Mechanical Engineering Gear Terminology

Gear Terminology and Calculations

• Whole depth: The distance between the addendum and dedendum circle of a gear. It's the sum of addendum and dedendum.
• Backlash: The minimum distance between the non-driving side of a tooth and the adjacent side of the mating tooth. It's the difference between tooth space width and engaging tooth thickness (measured on pitch circle).
• Fundamental deviation: The algebraic difference between the maximum limit and the basic size, or minimum limit and the basic size, whichever is closer to the basic size.
• Upper deviation: The algebraic difference between the maximum limit and the corresponding basic size.
• Lower deviation: The algebraic difference between the minimum limit and the corresponding basic size.
• Tolerance: The algebraic difference between the maximum and minimum size limits of a part.
• Addendum: The radial distance from the pitch circle to the top of a tooth.
• Dedendum: The radial distance from the pitch circle to the bottom of a tooth.

Shaft Design and Calculations

• Polar section modulus (Zj): A measure of a shaft's resistance to torsion. Calculated using the formula Zj = (πD³)/16 for a solid shaft.
• Torsional deflection: The angle of twist per unit length of a shaft under torque. Calculated using the formula θ = (32T)/(πD⁴G). Includes formulas with various units (in degrees per foot length).
• Water tank design: Minimum thickness of a cylindrical water tank can be calculated per maximum allowable stress (using the formula t = pD/(2s)).
• Stress: The internal force per unit area exerted within a stressed body.

Spring Design and Calculations

• Curve correction factor (Kc): Used in helical spring design to account for the stress concentration in the coils. Kc is calculated using curved formulas with various constants.
• Wahl factor (Kw): Used in helical spring design to account for stress concentrations in the coils. Calculated using specific spring design parameters.
• Bergstrassar factor (KB): Another parameter in spring design, also adjusting for stress concentration, calculated using spring-specific formulas.
• Resilience: The ability of a material to absorb energy when deformed elastically and return it upon unloading.

Beam Design and Calculations

• Beam: A structural member designed to support loads perpendicular to its longitudinal axis.
• Bending load: A load applied transversely to the longitudinal axis of a member.

Other Machine Design Concepts

• Fail-safe design approach: A design approach where no catastrophic loss can occur as a result of a component failure.
• Failure condition: The condition of a machine element when it is completely inoperable, cannot perform its intended function adequately, or is unreliable for continued safe use.
• Finite element analysis: A computational method used for solving complex machine shapes by replacing them with simple, interconnected elements.

Miscellaneous

• Gear pitch angle: The angle between the tooth profile and a perpendicular line to the gear axis.
• Mean diameter: The average of the maximum and minimum diameters.
• Major diameter (of a thread): The diameter of the imaginary cylinder bounding the crest of external and root of internal threads.
• Circular pitch: The distance measured along a pitch circle from a point on one tooth to the corresponding point on an adjacent tooth.
• Axial linear speed: The velocity of the screw's linear motion along its axis.
• Critical speed: The rotational speed at which a rotating shaft will experience significant vibrations or deflections from the central axis.
• Thermal stress (thermal shock failure): Momentarily high temperature gradient within a body may produce high stress gradients on a cold-quenched material capable of causing cracking during cooling.
• Coefficient of thermal expansion: The measure of the change in length of a material subjected to a change in temperature.
• Stress diameter: A diameter of a component or a gear that is used to find various stresses and deformations.
• Hoop stress: The tensile stress in a cylindrical component generated by internal pressure.
• Nominal shear stress: The shear stress at a component's surface, often calculated given a torque applied to the component.
• Poisson's ratio: A material property that relates axial strain to lateral strain under stress. Calculated by dividing modulus of rigidity by one-half the sum of one and Poisson's ratio and modulus of elasticity.

Material Properties

• Modulus of rigidity (G): The measure of a material's resistance to shear stress.
• Modulus of resilience: The strain energy per unit volume required to stress a material from an unloaded state to the point of yielding.
• Ultimate strength: The maximum stress a material can withstand before failing.
• Brinell Hardness Number (BHN): A measure of a material's hardness.

General Design Considerations

• Working strength: The load a component can safely carry under given conditions.
• Allowable stress: The level of stress on a component under operating conditions.
• Material factors: Used in calculating the endurance strength or ultimate strength of a component, accounting for material properties.
• Center distance: The distance between the centers of shafts or pulleys in mechanical systems.

Test your knowledge on essential gear terminology and calculations. This quiz covers important concepts such as whole depth, backlash, and tolerance, which are crucial for understanding gear design and function. Perfect for mechanical engineering students and enthusiasts alike.