CHEMORHEOLOGICAL RELAXATION, RESIDUAL-STRESS, AND PERMANENT SET ARISING IN RADIAL DEFORMATION OF ELASTOMERIC HOLLOW SPHERES

Recently, a constitutive theory for rubber-like materials has been dev eloped by which stress arises from different micromechanisms at differ ent levels of deformation. For small deformations, the stress is given by the usual theory of rubber elasticity. As the deformation increase s, there is scission of some junctions of the macromolecular microstru cture. Junctions then reform to generate a new microstructure. The con stitutive equation allows for continuous scission of the original junc tions and formation of new ones as deformation increases. The macromol ecular scission causes stress reduction, termed chemorheological relax ation. The new macromolecular structure results in permanent set on re lease of external load. The present work considers a hollow sphere com posed of such a material, also assumed to be incompressible and isotro pic, which undergoes axisymmetric deformation under radial traction Th ere develops an outer zone of material with the original microstructur e and an inner zone of material having undergone macromolecular scissi on, separated by a spherical interface whose radius increases with the deformation. The stress distribution, radial load-expansion response, residual stress distribution, and permanent set on release of tractio n are determined. It is found that a residual state of high compressiv e stress can arise in a thin layer of material at the inner boundary o f the sphere.