T.O. 33B-1-1Glossary 18CRACKS, FATIGUE: Progressive cracks which develop in the surface caused by the repeated loading and unloading ofthe part, or by what is called reverse bending.CRACKS, FORGING: Cracks developed in the forging operation due to forging at too low a temperature, resulting inrupturing of the steel.CRACKS, GRINDING: Thermal cracks due to local over-heating of the surface being ground, generally caused by lackof coolant, improper coolant, dull wheel, too rapid a feed, or too heavy a cut.CRACKS, HEAT TREATING: See CRACKS, QUENCHING.CRACKS, HOT: Same as CRACKS, COLD, but developing before the casting has completely cooled.CRACKS, MACHINING: A surface defect generally called machining tear and caused by too heavy a cut, a dull tool,chatter, or dragging the tool over the metal when not cutting cleanly.CRACKS, NOT OPEN: Indications which are difficult to discern or prove upon the use of contrast penetrant inspectiontechniques.CRACKS, OPEN: Those flaws which can be detected by contrast penetrant inspection techniques.CRACKS, PICKLING: Cracks caused by the release of internal stresses due to metal removal by immersion in acid orchemical solutions.CRACKS, PLATING: A crack developed by the plating process, usually occurring in parts having high internalstresses.CRACKS, QUENCHING: Ruptures produced in the tempering of metal, due to uneven cooling and contracting of oneportion of a part.CRACKS, SERVICE: Ruptures that occur on a part after all fabrication has been completed and the part placed in-service. Failure may be due to fatigue, corrosion, overstressing, or undetected processing discontinuities.CRATER:(1) In machining, a depression in a cutting tool face eroded by chip contact.(2) In arc welding, depressions at the termination of a bead or in the weld pool beneath the electrode.CREEP: Time-dependent strain occurring under stress. The creep strain occurring at a diminishing rate is calledprimary creep; that occurring at a minimum and almost constant rate, secondary creep; that occurring at anaccelerating rate, tertiary creep.CREEP STRENGTH:(1) The constant nominal stress that will cause a specified quantity of creep in a given time at constanttemperature.(2) The constant nominal stress that will cause a specified creep rate at constant temperature.CREVICE CORROSION: A type of concentration cell corrosion; corrosion of a metal that is caused by theconcentration of dissolved salts, metal ions, oxygen or other gases, and such, in crevices or pockets remote from theprincipal fluid stream, with a resultant building up of differential cells that ultimately cause deep pitting.
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