Effect of scratches

The effects of scratching tools were studied on three types of tools, 1.6-nim bcills from stainless steel and timgsten carbide, 10-micron sharp diamond stylus, and a novel tungsten carbide micro-blade, which is as sharp as the stylus (10 micron) but veiy wide (0.8 mm) [3]. 

A car instrument panel (Fig. 5.27) is a large injection moulding with a complex shape. The panel shape was optimised, in ways discussed earlier in this chapter, to increase its bending stiffness. The visual effects of scratching are minimised by having a textured surface on the mould. Figure 13.20... 

The IPEN rack exposed aluminium alloys 1060,6061 and 6262, used in the fabrication of fuel assemblies for IPEN s lEA-Rl research reactor. The composition of these alloys is given in Table 4.4. Besides 80 mm diameter coupons of the three alloys, the rack included coupons of 1060 in the processed and scratched condition (to simulate the effect of scratches formed on fuel assemblies during handling in the reactor) and various combinations of galvanic and crevice couples. Table 4.5 lists the sequence of the coupons in the IPEN rack. 

Alloys 1060, 6061 and 6262 are presently being used in IPEN for the manufacture of FAs for the lEA-Rl reactor. The compositions of the alloys are given in Table 6.4. Coupons of the three alloys, 1060 in the processed and scratched condition (to simulate the effect of scratches formed during handling of fuel elements in the reactor coolant), and various combinations of bimetallic couples were mounted in the rack (Fig. 6.2). Four coupons under each set of conditions were exposed. Coupon preparation and pretreatment were as mentioned earlier. This rack was also introduced into the lEA-Rl reactor, close... 

Effect of Scratch Velocity and Temperature. Another frequently investigated experimental parameter on the effect of scratch behavior of materials is the scratching rate or the scanning velocity. Since polymers are viscoelastic-viscoplastic in nature, the importance of scratching rate lies in its ability to change the strain and strain rate at the interface of the sample and the indenter and thus alters the deformation mode. The relationship between velocity and coefficient of fiction will depend on the relaxation state of the surface concerned, especially for nanoscratch (21,56,57,63-65). It was shown that rate and temperature interplay to affect nanotribological behavior of polymer films (57). 

The main value of salt-spray tests is in the evaluation of the effectiveness of phosphate coatings in restricting the spread of rust from scratches or other points of damage in a paint film. This feature is of particular interest to the motorcar industry, as vehicles are often exposed to marine atmospheres and to moisture and salt when the latter is used to disperse ice and frost from road surfaces. Great care is needed in the interpretation of a salt-spray test, as it has been found to favour thin iron phosphate coatings more than is justified by experience with natural weathering. In the motorcar industry the present custom is to use zinc phosphate coatings on the car bodies and all other parts exposed to the outside atmosphere. 

Bonilla et al. (1965) studied the effect of parallel scratches on a polished stainless steel plate when boiling mercury with a small portion of sodium as wetting agent. The mirror-finished stainless steel plate was scored by a tempered steel nee-... 

Diffuse reflectance is an excellent sampling tool for powdered or crystalline materials in the mid-IR and near-IR spectral ranges. Heated reaction chambers for diffuse reflectance allow the study of catalysis and oxidation reactions in situ, and can evaluate the effects of temperature and catalyst behavior. Scratching sample surfaces with abrasive paper and then measuring the spectra of the particles adhering to the paper allows for analysis of intractable solids. Perhaps one of the greatest additional benefits is that this system is amenable to automation. 

An issue that has been receiving increasing attention is the deleterious effect of fillers on the scratch resistance of polymers, as measured by the loss in surface appearance. The understanding of this problem is still at a rudimentary stage, but it appears that the problem can be minimised by control of particle morphology [28] and correct choice of surface treatments [29]. 

Secondary effects of irrigation fluids ex vivo eye irritation assay with four scratches on the cornea, incubated for 2 days and treated with artificial tears containing CaCl in 0.13 mmol/L concentration each 24 drops per day with 30 min of interval between phosphate and tear application. Second image is taken after 2 days with obvious comeal calcification. 

Protecting the can from the effect of corrosion is very important in order to achieve the very long shelf life that metal cans offer. Discussion with the can manufacturer will ensure the use of the appropriate grades of lacquers on the internal surfaces to prevent primary corrosion. The external surfaces must also be considered in order to prevent secondary corrosion, which will result in leakage. Handling on the filling line must ensure the smooth flow of cans and eliminate any sharp objects that may scratch or pierce them. A lot of moisture is present on the line because of the use of conveyor lubricants or from the pasteuriser, and it is important that cans are dried before being packed, particularly if they are to be shrink-wrapped. Cold cans, below the dew point, must be wanned to ambient temperature or else they will become wet when packed. 

Figure 62 Effects of surface finish and colour on resistance to scratching...

For certain clearcoat systems a partial healing of scratches can be observed on the time scale. In literature this is known as the reflow effect [21], Thermal relaxation phenomena may be used for a physical explanation of this effect. In connection with scratch resistance the cross-linking density of clearcoats is also a decisive factor. Meanwhile, dynamic mechanical analysis (DMA) has been established as a method to determine cross-linking density [21-23],... 

The major part of the scattered light originates at surface irregularities and other imperfections, such as scratches. Also in this case the dominant rimpling mechanism may be caused by flow defects (and their after-effects) and by crystallisation. Bennett and Porteus (1961) investigated the effect of surface roughness on the reflectance. This effect may be quantified by the equation... 

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