The sign of angle in Mohr's circle represents the orientation of the normal stress with respect to the x-axis. It also indicates the direction of shear stress with respect to the normal stress.
The sign of angle is determined by the direction of the shear stress with respect to the normal stress. If the shear stress is clockwise from the normal stress, the sign is negative. If it is counterclockwise, the sign is positive.
Yes, the sign of angle can change if the direction of the shear stress changes. This can happen if the applied loads or boundary conditions change.
The sign of angle is important for understanding the principal stresses and their directions in a material. It also helps in determining the failure criteria and predicting the failure mode of a material under different loading conditions.
While the sign of angle is a useful tool for stress analysis, it only applies to two-dimensional stress states. In three-dimensional stress states, a more complex approach is needed to determine the orientation of the principal stresses.