17.6 : الإجهاد: شروط التحميل العامة

Consider a body subjected to multiple loads. When dissected through a point using a plane parallel to the xy plane, it is observed that the shearing forces act on a small area surrounding the point.

Consider a portion of the body subjected to the previously shown loads, with the normal force acting along the z-axis

The shearing forces do not have a well-defined direction on a sectional plane, so they are resolved into two component forces parallel to the x and y axes.

The magnitude of each force is then divided by the area to obtain the stress components.

The first subscript in the stresses indicates that they are exerted on the surface perpendicular to the z-axis. The second subscript in shearing stresses identifies the direction.

When the other side of the vertical plane is analyzed, it yields the same stress components but in opposite directions.

By passing sections through the point parallel to the yz and zx planes, additional stress components can be defined.