Assumed reference flaw

If the principle of bond additivity were completely valid and experiments were without flaws or glitches , the quantity 5i(n, X) would be a constant independent of the value of n and of the substituent X. This is simply shown if we recast enthalpies of formation in terms of bond energies where the sum of bond energies for a molecule may be thermodynamically equated to the energy of atomization. Assuming both the enthalpies of formation and atomization energies refer to the molecule at the same temperature, a simple correction for... 

The simplest example is the case where changes in tensile strength relative to the undrawn, isotropic tensile strength are calculated for samples whose tensile axes are parallel to and perpendicular to the major draw direction These will be referred to as the axial and transverse directions, respectively. For the present purpose, it is assumed that the undrawn master sheet contained an isotropically distributed set of flaws all of the same ellipticity R. The problem is then deterministic. Con-... 

The accuracy of a measurement refers to how close it is to the true value. An inaccurate result occurs as a result of some flaw (systematic error) in the measurement the presence of an interfering substance, incorrect calibration of an instrument, operator error, and so on. The goal of chemical analysis is to eliminate systematic error, but random errors can only be minimized. In practice, an experiment is almost always done in order to find an unknown value (the true value is not known—someone is trying to obtain that value by doing the experiment). In this case the precision of several replicate determinations is used to assess the accuracy of the result. The results of the replicate experiments are expressed as an average (which we assume is close to the true value) with an error limit that gives some indication of how close the average value may be to the true value. The error limit represents the uncertainty of the experimental result. 

These factors can be discussed with reference to the polarization curves for the initial and changing conditions within the occluded region. The combined effects of a potential drop into the pit and the effect of the lowered pH, which raises Epp and increases icrit, are also analyzed by reference to Fig. 7.6 (Ref 20). As previously assumed, the solid anodic curve is taken as representative of a stainless steel in an environment of pH = 1. The dashed extension again represents the anodic polarization behavior in the absence of a passive film. At a potential, Ecorr (or Epot if the potential is maintained potentiostatically), the passive current density would be iCOrr,pass and the active corrosion current density would be iCorr,act- Assume that a small flaw through the passive film is associated with an (IR), drop that lowers the potential in the bottom of the flaw to E,. Since this potential is higher than the passivating potential, Epp, this flaw should immediately repassivate and not propagate. 

In relation (4.27), Cq refers to the penny-shaped flaw size at the moment of crack initiation. Kq is an intensity factor chosen as Kq = 2 MPa.m. The bridging-zone length, Db, prior to critical fracture, has a bridging stress, p, assumed to be constant. For the derivation of Eq. (4.27), the reader should consult the work of Chien-Wei Li et al. [34]. The estimated p for the FG, medium and... 

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