Andalusia PAU Technology and Engineering II flashcards

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

Young's modulus

Slope of the linear elastic part of the stress–strain curve, E = σ/ε, measured in pascals. It quantifies stiffness: a higher E means less deformation for the same applied stress.

Ductile vs brittle fracture

Ductile fracture involves plastic deformation, necking and high energy absorption; brittle fracture occurs with little deformation and flat cleavage surfaces. Charpy tests quantify the transition temperature.

Hall–Petch relationship

Yield strength increases as grain size decreases, because grain boundaries impede dislocation motion. Finer grains therefore give higher strength and usually better toughness.

Quenching and tempering

Quenching rapidly cools austenitized steel to form hard, brittle martensite; tempering reheats it to restore toughness and relieve internal stresses while retaining useful hardness.

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 outer fibre.

Simply supported beam deflection

Under a central point load P, deflection at mid-span is δ = PL³/(48EI); under a uniform load q it is 5qL⁴/(384EI). E is Young's modulus and I the second moment of area.

Grübler's mobility formula

For planar mechanisms, degrees of freedom M = 3(n−1) − 2j₁ − j₂, where n is the number of links, j₁ full joints and j₂ half joints.

Gear velocity ratio

For a pair of meshing gears, i = ω₁/ω₂ = z₂/z₁, where z is the number of teeth. Compound trains multiply the individual ratios.

von Mises criterion

A ductile material yields when the distortion energy reaches a critical value. The equivalent stress combines normal and shear components and is compared with the yield strength.

Ohm's law and power

V = I·R relates voltage, current and resistance. Power dissipated is P = V·I = I²R = V²/R. These relations apply to resistive DC circuits.

Kirchhoff's laws

The current law states that currents entering a node equal those leaving; the voltage law states that the sum of voltages around a closed loop is zero.

RMS value of AC

The root-mean-square value of a sinusoid equals peak/√2. It represents the equivalent DC value producing the same heating effect in a resistor.

Three-phase power

In a balanced three-phase system, total active power P = √3·V_L·I_L·cos φ, where V_L and I_L are line values and cos φ is the power factor.

Induction motor slip

Slip s = (ns − n)/ns, where ns = 60f/p is synchronous speed, f the supply frequency and p the number of pole pairs. Slip increases with load.

Wheatstone bridge

A four-arm resistive bridge used to measure unknown resistance or condition resistive sensors. It is balanced when the ratio of adjacent arms is equal.

Closed-loop control

The controller compares the measured output with the setpoint and acts on the error. Feedback reduces sensitivity to disturbances but can destabilize the system if poorly tuned.

PID controller terms

Proportional action responds to current error, integral action removes steady-state error, and derivative action anticipates change to reduce overshoot. Gains Kp, Ki and Kd are tuned.

Closed-loop stability

A linear system is stable if all poles of its closed-loop transfer function have negative real parts. Routh–Hurwitz, Bode and Nyquist methods assess stability.

PLC scan cycle

The PLC repeatedly reads inputs, executes the user program and writes outputs. Scan time affects response speed; timers and counters operate within this cyclic execution.

Incremental encoder

A sensor that produces pulses as a shaft rotates, giving position and speed by counting pulses. An index channel provides a reference zero position.

Pascal's law

Pressure applied to a confined fluid is transmitted undiminished in all directions. This principle underlies hydraulic presses and force multiplication.

Hydraulic cylinder force

Extension force F = p·A, where p is pressure and A the piston area. Retraction force uses the annulus area (A minus rod area).

5/2 directional valve

A valve with five ports and two positions that directs compressed air to extend or retract a double-acting cylinder. Solenoid or pilot actuation selects the position.

FRL unit

Filter-regulator-lubricator unit in a pneumatic circuit: it removes moisture and particles, sets the working pressure and adds oil mist for lubrication.

Turning vs milling

Turning rotates the workpiece against a single-point tool to produce cylindrical surfaces; milling rotates a multi-tooth cutter against a moving workpiece to produce flat or profiled surfaces.

ISO fits system

Holes and shafts are designated by letters and tolerance grades, e.g. H7/g6. Clearance, transition and interference fits are selected according to the required assembly behaviour.

Micrometer resolution

A standard outside micrometer reads to 0.01 mm using a 0.5 mm spindle pitch and a thimble with 50 divisions. It is used for precise external dimensions.

G-code and M-code

G-codes define motion and interpolation (e.g. G01 linear, G02 circular); M-codes control machine functions such as spindle on/off and coolant. CNC programs combine both.

Wind power proportionality

Available wind power is proportional to the cube of wind speed and to the swept rotor area: P = ½·ρ·A·v³·Cp, where Cp is the power coefficient.

Critical path method

A project scheduling technique that identifies the longest sequence of dependent tasks. Delays on the critical path delay the whole project; float exists on other paths.

First-angle projection

A standardized orthographic projection in which the object is placed between the observer and the projection plane. The top view appears below the front view.

Geometric tolerancing symbols

GD&T symbols specify form, orientation and position tolerances, such as flatness, perpendicularity, concentricity and position, with datum references and tolerance zones.