Dissertation Title: Analytical Framework for Static Contact Behavior in Nonpneumatic Wheels with Nonreciprocal Spokes and Laminated Rings
Date: 2025/05/21 - 2025/05/21
Dissertation Title: Analytical Framework for Static Contact Behavior in Nonpneumatic Wheels with Nonreciprocal Spokes and Laminated Rings
Speaker：Zhipeng Liu, Ph.D. candidate at UM-SJTU Joint Institute
Time: May 21, 2025, 13:00-15:00 (Beijing Time)
Location: Meeting Room 403, Longbin Building
Abstract
Nonpneumatic wheels (NPWs) have emerged as a promising alternative to traditional pneumatic tires, offering advantages such as puncture resistance, low maintenance, and recyclability. However, accurately modeling their mechanical behavior remains challenging due to the complex interactions among spokes, laminated rings, and road surfaces. Existing models often fail to capture key aspects, particularly the role of nonreciprocal elasticity in decoupling contact pressure from vertical stiffness and the influence of laminated ring structures on load distribution. Nonreciprocal elasticity, characterized by differing tensile and compressive stiffnesses, enhances load-carrying efficiency, while the anisotropic properties of laminated rings contribute to balancing flexibility and load distribution. However, traditional models often oversimplify or neglect these effects, limiting their predictive accuracy under realistic conditions. To address these gaps, this dissertation develops an advanced analytical framework integrating nonreciprocal elasticity, laminated ring mechanics, and contact modeling. The study begins with a spoke design framework that leverages nonreciprocal elasticity to achieve a high top-loading ratio, reduce local stress, and enhance load-carrying efficiency. Key design guidelines are provided for balancing top-loading performance with other wheel characteristics, such as vertical and longitudinal stiffnesses, as well as local stress. Building on this, an orthotropic ring model is introduced to predict contact behavior for moderately thick elastic rings against centrosymmetric rigid surfaces, offering a scalable de-sign map for facilitating the choice of geometry and materials, such as ring radius, thickness, and elastic moduli. The framework is then extended to investigate the interaction between nonreciprocal spokes and laminated rings under non-axisymmetric loading, establishing a unified approach for evaluating their combined performance in nonpneumatic wheel systems. This analytical framework offers a design map correlating radial foundation stiffness with the ring deformation, incorporating ring dimensions, laminate lay-up architecture, and lamina anisotropy to optimize engineering designs. Further refinements of the framework incorporate transverse compliance of the outer tread and the coupled effects of radial and tangential spoke stiffnesses to examine NPW-road interactions. Systematic evaluations under planar and cleat road profiles highlight the impact of tailored shear band structures on improving contact stress uniformity and validating the robustness of the proposed framework in addressing NPW design challenges. This dissertation provides critical insights into NPW mechanics by demonstrating that nonreciprocal elasticity is a key factor in decoupling vertical stiffness from contact pressure and achieving a high top-loading ratio. Additionally, it establishes that shear-dominated laminated rings significantly influence contact stress distribution, offering strategies to enhance uniformity and load transfer efficiency. The pro-posed analytical framework refines contact stress predictions and enables systematic parametric studies to optimize NPW design. These findings advance high-performance, durable, and scalable NPW solutions for next-generation transportation applications.
Biography
Zhipeng Liu received his B.S. degree from Hainan University in 2017 and his M.S. degree from Hunan University in 2020. He is currently a Ph.D. student at the University of Michigan-Shanghai Jiao Tong University Joint Institute, supervised by Prof. Jaehyung Ju since September 2020. His research focuses on the mechanical modeling and design of nonpneumatic wheels.