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Definitions A-B

Acetone: A colorless, flammable liquid which is a common solvent. Acetylene readily dissolves in acetone which is dispersed in a porous mass inside the acetylene cylinder shell.

Acetylene: A colorless and highly flammable gas; C2H2 can be explosive. It is unstable in pure form and is usually handled in solution.

Aerobic Bacteria: Any bacteria requiring free oxygen to assist in the metabolic breakdown of materials.

Anaerobic Bacteria: Any bacteria that does not require free oxygen to assist in the metabolic breakdown of materials.

Anode: A positively charged electrode (or area) such as an electrolytic cell or a storage battery.

Austenitized or Austenization: A high temperature heating process where the steel is heated above the austenization temperature (which varies with the composition of the steel). Holding above the austenization temperature converts the steel to a face centered cubic microstructure or phase with carbon dissolved in the austenite.

Back Flow Valve/Non-Return Valve: A mechanical valve which normally only allows liquids or gas to only flow in one direction.

Bar: Measure of pressure. One atmosphere is equal to 1.01325 Bar. One Bar is equal to 14.5038 psi.

Beach Marks or Clam Shell Marks: Created during the growth of a crack and are the result of a cessation and restarting of stress, a marked change in stress and/or a marked change in the chemical environment in which the component and progressing fatigue crack has been operating. A fatigue fracture will contain beach marks. Beach marks are mixed in with fatigue striations and are found on a fracture surface. Several beach marks are noted with arrows in the scanning electron micrograph, shown below.

Biological Corrosion: Corrosion activity which results in the deterioration of metal as a result of the activity of living organisms.

Blowpipe (see Torch): A handheld torch through which gases combine (for instance acetylene and oxygen) during welding or brazing. It can also be used in cutting.

Bolt: A fastener which is secured in place by a nut.

Bolt vs. Cap Screw: Fasteners which form or clamp a joint by being rotated into a nut or the nut rotated onto the bolt. A cap screw is a fastener that can look identical to a bolt that forms a joint by being rotated into a threaded hole.

Bolt Circle: A circle on which a number of bolt holes are located. The wheel stud holes in an automobile or truck wheel rim is an example of a bolt circle.

Bolt Holes: Circular holes in a split wheel rim through which the bolts pass. The rim bolt holes may be straight smooth holes or chamfered to assist centering of the wheel.

Bolt Shank: The unthreaded portion of a bolt. The bolt shank is the smooth cylindrical area below the bolt head which extends to the beginning of the bolt threads.

Boss: A large mass of reinforcing metal which increases the ability of a joint to accommodate and transfer stress.

Bowing The same as bending, plastic deformation or permanent deformation. When a metal is subjected to a stress it will bend or stretch just slightly. When that stress or load which caused the stretch is removed the stretch or bend disappears and the metal returns to its original shape/form. This type of stretch is called elastic deformation. When the stress or load exceeds a certain limit (elastic limit of the metal) or amount, the stretch or bend becomes permanent. This is described as permanent deformation.

Brass: Alloys of copper (Cu) and various amounts of additional alloying elements, in many cases, zinc (Zn).

Braze: A metal joining process where a filler metal (low melting point metal) is used to join two non-melted metal components.

Brazing: Process used to join two metals (sometimes dissimilar) components. A filler metal (brazing alloy) is used to fill a small gap between the two surfaces to be joined. The filler metal is headed and melted at a temperature above about 800° F. The filler metal adheres to both metals being joined (if those metals and their respective surfaces have been properly prepared) and when the filler metal solidifies forming a strong metallurgical bond joining the two metal pieces.

Breakout or Breakaway Torque (ft. lb.): In physics and mechancis, torque is rotational force, or the force necessary to cause an object to rotate around an axis. In most cases, more torque is needed to start the rotational motion than is needed to keep it going once it has begun. This initial force is called breakaway torque. 

Brittle Fracture: In contrast to ductile fracture, brittle fracture occurs without stretching. Metals that fail by brittle fracture are said to fail in a brittle mode or manner. Brittle failures are characterized by a lack of deformation (stretching or necking), especially at the fracture face or surface. An example of brittle fracture is shown in the below photographs.

Screwdriver Brittle Fracture
Overall view of failed screwdriver shaft.

A close-up, magnified view of the screwdriver shaft brittle fracture is shown in the photograph below.

Failed Screwdriver Shaft
Closeup of brittle fracture on screwdriver shaft.

Bucked End: The end of the rivet opposite the rivet head. This end is often referred to as the field end or the bucked end; it is the end of the rivet which is formed during the joining process.

Burnishing: Plastic (permanent) deformation resulting from one surface sliding on another object. Metal polishing and/or metal transfer may result.

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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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