Crack development

Such behavior is observed with alkah and alkahne earth oxidations where the oxide volume is less than the metal volume and cracks develop in the product coat, permitting ready access for further reaction. 

Coupon tests involved a number of metallurgies and were done to evaluate precipitator-plate alloys. Test stainless steel plates failed, not only because of pitting but also because stress-corrosion cracks developed. 

When diene rubbers are exposed to ozone under stressed conditions cracks develop which are perpendicular to the direction of stress. Whilst ozone must react with unstressed rubber no cracking occurs in such circumstances nor when such rubber is subsequently stressed after removal of the ozone environment. For many years such rubbers were protected by waxes which bloomed on to the surface of the rubber to form an impermeable film. This was satisfactory for static applications but where the rubber was operating under dynamic conditions the wax layer became broken and hence less effective. 

When an iron is exposed to an oxidising atmosphere, it develops a scale which consists of a series of layers of oxides of varying composition. The thickness of the scale naturally depends on the temperature and the duration of oxidation (/). The scale does not, however, thicken at a uniform rate with time since its very presence reduces the accessibility of the metal surface to the oxidising gases. Ideally, the thickness of the scale should increase as /t, but in practice cracks develop in the scale, and these allow the gases to reach the metal surface somewhat more readily than is postulated by this relationship. Cracking will always tend to occur as the film... 

TP cracking develops under certain conditions of stress and environment sometimes on a microscale. Because there are no fib-... 

For the designer it is not important whether cracking develops upon exposure to a benign or an aggressive medium. The important considerations are the embrittlement itself and the fact that apparently benign environments can cause serious brittle fractures when imposed on a product that is under sustained stress and strain, which is true of certain plastics. 

Stress- and thermal-related cracks develop caused by rapid load swings. 

Cracking can be caused by numerous physical and chemical phenomena in Portland cement materials. For example, freeze-thaw damage and ASR manifest themselves through crack development that may be studied using MRI. In addi-... 

A typical and stressing problem of cryogenics is that defects, leak or cracks develop when the system is at low temperature and in vacuum, but the repair is only possible at room temperature. 

Ab der-Halden A continuous process for distilling coal tar. It is operated under reduced pressure with the heat provided by five, superheated steam. This provides a clean separation of the products, without cracking. Developed in France in the 1920s by C. Ab der-Halden who formed the company PROABD to exploit it. PROABD is now a division of BEFS Technologies, Mulhouse, France, which offers this process and others under the same trade name. Not to be confused with the Abderhalden reaction in biochemistry. 

DCH (1) [Direct contact hydrogenation] A process which uses catalytic hydroprocess-ing to re-refine spent lubricating oils to produce clean fuel, lubricating oil base stocks, or hydrocarbon feedstock for cracking. Developed by UOP but not commercialized as of 1991. 

Gasmaco [Gas Machinery Company] A process for making a substitute natural gas from petroleum fractions and residues by thermal cracking. Developed from the Hall (2) process in the 1940s by the American Gas Association. See also Petrogas. 

Gulf HDS A process for hydrorefining and hydrocracking petroleum residues in order to make fuels and feeds for catalytic cracking. Developed by the Gulf Research Development Company. See also hydrodesulfurization. 

MHC Unibon [Mild hydrocracking] A mild hydrocracking process for desulfurizing gas oil and converting it to lower molecular weight hydrocarbons, suitable for further processing by catalytic cracking. Developed by UOP. 

MHDV [Mobil Hydrogen Donor Visbreaking] A modified visbreaking process in which a hydrogen donor stream from the oil refinery is added to the heavy hydrocarbon stream before thermal cracking. Developed by Mobil Corporation... 

THERMOCAT A petroleum cracking process which combines frxed-bed catalytic cracking with steam cracking. Developed by Veba Oel and Linde from 1994. See PYROCAT. 

UMATAC A process for extracting hydrocarbons from tar sands. The sand is heated in a rotating kiln in which the tar is thermally cracked. Developed in Calgary, Canada, in the 1970s by UMATAC Industrial Processes. It had not been commercialized byl984. 

A kind of shelter was built around the Chernobyl nuclear block after it exploded. It was okay for some time, but then huge cracks developed. It still spews radiation, which comes through all the cracks. On certain days you can feel it. Anyone can tell you when there was another spew of radiation, because you feel dizzy or you get a headache. One of my students had family who lived near Chernobyl, and... 

What if cracks develop in the ton cylinder flexible connection ... 

Thinning of the anodic oxide coverage is found at sharp 90° edges of the substrate. This effect has been ascribed to oxide stress, because similar results are found for low-temperature thermal oxidation under conditions where viscous flow is not present. For oxide thicknesses in excess of about 100 nm, cracks develop in... 

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