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Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. [4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to ...
The formula to calculate average shear stress τ or force per unit area is: [1] =, where F is the force applied and A is the cross-sectional area.. The area involved corresponds to the material face parallel to the applied force vector, i.e., with surface normal vector perpendicular to the force.
In physics, the Young–Laplace equation (/ l ə ˈ p l ɑː s /) is an algebraic equation that describes the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of surface tension or wall tension, although use of the latter is only applicable if assuming that the wall is very thin.
A classical torsion wire-based du Noüy ring tensiometer. The arrow on the left points to the ring itself. The most common correction factors include Zuidema–Waters correction factors (for liquids with low interfacial tension), Huh–Mason correction factors (which cover a wider range than Zuidema–Waters), and Harkins–Jordan correction factors (more precise than Huh–Mason, while still ...
Cauchy observed that the force across an imaginary surface was a linear function of its normal vector; and, moreover, that it must be a symmetric function (with zero total momentum). The understanding of stress in liquids started with Newton, who provided a differential formula for friction forces (shear stress) in parallel laminar flow.
Surface tension – Tendency of a liquid surface to shrink to reduce surface area; Tribology – Science and engineering of interacting surfaces in relative motion; Unilateral contact – Mechanical constraint which prevents penetration between two bodies; Wetting – Ability of a liquid to maintain contact with a solid surface
The most common method to calculate the surface stresses is by calculating the surface free energy and its derivative with respect to elastic strain. Different methods have been used such as first principles , atomistic potential calculations and molecular dynamics simulations, with density functional theory most common.
EN8 bright has a tensile strength of 800 MPa and mild steel, for comparison, has a tensile strength of 400 MPa. To calculate the force to shear a 25 mm diameter bar of EN8 bright steel; area of the bar in mm 2 = (12.5 2)(π) ≈ 490.8 mm 2 0.8 kN/mm 2 × 490.8 mm 2 = 392.64 kN ≈ 40 tonne-force