Macroscopic flaws

Macroscopic flaws such as impurities, cracks, charge-to-charge adhesion, and bubbles. 

It is clear that macroscopic and microscopic flaws affect the properties of PTFE parts. It is important to characterize their impact quantitatively. These flaws can be directly measured by a number of techniques. The measurement methods are complex and not suitable for routine quality control. Macroscopic flaws are frequently detectable visually or by a simple magnifying glass. Internal defects can be detected by x-ray techniques such as radiography. ASTM E94 can be applied as a guideline in establishing procedures. 

Macroscopic Flaws - Defects such as cracks or inclusions in fluoropolymer parts which can be detected visually or by the use of a simple magnifying glass. 

An obvious way to overcome some of the difficulties and to have a frame for reproducible measurements is the preparation of special samples which have a macroscopic flaw where the fracture then starts, followed by a propagation of the crack in a controlled manner. Although this procedure cannot remove the principal difficulty encountered in the assessment of the fracture behavior of a given sample, it can provide true material parameters for use in comparisons of different materials. Figure 8.29 depicts a standard configuration, with a sharp crack introduced in a plate. Applying stress, the fracture starts at the two edges of the crack. Linear fracture mechanics deals with these conditions and describes the behavior of sharp cracks cut into a linear elastic material. 

Nonetheless, mathematical analyses of milling operations, particularly for ball mills, roller mills, and fluid energy mills, have been moderately successful. There continues to be a pronounced need for more complete understanding of micromeritic characteristics, the intrinsic nature of the milling operation itself, the influence of fines on the milling operation, and phenomena including flaw structure of solids, particle fracture, particulate flow, and interactions at both macroscopic and microscopic scales. 

This phenomenological identification of A and B has been utilized by Einstein and others with great success (section 3), but only for linear Fokker-Planck equations. If the macroscopic law is nonlinear a difficulty arises, first pointed out by D.K.C. MacDonald. The flaw in the argument lies in the identification of the coefficient A y) with the macroscopic law. The two may well differ by a term of the same order as the fluctuations once one neglects the fluctuations such a term is invisible anyway. The consequence was that different authors obtained different, but equally plausible expressions for noise in nonlinear systems. This difficulty led to the more fundamental approach in chapter X. 

The flaw in Bohr s view lies in the assumption that the measuring device must be macroscopic and "reality" the one emerging in our daily life, to be communicated with everyday language. 

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