Fatigue notch effect

The mechanical properties of aluminum-sprayed steel remain unimpaired other than a slight loss in fatigue strength owing to the notch effects caused by preliminary grit blasting. The fatigue... 

Ratio of the maximum stress in the region of a notch, or another stress raiser, to the nominal corresponding stress. SCF is a theoretical indication of the effect of stress concentration on mechanical behavior. Since it does not take into account the stress relief due to plastic deformation, its value is usually larger than the empirical fatigue notch factor or strength reducing ratio. External or internal cracks in a plastic caused by imposed stresses. 

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 ... 

Gonyea, D.C., Method for low-cycle fatigue design including biaxial stress and notch effects. Fatigue at Elevated Temperatures, ASTM STP 520, American Society for Testing and Materials, Philadelphia, 1973, pp. 673-687. 

High- and low-cycle fatigue data for smooth and notched specimens of Ti-6211 tested in air and in salt water exhibited a decrease in the fatigue strength for notched specimens at all cychc hves. The Severn River salt water, however, had no significant detrimental effect. The notch effect was... 

The reason to subtract unity from both numerator and denominator in Eq. (7.4) is to provide a scale for q that ranges from zero for no notch effect to unity for fiiU notch effect. In this latter case kf is exactly equal to kf. A deep analysis of fatigue limit experimental data brought Peterson to make the hypothesis that fatigue damage became critical in relation to the stress level Opeak at a small distance b below the surface of notch root where the stress gradient is very steep... 

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

Frost, N.E. Notch effect and the critical alternating stress required to propagate a crack in an aluminum alloy subject to fatigue loading. J. Mech. Eng. 2, 109 (1960)... 

Pluvinage G, Gjonaj M, editors. Notch effects in fatigue and fracture. Nato Science Series. Boston Kluwer Academic Publishers 2001. 

These values are determined by experiment. It is, however, by no means a trivial task to measure the lamina compressive and shear strengths (52,53). Also the failure of the first ply of a laminate does not necessarily coincide with the maximum load that the laminate can sustain. In many practical composite laminates first-ply failure may be accompanied by a very small reduction in the laminate stiffness. Local ply-level failures can reduce the stress-raising effects of notches and enhance fatigue performance (54). 

The data presented in Figure 19.7 were obtained on a Sonntag-Universal machine which flexes a beam in tension and compression. Whereas the acetal resin was subjected to stresses at 1800 cycles per minute at 75°F and at 100% RH, the nylons were cycled at only 1200 cycles per minute and had a moisture content of 2.5%. The polyethylene sample was also flexed at 1200 cycles per minute. Whilst the moisture content has not been found to be a significant factor it has been observed that the geometry of the test piece and, in particular, the presence of notches has a profound effect on the fatigue endurance limit. 

Fig. 48 Notch (fatigue) effect resulting at inserted openings from the application of force. The only crack running through the wall proceeds,...

Figure 48 Notch (fatigue) effect resulting at inserted openings...

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