Flake


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flake

Archaeol
a. a fragment removed by chipping or hammering from a larger stone used as a tool or weapon
b. (as modifier): flake tool

Flake

 

in archaeology, the name for chips struck from a piece of flint or flint core by human hands. Flakes varied in shape and size. During the Stone and Bronze ages, tools, including knives, were made from flakes.


Flake

 

an internal crack in forged or rolled steel products, and sometimes ingots and cast articles, that markedly detracts from the desired mechanical properties of the steel. In pickled micro-sections, flakes are identified as hairline cracks; in the fracture testing of hardened specimens, flakes are oval, crystalline spots of a silvery white color distinguishable from the primary gray mass of the fracture. The steels most susceptible to flake damage are alloyed and carbon martensitic and pearlitic steels used for structural members, bearings, armor, and rails. Defects of this type are not found in austenitic or carbide steels (stainless and high-speed steels).

The principal cause of the formation of flakes is the presence of excessive hydrogen, and the mechanism most likely responsible is adsorption of hydrogen on the surfaces of microscopic irregularities, which reduces surface energy and makes destruction easier. Flakes originate in zones with heightened adsorption of hydrogen. The formation of such zones stimulates internal tensile stresses that arise in the steel during structural transformations, plastic deformation, and uneven cooling. Flake development is also promoted by a reduction in the metal’s resistance to destruction in places where stresses have concentrated near accumulations of defects of the crystal lattice, as well as by concentrations of nonmetallic inclusions and segregated inhomogeneities. Flakes may be controlled by thermal treatment of the parts under special conditions and by subjecting the molten steel to a vacuum, which reduces the hydrogen content to a safe level.

REFERENCES

Dubovoi, V. la. Flokeny v stali. Moscow, 1950.
Moroz, L. S., and B. B. Chechulin. Vodorodnaia khrupkost’ metallov. Moscow, 1967.

V. L. SAFONOV and M. L. BERNSHTEIN

flake

[flāk]
(materials)
Dry, unplasticized, cellulosic plastics base.
Plastic chip used as feed in molding operations.
A small, flat wood particle of predetermined dimensions and uniform thickness, with fiber direction essentially in the plane of the flake.
(metallurgy)
Discontinuous, internal cracks formed in steel during cooling due usually to the release of hydrogen. Also known as fisheye; shattercrack; snowflake.
Fish-scale, flat particles in powder metallurgy. Also known as flake powder.
References in classic literature ?
One winter's day, when the flakes of snow were flying about, he spread the skirts of his blue coat, and caught the snow as it fell.
he said, shaking the white flakes from his clothes;
The darkness grew apace; a cold wind began to blow in freshening gusts from the east, and the showering white flakes in the air increased in number.
The narrative commenced by a description of a Saxon peasant's hut, situated within the confines of a great, leafless, winter forest; it represented an evening in December; flakes of snow were falling, and the herdsman foretold a heavy storm; he summoned his wife to aid him in collecting their flock, roaming far away on the pastoral banks of the Thone; he warns her that it will be late ere they return.
The stones fell thick as the flakes of snow which some fierce blast drives from the dark clouds and showers down in sheets upon the earth--even so fell the weapons from the hands alike of Trojans and Achaeans.
As I thus mused, with half-shut eyes, while the sun sank rapidly to rest, and eddying currents careered round and round the island, bearing upon their bosom large, dazzling, white flakes of the bark of the sycamore-flakes which, in their multiform positions upon the water, a quick imagination might have converted into any thing it pleased, while I thus mused, it appeared to me that the form of one of those very Fays about whom I had been pondering made its way slowly into the darkness from out the light at the western end of the island.
It was the middle of winter, when the broad flakes of snow were falling around, that the queen of a country many thousand miles off sat working at her window.
Smoke lowering down from chimney-pots, making a soft black drizzle, with flakes of soot in it as big as full-grown snowflakes--gone into mourning, one might imagine, for the death of the sun.
Where the paint has yielded to age and exposure and is peeling off in flakes and patches, the effect is not happy.
Flakes of falling snow were fluttering in that light.
There had been no snow up to this time, but as Diana crossed the old log bridge on her homeward way the white flakes were beginning to flutter down over the fields and woods, russet and gray in their dreamless sleep.
The flakes fell fast and thick, soon covering the ground some inches deep, and spreading abroad a solemn stillness.