PEC EPE Mechanical key terms

An integral transform that converts a function of time into a function of a complex variable, turning linear differential equations into algebraic equations that are easier to solve.

A representation of a periodic function as a sum of sine and cosine waves at integer multiples of a fundamental frequency, used to analyze vibrations and periodic signals.

A scalar by which a nonzero vector is scaled when a linear transformation is applied to it; eigenvalues describe natural frequencies and stability in engineering systems.

An expansion of a function around a point using its derivatives at that point, allowing nonlinear functions to be approximated by polynomials for analysis and computation.

A family of methods, such as trapezoidal or Simpson's rule, that approximate the definite integral of a function using sampled values rather than an exact antiderivative.

Internal force per unit area within a material, commonly expressed in megapascals; normal stress acts perpendicular to a surface and shear stress acts parallel to it.

The deformation of a material relative to its original size, often expressed as dimensionless length change per unit length or as angular distortion for shear.

The linear relationship stating that stress is proportional to strain within a material's elastic range, with the constant of proportionality being the elastic modulus.

The ratio of a material's or component's strength to the maximum expected service load or stress, providing margin against uncertainty, overload, and material variability.

The stress amplitude below which a material can endure an unlimited number of load cycles without failure, applicable to steels but not to many nonferrous metals.

Localized increase in stress around a geometric feature such as a hole, notch, or fillet, quantified by a factor that multiplies the nominal stress.

A graphical construction on a plot of normal stress versus shear stress that represents the state of stress at a point and helps determine principal stresses and maximum shear.

The principle of energy conservation for a system: the change in internal energy equals heat added minus work done by the system, with sign conventions stated explicitly.

A property that measures the dispersal of energy in a system; for an isolated system it cannot decrease, and it increases during irreversible processes such as friction and mixing.

The maximum theoretical efficiency of a heat engine operating between two reservoirs, equal to one minus the ratio of cold to hot absolute temperatures.

A material property quantifying the rate at which heat conducts through a unit thickness per unit area and temperature gradient, typically in watts per meter-kelvin.

A parameter describing the rate of heat transfer between a solid surface and a moving fluid per unit area and temperature difference, usually in watts per square meter-kelvin.

An energy statement for steady, incompressible, frictionless flow along a streamline relating pressure, velocity, and elevation, expressed as head or energy per unit weight.

A dimensionless ratio of inertial to viscous forces that indicates whether flow is laminar, transitional, or turbulent; the critical value depends on geometry.

The absolute pressure margin above a liquid's vapor pressure at a pump inlet; insufficient NPSH causes cavitation that damages the impeller and reduces performance.

Friction loss in a straight pipe due to viscosity, estimated with the Darcy-Weisbach equation using pipe length, diameter, roughness, and a friction factor.

A statement of mass conservation for steady flow, stating that the mass flow rate through a pipe is constant, so velocity changes inversely with area for incompressible fluids.

A heat treatment that heats a metal and cools it slowly to soften it, relieve internal stresses, and refine grain structure, improving ductility and machinability.

The increase in strength and hardness that occurs when a metal is plastically deformed at low temperature, accompanied by reduced ductility and increased dislocation density.

A process in which molten metal is poured into a sand mold cavity, allowed to solidify, and removed as a casting, suitable for complex shapes in moderate quantities.

A chart showing which phases exist in iron-carbon alloys at equilibrium as temperature and carbon content vary, guiding steel heat treatment and cast iron selection.

A measure of the fine irregularities of a machined surface, usually the arithmetic average deviation from a mean line, affecting friction, wear, and fatigue.

The available production time divided by customer demand, setting the pace at which one unit must be completed to meet demand without excess inventory.

The order quantity that minimizes the total of ordering and holding costs under constant demand, unit cost, and lead time assumptions.

A model stating that unit labor time or cost decreases by a constant percentage each time cumulative production doubles, reflecting improved skill and process familiarity.

A work measurement technique that times a task with a stopwatch, applies performance rating and allowances, and produces a standard time for planning and incentives.

Allocating tasks to workstations so that station times are as equal as possible and the line meets the required cycle time with minimum idle time.

The longest sequence of dependent activities through a project network, which sets the minimum project duration and has zero total float.

A project control method comparing planned value, earned value, and actual cost to assess schedule and cost performance through indices and variances.

A hierarchical decomposition of project scope into manageable deliverables and work packages, forming the basis for estimating, scheduling, and control.

The amount of time an activity can be delayed without delaying the project finish date, equal to late finish minus early finish.

A situation in which an engineer's personal, financial, or other interest could improperly influence professional judgment, requiring disclosure and often removal from the decision.

Reporting an employer's illegal, unsafe, or unethical practice to an internal or external authority, ideally after internal channels fail and with attention to public safety.

Failure to exercise the care, skill, and judgment that a reasonably competent engineer would provide in similar circumstances, resulting in harm or loss.