Castilla y León 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.

Pearlite

Lamellar microstructure of alternating ferrite and cementite (Fe3C) that forms in carbon steels during slow cooling of austenite; it is harder and stronger than pure ferrite but more brittle.

Charpy impact test

Test in which a swinging pendulum strikes a notched specimen and the absorbed energy is recorded, revealing toughness and the ductile-to-brittle transition temperature of the material.

Brinell hardness

Hardness test that presses a 10 mm hardened steel or tungsten carbide ball into the surface with a standard load and measures the resulting indentation diameter to obtain HBW.

Stainless steel passivation

Corrosion protection of stainless steels from a thin, self-healing chromium oxide (Cr2O3) surface layer that forms when chromium content exceeds roughly 10.5 percent.

Static equilibrium conditions

A rigid body at rest satisfies that the vector sum of all forces is zero and the sum of moments about any point is also zero; used to compute support reactions.

Gear train ratio

Speed ratio of a gear train equals the product of the teeth of driven wheels divided by the product of the teeth of driving wheels; an idler changes direction only.

Rotational power

Mechanical power transmitted by a rotating shaft equals torque multiplied by angular velocity in rad/s; angular velocity is 2π times revolutions per second.

Bearing L10 life

Basic rating life of a rolling bearing: the number of millions of revolutions reached by 90 percent of identical bearings under the same load, computed as (C/P)^p.

Thevenin equivalent

Any linear two-terminal circuit can be replaced by a voltage source equal to the open-circuit voltage in series with a resistance measured with all independent sources deactivated.

RC time constant

Product of resistance and capacitance, in seconds; after one time constant a charging capacitor reaches about 63 percent of its final voltage, and after five about 99 percent.

Bridge rectifier output

A full-wave diode bridge converts AC to pulsating DC; the average output voltage equals twice the peak voltage divided by pi, ignoring diode drops.

Inverting amplifier gain

For an ideal operational amplifier with feedback resistor Rf and input resistor Rin, the closed-loop voltage gain is minus Rf divided by Rin.

PID controller terms

Proportional action responds to present error, integral action accumulates past error to remove steady-state offset, and derivative action anticipates future error to damp the response.

Closed-loop transfer function

For a plant G with unity negative feedback, the ratio of output to reference is G divided by (1 + G); its poles determine stability.

PT100 sensor

Platinum resistance temperature detector with 100 ohms at 0 degrees Celsius, nearly linear, roughly 0.385 ohms per degree, used in industrial temperature measurement.

PLC scan cycle

Repeated sequence in which a programmable logic controller reads input modules, executes the user program, updates outputs, and performs housekeeping, taking milliseconds.

Hydraulic press force

By Pascal's principle, force on the large piston equals input force multiplied by the ratio of piston areas; the small piston must travel proportionally farther.

Meter-out speed control

Throttle valve placed in the cylinder exhaust line; it controls extension speed and prevents runaway of overrunning loads by maintaining back pressure.

5/2 directional valve

Pneumatic valve with five ports and two positions, typically pilot-operated, that alternately pressurises and exhausts both chambers of a double-acting cylinder.

Cylinder extension speed

Speed at which a piston rod extends equals volumetric flow supplied by the pump divided by the effective piston area; larger bore means slower movement for the same flow.

Cutting speed formula

For turning, cutting speed in metres per minute equals pi times workpiece diameter in millimetres times spindle speed in rpm divided by one thousand.

Vernier caliper resolution

Typical resolution is 0.02 mm when the vernier has 50 divisions; the reading is the main scale value plus the vernier division that aligns with a main mark.

ISO clearance fit

Assembly in which the hole is always larger than the shaft, leaving play; example H7/g6, used for parts that must slide or rotate freely.

Process capability Cpk

Index measuring how well a centred process fits within specification limits; it equals the smaller distance from the mean to either limit divided by three sigma.

Break-even point

Production volume at which total revenue equals total cost, calculated as fixed costs divided by the difference between unit selling price and unit variable cost.

Net present value

Sum of discounted future cash flows minus the initial investment; a positive value at the chosen discount rate means the project is economically acceptable.

Life cycle assessment

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

Gantt chart

Bar chart showing project tasks along a time axis, their durations, start and finish dates and overlaps, used for scheduling and progress control.

Two's complement

Binary encoding of signed integers in which the most significant bit has negative weight; negation is performed by inverting all bits and adding one.

TCP versus UDP

TCP is connection-oriented, acknowledges segments and retransmits lost data; UDP is connectionless, has lower overhead and no delivery guarantee, suited to streaming.

IPv4 subnet mask

A 32-bit mask whose leading ones identify the network portion of an address; a /24 mask leaves eight bits, or 254 usable hosts, for devices.

Binary search complexity

Search algorithm that halves a sorted array at each step, requiring about log base 2 of n comparisons, far faster than linear search on large datasets.