- Aerobic Bacteria
- Anaerobic Bacteria
- Back Flow Valve
- Beach Marks
- Biological Corrosion
- Bolt vs. Cap Screw
- Bolt Circle
- Bolt Holes
- Bolt Shank
- Breakout/Breakaway Torque
- Brittle Fracture
- Bucked End
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.
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.
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.
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.
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.
Overall view of failed screwdriver shaft.
A close-up, magnified view of the screwdriver shaft brittle fracture is shown in the photograph below.
Closeup of brittle fracture on screwdriver shaft.