| U-bend |
U-bend A 180° bend in a pipe. |
| U-bolt |
A rod threaded at both ends and bent into a U-shape. It is used for clamping. |
| U-bolt |
An externally threaded fastener bent in the shape of the letter U and with both ends threaded. |
| Ultimate strength |
The maximum tensile strength a bolt or material can support prior to rupture. Always found in the plastic region of the stress–strain or force–elongation curve, and so is not a design strength. Also called Tensile strength and ultimate tensile strength. |
| Ultimate strength |
The maximum stress (tensile, compressive, or shear) a material can sustain without fracture, determined by dividing maximum load by the original cross-sectional area of the specimen. Also known as nominal strength or maximum strength. |
| Ultrasonic extensometer |
An electronic instrument which measures the change in length of a fastener ultrasonically as, or before and after, the fastener is tightened. |
| Ultrasonic method |
Measuring elongation uses a sound pulse, generated at one end of a bolt, that travels the length of a bolt, bounces off the far end, and returns to the sound generator in a measured period of time. |
| Uniaxial strain |
Increase (or decrease) in length resulting from a stress acting parallel to the longitudinal axis of the specimen. |
| Uniform elongation |
The elongation at maximum load and immediately preceding the onset of necking in a tension test. |
| Uniform strain |
The strain occurring prior to the beginning of localization of strain (necking); the strain to maximum load in the tension test. |
| Union (union joint) |
A threaded pipe fitting that allows two pipes to be connected anddetached without the need for either to be rotated, and without damaging the pipe ends. |
| Unison ring |
In a turbomachine with adjustable guide or stator vanes, the ring to which a set of vanes is linked such that when the ring is rotated, all vane angles are adjusted. |
| Unit |
A numerical indication of the magnitude of a physical quantity. The basic units of mass, length, time, etc. are relative to agreed standards. |
| Universal joint (Hooke’s joint) |
A double-pivoted connection that allows power and torque to be transmitted between two shafts at an angle to each other. For constant driving angular velocity of the input yoke, the angular velocity of the output yoke fluctuates by amounts depending on the angle of intersection of the shafts. Speeds of the driving and driven shafts may be made identical (giving a constant-velocity joint) when an intermediate shaft, at each end of which there is a universal joint, is interposed. The driving and driven shafts must be equally inclined to the intermediate shaft, the two forks of which must lie in the same plane. |
| U-tube |
A device consisting of two vertical tubes connected at either the top or bottom by a length of tubing such that a U-shape is formed. |
