UPDA Mechanical flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Public safety paramount

In engineering ethics, the safety, health, and welfare of the public take precedence over obligations to clients, employers, and the profession when the two conflict.

Conflict of interest disclosure

A written disclosure made to all affected parties before accepting work, identifying any financial or personal interest that could bias professional judgment on the project.

Seal and signature rule

A licensed engineer signs and seals only drawings and reports that they personally prepared or directly supervised, accepting legal responsibility for their technical content.

First law steady flow

For a steady-flow control volume, heat added minus work done equals the change in enthalpy plus kinetic and potential energy between inlet and outlet.

Carnot efficiency

The maximum thermal efficiency of any heat engine operating between hot and cold reservoirs at absolute temperatures TH and TL is 1 minus TL/TH.

Critical insulation radius

The insulation outer radius at which heat loss from a cylinder is maximum, equal to thermal conductivity divided by external convection coefficient; adding insulation beyond it reduces heat loss.

LMTD method

Heat exchanger duty equals overall heat transfer coefficient times area times log-mean temperature difference, corrected by a factor F for multipass and cross-flow arrangements.

Reynolds number

A dimensionless ratio of inertial to viscous forces, rho times velocity times diameter divided by viscosity, used to classify pipe flow as laminar, transitional, or turbulent.

Bernoulli equation

For steady, incompressible, frictionless flow along a streamline, pressure head plus elevation head plus velocity head remains constant; it is an energy conservation statement.

NPSH available

The absolute pressure head at a pump suction flange above the liquid vapor pressure, calculated from atmospheric pressure, static head, and suction line losses.

Pump affinity laws

For geometrically similar pumps, flow varies with speed, head with speed squared, and power with speed cubed, assuming impeller diameter and efficiency remain unchanged.

Euler buckling load

The critical axial compressive load for a slender column, pi squared times modulus times moment of inertia divided by effective length squared, valid in the elastic range.

Flexure formula

Bending normal stress at a distance y from the neutral axis equals bending moment times y divided by the second moment of area about that axis.

Torsion formula

Shear stress in a circular shaft at radius r equals torque times r divided by the polar second moment of area, maximum at the outer surface.

Thermal stress restrained bar

A bar fully restrained against axial expansion develops stress equal to modulus times coefficient of thermal expansion times temperature change, compressive when heated.

Bearing basic rating life

L10 life in millions of revolutions equals dynamic load rating divided by equivalent load, raised to the third power for ball bearings.

Goodman fatigue criterion

A conservative design line relating alternating and mean stress: alternating stress divided by endurance limit plus mean stress divided by ultimate strength must not exceed one.

Bolt preload torque

Tightening torque approximately equals the torque coefficient, typically 0.2 for dry steel, times preload times nominal bolt diameter.

Chvorinov rule

Solidification time of a casting is proportional to the square of volume divided by surface area, with the constant depending on mold material and superheat.

Carbon equivalent

A welding index combining carbon with manganese, chromium, molybdenum, vanadium, nickel, and copper to estimate hardenability and preheat requirements in steel.

Taylor tool life

Cutting speed times tool life raised to exponent n equals a constant; higher speeds shorten tool life, and n depends on tool and workpiece material.

Sensible heat air

Cooling or heating load for air in watts approximately equals 1.23 times volumetric flow in liters per second times dry-bulb temperature difference in kelvin.

Coefficient of performance

Refrigeration COP equals useful cooling effect divided by work input; for chillers it also equals 3.517 divided by kW per ton.

Air changes per hour

The number of times the total room air volume is replaced in one hour, equal to supply volumetric flow divided by room volume.

PID control law

Controller output equals proportional gain times error plus integral gain times integral of error plus derivative gain times rate of change of error.

Four to twenty milliamp loop

An analog industrial signal standard in which 4 mA represents the zero or live-zero value and 20 mA the full-scale value, allowing open-circuit detection.

Control valve fail-safe

The valve position assumed on loss of actuating signal, selected so that air failure, power failure, or instrument failure leaves the process in a safe state.

Critical path

The longest sequence of dependent activities through a project network, determining minimum project duration and having zero total float.

Cost performance index

Earned value divided by actual cost; a value below one indicates the project is spending more than the value earned to date.

Earned value variance

Cost variance equals earned value minus actual cost, while schedule variance equals earned value minus planned value; negative values indicate adverse performance.

Hierarchy of controls

Risk control preference order: elimination, substitution, engineering controls, administrative controls, and personal protective equipment, with elimination most effective and PPE least.

Lockout tagout

A procedure that isolates hazardous energy sources, applies locks and tags, verifies zero energy, and prevents unexpected startup during maintenance or servicing.