Crack characteristic

Multiftmctional SO removal catalyst systems have been ia commercial use siace 1985 ia the United States. Such systems have successfully reduced SO emissions in the FCCU regenerator by 50% when the regenerator is operating in the complete CO combustion mode (45). Modern-day additives can achieve a 50% SO reduction with only IS—2% of the additive in the circulating inventory, an amount small enough not to interfere with the cracking characteristics of the bulk FCC catalyst (45). 

It would be desirable to make sample prototype tooling and analyze the flow effects on a product that is likely to present a flow problem. In addition to the usual physical testing of the product, the use of photo-stress analysis techniques plus the exposure to selected solvents to check for stress crack characteristics would lead to changes in the product to minimize the effects of the molding on the product performance. As an example there have been cases in the past where piano keys with frozen-in stresses have been released from perspiration, leaving open flow lines (Chapter 5, STRESS ANALYSIS). 

The earliest catalyst developed for commercial use was produced from naturally occurring bentonitic-type clays. Such clays are carefully selected and further refined and activated by chemical means to bring out their latent cracking characteristics. A typical analysis of this type of commercial catalyst follows ... 

Fig. 6.2.9. Indentation /strength model system, (a) Vickers indenter, peak load P, generates median/radial crack, characteristic dimensions (value c0 at completion of contact cycle, with further post-indentation, supercritical extension to c0, if exposed to moisture), (b) Tensile field a in combination with residual ( ghost ) contact field, drives crack system to failure. (After Marshall and Lawn, 1980)...

Miskokzi et al. [8] stndied the cracking characteristics of low-density PE in the presence of different zeolite catalysts (Figure 27.10) H-ZSM-5, FCC catalysts and clinoptilolite... 

In the process of catalytic cracking, characteristic reactions such as chain scission, hydrogen transfer and condensation take place under certain temperature and pressure conditions and when an appropriate catalyst is utilized, products with certain range of molecular weights and structures are obtained. Catalysts with surface acid sites and with the ability of hydrogen ion donation such as silica-alumina and molecular sieve catalyst have been already widely utilized. These catalysts can also enhance the isomerization of products and increase the yield of isomeric hydrocarbons. However, large amounts of coke will deposit on the surface of catalysts and consequently lead to their deactivation. Therefore, the recycling of catalysts is difficult to achieve. 

This factor has been shown to be additive on a weight basis. It was originally devised to show the thermal cracking characteristics of heavy oils thus, highly paraffinic oils have K of from 12.5 to 13.0 while naphthenic oils have K of from 10.5 to 12.5. 

H.C. Choe, Stress corrosion cracking characteristics of shot-peened stainless steel containing Ti, Han guk Pyomyon Konghak Hoechi 37 (2004) 350-359. 

Bentur A. and Kolver K. Evaluation of early age cracking characteristics in cementitious systems. Materials and Structures 2003 36(4) 183-190. 

Comprehensive evaluation of cracking characteristics of box girder high... 

Malfunction Under Static Load. Whenever pipes are subjected to excessive stress by static interior pressure to such a degree that they malfunction, the attained stress level is closely related to the quality of the pipe in question. The static stress level KS is defined as KS = ajcrs, whereby a stands for the rated stress in the direction of the pipe circumference, while ag constitutes the cracking resistance of the pipe material. The pipe quality— one measure for it is the defect magnitude in the pipe section—is described by the nondimension al crack characteristic... 

According to Equation (5-22), a static stress level of that magnitude requires a mean crack characteristic of... 

The actual crack characteristic of the pipe section with a crack length / L = 100 mm, a crack depth 3 mm, and a wall thickness 5 = 8 mm is... 

Figure 5.17 Interrelationship between crack characteristic, dynamic load, and endurable number of stress cycles [5-21].

Equation (5-25) can be practically applied as follows. The pipe section to be examined has a specific crack characteristic KR subjected to a stress KG. Equation (5-26) permits the computation of a mean endurable number of stress cycles Nq. However, if the pipe section has been subjected to N number of stress cycles, the failure probability is expressed by... 

The following example reveals the type of results which can be obtained with the help of Equation (5-27). The pipe section is again the same one which has been used for the explanation of static behavior. However, now it is assumed that the pipe section is subjected to a dynamic stress with a characteristic/CC = 187.5. A crack characteristic A"/ = 4.7 has already been determined for the pipe section. During the operation time given, the pipe section is scheduled to sustain N = 2500 stress reversals of the stress magnitude KG. The question is What is the failure probability of the pipe section at the end of the stress period (operation period) ... 

The Failure Rate of Pipe Sections. Based on Equation (5-26), it will be possible to determine the failure rate of pipes as a function of operation time, stress frequency, and pipe quality. The pipe quality is thereby characterized by the crack characteristic KR. With the help of an example, the failure rate is determined and compared to values from the literature. 

In the case of defective pipes, however, the failure rate undergoes a drastic change. For crack characteristic KR = 5, the computation was... 

Testing in gaseous hydrogen results in the same crack characteristics produced in aqueous solution test [34,40]. 

Durability of the ferrocement elements is a function of cover depth and cracking characteristics. When improved durability in a corrosive environment is required, a small diameter reinforcement with high specific surface should be used, and impermeability of the matrix should be ensured by additional measures. In such a case, as well as for liquid retaining structures, the admissible crack width is up to 0.02-0.05 mm, while for ordinary structures and in ordinary conditions 0.10 mm is considered as acceptable for ferrocement. 

The importance of the angle 0 between aligned fibres and the direction of principal tension has been confirmed for various measures of fibre efficiency. The strength and cracking characteristics depend directly on that angle. However, the shape of all obtained curves is essentially different from that shown for advanced composites, for example by Kelly and Davies (1965). The difference is due to such mechanisms as pull-out of fibres and passing of... 

A powerful and persistent antioxidant/emtiozonant having excellent anti-flex and anti-groove cracking characteristics coupled with long term antiosonant properties. Not leached out by water. 

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