Cracks probability

Dr. Heredy We agree that cracking probably occurs, and the resulting radicals react with phenanthrene. However, we are not sure how important hydrogen availability is for the dissolution process although hydrogen exchange does occur with coal, it occurs only to a small extent or not at all in the dissolution of model compounds. 

When solids deform almost to the breaking point, they exhibit brittle behavior the stress at fracture is several orders of magnitude lower than the computed strength. The loss is ascribed to the presence of minute cracks probably formed during solidification. Compressive stress can induce crack propagation the magnitude of the stress at... 

The carbon number dependence reflects the relative reactivity of carbon—carbon bonds in cracking reactions (133,134). In this kinetic scheme, cracking does not occur at the three C—C bonds nearest the end of a molecule but occurs with equal probability at all other C—C bonds. Such reactive trends are qualitatively similar to those reported for carbenium ion-type cracking reactions on acid catalysts (56,133,134). We express the cracking probability as a ratio (j8c//8r) in order to describe the competition between cracking and readsorption pathways for available a-olefins. Also,... 

Traces of nitrogen oxides may also cause stress-corrosion cracking, probably because such oxides are converted to ammonium salts on the brass surface by chemical reaction with the metal. In one instance of this kind, premature failure of yellow brass brackets in the humidifier chamber of an air-conditioning system was traced to this cause [30], The air had passed through an electrostatic dust... 

Fig. 8.31 A ligamentary microcrack [arrowed in (a)] is seen to close in (b) after propagation of the main crack, probably due to the influence of the residual thermal stresses in the material. Micrographs from video recording [55]. With kind permission of Elsevier...

Fracture occurs when an applied stress procedures a stress intensity factor which exceeds the fracture toughness for the crack. Probability Of Fracture (POF) can be calculated as POF = P (r> Critical value of stress can be calculated form (2) as cT = KjJ a)y[m. Distribution of maximum stress peak in a flight can be model by Gumbel distribution function H ). 

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