Cracks microcracks

All large lumps or particles contain cracks, microcracks or lines of weakness. Any normal particle structure will contain imperfections, dislocations and... 

M. Kachanov, On Modelling of a Microcracked Zone by a Weakened Elastic Material and Statistical Aspects of Crack-Microcrack Interactions, Inti. J. Fract., 37, R55-R62 (1988). 

The effects of tensile stress in the various layers of nickel plus chromimn coatings are complex, and internal stress in both chromium and nickel (postnickel strike or PNS) layers can be harnessed to produce beneficial cracking ( microcracking ). 

Also optional (as prevention is imperative but not for all purposes sufficient) is a 100% inspection by highly sophisticated camera systems to eliminate any remaining cracks, microcracks, etc., e.g., TopLine vials by Forma Vitrum. 

According to petrographic analysis, abundant gypsum deposits were detected in large and small cracks, microcracks and voids near the surface of concrete. However, the authors presented two points to show that gypsum cannot result in concrete damage ... 

A new reinforced concrete structure containing discontinuous cracks, microcracks and pores... 

Cracks, microcracks and pores become more interconnected... 

Specimen 1 contained a crack of 0,91 mm depth and a width between 0,001 mm and 0,011 mm. The tightness ring contained microcracks. 

Hard plating is noted for its excellent hardness, wear resistance, and low coefficient of friction. Decorative plating retains its brilliance because air exposure immediately forms a thin, invisible protective oxide film. The chromium is not appHed directiy to the surface of the base metal but rather over a nickel (see Nickel and nickel alloys) plate, which in turn is laid over a copper (qv) plate. Because the chromium plate is not free of cracks, pores, and similar imperfections, the intermediate nickel layer must provide the basic protection. Indeed, optimum performance is obtained when a controlled but high density (40—80 microcrack intersections per linear millimeter) of microcracks is achieved in the chromium lea ding to reduced local galvanic current density at the imperfections and increased cathode polarization. A duplex nickel layer containing small amounts of sulfur is generally used. In addition to... 

Decorative chromium plating, 0.2—0.5 ]lni deposit thickness, is widely used for automobile body parts, appHances, plumbing fixtures, and many other products. It is customarily appHed over a nonferrous base in the plating of steel plates. To obtain the necessary corrosion resistance, the nature of the undercoat and the porosity and stresses of the chromium are all carefliUy controlled. Thus microcracked, microporous, crack-free, or conventional chromium may be plated over duplex and triplex nickel undercoats. 

Kic = fracture toughness a, = size of widest microcrack (crack width for surface crack crack half-width for buried crack). 

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