The Load Capacity Model and Experimental Tests of a New Yielding Steel Prop

Figure 4

The specific cross-section of contact area between the steel ball and the inner tube. is embedded depth between the steel ball and inner tube in position in a specific cross-section of contact area, is the projection of the contact area in direction, is the radius of cross-section of the steel ball in position, is the maximum plastic zone depth in direction under the stable load capacity, and and are the normal force and twisting force, respectively.