University of Utah Department of Mechanical Engineering

Brief Early History of Theoretical Linearized Elasticity
o c 1630 : Isaac Beeckman
Realizes that strain (change in length/length) should enter an elastic law.
o 1687 : Isaac Newton
Publishes "Principia" which provide the laws of motion : inertia, conservation of momentum, and balance of forces, though inertia and momentum remained undefined.
o 1684 : Leibniz
Find the relation between bending moment and the moment of inertia of a linear elastic beam.
o 1691-1704 : James Bernoulli
Derives the general equations of equilibrium using different methods : balance of forces, balance of moments, and the principle of virtual work.
Finds that the stress (force/area) as a function of strain characterizes a material and thus proposes the first true stress-strain relation and a material property.
o 1713 : Parent
Determines the position of the neutral fiber and postulates the existence of shear stresses.
o 1736 : Euler
Publishes "Mechanics" where he defines a mass-point and acceleration. Also introduces vectors. Most of the equations in mechanics in use today can be traced to the work of Euler.
o 1742 : John Bernoulli
First to refer all positions to a single, rectangular Cartesian co-ordinate system.
o 1743 : D'Alembert
First to derive a partial differential equation as the statement of a law of motion.
o 1750-1758 : Euler
Formulates the principles of conservation of linear momentum and moment of momentum. Distinguishes mass from inertia.
o 1773 : Coulomb
Proved that shear stresses exist in a bending beam.
o 1788 : Lagrange
Publishes "Mechanique Analitique" which contains much of the mechanics known until that time.
o 1822 : Cauchy
Discovers the stress principle - relating the total forces and total moment to internal and external tractions. Cartesian co-ordinate system. This is basically the first description of the stress tensor. Cauchy also presented the equations of equilibrium and showed that the stress tensor is symmetric.
o 1833 : Poisson
Publishes statement and proof that a system of pairwise equilibriated an dcentral forces exerts no torque. This is fundamental to the principle of conservation of moment of momentum. More details can be found in the books by Timoshenko and Love.

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