Failure Fluidity

Clofibrate causes a necrotizing myopathy, particularly in patients with renal failure, nephrotic syndrome or hypothyroidism. The myopathy is painful and myokymia of unknown origin is sometimes present. The mechanism of damage is not known, but p-chlorophenol is a major metabolite of clofibrate and p-chlorophe-nol is a particularly potent uncoupler of cellular oxidative phosphorylation and disrupts the fluidity of lipid membranes. Muscle damage is repaired rapidly on the cessation of treatment. 

Crosslinking is distinguished by the occurrence of gelation at some point in the polymerization. At this point, termed the gel point, one first observes the visible formation of a gel or insoluble polymer fraction. (The gel point is alternately taken as the point at which the system loses fluidity as measured by the failure of an air bubble to rise in it.) The gel is insoluble in all solvents at elevated temperatures under conditions where polymer degradation does not occur. The gel corresponds to the formation of an infinite network in which polymer molecules have been crosslinked to each other to form a macroscopic molecules. The gel is, in... 

The gel point is usually determined experimentally as that point in the reaction at which the reacting mixture loses fluidity as indicated by the failure of bubbles to rise in it. Experimental observations of the gel point in a number of systems have confirmed the general utility of the Carothers and statistical approaches. Thus in the reactions of glycerol (a triol) with equivalent amounts of several diacids, the gel point was observed at an extent of reaction of 0.765 [Kienle and Petke, 1940, 1941], The predicted values of pc, are 0.709 and 0.833 from Eqs. 148 (statistical) and 2-139 (Carothers), respectively. Flory [1941] studied several systems composed of diethylene glycol (/ = 2), 1,2,3-propanetricarboxylic acid (/ = 3), and either succinic or adipic acid (/ = 2) with both stoichiometric and nonstoichiometric amounts of hydroxyl and carboxyl groups. Some of the experimentally observed pc values are shown in Table 2-9 along with the corresponding theoretical values calculated by both the Carothers and statistical equations. 

On the other hand, in the water, we observe a clearer critical strength point of 1.7 nm HAP than that of 1.7 nm HAP in the vacuum. This means the mechanical properties are affected by the interactions between HAP and the environments. Thin HAP (under 2 nm) shows more ductility and fluidity because of the relatively disordered structure. Although the structure is more amorphous and the structural deformation occurs across the entire system during the tensile deformation with the thin HAP, the deformation and failure of HAP become more localized as the thickness of HAP increases. Because of the thinness of the minerals, the interactions with environments such as proteins and water can disturb or stabilize the HAP structure, making the minerals lose or gain their bulk properties. 

The failure to jam in the predicted manner has been attributed to the crossover in relaxation mechanism at some temperature between normal liquid (high fluidity, short relaxation times) temperatures and the glass transition temperature, an occurrence which was anticipated by Goldstein in a 1969 paper which is now a classic. 

Fluidity of liquids, see viscosity of powders, see mohr-coulomb failure law. 

A1 in Mg alloys increases strength and fluidity in casting. Mg-Al alloys are susceptible to SCC [63,100,101,103-109] in air, distilled water and chloride-containing solutions. SCC-induced fractures may occur at stresses as low as 50% of the yield strength. Figure 8.4(a) shows that SCC susceptibility increased as the Al content increased from 1% to 8% [106]. If the failure stress at 100000s is compared with values of tensile yield stress [110,111], the (ratio of failure stress)/(tensile yield stress) decreases to values somewhat lower than those in Table 8.1. The tensile stress values are for comparable material but may not be exactly the same as those in [106]. Nevertheless, Fig. 8.4 does indicate the high SCC susceptibility of some alloys. 

---