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Definitions C

Capping Pass: The final pass in welding a joint sometimes conducted for cosmetic purposes.

Cartridge: Consists of casing (into which powder is loaded), bullet/projectile powder, and primer. Primer is seated into the cartridge, which is then filled with powder. Lastly, the bullet/projectile is inserted into the cartridge casing. The insertion depth of the bullet into the casing is defined by serrations rolled into the bullet.

Casing: Outside piping which is usually larger than the drill pipe and separates the geological formation from the drill pipe that is drilling into the geological formation.

Casting Porosity: A property of cast metal that causes the metal to appear sponge-like under high magnification. Porosity is inherent in the casting process. A casting cannot be produced with porosity at some level. It can be caused by internal shrinkage, gas evolution, oxide films, inclusions, etc. The presence of casting porosity does not render the casting defective. A certain level of casting porosity is acceptable in most products.

Casting Porosity in aluminum
Casting porosity in aluminum electric motor cooling fan.
 

Cathode: A negatively charged electrode space as in an electrolytic cell or a storage battery.

Cathodic Protection A technique used to control the corrosion of a metal surface by making the metal surface to be protected a cathode of an electrochemical cell.

CD4MCu: CD4MCu is a short notation for a type of duplex stainless steel alloy. The chemical composition or chemical makeup, consists of intentional additions of chromium (Cr), nickel (Ni), copper (Cu), and molybdenum (Mo) added to iron (Fe). The annealed duplex microstructure should consist of two major components ferrite and austenite. Properly cast, the result will be an alloy with moderately high strength and hardness combined with good impact and ductility properties. Alloy CD4MCu has superior resistance to abrasion and erosion-corrosion. In environments containing chlorine (or chlorides) this alloy is highly resistant to stress-corrosion cracking.

Charpy Impact Test: A standard test where a specially machined test specimen is subjected to a very sudden impactn  force. The Charpy impact test is conducted in equipment specifically designed for impact testing. The results indicate the toughness or ability to absorb impact loading of the metal.

Cheater Bar: A length of bar or pipe which, when placed into or over an object or handle or pipe, allows more movement arm leverage or rotational force to be exerted on the device.

Chemical Analysis: A laboratory process of ascertaining the chemical constituents or makeup of an item of interest. For example, just as a cake may have certain constituents like flour, sugar, chocolate, etc., a piece of steel will be made up of a variety of chemical constituents such as iron, carbon, manganese, silicon, chromium, etc.

Chevron Marks: Often left on a fracture surface because of a fracture process. Physical features created because of fractures, which rapidly progress through the structure. Chevron marks are extremely useful to the failure analyst and point to where the crack ultimately originated.

A clear set of chevron marks is shown below. The chevrons point towards the left indicating the fracture origin for the portion of the crack is located to the left.

Chevron Marks
 

Chevrons, in the lower smooth fracture of a turntable slewing bearing are shown below. The chevrons in the hardened bearing case clearly point to the right. Therefore, this particular crack originated towards the right in this Photograph.

Chevrons from Turntable Slewing Bearing Fracture
 

Clamping Force: The compressive force that a tightened joint exerts as a result of the bolted joint.

Clamshell Marks: See Beach Marks.

Cleavage Fracture: Fracture mechanism that is found in stronger metal and occurs at lower temperatures. Cleavage can also be associated or found when failure occurs at high rates of energy input. In cleavage fracture, the fracturing process is occurring along selected atomic planes; for example, the cleavage planes, within the individual metal grains.

The photograph below shows an example of cleavage fracture produced by an SEM.

SEM of Cleavage Fracture
cleavage fracture in steel at a magnification of 2000x.
 

Cold Work: Deformation of a metal at temperatures below the temperature at which the metal will recrystallize.

Collar: The threaded coupling that is threaded onto the upper end of a joint of pipe. The coupling is the end of the tool joint facing up during drilling of the well. The coupling is threaded to receive the threaded or pin end of the upper drill pipe joint.

Corrodent: Any chemical species or compound, which will by chemical action, oxidize, rust or eat away a metal.

Corrosion Failure: Occurs when the metal wears away or dissolves or is oxidized due to chemical reactions, mainly oxidation. It occurs whenever a gas or liquid chemically attacks an exposed surface, often a metal. Corrosion is accelerated by warm temperatures and by acids and salts. Corrosion products such as rust or patina can remain on the surface and protect it. Removing these deposits re-exposes the surface, and corrosion restarts and/or continues. Some materials resist corrosion naturally; others can be treated to protect by coating, painting, galvanizing, or anodizing against corrosion. An example of salt-water corrosion of a cast iron bathtub is shown in the photograph below.

Example of corrosion on cast iron metal surface.
Example of salt water corrosion on cast iron metal surface.
 

Cases involving corrosion failures:

Swimming Pool Corrosion Staining
Corroded Pipe
Corrosion Failure Analysis
Failed Ammonia Pipe

Coupling: A section of tubing with internal threads from both ends which is used to joint two pieces of pipe together. Typically, a coupling has a larger diameter than the pipe to be joined.

Crack: A disruption in the normal continuum of a metal structure or component. Cracks normally, but not always, start or initiate at the metal surface. A surface crack may be visible to the unaided eye but can be more easily observed using non-destructive testing/inspection methods (NDT). For iron, steel and magnetic materials a magnetic particle inspection (MPI) is an easy and reliable inspection method. Another NDT method is x-radiography. Surface inspection and x-radiography are limited in that they do not readily indicate the depth and therefore the full extent and criticality of the crack. Other NDT techniques and destructive testing are used to fully assess the extent, magnitude and criticality of a crack.

Crack Stop Mark: When a crack is proceeding through a structure there may not be sufficient energy or driving force to extend the crack all the way through the structure. When the crack halts and then later restarts, a crack stop mark will be created on the fracture surface after the component fails. Such a crack stop mark on the fracture surface is literally a fingerprint that identifies the cracking process as being intermittent cracking; for example the crack intermittently progressed, as opposed to complete, instantaneous fracture.

Crack Weeping: When a very minor amount of fluid weeps or seeps from tight cracks. This weeping enhances visualization of many tight cracks.

Creep Failure: A deformation and failure process whereby the metal in question will deform at a low temperature and under the influence of a low stress. Typically metals are believed to creep (stretch and deform as time passes) at stresses below their yield strength. Typically creep will occur at 30-40% of the metal’s melting point.

Crimp: Process whereby two pieces of metal are squeezed together. The crimping process in the subject crimp clamps tightens the clamp because one end, the tension strap, is fixed (not moveable) and the clamp circumference and diameter are reduced around the plastic PEX pipe.

Crimping Serrations: Serrations circumferentially placed on the bullet where the bullet makes contact with the cartridge casing. Serrations provide mechanical joints between the bullet and the casing.

Crystallographer: One who studies the crystal structure and how the individual atoms are arranged on a three-dimensional lattice in space.

Cup and Cone Fracture: When a circular wire, rod or round tensile test specimen is stressed by tension/pulling beyond the yield point or yield strength, the metal will become plastic and will flow at the weakest location. The circular cross-section at this location will be diminished (necking). As the stressing/pulling continues, the metal will separate or fail at this location. The resultant fracture surface will have a characteristic appearance. One side of the fracture will appear to be a cup and the mating pointed fracture will appear to be a cone. This type of tensile overload fracture is referred to as cup and cone.

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J.E.I. Metallurgical, Inc.

5514 Harbor Town
Dallas, Texas 75287

Phone: (972) 934-0493
Fax: (469) 737-3938
Email: r.c.jerner@metallurgist.com

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