Consolidation defects

Gomez-Barrena E., S. Li, B.S. Furman, et al. 1998. Role of polyethylene oxidation and consolidation defects in cup performance. Clin Orthop 352 105-117. 

Edcfy-cufrent NDT inspections using spatial data (sampled scans) ha >e many benefits. They separate the two conflicting aspects of an inspection scanning and signal interpretation. An instrument/display (client/server) based NDT inspection based on sampled scan data aides in the training and certification of inspectors. It can be used over the Internet or in-house Intranet networks to train or examine inspectors at multiple or remote sites. This saves travel time and resources as defects, instrumentation and teaching can all be consolidated Samples can be maintained and distributed from a central certification body providing more control andflexibility. 

In a number of studies a correlation was seen between the amount of nonstoi-chiometric oxygen in the spinel and the spinel s activity. It appears that excess oxygen consolidates the spinel s defect structure with a large number of active sites. Strong anodic polarization leads to ordering of this structure and thus to a decrease in catalytic activity. 

The Raman spectra (0-1400 cm l) shown in Fig re 6 illustrate the structural changes which accompany the consolidation of silica gels. The 1100°C sample is fully dense, whereas the 50 and 600°C samples have high surface areas (1050 and 890 m2/g), respectively. The important features of the Raman spectra attributable to siloxane bond formation are the broad band at about 430 cm 1 and the sharp bands at 490 and 608 cm 1(which in the literature have been ascribed to defects denoted as D1 and D2, respectively). The D2 band is absent in the dried gel. It appears at about 200°C and becomes very intense at intermediate temperatures, 600-800°C. Its relative intensity in the fully consolidated gel is low and comparable to that in conventional vitreous silica. By comparison the intensities of the 430 and 490 cm 1 bands are much more constant. Both bands are present at each temperature, and the relative intensity of the 430 cm 1 band increases only slightly with respect to D1 as the temperature is increased. Figure 7 shows that in addition to elevated temperatures the relative intensity of D2 also decreases upon exposure to water vapor. 

This process also called just bag molding. It is the conventional hand lay-up or spray-up that is allowed to cure without the use of external pressure. For many applications this is sufficient, but maximum consolidation may not be reached. There can be some porosity fibers may not fit closely into internal corners with sharp radii but tend to spring back. Resin-rich and/or resin-starved areas may occur because of draining, even with thixotropic agents. With moderate pressure (hand rollers, etc.) these defects or limitations can be overcome with significant improvement in mechanical properties. 

The sheets of SMC are cut into a desirable shape (charge is weighed in case of BMC) and stacked on the lower half of the mold, and the movable upper half is brought down to close the mold. BMC material is normally consolidated by hand before they are placed in the mold in most cases the charge is placed centrally in the mold. The placement determines the quality of the part as it influences the length of the flow in the mold, fiber orientation, flow line, and other surface defects. 

Figure 3 shows the results of EDX analyses of the two systems. Both the back electron images in (a) and Ka-line images of constitutional elements clearly indicate that the continuous compositional changes were achieved in each system. It is concluded that the FGM produced by the underwater-shock consolidation has fully densified microstructure ever3 here in an overall cross section without any discontinuity and defects. 

To study filtration permeability, the compositions of SPC samples were accepted in accordance with the optimal composition given in Table 3.5. Water was used as a filtration liquid because it did not influence consolidation of the concrete. This allowed determinations about the presence or absence of filtering defects in investigated compositions and estimation of the influence of additives on filtration permeability. For SPC compositions tested with water, a filtration of acids is absent, as the effect of consolidation of the material in this case is shown. 

The Arbegast model can be used to explain two of the more common weld defects in terms of the processing parameters. The first is a worm-hole or tunnel defect that runs the length of the weld and is attributed to insufficient forming pressure under the tool shoulder, which prevents the material from consolidating. The second defect is a lack of penetration on the root surface next to the anvil. This can result when the weld tool does not sufficiently penetrate into the metal plates, most likely from atoo short pin tool. 

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