack growth measurements are made difficult because of the “T” geometry in that region.Originality/valueA complete picture of the striation spacing during the fatigue crack growth up to final fracture of a two‐stiffener flat panel is provided for three different manufacturing processes: high‐speed machining, laser beam welding and friction stir welding.

Surface Small Crack Growth Behavior of Type 304 Stainless Steel in Low-Cycle Fatigue at Elevated Temperature

1988 ◽  
Vol 110 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Masakazu Okazaki ◽  
Tomohiro Endoh ◽  
Takashi Koizumi
Keyword(s):  
Growth Rate ◽  
Grain Size ◽  
Crack Growth Rate ◽  
Grain Boundaries ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Small Crack ◽  
Average Grain Size ◽  
Small Crack Growth ◽  
Macroscopic Crack

Surface small crack growth behavior of Type 304 stainless steel during low cycle fatigue under fast-fast and slow-fast cyclings was investigated at a temperature of 873 K by using the smooth specimens which had the different grain sizes. It was shown that the crack, which had already grown up to a few grain size, predominantly propagated with strain cycling, and that it was very important for the safety assessment of the components in service to detect the crack of a few grain sizes. It was also shown that small crack growth rate showed the minimum when they arrived at the grain boundaries. Above behavior resulted from that the grain boundaries temporarily impeded the small crack growth. The crack length below which the grain boundaries notably affected the small crack growth rate was also given as the function of relative length to the average grain size. Furthermore, the small crack growth rate was compared with the macroscopic crack growth one. In fast-fast cycling, the small crack growth rate was about ten times as large as the macroscopic crack growth one, where its length was comparable to the grain size. Based on the results thus obtained, the application limit of macroscopic crack growth law to the surface small crack growth was discussed. The application limit proportionally increased with the grain size, and it was about ten times average grain size in both fast-fast and slow-fast cyclings.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

A unification of small- and large-crack growth laws

1999 ◽  
Vol 22 (8) ◽  
pp. 711-722
Author(s):  
Hamm ◽  
Johnson
Keyword(s):  
Crack Growth ◽  
Large Crack ◽  
Growth Laws

A discrete dislocation analysis of fatigue crack growth

2001 ◽  
Vol 11 (PR5) ◽  
pp. Pr5-69-Pr5-75
Author(s):  
V. S. Deshpande ◽  
H. H.M. Cleveringa ◽  
E. Van der Giessen ◽  
A. Needleman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Discrete Dislocation
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