Fatigue notch factor

Table 7.1 Summary of the parameters of fatigue curves and fatigue notch factors for [0/90] woven glass/polyester tubes under pulsating tension—torsion loading [38]...

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. 

Fatigue notch factor The ratio of the fatigue strength of a specimen with no site of stress concentration (notch) to that of a duplicate specimen having a notch. 

Leis, B.N., Gowda, C.V.B., Topper, T.H. Cyclic inelastic deformation and the fatigue notch factor. Cyclic stress-strain behavior—analysis, experimentation and failure prediction. Am. Soc. Test. Mater., ASTM STP 519, 133-159 (1973)... 

Table lc.24 Influence of the notch factor on the fatigue strength of Ti6A14V... 

Notch Factor Stress Ratio R Fatigue Strength (MPa)... 

Note that for any given value of stress level cr the hrst member of Eq. (6.31) is a constant, also known as Neuber s constant, so that (6.31) is the equation of a hyperbola. The intersection of the Neuber s hyperbola with the stress-strain curve of the material yields the solution of the elastic-plastic problem. This is schematically shown in Eig. 6.21 where the coordinates of point A = (s.cr) are the notch tip strain and stress, respectively. Moving from monotonic loading to fatigue cycles Neuber s rule applies substituting the theoretical stress concentration factor ki with the notch factor fey (see Sect. 7.1), as suggested by Wetzel [31] in 1968 and Topper et al. [32] in 1969, obtaining what is known as the Neuber modihed equation... 

It can be concluded that the geometry considered is not capable to withstand fatigue for more than 10 cycles. It will be necessary, at least, to increase the shoulder fillet radius that is too small, resulting in a notch factor too high. 

General description. In incomplete fusion, complete melting and fusion between the base metal and the weld metal or between individual weld beads does not occur (Fig. 15.8). Incomplete fusion that produces crevices or notches at surfaces can combine with environmental factors to induce corrosion fatigue (Chap. 10), stress-corrosion cracking (Chap. 9), or crevice corrosion (Chap. 2). See Fig. 15.9. 

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. 8.75 Relation between (k — l)/n) and tj in 1% NaCl, where k is the ratio of fatigue strength in air to that in a corrosive environment, the notch sensitivity factor on fatigue strength, the corrosion current density at start of fatigue cycling, and jy the total life in...

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