Concept
Section modulus
2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
The material far from the middle does nearly all the work
A strip of steel contributes to bending stiffness in proportion to the square of its distance from the centre. Move the same steel outward and the section gets stiffer for nothing.
Bending is a pair of forces, pushing and pulling
A bending moment is not a mysterious twisting. It is a push near the top of a section and a pull near the bottom, separated by a lever arm — a couple, made out of stress.
Named alongside it
The objects these essays reach for when they reach for this one.
CentroidNeutral axisElastic limitI-sectionLever armParallel axis theoremPlane sectionsPlastic momentSecond moment of areaStress block