Mechanical engineering, explained
The ideas every Mechanical Engineering degree is built on, each on one page: what it says, the formulas, a worked number and the mistakes to avoid.
- מחזור קרנו
The Carnot cycle, explained
The Carnot cycle is the ideal reversible heat engine. Its efficiency, 1 − T_C/T_H, is the ceiling for any engine running between the same two temperatures.
Read - משוואת ברנולי
Bernoulli’s equation, explained
Along a streamline in steady, inviscid, incompressible flow, pressure, kinetic energy and height trade off with their sum held constant. That is Bernoulli’s equation.
Read - מספר ריינולדס
The Reynolds number, explained
The Reynolds number, Re = ρVL/μ, is the ratio of inertial to viscous forces in a flow. It decides whether the flow is laminar or turbulent.
Read - מעגל מוהר
Mohr’s circle, explained
Mohr’s circle turns a 2D stress transformation into geometry. One circle gives the principal stresses, the maximum shear stress and the stress on any plane through a point.
Read - מאמץ פון מיזס
Von Mises stress, explained
Von Mises stress turns a 3D stress state into one number you can compare with the yield strength from a tensile test. That is why every FEA stress plot shows it.
Read - קריסת אוילר
Euler buckling, explained
Euler’s formula gives the axial load at which a slender column suddenly bows sideways: P_cr = π²EI/(KL)². It depends on stiffness and length, not on strength.
Read - אנטרופיה
Entropy, explained
Entropy measures how spread out a system’s energy is. The second law says the total entropy of a system and its surroundings never decreases, and that is what makes processes run one way.
Read - החוק הראשון של התרמודינמיקה
The first law of thermodynamics, explained
The first law of thermodynamics is conservation of energy: heat added to a system minus the work it does equals the change in its stored energy.
Read - מחזור רנקין
The Rankine cycle, explained
The Rankine cycle is the steam power cycle: pump water to high pressure, boil and superheat it, expand it through a turbine, and condense it back to liquid.
Read - מחליף חום ו־LMTD
Heat exchangers and LMTD, explained
A heat exchanger’s duty is Q = U·A·ΔT_lm. The log mean temperature difference, LMTD, is the correct average of the temperature difference that drives heat across it.
Read - מומנט התמד
Second moment of area, explained
The second moment of area, I, measures how a cross-section’s area is spread away from the bending axis. It sets a beam’s bending stiffness, and it is why an I-beam is shaped like an I.
Read - שקיעת קורות
Beam deflection, explained
A beam’s deflection comes from EI·v″ = M(x): bending moment over bending stiffness gives curvature, and integrating twice gives the shape. For standard cases the answer is a one-line formula.
Read - ריכוז מאמצים
Stress concentration, explained
A hole, notch or sharp step raises the local stress above the nominal value by the factor K_t. A small hole in a wide plate under tension triples it.
Read - עייפות חומרים
Fatigue and the S–N curve, explained
Fatigue is failure under repeated load at stresses well below yield. The S–N curve gives how many cycles a material survives at each stress amplitude, and the Goodman line adds the effect of mean stress.
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