The hysteretic loss associated with cyclic shear in the elastomeric shear layer is one of the prevailing concerns for the development of a low rolling loss non-pneumatic wheel. We propose to eliminate the hysteretic losses associated with the elastomeric shear layer and thus, reduce the corresponding rolling resistance by using linear elastic materials which are inherently non-hysteretic.
Since the shear modulus of a viscoelastic shear layer is less than that of an elastic material by several orders of magnitude, the challenge to achieve a low effective shear modulus shear layer with linear elastic materials directs towards the development of a new class of materials known as metamaterials. These are engineered materials with exceptional qualities usually not encountered in nature and there is a need to determine their properties for any given application.
This thesis presents work on the material and geometric requirements determination of a low rolling loss non-pneumatic wheel shear beam (shear beam is an integrated structure composed of a shear layer and inner and outer inextensible membranes) through a systematic optimization approach. Six different configurations of the non-pneumatic wheel are explored. Each design configuration is a unique combination of the type of linear elastic material model used for the shear layer and the material used for the outer and inner inextensible membranes.
In each case, the choice of an appropriate geometric and material property of the shear beam is treated as a single-objective constrained optimization problem. The goal is to target a sufficiently large strain to guarantee enough deformation in the shear layer while constraints on the average and maximum contact pressure are satisfied. The study identifies the driving design variables from a statistical analysis and proposes a relation between them to meet the functional requirement of a low rolling-loss non-pneumatic wheel. The resulting constitutive metamaterial properties of the shear layer can be used as prescribed constitutive properties to tailor the periodic structure of a material by means of the topology optimization.
Due to the need for an integrated design environment capable of generating the training set by coupling FEA tool (Abaqus)within a DOE sequence, offering multiple DOE sequence generation, metamodeling, and optimization techniques, with an easy-to-use graphical user interface (GUI) capable of performing statistical analysis and data visualization, a commercial Process Integration and Design Optimization (PIDO) tool called modeFRONTIER (from ESTECO) is used in this research. Although there are several commercial PIDO tools available, this software is selected since it is used extensively in the literature for various applications.