Experimental study on optimal plastic rings in the range of large displacements

Circular optimal rings were designed for maximum limit value of load assuming an ideal rigid-plastic material. The paper presents P - δ relations in the range of large displacements obtained in compression and tension tests which were carried out on four types of duraluminum rings with different geometric constraints described by the angle within which the cross section remains constant. Applicability of rigid-plastic theory to initial optimization of structures exhibiting sensitivity to geometry changes and material hardening is discussed. The optimal rings without any geometric constraints showed the sensitivity to imperfections and sudden loss of stability with qualitative change of deformation mode. The determination of the best geometric constraints appears as a new optimization criterion when large plastic deformations are present.