4. Glossary and acronyms

Main constraint; Main stress

Value of the normal stress (positive or negative) observable along a direction in which shear is zero. In a 3D elastic medium, three principal stresses exist (σ ₁ , σ ₂ , σ ₃ ), and their conventional designation is: σ ₁ > σ ₂ > σ ₃ .

Ligne isostatique; Isostatic line

A line such that the tangent at any point is directed along one of the principal constraints. In 2D, isostatic lines form a network of orthogonal curves.

Ligne isocline; Isoclinal line

A line such that...