Notch factor

In all tests, as shown in Fig. 3, the ratio NTS/UNTS has exceeded 0.9 at -- 320°F for a notch factor Kt — 6.3, and has been 0.89 or higher at — 320°F even with the most severe notch factor. This is considered satisfactory for most cryogenic applications. However, when necessary, increased toughness can be obtained at low temperatures with some reduction in tensile strength. For example, in the -T61 temper, the NTS/UNTS ratio at - 320°F is above 1.0, while the tensile strength is about 64,000 psi or lower. 

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]...

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

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

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. 

A notched specimen is a test specimen that has been deliberately cut or notched, usually in a V-shape, to induce and locate the point of failure. The notch factor is the ratio of a property, such as impact strength, determined on a plain specimen to the property determined on the notched specimen. 

Equation (7.16) is often represented by a different symbol, Kf, the notch factor, relating the strength of smooth specimens to that of notched specimens, but having the same meaning as ... 

Ti-15iyio-5Zr-3AI Effect of notch factor on notch tensiie strength... 

Axial loaded, room-temperature test. Notch factor of bolt threads were unspecified. 

Long-term tests under static load are performed under a variety of conditions e.g., under tensile, compressive, bending and flexural loads, under uni- or multi-axial load, under combined load, and as a function of temperature, processing influences, environmental conditions and depending on design features (notch factor). In practice, creep tests are typically performed under tensile load. 

But which material is the ideal one for pulsating pressure stress. Of course, the following rule applies the higher the pressure, the greater the stability. Nevertheless, the materials have to remain ductile at any pressure. A rupture elongation of >10% therefore has to be observed implicitly. Thinking of the notches, however, it can easily be imagined that a softer material is able to react on too much tension with plastic strain, and thus reduce the notch factor. 

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... 

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