Unnotched Fatigue Strength

The effect of temperature on the notch effect of the weldment is shown in Fig. 15. In this figure the fatigue strength reduction factor is shown as a function of cycle life for both bead-on and bead-off conditions for the two test temperatures, 75 and -300 F. (This ratio assumes the plate to be the unnotched condition and the bead-on, bead-off to be the notched condition.) The factor/if ... 

Fatigue tests on unnotched samples have demonstrated that the fatigue strength (the stress corresponding to failure at a given number of cycles) is reduced by as much as 30% when nylon-6,6 is equilibrated at 50% rh (152) (see Fig. 34). In marked contrast, it has been found that fatigue growth rates in nylon-6,6 exhibit a pronoimced minimum at an absorbed moisture content of 2.6 wt% water, and... 

At and near room temperature, metals have well-defined, almost constant, moduli and yield strengths (in contrast to polymers, which do not). And most metallic alloys have a ductility of 20% or better. Certain high-strength alloys (spring steel, for instance) and components made by powder methods, have less - as little as 2%. But even this is enough to ensure that an unnotched component yields before it fractures, and that fracture, when it occurs, is of a tough, ductile, type. But - partly because of their ductility - metals are prey to cyclic fatigue and, of all the classes of materials, they are the least resistant to corrosion and oxidation. 

Strength approach a constant value, we find decreased crack propagation rates in pre-cracked specimens and a continued rise in fatigue lifetimes in unnotched specimens. 

Most commercial WPCs are considerably more flexible than solid wood. WPCs creep more than solid wood, are less tough, and can handle less fatigue before failure [5, 38]. The use of wood fibers as reinforcing agents rather than just as fillers increases MOE, MOR, and the ultimate tensile strength (UTS) [39] as well as the unnotched energy... 

Professor S. Suresh of Brown University visited GAPD In December 1989, to present recent developments in cyclic fatigue, cyclic compression fatigue pre-cracking, and mixed-mode fracture testing of ceramics. Professor Suresh will be contracted to perform mixed-mode I III fracture toughness tests of notched cyclic compression pre-cracked tension-torsion specimens, and multiaxial strength tests on unnotched tension-torsion specimen. 

Notched and unnotched tension-tension fatigue properties of Tl-4AI-3MO-1V sheet, solution treated and aged. Room-temperature ultimate tensile strengths were 1340 and 1350 MPa (194 and 196 ksi) in the longitudinal and transverse directions, respectively. Yield strengths (0.2%) were 1117 and 1170 MPa (162 and 1701 ), respectively, and elongation was 6 and 5%, respectively. R= 0.4. 

Fig. 7.16 Notch effect on notched and unnotched specimen applying a scaling factor fcy to both the fatigue limit and the ultimate strength...

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