Page 337 - Mechanical Engineer's Data Handbook

GLOSSARY OF TERMS 325

second moment of area The second moment of area a vertical shaper, broach or grinding wheel.
of a plane figure about any axis XX is I,,=Zar2, S-N curve A graph of stress to cause fracture against
where a = an element of area, r = perpendicular dis- number of stress fluctuations in fatigue tests.
tance of a from XX. soldering A similar process to brazing, but with a
seizing The stopping of a moving part by a mating low-melting-point filler, e.g. alloy of lead, tin, anti-
surface due to excessive friction caused by ‘galling’. mony.
sets In mathematics, any collection of ‘entities’ (el- solenoid A current-carrying coil often with an iron
ements) defined by specifying the elements. See: ‘Venn core used to produce a mechanical force.
diagram’. solution heat treatment Heating an alloy and allow-
shaft A circular section solid or hollow bar used for ing one or more constituents to enter into solid
the transmission of motion and/or power. solution.
shaft coupling A solid or flexible device for connect- spark erosion machining The removal of metal by
ing, usually coaxial, shafts. means of a high-energy spark between the workpiece
shear A force causing or tending to cause adjacent and a specially shaped electrode, all immersed in a
parts of a body to slide relative to one another in the bath of electrolyte.
direction of the force. specific fuel consumption The mass of fuel used in an
shearing process A machine process in which shapes engine per unit of energy delivered. Unit: kilograms
are produced from plate by shearing through the per megajoule (kg MJ-I).
material. specific heat capacity The quantity of heat required
shear modulus (modulus of rigidity, torsional to raise the temperature of unit mass of a substance by
modulus) The ratio of shear stress to shear strain one degree. Unit: J kg-’K-’.
within the elastic limit. specific speed A dimensionless quantity used in the
shear stram and stress See: ‘strain’ and ‘stress’. study of rotodynamic pumps and turbines. It is the
shell mding A mould of thermosetting resin same for geometrically similar machines.
bonded with sand formed on a heated metal pattern to specific volume The volume per unit mass of sub-
give a ‘shell‘. stance. Unit: cubic metres per kilogram (m3 kg-’).
shim A thin piece of metal used between two mating spinning Shaping of hollow metal sheet parts by
surfaces to obtain a correct fit, alignment or adjust- rotating and applying a force.
ment. splines Narrow keys integral with a shaft engaging
shrink fit An ‘interference fit’ between a hub and with similarly shaped grooves in a hub used instead of
shaft, for example obtained by heating an under-sized keys.
hub to give a clearance and allowing it to cool on the spot facing Machining flat circular faces for the
shaft. Alternatively, the shaft may be cooled, e.g. by seating of nuts, bolts, etc.
using ‘dry ice’. spring A device capable of elastic deflection for the
silver solder A brazing alloy of low melting point purpose of storing energy, absorbing shock, maintain-
containing silver. ing a pressure, measuring a force, etc.
simple hprmoRic motion Oscillatory motion of spring wpsber A name for many types of washer
sinusoidal form, e.g. simple pendulum, mass and which deflect when compressed and prevent a nut, etc.,
spring, electric current in a tuned circuit. It follows the from slackening.
law d2x/dt2 = --wxz. Abbreviation: s.h.m. stagnation temperature The temperature which
sine bar A hardened steel bar carrying two plugs of would be reached by a stream of fluid if it were brought
standard diameter accurately spaced to a standard to rest adiabatically.
distance. Used in setting out angles to a close toler- standard deviation The root of the average of the
ance. squares of the differences from their mean X of a
single-point tool A machine tool which has a single number n of observations x: standard deviation
cutting point as opposed to a number of points, e.g. a a = J W
lathe tool. static balancing Balancing of a rotating mass in one
sintering The bonding of particles by heating to form plane only. See: ‘dynamic balancing’.
shapes. static pressure The pressure normal to the surface of
slotting Cutting a groove with a reciprocating tool in a body moving through a fluid.