Machine Design and Manufacturing Practice Review

A collection of 100 flashcards based on the Machine Design Reviewer lecture covering terminology for pressure vessels, shafts, keys, springs, and manufacturing processes.

Thin-wall Pressure Vessel

A vessel where the ratio of plate thickness to internal diameter $t/D_i$ is equal to or less than $0.1$.

Circumferential tensile stress

Also known as hoop or tangential stress, represents the fluid force resisted by the longitudinal section of a pressure vessel, expressed as $\frac{pD_i}{2t}$.

Longitudinal tensile stress

The stress resulting from fluid force acting on a ring section of a pressure vessel, equated as $\frac{pD_i}{4t}$.

Joint efficiency

The ratio of the minimum strength of a joint to the strength of the solid plate, denoted as $\eta$.

Factor of safety

A design margin taken as $5$ for specified material strengths in pressure vessel contexts.

Thick-wall cylinder

A vessel whose plate thickness is large relative to its diameter, where the ratio $t/D_i > 0.1$.

Lame's formula

A set of equations used to determine tangential and radial stresses in thick-wall cylinders.

Radial stress

The stress ($\sigma_r$) acting in the direction of the radius in thick-wall cylinders, formulaicly defined by Lame's equations.

Shaft

A rotating machine element used to transmit power by tangential force and setup torque.

Axle

A stationary member that carries rotating elements such as wheels or pulleys.

Transmission shafts

Shafts used to transmit power between a source and the absorbing power unit.

Machine shafts

Shafts that are an integral part of the machine itself, such as a crank shaft.

Lineshaft

A main shaft driven directly by a primemover.

Countershafts

Intermediate shafts located between a lineshaft and a driven machine; also called jackshafts or headshafts.

Spindles

Short shafts typically found on machines.

Torsional shear stress

The stress setup in a shaft due to the transmission of torque, related to the polar moment of inertia ($J$).

Equivalent twisting moment

Defined as $T_e = \sqrt{M^2 + T^2}$, used in the design of shafts for ductile materials under maximum shear theory.

Equivalent bending moment

Defined as $M_e = \frac{1}{2}(M + \sqrt{M^2 + T^2})$, used in shaft design for brittle materials under maximum normal stress theory.

Torsional rigidity

A design basis for shafts determined by the relationship between torque ($T$), length ($L$), and angular deflection ($\theta$).

Lateral rigidity

A design basis for shafts to limit linear deflection, calculated using the modulus of elasticity ($E$) and moment of inertia ($I$).

Key

A piece of mild steel inserted between a shaft and a hub to connect them and prevent relative motion.

Keyway

A slot or recess machined into a shaft or hub to accommodate a key.

Flat key

A rectangular section key with the smaller dimension placed in a radial direction.

Square key

A key that is square in section and may or may not be tapered.

Round key

A circular section key that fits into holes drilled partly in the shaft and partly in the hub.

Barth key

A square key with its bottom two corners bevelled.

Gib-head key

A square or flat tapered key featuring a head provided to facilitate removal.

Saddle key

A tapered key used without a keyway on the shaft, either hollow with a curvature or flat.

Flat saddle key

A taper key that fits in a hub keyway but sits flat on the shaft surface.

Hollow saddle key

A taper key shaped at the bottom to fit the curved surface of the shaft.

Woodruff key

A key that fits into a semi-cylindrical seat on the shaft.

Feather key

A key that prevents rotation while permitting the hub to move axially along the shaft.

Kennedy key

A tapered square key assembled with the diagonal dimension virtually in a circumferential direction; also called a tangential key.

Rollpin

A key driven into a hole small enough to close its slit, assembled in a radial direction.

Splines

Keys that are integral with the shaft and fit into keyways broached in the hub.

Shaft couplings

Devices used to make permanent or semi-permanent connections between shafts.

Rigid coupling

Used to connect two shafts that are perfectly aligned.

Flange coupling

A type of rigid coupling comprising two separate cast iron flanges keyed to shaft ends.

Compression coupling

Utilizes two split cones drawn together by bolts to create a tightening wedging action.

Flexible coupling

Used to connect two shafts having both lateral and angular misalignment.

Oldham coupling

A flexible coupling specifically used for shafts with lateral misalignment.

Universal Coupling

Also known as Hooke's coupling, it connects shafts whose axes intersect at a small angle.

Flywheel

A rotating member that acts as an energy reservoir, storing energy when supply exceeds demand and releasing it when demand exceeds supply.

Maximum fluctuation of speed

The difference between the maximum and minimum speeds of a flywheel during a cycle.

Coefficient of fluctuation of speed

The ratio of the maximum fluctuation of speed to the mean speed of a flywheel ($C_f$).

Screw thread

A continuous helical groove cut on a cylindrical surface.

Major diameter

The largest diameter of an external or internal screw thread, also known as the nominal diameter.

Minor diameter

The smallest diameter of a screw thread, also called core or root diameter.

Pitch diameter

The diameter of an imaginary cylinder where thread width and space width are equal; also called effective diameter.

Pitch

The axial distance from a point on one thread to the corresponding point on the next thread.

Lead

The distance a screw thread advances axially in one rotation of the nut.

Crest

The top surface of a screw thread.

Root

The bottom surface created by two adjacent flanks of a thread.

Depth of thread

The perpendicular distance between the crest and the root of a thread.

Through bolt

A cylindrical bar with threads for a nut at one end and a head at the other.

Tap bolt

A bolt screwed into a tapped hole without the use of a nut.

Studs

Round bars threaded at both ends, with one end screwed into a part and the other receiving a nut.

Cap screws

Small screws similar to tap bolts with various head shapes available.

Machine screws

Similar to cap screws but featuring a slotted head for a screwdriver.

Set screws

Used to prevent relative motion between two parts that tend to slide over one another.

Power screws

Also called translation screws, used to move machine parts against resisting forces.

Axial pitch

The distance measured axially from a point on one thread to the corresponding point on an adjacent thread in power screws.

Lead (Power screw)

The distance the nut moves along the axis in one turn of the screw.

Lead angle

The angle ($\lambda$) between a tangent to the pitch helix and a plane normal to the axis of the screw.

Spring

An elastic body that distorts when loaded and recovers its original shape when the load is removed.

Helical springs

Wire coiled into a helix intended for compressive or tensile loads.

Conical and volute springs

Telescoping springs with a spring rate that increases with the load.

Torsional springs

Helical or spiral springs where the load tends to wind up the coils or increase the number of coils.

Laminated or leaf springs

Flat plates of varying lengths held together by clamps, commonly called carriage springs.

Disc or Belleville springs

Conical discs held by a central bolt used for high spring rates and compact units.

Solid length

The product of the total number of coils and the diameter of the wire in a spring.

Free length

The length of a spring in the unloaded condition.

Spring index

The ratio of the mean diameter of the coil to the diameter of the wire ($C = D/d$).

Spring rate

Defined as the load required per unit deflection ($k = F/\delta$), also called stiffness.

Wahl’s stress factor

A factor ($K$) used in spring design to account for stress concentration and curvature.

Flat belt

Used in factories for moderate power transmission where pulleys are not more than 8 metres apart.

V-belt

A belt used for great power transmission when pulleys are very near each other.

Net Belt Pull

The difference between the maximum tension ($F_1$) and the force on the receding side ($F_2$).

Open Belt Drive

A drive configuration where the belt does not cross between the two pulleys.

Crossed Belt Drive

A belt drive where the belt crosses itself between pulleys, used to reverse rotation.

Initial Tension

The tension ($F_o$) present in a belt at rest.

Bush roller chain

A power transmission chain consisting of outer plates, inner plates, pins, bushes, and rollers.

Silent chain

Also known as inverted tooth chain, designed to eliminate noise and allow links to ride higher as the chain stretches.

Wire Ropes

Cold-drawn wires wrapped into strands, which are then wrapped into helices about a core.

Regular Lay

Wire rope construction where wires and strands are twisted in opposite directions.

Lang Lay

Wire rope construction where wires and strands are twisted in the same direction.

Spur gears

Toothed wheels with straight elements parallel to the shaft axis used for parallel shafts.

Pitch circle

An imaginary circle in gearing that would give the same motion as the actual gear through pure rolling action.

Addendum

The radial distance between the pitch circle and the outer end of the tooth.

Dedendum

The radial distance from the pitch circle to the root circle.

Whole depth

The total radial distance between the addendum circle and the dedendum circle.

Backlash

The difference between the tooth space and the tooth thickness measured on the pitch circle.

Circular pitch

The distance measured along the pitch circle between points on adjacent teeth ($P_c$).

Diametral pitch

The ratio of the number of teeth to the pitch diameter in inches ($P_d$).

Module

The ratio of the pitch circle diameter in mm to the number of teeth ($m_o$).

Helical gears

Gears with teeth cut in the form of a helix used to connect parallel shafts.

Bevel Gears

Gears used to connect intersecting shafts, typically at right angles.

Worm gears

Used for high velocity ratios between non-intersecting shafts at right angles.

Brakes

Friction devices used to regulate the motion of bodies by slowing them down or holding them at rest.