Chapter U: U U.V.

Udimet 700

A nickel-based cobalt alloy containing 47-59% nickel, 17-20% cobalt, 13-17% chromium, 4.5-5.7% molybdenum, 3.7-4.7% aluminum, 3-4% titanium, 0-1 iron, and 0-0.1% carbon.

UEL

Abbreviation for upper explosive limit.

UL

Abbreviation for Underwriters Laboratories, Inc.

ultimate strength

The maximum unit stress (tensile, compressive, or shear) that a material can withstand before or at rupture.

Ultimet

A trademark of Haynes International, Inc. for a line of cobalt-based alloys having high-strength, excellent resistance to corrosion, and exceptional wear resistance. Used in welding electrodes and wire.

ultrahard abrasive

Another name for superabrasives.

ultrasonic frequency (ultrasonics)

Describing high-frequency sound vibrations beyond the limit of human hearing of audible frequencies (about 20 kHz= 20,000 cycles per second). Used for descaling and cleaning metal parts, friction welding and fluxless soldering, degassing and solidification of molten metals, electroplating, drilling very hard materials, nondestructive testing of materials.

ultrasonic waves

Waves or vibrations of high-frequency sound. They include longitudinal, transverse, surface, and standing waves.

ultrasonic welding

A rapid, fluxless welding process using high-frequency (20-40 kHz) sound waves (ultrasonic vibrations) to create vibrational energy that is directed to the interfaces to be joined. This focused energy creates friction caused by molecular excitation, becoming the heat source that causes the plastics to melt. Thus, it is a kind of friction welding. Metals that can be soldered by this method include aluminum, brass, copper, germanium, magnesium, silicon, and silver.

undercut, gear

A condition in generated gear teeth when any part of the fillet curve lies inside of a...