By means of the Mohr circle the moments Mx, My en Mxy can be transferred to the principal moments M1 and M2 (i.e. a plane is found with the angle θp and with the global X-axis (or with the local X’ –axis), the torsion moment on all the edges of this plane is 0, and M1 respectively M2 can assume the smallest respectively largest possible value.
θp is defined by the following formula 
M1 and M2 are defined by the following formula 
Same rules are also valid for decomposition of principle axial forces e.g. stresses
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