Stress analysis of a stepped rounded D‐ring with a ratio of H1/H2 = 3.0 under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

Stresses occurring in a stepped rounded D‐ring designed to have a ratio of H₁/H₂ = 3.0 and compressed to 20% squeeze and pressurized with internal pressures of 0 MPa, 0.98 MPa, 1.96 MPa, 3.92 MPa, 4.9 MPa and 5.89 MPa are analyzed using photoelastic experimental hybrid method. It was observed that when a pressure of 0 MPa and 20% compression are applied, the photoelastic isochromatic fringes of the stepped rounded D‐ring with a ratio of H₁/H₂ = 3.0 were almost symmetrical. However, as the applied internal pressure increased, the circular portion of the D‐ring moved over the step on the front side along the points 1_r–2_r towards the restraining wall of the front side of the groove. During the motion of the circular portion, the space between the restraining wall and the step on the front side was slowly filled; but unlike the D‐ring with a ratio of H₁/H₂ = 1.0 where complete filling occurred earlier before extrusion, complete filling of this space delayed until the portion of the D‐ring near the extrusion gap extruded. It was further noted that an internal pressure of up to 5.89 MPa was required to initiate extrusion in the D‐ring with a ratio of H₁/H₂ = 3.0.