PAU Technology & Engineering II (Cantabria) flashcards

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

Elastic modulus E

Slope of the stress–strain curve in the linear elastic zone; measured in Pa or GPa. It quantifies stiffness: a higher E means less deformation for the same applied stress.

Yield strength σ_y

Stress at which a material begins to deform permanently. Below it, deformation is reversible; above it, plastic strain remains after unloading. Key for design against permanent deformation.

Ductile vs brittle fracture

Ductile fracture shows plastic deformation and necking before failure; brittle fracture occurs suddenly with little deformation, typically at low temperature or under impact.

Static equilibrium conditions

A body at rest satisfies the sum of forces equal to zero and the sum of moments about any point equal to zero. Both conditions are needed to solve reactions and internal forces.

Bending stress formula

σ = M·y/I, where M is the bending moment, y the distance from the neutral axis and I the second moment of area. Maximum stress occurs at the outermost fibre.

Gear train ratio

i = ω_in/ω_out = Z_out/Z_in for a simple train. Speed is reduced when the driven gear has more teeth, and torque increases in the same proportion.

Grashof condition

For a four-bar linkage, s + l ≤ p + q, where s and l are the shortest and longest links, guarantees at least one link can rotate fully.

Kirchhoff's voltage law

The algebraic sum of voltage drops around any closed loop of a circuit is zero. It follows from energy conservation and is used to write mesh equations.

Three-phase star connection

In a star connection the line voltage is √3 times the phase voltage and the line current equals the phase current. Used for motors and distribution networks.

Zener diode

A diode designed to operate in reverse breakdown at a well-defined voltage. Biased in reverse, it holds a stable voltage and serves as a reference or clamp.

De Morgan's theorems

The complement of a product equals the sum of the complements, and the complement of a sum equals the product of the complements. Used to simplify logic circuits.

Open vs closed loop

Open loop applies an action without checking the result. Closed loop measures the output with a sensor, compares it to the setpoint and corrects the error.

PID controller terms

Proportional output follows the error, integral accumulates error to remove steady-state offset, derivative responds to the rate of change to reduce overshoot.

PLC scan cycle

The PLC reads all inputs, executes the program from memory, then updates all outputs, repeating cyclically. Scan time limits the fastest response achievable.

Ladder logic AND/OR

Contacts in series implement AND because all must close; contacts in parallel implement OR because any one closes the path. Normally closed contacts invert the signal.

Pascal's principle

Pressure applied to a confined fluid is transmitted equally in all directions. It gives the hydraulic force multiplier F₂ = F₁·A₂/A₁ in connected cylinders.

Meter-out speed control

A flow control valve placed on the exhaust side of a pneumatic cylinder. It gives smoother, more stable speed than meter-in because the air is compressed.

5/2 directional valve

A valve with five ports and two positions, used to extend and retract a double-acting cylinder. Ports 1, 2, 4, 3 and 5 follow ISO 1219 numbering.

FRL unit

Filter, regulator and lubricator group placed upstream of a pneumatic circuit. It cleans the air, sets the working pressure and adds oil for lubrication.

Cutting speed formula

v = π·D·n, where D is the workpiece or tool diameter and n the rotational speed in rev/min. It determines tool wear and surface finish.

Micrometer resolution

A standard outside micrometer reads to 0.01 mm using a 0.5 mm pitch screw and a thimble with 50 divisions. Used for precise shaft and thickness measurement.

Interference fit

A fit where the shaft is larger than the hole before assembly, producing contact pressure after assembly. It transmits torque without keys but needs heating or pressing.

Poka-yoke

A mistake-proofing device or design that prevents an error from being made or makes it immediately visible. Example: a jig that only accepts the part one way.

Kilowatt-hour

A unit of energy equal to one kilowatt of power for one hour, i.e. 3.6 MJ. Domestic electricity bills are expressed in this unit.

PV cell efficiency

Ratio of electrical power produced to incident solar power under standard test conditions. It decreases as cell temperature rises, so ventilation matters.

Life-cycle analysis

Assessment of environmental impacts from raw material extraction through manufacture, use and disposal. It prevents shifting the burden from one stage to another.

Circular economy

A model in which materials are reused, repaired and recycled rather than discarded. It reduces resource extraction and waste, and is central to sustainable design.

Gantt chart

A bar chart showing tasks against calendar time, with durations and overlaps. It visualises the schedule but does not by itself identify the critical path.

Critical path

The longest sequence of dependent tasks in a project network; it sets the minimum project duration. Tasks on it have zero float.

Bill of materials

A structured list of all components, quantities and references needed to build a product. It feeds purchasing, assembly and the project budget.

Project budget

Sum of material, labour, tooling and indirect costs plus a contingency allowance, with applicable taxes. Labour is estimated as hours multiplied by the hourly rate.

Fatigue limit

The stress amplitude below which a material withstands an unlimited number of cycles. Steels show a fatigue limit; aluminium alloys generally do not.

Thermoplastic vs thermoset

Thermoplastics soften on heating and can be remelted and recycled; thermosets cure irreversibly into a cross-linked network and cannot be remelted.