ABSTRACT
According to Fig. 3.1, in each point P in the solid, three curves intersect each other. The first curve is θ3 designated by P P3 and in the deformed solid the covariant-based vector G3 is tangent to P P3. Similarly 2nd curve is θ2 designated by P P2 and G2 is tangent to P P2, also 3rd curve is θ1 designated by P P1 and G1 is tangent to P P1. It should be reminded that in this section
we discuss the general definition of the stress in non-orthogonal coordinate system and the triangle PP P1 2 3 represents a area in the deformed solid.
