Quill shaft coupling

A coupling that is both laterally and torsionally flexible. Angular misalignment, parallel offset, and torsional fluctuation are accommodated by elastic deformation of a relatively long slender shaft. Quill shaft couplings cannot accommodate for axial displacement.

Quench Annealing

Annealing an austenitic ferrous alloy by solution heat treatment followed by rapid quenching.

Quench Cracking

Fracture of a metal during quenching from elevated temperature. Most frequently observed in hardened carbon steel, alloy steel, or tool steel parts of high hardness and low toughness. Cracks often emanate from fillets, holes, corners, or other stress raisers and result from high stresses due to the volume changes accompanying transformation to martensite.

Quench Hardening

(1) Hardening suitable alpha-beta alloys (most often certain copper to titanium alloys) by solution treating and quenching to develop a martensitic-like structure. (2) In ferrous alloys, hardening by austenitizing and then cooling at a rate such that a substantial amount of austenite transforms to martensite.

Quench-Age Embrittlement

Embrittlement of low-carbon steels resulting from precipitation of solute carbon at existing dislocations and from precipitation hardening of the steel caused by differences in ferrite at different temperatures. Quenchage embrittlement usually is caused by rapid cooling of the steel from temperatures slightly below Ac1 (the temperature at which

Quenching

Rapid cooling. When applicable, the following more specific terms should be used: brine quenching , caustic quenching , cold die quenching , forced-air quenching , intense quenching , oil quenching , press quenching , spray quenching , direct quenching , fog quenching , hot quenching , interrupted quenching , selective quenching , time quenching , and water quenching .

Q Bridge

An alternating-current bridge used principally to determine the Q of capacitors and inductors. Bridges are usually used for audio-frequency Q determinations; resonant-type Q meters are generally used for measurement of radio-frequency Q.

Quality Engineering

A field of engineering that deals with quality assurance and quality control in the production of components, circuits, and systems.

Quantization Distortion Power

The level of the distortion in a signal resulting from QUANTIZATION. It is expressed in microwatts, milliwatts, or watts. It can also be expressed as a percentage, or as a level in decibels, relative to the power level of the input signal.

Quantum Theory

The theory that the emission or absorption of energy by atoms or molecules occurs in discrete packages or units, rather than continuously. Each unit is the emission or absorption of an energy packet called a QUANTUM. Thus, radiant energy is thought to be divided into quanta.