Crack aspects

A semi-elliptical surface crack of 100 pm in surface length was made at the center of the polished surface of the as-polished specimen with a Vickers indenter, using a load of 19.8 N. The indentation crack, as shown in figure 2, is called a pre-crack in this paper. The ratio of the depth d) to half the surface length (c) of the crack (aspect ratio cUc) was 0.9. We call these specimens the as-cracked specimens . 

A fatal accident and some other disasters, which were caused by small cracks, lead to a more strict consideration of the security of these steam drums. Parallel to these the economical pressure, due to the globalisation of the today s industry, lead to the increase of the pressure and the rotation speed of the paper production machines for a higher output of the production, which means, that all safety aspects from the design and the material will be exploited totally. On the other hand cast iron is also not a ductile and comfortable material, like the most steels for the pressure equipment. 

Telega J.J., Lewinski T. (1994) Mathematical aspects of modelling the macroscopic behaviour of cross-ply laminates with intralaminar cracks. Control and Cybernetics 23 (3), 773-792. 

One aspect of pressure vessel design which has received considerable attention in recent years is the design of threaded closures where, due to the high stress concentration at the root of the first active thread, a fatigue crack may quickly initiate and propagate in the radial—circumferential plane. Stress intensity factors for this type of crack are difficult to compute (112,113), and more geometries need to be examined before the factors can be used with confidence. 

The principal advantage of plastic dmms and liners is their resistance to corrosion. This aspect of their performance requires the lading to be investigated in terms of capacity for chemical attack on the dmm. Stress-cracking tests should be performed in all instances where the compatibiUty of jading and dmm material has not been estabUshed (6). 

Raw Material and Energy Aspects to Pyridine Manufacture. The majority of pyridine and pyridine derivatives are based on raw materials like aldehydes or ketones. These are petroleum-derived starting materials and their manufacture entails cracking and distillation of alkanes and alkenes, and oxidation of alkanes, alkenes, or alcohols. Ammonia is usually the source of the nitrogen atom in pyridine compounds. Gas-phase synthesis of pyridines requires high temperatures (350—550°C) and is therefore somewhat energy intensive. 

Deflection rarely operates as the sole toughening mechanism in a system, although its contribution in some systems may be significant. Crack deflection, however, is a major aspect of bridge formation processes that leads to toughening via bridging ligaments. 

An important aspect of economic consideration is the prevention of egg and egg product loss to the drain or the atmosphere, eg, a checked or cracked egg may be broken in the washer, and the contents go down the drain with the wash water. Other measurable losses during egg product production are Hsted in Table 5. 

Dente and Ranzi (in Albright et al., eds.. Pyrolysis Theory and Industrial Practice, Academic Press, 1983, pp. 133-175) Mathematical modehng of hydrocarbon pyrolysis reactions Shah and Sharma (in Carberry and Varma, eds.. Chemical Reaction and Reaction Engineering Handbook, Dekker, 1987, pp. 713-721) Hydroxylamine phosphate manufacture in a slurry reactor Some aspects of a kinetic model of methanol synthesis are described in the first example, which is followed by a second example that describes coping with the multiphcity of reactants and reactions of some petroleum conversion processes. Then two somewhat simph-fied industrial examples are worked out in detail mild thermal cracking and production of styrene. Even these calculations are impractical without a computer. The basic data and mathematics and some of the results are presented. 

Staehle, R. W. Comments on the History of Engineering and Science of Stress Corrosion Cracking, in Proc. Fundamental Aspects of Stress Corrosion Cracking (Houston, TX National Association of Corrosion Engineers, 1969). 

The mechanisms of comminution are complex involving breakage along particle cracks and fissures etc., and depend on the hardness and structure of the feed particle. The Institution of Chemical Engineers (London) produced a major report on comminution (IChem, 1975), which was followed by reviews by Bemrose and Bridgwater (1987), Prior etal. (1990) and Jones (1997). These reviews included sections on both the fundamental and practical aspects of comminution and attrition in process equipment, test methods and an extensive list of references. 

An important aspect of Clark s technology was that the oil being cracked, which flowed through the tubes and in a near vapor state, was maintained in a continually dynamic or turbulent condition. This meant that the coke particles which formed were prevented from... 

The most important mechanism involved in the corrosion of metal is electrochemical dissolution. This is the basis of general metal loss, pitting corrosion, microbiologically induced corrosion and some aspects of stress corrosion cracking. Corrosion in aqueous systems and other circumstances where an electrolyte is present is generally electrochemical in nature. Other mechanisms operate in the absence of electrolyte, and some are discussed in Section 53.1.4. 

Since 1977, Reza Sadeghbeigi has been involved in various aspects of cat cracking at major and independent oil companies focusing on technical services, troubleshooting, process design, and project management—including major FCC revamps. 

The first edition of this book was published nearly five years ago. The book was well received and the positive reviews were overwhelming. My main objective of writing this second edition is to provide a practical transfer of experience to the readers of the knowledge that 1 have gained in more than 20 years of dealing with various aspects of the cat cracking process. 

Heterogeneities associated with a metal have been classified in Table 1.1 as atomic see Fig. 1.1), microscopic (visible under an optical microscope), and macroscopic, and their effects are considered in various sections of the present work. It is relevant to observe, however, that the detailed mechanism of all aspects of corrosion, e.g. the passage of a metallic cation from the lattice to the solution, specific effects of ions and species in solution in accelerating or inhibiting corrosion or causing stress-corrosion cracking, etc. must involve a consideration of the detailed atomic structure of the metal or alloy. 

Pourbaix, M., Electrochemical Aspects of Stress-corrosion Cracking , CEBELCOR Rapp. Tech., 118(RT 199) (1971) C.A., 76, 12065e... 

Any test (several such tests are used) in which time to failure of smooth specimens is determined is an overall measure of the incubation period to initiate a crack, the ability to resist the propagation of a stress corrosion crack and the ability to resist final mechanical fracture. Since this test does not indicate the relative merits of an alloy in each individual aspect of the... 

Conference on Fundamental Aspects of Stress Corrosion Cracking, Ohio State Univ. (1967), N.A.C.E., Houston (1969)... 

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