Glossary 357
thermoplastic: A type of plastic that can be
easily reheated and reshaped with little or no
damage to the plastic because there is little or
no bonding between the chains. (14)
thermoset plastic: A type of plastic that is
generally stronger than thermoplastic
because it is cured with heat and pressure
to crosslink the chains. Once they have been
cured, it can no longer be reshaped and will
remain rigid even when heat is applied. (14)
three-dimensional (3-D) model: A type of model
that can be made out of products like clay,
plastic, wood, and foam, or can be drawn
using 3-D CAD software. (2)
thrust: The forward force acting on an aircraft
or spacecraft created by air or gasses being
pushed to the rear. (13)
thumbnail sketch: See rough sketch. (4)
ties: Braces that resist tension. (9)
torque: The measure of how much force acting
on an object causes that object to rotate. (10)
torsion: A turning force that is applied to a
material or structure. (9)
total robotic station: Tracks the survey rod and
calculates the distance and angle without the
need of the surveyor standing at the station. (9)
total station: A surveying instrument designed
to measure both distance and angles. (9)
trade-off: Something an engineer gives up in
order to meet specifi cations while staying
within the constraints; the consideration
that gaining one positive quality in a design
means you lose one other quality. (1, 4)
tradespeople: Workers who create the design
products. (1)
transistor: A device used as a solid state switch
or amplifi er. (8)
troubleshoot: To systematically search for the
cause of a failure. (8)
truss: A structural element used in a number of
civil engineering structures, as supports for
roofs and fl oors to bridges. (9)
truss bridge: A type of bridge that uses a truss,
which allows for the load to be spread out
through all of the structural members in the
truss. (9)
turbulent fl ow: A chaotic or abnormal fl ow
consisting of swirls, or eddies. (15)
U
ultrasonic test: A test that uses sound waves
that “bounce off” changes in the material
to determine the internal composition of a
material. (7)
United States Army Corps of Engineers: The
largest employer of civil, structural, and
architectural engineers, as well as land
surveyors. This organization is responsible for
building military and civil works throughout
the United States and the world. (9)
V
valence shell: An atom’s outer ring of
electrons. (8)
valve: A device used to control either the rate or
direction of the fl uid fl ow. (10)
variable resistor: A resistor whose resistance can
be changed, usually by rotating a knob or
sliding a switch. (8)
velocity fl owmeter: A type of fl owmeter that
measures the speed of passing fl uid and the
depth of the fl uid. (15)
viscosity: The thickness of a liquid, or its
resistance to being deformed. (15)
volt: The base unit of voltage. (8)
voltage: The amount of pressure behind the fl ow
of electrons. (8)
voltmeter: A meter that is used to measure
voltage. (8)
volt-ohm-milliammeter (VOM): A meter that
is used to measure voltage, current, and
resistance. (8)
W
waste: A by-product of chemical operations.
Some waste materials can be reused in the
plant or sold to other companies. Waste that
cannot be reused or sold must be disposed of
in compliance with local regulations. (15)
watt: A unit of electrical power. (8)
Watt’s law: The law that states that power equals
effort multiplied by rate. (8)
wedge: A simple machine that is a combination
of two inclined planes. (10)