| Elastomer-covered rollers are commonly used in nip systems. This dissertation is built upon purely elastic constitutive relationships to model three elastomers: an open-cell polyurethane foam, a closed-cell ethylene propylene diene methylene (EPDM) expanded rubber, and a nearly incompressible urethane rubber. The first two materials are categorized as compressible and analyzed in the large strain region ({dollar}>{dollar}15% compressive nominal strain) using hyperelastic strain-energy functions. Evaluation of urethane rubber is limited to small strains and Hooke's law because of its large stiffness. The compressible materials are experimentally tested under uniaxial compression and simple-shear deformation modes. Measurements of compressive stress, transverse strain, shear stress, and Poynting stress are utilized to evaluate two strain-energy functions: the "Blatz-Ko law for polyurethane foam" and the general "Ogden-Hill" form. The material data demonstrates that the Blatz-Ko form lacks sufficient generality to model, even qualitatively, these compressible materials for this range of deformation. Results establish that the highly nonlinear nature of the Ogden-Hill form allows for good quantitative predictions with two-term models. Experimental measurements of the urethane rubber using an ultrasound technique yield a Poisson's ratio of 0.4997.; Based on the constitutive laws, nip parameters of load/deflection, nip width, media speed ratio, and media skew are studied. Comparisons between implicit static and explicit dynamic finite element methods demonstrate the superior robustness of the latter in solving large-deformation frictional rolling problems. Experimental results on nip systems demonstrate that the analytical models yield good qualitative and reasonable quantitative predictions. These results establish that purely elastic material formulations capture the dominant behavior, but that material hysteresis, especially for the compressible materials, is needed for improved accuracy. In particular, non-rolling indentation-type predictions are more accurate than analyses which involve rolling (cyclic loading). Analysis of tire-like nip systems made of nearly incompressible urethane shows that the commonly used plane strain assumption causes significant overprediction of the media speed ratio. Assessment of nip parameter sensitivity to elastomer type and loading conditions indicates that media speed ratio is the most sensitive variable and nip width is the least. |
