Maximum allowable stress typical values

Typical maximum allowable stress values for some common materials are shown in Table 13.2. These values may be used for preliminary designs. The ASME BPV Code should be consulted for the values to be used for detailed vessel design. 

Another model, which has been derived from end milling of aluminum, explains the typical gradient as a result of pure mechanical influence, as in the investigated process, the temperature development could be neglected (de Le6n 2009). This model allows a parametrization of the curve and a definition of typical values, e.g., surface residual stress (7surf, maximum residual stress ffmax, depth of maximum residual stress (Tmax, or depth of stress absence (Fig. 11) (de Le6n 2009). 

Equation (3) is plotted with two different time scales in Figures 1 and 2 for values somewhat typical of an elastomer. All the initial deformation takes place in the spring at a later time the dashpot starts to relax and allows the spring to contract. Most of the relaxation takes place within one decade of time on both sides of the relaxation time, but this is shown clearly only in Figure 2. On the logarithmic time scale, the stress-relaxation curve has a maximum slope at the time / = T and the stress ratio cr/cr is 0.3679 ore. The stress relaxation may also be given in terms of a stress-relaxation modulus Er(t) ... 

The design requirements in ASME Section III limit the primary (pressure only) membrane stress to a value of about 13.8 MPa. As a result, the thickness of a PWR RPV is typically about 20-25 cm, while the wall of a BWR RPV is about 15 cm thick. Section VIII requirements limit the maximum stress to a lower allowable level which means that the RPV wall thickness must be greater to reduce the primary stresses. 

There is a direct relationship between hydrogen sulfide concentration and the allowable maximum hardness value of the heat-affected zone (HAZ) on one hand and cracking threshold stress on the other. Typically, the allowable maximum hardness value decreases 30 HB, and the allowable threshold stress decreases by 50% for a tenfold increase in hydrogen sulfide concentration. 

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