FE Other Disciplines key terms

A design method that compares computed working stresses from service loads against a fraction of the material's strength, using a factor of safety greater than one. Widely applied to structural steel, timber, and masonry proportioning.

A design approach that multiplies nominal loads by load factors and nominal resistances by resistance factors so that factored strength equals or exceeds factored demand. It accounts for variability in both loading and material behavior.

The ratio of a structure's or component's capacity to the maximum expected demand. Values above one indicate margin against failure; the margin covers uncertainty in loads, material properties, analysis assumptions, and construction quality.

The maximum stress or load a material or member can sustain before rupture or collapse. For ductile metals it corresponds to the peak of the stress-strain curve, beyond which necking and eventual fracture occur.

The stress at which a material begins to deform permanently, marking the end of elastic behavior. For steels without a distinct yield point, it is commonly defined by the 0.2 percent offset method.

The slope of the linear portion of a stress-strain curve, expressing stiffness as stress per unit strain. It relates elastic deformation to applied stress in Hooke's law and is largely independent of strength.

The negative ratio of lateral strain to axial strain for a material loaded uniaxially in its elastic range. Typical values are near 0.3 for metals and about 0.5 for rubber-like materials.

Stress acting parallel to a material cross-section, tending to cause sliding of adjacent layers. It arises in bolts, welds, beams carrying transverse load, and shafts transmitting torque.

The internal couple produced by transverse loads that causes a beam to curve. Its magnitude at a section equals the sum of moments of all forces on one side of that section about the section.

A geometric property describing how an area's points are distributed about an axis, governing resistance to bending. For a rectangle of width b and height h about its centroidal axis it equals b times h cubed over twelve.

The ratio of a cross-section's moment of inertia to the distance from the neutral axis to the extreme fiber. It converts bending moment directly into maximum bending stress through the flexure formula.

Sudden lateral deflection and loss of load capacity in a slender compression member when the applied load reaches a critical value. Euler's formula predicts this critical load from stiffness, length, and end conditions.

The effective length of a compression member divided by its least radius of gyration. Larger values indicate greater susceptibility to buckling and lower allowable compressive stress in design codes.

A multiplier greater than one applied to nominal stress to estimate local peak stress near holes, notches, fillets, or abrupt section changes. It depends on geometry and loading type, not on material.

Progressive fracture of a material under repeated or fluctuating stress at levels below its static strength. Cracks typically initiate at stress raisers and grow until the remaining section cannot carry the load.

The fractional change in length of a material per unit temperature change. It governs thermally induced strain and, when expansion is restrained, the resulting thermal stress.

Energy is conserved: the net heat added to a closed system minus the work it performs equals the change in its internal energy. For steady-flow devices, enthalpy and kinetic energy terms replace internal energy.

Entropy of an isolated system never decreases, and no cycle can convert heat entirely into work. It establishes the direction of spontaneous processes and the maximum efficiency of heat engines.

A state property measuring the dispersal of energy in a system, defined by the reversible heat transfer divided by absolute temperature. It increases in irreversible processes and remains constant in reversible adiabatic ones.

A thermodynamic property defined as internal energy plus the product of pressure and volume. It is convenient for steady-flow devices because heat transfer at constant pressure equals the enthalpy change.

An idealized process in which entropy remains constant, approximated by a reversible adiabatic process. It provides the reference compression and expansion paths used to compute isentropic efficiency of turbines and compressors.

The maximum possible thermal efficiency of any heat engine operating between two reservoirs, equal to one minus the ratio of cold to hot absolute temperatures. No real cycle can exceed this value.

A dimensionless ratio of inertial to viscous forces in fluid flow, equal to density times velocity times length divided by viscosity. It indicates whether flow is laminar, transitional, or turbulent.

Smooth, orderly fluid motion in parallel layers with no macroscopic mixing, occurring at low Reynolds numbers. Viscous effects dominate, and pressure drop in pipes varies linearly with flow rate.

Chaotic fluid motion with rapid fluctuations and mixing across the flow, occurring at high Reynolds numbers. It produces higher friction losses and flatter velocity profiles than laminar flow.

An energy relation for steady, incompressible, frictionless flow stating that pressure head plus velocity head plus elevation head is constant along a streamline. It underlies flow measurement and pipe analysis.

A statement of mass conservation for steady flow, requiring that density times cross-sectional area times velocity stays constant along a streamtube. For incompressible flow, area and velocity are inversely related.

The mass of fluid passing a cross-section per unit time, equal to density times area times average velocity. It is conserved in steady flow through ducts without leakage or accumulation.

A proportionality constant relating convective heat flux to the temperature difference between a surface and adjacent fluid. Its magnitude depends on fluid properties, velocity, and geometry.

A material property expressing the rate of heat conduction per unit area per unit temperature gradient. Metals are high, insulators low; it appears in Fourier's law of conduction.

A dimensionless heat transfer parameter equal to the convective heat transfer coefficient times a characteristic length divided by fluid thermal conductivity. It characterizes convection relative to pure conduction.

Any linear two-terminal network can be replaced by a single voltage source in series with a single resistance. The source equals the open-circuit voltage and the resistance equals that seen with sources deactivated.

Any linear two-terminal network can be replaced by a current source in parallel with a resistance. The current equals the short-circuit current and the resistance matches the Thevenin equivalent resistance.

In linear circuits, the response to several independent sources equals the sum of responses to each source acting alone, with other sources deactivated. It does not apply to power, which is nonlinear in voltage and current.

The cosine of the phase angle between voltage and current in an alternating-current circuit, equal to real power divided by apparent power. Low values indicate reactive load and higher transmission losses.

The total opposition to alternating current, combining resistance and reactance as a complex quantity. Its magnitude equals voltage amplitude divided by current amplitude in a linear AC circuit.

The effective value of a varying quantity, equal to the square root of the mean of its squared values. For a sinusoid it equals peak value divided by the square root of two.

The requirement that every additive term in a valid physical equation carry identical units. Checking it catches algebraic errors and justifies converting quantities into consistent unit systems before computation.

The digits in a measured or computed value that carry meaningful information about precision. Reported results should not imply greater precision than the least precise input permits.

The process of expressing a quantity in different units by multiplying by ratios equal to one. Consistent base units, such as slug-foot-second or kilogram-meter-second, prevent errors in force and energy calculations.