Mechanical Engineering Design - The Ultimate Course

Explore how design formulates plans to satisfy needs and solve mechanical engineering problems, using an iterative, communicative process across mechanical design, energy, and motion.

Identify needs, define problems with measurable quantities, synthesize multiple solutions, analyze and optimize with CAD and finite element analysis, evaluate and present the final design iteratively.

Apply standards and codes to achieve uniformity, efficiency, and quality in mechanical designs by using standard parts and materials, ensuring safety and feasibility across the world.

Explore how design economics drives affordable machinery by using standard parts and tolerance to cut costs. Apply break-even analysis to compare design options and choose the most economical solution.

Apply design factor to mitigate uncertainties in mechanical design by accounting for worst-case strength and maximum allowable load, ensuring safety across variable loading scenarios.

Organizations assign a design factor to ensure safety, which sets the allowable load, then engineers choose dimensions from standard catalogs to balance safety and cost reduction—introducing the factor of safety.

Solve a factor-of-safety problem for a tension-loaded cylindrical rod by deriving the minimum diameter, then choose the 16 mm standard and obtain a 3.73 safety factor.

Explore dimensions and tolerances in mechanical design, including nominal dimensions, clearance and interference, bilateral and unilateral tolerances, and single reference line dimensioning to avoid stackup.

Explore how material selection in mechanical design balances functionality, cost, manufacturing, and availability. A heat sink example shows conduction and convection and why aluminum is preferred over silver.

Explore how stress, defined as internal reaction to applied pressure per unit area, and strain, the resulting change in a body's dimension, relate to material properties.

Explore how tensile tests reveal material properties through stress-strain curves, identifying elastic limit, Young's modulus, plastic deformation, ultimate strength, fracture, ductility, brittleness, and hardness.

Temperature inversely affects material strength and elastic limit; yield strength and ultimate strength fall with temperature, enabling forging by easing plastic deformation.

Explore four solid material types—metals, polymers, ceramics, and composites—covering ore origins, metal malleability and conductivity, polymer monomers with covalent bonds, and ceramic brittleness.

Explore metals in mechanical engineering, learn why metals dominate designs, their metallic bonding and delocalized electrons, and how they confer high conductivity, strength, and high melting points.

Learn how UNs and AISI metal numbering systems classify ferrous and non-ferrous metals, using G, S, C, and A designations and impurity and carbon-content codes.

Learn how heat treatment alters metal properties by heating and cooling at different rates. Annealing, normalizing, and quenching show how cooling rates affect ductility, hardness, and microstructure.

Use hp charts to select materials with high strength and low density by comparing elasticity-to-density and strength-to-density ratios, shifting guidelines to identify aluminum alloys for minimum mass designs.

Balance all forces and moments to achieve equilibrium, distinguishing static and dynamic cases. Use free body diagrams to represent a body, its forces, and analyze stresses on components.

Explore how normal and shear stresses arise from force per unit area relative to the area vector; normal stress is parallel, while shear stress is perpendicular, denoting sigma and tau.

Learn to construct shear force and bending moment diagrams for beams using free-body diagrams and equilibrium, applying sign conventions for compression and tension.

Explore Cartesian stress coordinates, including normal stresses sigma_xx and sigma_yy, and shear stresses tau_xy and tau_yx, within plane stress and extend to a three-dimensional stress matrix.

Explore plane stress transformations by rotating stress components and obtaining transformed normal and shear stresses from sigma_x, sigma_y, and tau_xy. Identify principal stresses and principal angles where shear is zero.

Mohr circle offers a graphical method to transform stresses using sigma x, sigma y, and tau xy, revealing principal stresses, maximum shear, and transformed states alongside the analytical approach.

Compute principal stresses and angles for sigma_x=80, sigma_y=0, tau_xy=50 MPa, yielding sigma_max ≈ 104.03 MPa and sigma_min ≈ -24 MPa, plus tau_max ≈ ±64.03 MPa, and construct the Mohr circle.

Explore elastic strain and Poisson's ratio, including Hooke's law, sign conventions for tensile and compressive strains, and how axial strains relate in two-dimensional and three-dimensional bodies via Poisson's ratio.

Explore stresses in beams under pure bending, identify the neutral axis, and compute bending stress with sigma = M y / I, plus tau = V Q /(I b).

Use free-body, shear force, and bending moment diagrams to compute sigma max and tau max for a 20×40 mm beam, yielding 84.4 MPa and 56.3 MPa.

Learn to prevent failure under static loading by grasping constant magnitude and direction, fixed supports, and failure modes such as fracture and permanent deformation in beams.

Study six static loading failure theories—three for ductile and three for brittle materials—used to avoid fracture and plastic deformation.

Explore the maximum shear stress theory (Tresca) for predicting yielding in ductile materials, using principal stresses, tau max, and 2D/3D cases with a safety factor and the stress envelope.

Explore distortion energy theory (von Mises) for ductile materials, defining yield via distortional strain energy and von Mises stress, using hydrostatic stress concepts and comparisons with maximum shear stress theory.

Examine Gilmore and Coulomb-Mohr ductile failure theories, using three tests to build a 3-circle tangent failure envelope and a 2D plane-stress design criterion with design factor n.

Explore brittle material failure via three theories: maximum normal stress theory, brittle Coulomb more theory, and modified more theory; all use ultimate strength and principal stresses to predict fracture.

Select failure criteria by material type: brittle materials use modified more theory or maximum normal stress theory; ductile materials apply distortion energy theory if yields are equal, otherwise Goulem theory.

Explore how dynamic loading causes fatigue failure in metals, revealing how repeated, alternating, and fluctuating stresses produce cracks that lead from microscopic initiation to sudden fracture.

Explore fatigue testing with a polished specimen to determine fatigue strength, plot S-N curves, and distinguish low cycle fatigue from high cycle fatigue, endurance limit, and infinite life.

Learn how the specimen endurance limit from fatigue testing is transformed into the actual machine element endurance limit using six multiplying factors: surface, size, load, temperature, reliability, and miscellaneous.

Quantify fluctuating stresses by separating them into mid-range and alternating components and apply fatigue theories such as Soderbergh, Goodman, Gerber, and Langer against endurance limit to safeguard against fatigue.

Design shafts as rotating elements that transmit power between gears, pulleys, and flywheels under dynamic loads, using steel for strength, with short length, near-load locations, two bearings, and easy assembly.

Design shafts to resist fatigue failure by evaluating fluctuating normal and shear stresses at surface-critical locations, using stress concentration factors and von Mises stress with Goodman or Soderberg criteria.

Explore how shaft critical speed arises from manufacturing eccentricity causing centrifugal deflections, and apply Reilly's equation with influence coefficients to evaluate multi-load shafts and avoid resonance.

Use Dunkerley’s equation to determine the three critical speeds of a shaft with multiple loads, using delta11, delta22, delta33, and an equivalent-load approach to ensure safe operating speeds.

Explore non-permanent joints and fasteners, including thread standards, major and minor diameters, pitch, pitch diameter, lead, power screws, and thread angle, under metric and unified systems.

Explore power screws that convert rotational motion into linear motion with square and Acme threads. Analyze forces, friction, and torque for raising and lowering a nut.

Derives raising and lowering torque for power screws, explains self-locking and thread efficiency, and discusses square versus acme threads and stresses including torsion and bending.

Explore the stiffness of a bolt in a bolted joint, define preload and grip, and model unthreaded and threaded regions as springs in series to compute equivalent stiffness.

Learn how to quantify external loads on bolted joints by splitting the load between bolt preload and member, using a stiffness-based fraction c to compute bolt and member loads.

Analyze fatigue loading in bolted tension joints under dynamic loads, accounting for preload and alternating and mid-range stress components, and apply Goodman criteria to estimate safety factors.

Explore permanent joints and welding, focusing on standard welding symbols, process types, and geometry such as bead, fillet, butt, plug, square, and bevel welds, plus residual stresses and heat treatment.

derive stress expressions for butt welds and fillet welds, covering tensile, compressive, and shear, and determine weld throat and thickness using theta and law of sines toward von Mises stress.

Develop equations for stresses in welded joints under torsion and bending, deriving shear stress from shear force and bending moment, and applying polar moment of inertia and weld geometry.

Explain how weld joint strength depends on joint type, finish, and welding speed, and apply allowable stresses as a fraction of yield or ultimate strength for tension, bending, and shear.

Explore resistance welding and adhesive bonding as two permanent joint methods, including spot and seam welding via electrical resistance heating of thin sheets, and note adhesive types and load classes.

Explore how bearings reduce friction to support rotation and learn the rolling contact bearing nomenclature, including ball and cylindrical types, inner and outer rings and grooves.

Relate bearing life to radial load through rating life and catalog load rating (C10) for 90% reliability. Learn to select bearings from manufacturer catalogs using a desired load and life.

Compute the equivalent load Fe for combined radial and thrust loading using Fr, Fa, and a rotation factor, then derive C10 and estimate L10 life at the given speed.

Bearing selection for two shafts using ABMA tables, balancing radial and axial loads, life, and rpm, with cylindrical bearing at D and ball bearing at C.

Learn bearing selection at point z by calculating the equivalent load f_e, applying conservative assumptions, and iterating between ball and cylindrical bearings to meet catalog load ratings.

Lubrication creates a protective film between rolling and sliding surfaces in bearings and gears, reducing friction and wear while dissipating heat to prevent corrosion.