Engineering Glossary

Comprehensive glossary of engineering terms and definitions. Browse by discipline to find explanations for structural, mechanical, electrical, and manufacturing concepts.

🏗️ Structural Engineering (19)⚡ Electrical Engineering (16)⚙️ Mechanical Engineering (12)🏭 Manufacturing & Production (16)💧 Fluid Mechanics (12)🌡️ Heat Transfer & Thermal (6)

🏗️ Structural Engineering Terms

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Elastic Modulus (Young's Modulus)
A measure of a material's stiffness, defined as the ratio of stress to strain in the linear elastic region. Denoted as E, it represents how much a material will deform under a given load.
Moment of Inertia (Second Moment of Area)
A geometric property that describes how a cross-section's area is distributed about an axis. It determines a beam's resistance to bending and is denoted as I.
Deflection
The displacement of a structural element from its original position under load. Maximum deflection is often limited by building codes to prevent serviceability issues.
Bending Moment
The internal moment that causes a beam to bend when subjected to external loads. It represents the sum of moments about a point in the cross-section.
Bending Stress
The normal stress induced in a beam due to bending. Calculated as σ = M·c/I, where M is bending moment, c is distance from neutral axis, and I is moment of inertia.
Slenderness Ratio
The ratio of effective column length to radius of gyration (λ = KL/r). It characterizes how prone a column is to buckling. Higher values indicate more slender columns that are more susceptible to elastic buckling.
+13 more terms in Structural Engineering

⚡ Electrical Engineering Terms

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Voltage Drop
The reduction in voltage along a conductor due to its electrical resistance. Occurs as current flows through wires and is proportional to wire length and current magnitude.
AWG (American Wire Gauge)
A standardized wire gauge system used primarily in North America. Lower AWG numbers indicate thicker wires with lower resistance and higher current capacity.
Conductor Resistance
The opposition to current flow in an electrical conductor, measured in ohms. Depends on material, length, cross-sectional area, and temperature.
Single-Phase Power
An AC power distribution method using two wires (hot and neutral). Common in residential applications and smaller commercial loads.
Three-Phase Power
An AC power distribution method using three conductors carrying currents 120° out of phase. More efficient for large loads and motors.
Motor Torque
The rotational force produced by a motor shaft, calculated as T = P/ω where P is power and ω is angular velocity. Measured in N·m or lb·ft. Determines acceleration capability and load driving ability.
+10 more terms in Electrical Engineering

⚙️ Mechanical Engineering Terms

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Gear Ratio
The ratio of the number of teeth on the driven gear to the driver gear. Determines the mechanical advantage and speed reduction in a gear train.
Mechanical Efficiency
The ratio of output power to input power, expressed as a percentage. Accounts for energy losses due to friction, heat, and other factors.
Spring Rate (Spring Constant)
The force required to compress or extend a spring by one unit of length. Denoted as k, it is calculated as k = Gd⁴/(8D³n) for helical springs, where G is shear modulus, d is wire diameter, D is mean coil diameter, and n is active coils.
Shear Modulus (Modulus of Rigidity)
A material property that describes its resistance to shear deformation. Denoted as G, it relates shear stress to shear strain in the elastic region. For most metals, G ≈ E/(2(1+ν)) where E is elastic modulus and ν is Poisson's ratio.
Wahl Factor
A stress correction factor for helical springs that accounts for wire curvature and direct shear effects. Calculated as K = (4C-1)/(4C-4) + 0.615/C, where C is the spring index (D/d).
Belt Tension
The tensile force in a belt, consisting of tight side tension (T₁) and slack side tension (T₂). The difference transmits power: P = (T₁ - T₂) × v. Initial tension is set to prevent slip under load.
+6 more terms in Mechanical Engineering

🏭 Manufacturing Terms

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Bolt Preload
The initial tension force in a bolt created during tightening. Preload clamps joint members together and must be sufficient to prevent joint separation under service loads while staying below bolt yield strength.
Nut Factor (K Factor)
A dimensionless coefficient relating applied torque to achieved bolt preload in the equation T = K × D × F. It accounts for friction in threads and under the bolt head or nut bearing surface.
Proof Load
The maximum load a fastener can withstand without permanent deformation. It is typically 85-95% of yield strength and represents the practical upper limit for bolt preload.
Density
Mass per unit volume of a material, typically expressed in kg/m³ or lb/ft³. A fundamental property used in weight calculations and fluid mechanics.
Fillet Weld
A triangular cross-section weld joining two surfaces at approximately right angles. The most common weld type, used for lap joints, T-joints, and corner joints. Specified by leg size.
Weld Throat (Effective Throat)
The shortest distance from the root of a weld to its face, which determines weld strength. For equal-leg fillet welds, throat = 0.707 × leg size. Stress is calculated based on throat area.
+10 more terms in Manufacturing & Production

💧 Fluid Mechanics Terms

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Reynolds Number
A dimensionless quantity that predicts flow patterns. Defined as Re = ρVD/μ, it indicates whether flow is laminar (Re < 2300), transitional, or turbulent (Re > 4000).
Friction Factor (Darcy)
A dimensionless number used in the Darcy-Weisbach equation to calculate pressure drop. Depends on Reynolds number and pipe relative roughness.
Darcy-Weisbach Equation
An empirical equation for calculating pressure loss in pipes: ΔP = f·(L/D)·(ρV²/2). It accounts for pipe length, diameter, fluid properties, and flow regime.
Bore Diameter
The inner diameter of a hydraulic cylinder barrel, which defines the piston area. The bore area determines the extend (push) force: F = P × A_bore. Larger bore diameters provide more force at the same pressure.
Annular Area
The effective piston area on the rod side of a hydraulic cylinder, calculated as A_annular = A_bore - A_rod. This area determines retract (pull) force and flow requirements for retraction.
Stroke Length
The distance a hydraulic cylinder piston can travel from fully retracted to fully extended position. Stroke length determines the volume of fluid required for each cycle and affects rod buckling calculations.
+6 more terms in Fluid Mechanics

🌡️ Heat Transfer Terms

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Thermal Conductivity
A material property indicating how well it conducts heat, denoted as k with units W/(m·K). It represents the rate of heat transfer through a unit thickness of material per unit area per degree temperature difference.
R-Value (Thermal Resistance)
A measure of thermal resistance to heat flow, calculated as R = L/k where L is thickness and k is thermal conductivity. Higher R-value means better insulation. R-values are additive for layers in series.
U-Value (Thermal Transmittance)
The overall heat transfer coefficient, calculated as U = 1/R_total. It represents the rate of heat transfer per unit area per degree temperature difference through a complete building element or assembly.
Coefficient of Thermal Expansion (CTE)
A material property indicating how much a material expands per unit length per degree of temperature change, denoted α. Units are 10⁻⁶/°C (ppm/°C). Linear expansion is calculated as ΔL = α × L₀ × ΔT.
Thermal Stress
Stress that develops in a material when thermal expansion or contraction is constrained. Calculated as σ = E × α × ΔT, where E is elastic modulus, α is CTE, and ΔT is temperature change. Can cause yielding or buckling.
Expansion Loop
A U-shaped or Z-shaped configuration in piping that absorbs thermal expansion through bending rather than developing axial stress. The loop flexes as the pipe expands, keeping stresses within acceptable limits.

About This Engineering Glossary

This technical glossary provides clear definitions and practical explanations for common engineering terms. Each entry includes real-world applications, related formulas, and links to calculators where you can apply these concepts in your designs.

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