Intensity factor effects

The computational process of analysis is hidden from the user, and visually the analysis is conducted in terms of M-02-91 or R6 [6] assessment procedure On the basis of data of stress state and defect configuration the necessary assessment parameters (limit load, stress intensity factor variation along the crack-like defect edge) are determined. Special attention is devoted to realization of sensitivity analysis. Effect of variations in calculated stress distribution and defect configuration are estimated by built-in way. 

Figure 7 shows these results schematically for both twist and tilt crack deflections. Thus, for the stress intensity factor required to drive a crack at a tilt or twist angle, the appHed driving force must be increased over and above that required to propagate the crack under pure mode 1 loading conditions. Twist deflection out of plane is a more effective toughening mechanism than a simple tilt deflection out of plane. 

Correspondingly, the effective stress intensity factor range, may be expressed as... 

An analysis of loading mode effects has also provided evidence of the critical role of hydrogen. A stress-intensity factor (K) can be achieved in either a tensile loading mode (mode I) or a shearing mode (mode III) (Section 8.9). Under mode I conditions the volume of metal immediately in... 

Similar results have been reported for DMA/PEMA (14). Figure 11 shows data for DSAE/PPSQ. Although the same effect is present, it is quantitatively different. The reduction in T is about a factor of 3 for a film initially bleached to T=32%, while for DPA about the same reduction is seen with T(initial) = 8% thus it is apparently less severe for DSAE. The most interesting result is that DMA/PEMA, when irradiated under N2 at 260 nm (+/-8nm FWHM bandwidth) by an Hg-Xe lamp, shows absolutely no change in transmittance with a dose of 100 J/cm2 (15). Thus the antibleaching is an intensity dependent effect that is absent at low intensities and occurs only with the excimer laser (typically -0.1-1 mJ/cm2 in -35 nsec). 

The expressions for scattered light intensity (and Rayleigh ratio) must be corrected by dividing by the appropriate Cabannes factor. Effectively this is equivalent to replacing the optical constant K as defined in Eq. (24) by Kf and by 2 Kfj for unpolarised and vertically polarised incident light respectively. 

The last issue that remains to be addressed is whether the MBL results are sensitive to the characteristic diffusion distance L one assumes to fix the outer boundary of the domain of analysis. In the calculations so far, we took the size L of the MBL domain to be equal to the size h - a of the uncracked ligament in the pipeline. To investigate the effect of the size L on the steady state concentration profiles, in particular within the fracture process zone, we performed additional transient hydrogen transport calculations using the MBL approach with L = 8(/i — a) = 60.96 mm under the same stress intensity factor Kf =34.12 MPa /m and normalized T-stress T /steady state distributions of the NILS concentration ahead of the crack tip are plotted in Fig. 8 for the two boundary conditions, i.e. / = 0 and C, =0 on the outer boundary. The concentration profiles for the zero flux boundary condition are identical for both domain sizes. For the zero concentration boundary condition CL = 0 on the outer boundary, although the concentration profiles for the two domain sizes L = h - a and L = 8(/i - a) differ substantially away from the crack tip. they are very close in the region near the crack tip, and notably their maxima differ by less than... 

Using the MBL formulation, we performed additional transient hydrogen transport calculations with L — 5.10, 9.96, 16.04, 21.36. 31.28. 41.63, 50.38 mm, stress intensity factor K, =34.12 MPaVm. T Icsa =-0.316, and zero hydrogen concentration C, prescribed on the outer boundary. For these domain sizes, we found the values of the effective time to steady state r to be 240. 608. 1105. 1538. 2297, 2976. and 3450 sec, respectively. Although the MBL approach does not predict the effective time to steady state accurately in comparison to the full-field solution, it can be used to provide a rough approximation. The non-dimensional effective times to steady-state r = Dl jb and the... 

To model diffraction intensities, detector effects and the background intensity from thermal diffuse scattering must be included. A general expression for the theoretical intensity considering all of these factors is... 

In a fluid such as milk, which contains several oxidation-reduction systems, the effect of each system on the potential depends on several factors. These include the reversibility of the system, its E0 value or position on the scale of potential, the ratio of oxidant to reductant, and the concentration of active components of the system. Only a reversible system gives a potential at a noble metal electrode, and this measured potential is an intensity factor analogous to the potential measured on a hydrogen electrode in determining hydrogen ion concentrations. 

The third example of time effects in elastic fracture concerns accelerated crack growth. Up to the early 80 s it has been assumed that a unique relation exists between the stress intensity factor K and the rate of crack growth da/dt. This contention had been confirmed in many steady crack growth experiments. Using three point bending specimens Chan and Williams [33] obtained for HDPE in water the following relation between da/dt, and the acting stress intensity factor Kc ... 

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