Catalonia PAU Technology and Engineering II flashcards

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

Young's modulus

Slope of the stress–strain curve in the elastic region, E = σ/ε. It measures stiffness: a higher E means less deformation for the same applied stress.

Ductility

Ability of a material to deform plastically before fracture, measured as percentage elongation or reduction of area in a tensile test. Low ductility means brittle behaviour.

Martensite

Hard, brittle phase formed when austenite is quenched rapidly; carbon is trapped in a distorted lattice. Tempering afterwards restores toughness.

Galvanic corrosion

Electrochemical attack when two dissimilar metals contact in an electrolyte; the more active metal becomes the anode and corrodes. Prevented by insulation or sacrificial anodes.

Gear ratio

Ratio i = z2/z1 = n1/n2 between driven and driving gears. Speed decreases as torque increases by the same factor in an ideal transmission.

Module (gears)

m = d/z, the ratio of pitch diameter to number of teeth in millimetres. Two gears mesh only if they share the same module and pressure angle.

Crank-slider mechanism

Converts rotation into reciprocating translation. The stroke of the slider equals twice the crank radius, independent of the connecting-rod length.

Tapered roller bearing

Rolling bearing with conical rollers that supports combined radial and axial loads. Often mounted in opposed pairs to adjust clearance and preload.

Self-locking screw

A screw thread where the friction angle exceeds the lead angle, so an axial load cannot make it rotate backwards. Typical of standard metric threads.

Kirchhoff's voltage law

The algebraic sum of voltages around any closed loop of a circuit is zero. It expresses conservation of energy in the loop.

RMS voltage

Effective value of a sinusoidal voltage, V_rms = V_peak/√2. It produces the same heating power in a resistor as an equal DC voltage.

Impedance

Total opposition to alternating current, Z = √(R² + (X_L − X_C)²). It combines resistance and reactance and is measured in ohms.

Zener diode

Diode designed to operate in reverse breakdown at a defined voltage. Used to regulate or clamp voltage in simple power supplies.

Voltage divider

Two resistors in series across a source give V_out = V·R2/(R1+R2). Used to obtain a fraction of a voltage, but it loads the circuit.

Closed-loop control

System that measures the output with a sensor, compares it with the reference to obtain the error, and acts to reduce that error.

PID controller

Controller combining proportional, integral and derivative action on the error. P reduces error, I removes steady-state error, D damps oscillations.

Feedback transfer function

For a forward block G and feedback block H, the closed-loop transfer function is G/(1+G·H) with negative feedback.

Thermistor NTC

Temperature sensor whose resistance decreases as temperature rises. Cheap and sensitive, but non-linear and limited in range.

Stepper motor

Actuator that rotates in fixed angular steps for each electrical pulse. Allows open-loop position control without a feedback sensor.

De Morgan's laws

Boolean identities: the complement of a product equals the sum of complements, and the complement of a sum equals the product of complements.

Pascal's principle

Pressure applied to a confined fluid is transmitted equally in all directions. It is the basis of hydraulic presses and cylinders.

5/2 directional valve

Pneumatic valve with five ports and two positions, used to extend and retract a double-acting cylinder. Usually solenoid-actuated with spring return.

Meter-out speed control

Flow-control valve placed on the exhaust side of a cylinder. It gives smooth, stable speed control when the load tends to overrun.

Cylinder retraction force

F = p·(A_piston − A_rod). The rod reduces the effective area, so retraction force is lower than extension force at the same pressure.

Turning vs milling

Turning rotates the workpiece against a single-point tool on a lathe; milling rotates a multi-tooth cutter while the workpiece translates.

Springback

Elastic recovery of sheet metal after bending is released. It is compensated by overbending or by coining the bend radius.

First-angle projection

European drawing convention where the object lies between observer and projection plane. The left-side view is placed on the right of the front view.

Section view

Drawing showing the interior of a part cut by an imaginary plane. Cut material is hatched at 45 degrees and hidden edges behind the cut are shown.

Dimensioning rule

Each dimension appears once, in millimetres without units, with dimension lines parallel to the measured edge and extension lines from the object.

Energy efficiency

Ratio of useful energy output to energy input, always below one. Losses appear as heat, noise or friction in each conversion stage.

Wind power cube law

Available wind power is proportional to the cube of wind speed and to the swept area. Doubling wind speed multiplies power by eight.

Life-cycle assessment

Method that quantifies environmental impacts of a product from raw material extraction through manufacture, use and end-of-life disposal or recycling.

Weighted decision matrix

Design evaluation tool that scores each alternative against weighted criteria and sums the products. The highest total indicates the preferred solution.

Work breakdown structure

Hierarchical decomposition of a project into manageable tasks. It is the basis for scheduling, budgeting and assigning responsibilities.