Critical zone

Figure 1 presents a turbine blade and shows the critical zone where cracks have to be detected within an aircraft inspection. 

This paper presents solutions of two different NDT problems which could not be solved using standard ultrasonic systems and methods. The first problem eoncems the eraek detection in the root of turbine blades in a specified critical zone. The second problem concerns an ultrasonie thiekness measurement for a case when the sound velocity varies along the object surface, thus not allowing to take a predetermined eonstant velocity into account. 

Differential temperature as well as differential pressure can be used as a primary control variable. In one instance, it was hard to meet purity on a product in a column having close boiling components. The differential temperature across several bottom section trays was found to be the key to maintaining purity control. So a column side draw flow higher in the column was put on control by the critical temperature differential. This controlled the liquid reflux running down to the critical zone by varying the liquid drawn off at the side draw. This novel scheme solved the control problem. 

It is current practice to select the rotary shoulder connection that provides the balanced bending fatigue resistance for the pin and the box. The pin and the box are equally strong in bending if the cross-section module of the box in its critical zone is 2.5 times greater than the cross-section module of the pin at its critical zone. These critical zones are shown in Figure 4-127. Section modulus ratios from 2.25 to 2.75 are considered to be very good and satisfactory performance has been experienced with ratios from 2.0 to 3.2 [39]. 

Although RPLC is a very powerful technique that solves the majority of separation problems, a few critical zones in the chromatogram can be indicated (Figure S) ... 

In short fiber composites, energy absorption mechanisms, such as interfacial debonding and matrix cracking, most often occur at the fiber ends (Curtis et al., 1978). The damage model proposed by Bader et al. (1979) assumes that short fiber composites fail over a critical cross-section which has been weakened by the accumulation of cracks, since the short fibers bridging this critical zone are unable to carry the load. In fatigue loading, sudden fracture takes place as a direct result from the far-field effect of the composite, rather than due to the near field of the crack tip... 

This value of the Reynolds number lies within the critical zone. If the flow were laminar, the value of R/pu2 from Fig. 3.7 would be 0.003. If the flow were turbulent, the value of R/pu2 would be considerably higher, and this higher value should be used in subsequent calculation to provide a margin of safety. If the roughness is taken as 0.05 mm, e/d = (0.05/25) = 0.002 and, from Fig 3.7, R/pu2 = 0.0057. 

The sorption data showed that the change proceeded in an isobaric manner which was strongly temperature-dependent, varying from 4 to 5 mm. at 0° C. to 4000 mm. at 200° C. Sievertz and Briinig (18) constructed a critical zone, similar to those found in gas condensations, under which the amount adsorbed was small and above which the pressure increased sharply. Gillespie and Galstaun (1) found the critical point to be 295.3° C. at 19.87-atm. pressure. Here the H/Pd ratio equalled 0.270. Above this temperature the isotherms showed almost normal character. Sievertz and Briinig (18) found that the log P at which the transformation took place varied inversely as the absolute temperature. 

Determine the type of flow that exists. Flow is laminar (also termed viscous) if the Reynolds number Re for the liquid in the pipe is less than about 2000. Turbulent flow exists if the Reynolds number is greater than about 4000. Between these values is a zone in which either condition may exist, depending on the roughness of the pipe wall, entrance conditions, and other factors. Avoid sizing a pipe for flow in this critical zone because excessive pressure drops result without a corresponding increase in the pipe discharge. 

MFAs around 30-40° seem to be the critical zone for certain physieal responses of a wood fibre, for example the growing strain of a maturing xylem eell switehes between eontraetion and expansion when MFA is around 30° (Guitard et al., 1999). 

Keywords Aral Sea, Central Asia, Critical zones, Disaster, Environment... 

Two of the most important factors which control the solubility of chemical compounds are the pH and the redox potential of the environment in which the material is present. Many contaminants exhibit a sharp change in solubility over small changes in pH or redox potential (van der Sloot etal. 1997). For all leaching tests and assessments of environmental impact, it is important to identify the critical zone in the pH value or redox potential and how it relates to the environment in which the material is located or into which it will be placed and how the pH and redox potential of that environment may change with time. 

---