Figure 2 shows the geometry of a piston cup and loading for power stroke in z-r axes, and figure 3 shows its undeformed geometry. Piston cup - loading. Piston cup - undeformed geometry. For definition of stress-deformed state of a piston cup is used the known method of a stress function. At the solution of a problem are used usual methods of theory of elasticity.
Scientific novelty is in accepted stress function for the solution of a problem.
The boundary conditions are satisfied on each contour approximately. Their precise correspondence is fulfilled only in isolated points of a contour, with their arbitrary number. Thus the magnification of these points gives the precision of the solution. These points are shown on fig. The obtained solution precisely satisfies to all equations of the theory of elasticity and approximately, as much as precise, for boundary conditions.