Dynamic Interactions Between Multidimensional Viscoelastic Joints and an Elastic Frame Structure

The topic of the scholarly research is motivated by the practical needs in the automotive industry to judiciously design elastomeric joints at the interfaces between elastic structures that balance the competing needs of ride and handling, durability, and vibration isolation for the next generation fuel efficient vehicles. A typical elastomeric joint is geometrically shaped to provide favorable properties in certain directions say based on the diagonal terms; even though, non-diagonal (coupling) terms are intrinsic to the design of automotive assemblies. The chief objective of this research is therefore to gain a fundamental understanding of how the multidimensional joint properties (including non-diagonal terms) interact with an elastic structure. Simpler structural elements are often used in the scientific literature to represent complex structures such that fundamental insight is gained as their static and dynamic properties are easily scaled to match real-world systems; thus, an elastic beam is selected for this research. The problem is examined using direct and inverse analytical, experimental, and computational methods. The specific contributions of this research include the following. First, new mathematical models (in terms of both partial and ordinary differential equations) are developed to describe the dynamic behavior of an elastic beam element with multidimensional viscoelastic joints. Assumptions made by prior researchers are relaxed to examine the complex eigensolutions of coupled flexural and longitudinal eigenfunctions in a beam. The resulting closed form solutions could be efficiently used to analyze the subsystem damping, eigenfunction complexity, and force transmissibility. Second, a new method for the identification of multidimensional joint properties is developed where the inverse problem is solved. The formulation should permit direct integration with computational modeling and experimental modal analysis. New benchmark laboratory experiments are designed and conducted to validate the models and identification method. Finally, the role of mean load on the joint-structure system is analytically examined. Asymmetries appear in the effective joint stiffness matrices as the result of a mean operating load, which render the system non-selfadjoint; thus, analysis requires knowledge of both the adjoint and the original system. Although the system remains linear at a given operating point, the assumption of reciprocity is no longer valid. The presence of asymmetries in such a system has consequences in computational modeling and in modal experiments. On a mathematical basis, this work should provide insight to other disciplines that are governed by partial differential equations with non-selfadjoint boundary conditions. The analytical and experimental studies should be beneficial to the automotive industry in selecting optimal elastomeric joint properties and provide insights for interpreting component test data with system data, even when the selected elastomeric joints exhibit strong amplitude and mean load dependent properties. Finally, this research is applicable to the general class of jointed assemblies with applications to mechanical, building, and aerospace structures.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Noll, Scott A.

Contributors dc:contributor

• Singh, Rajendra
• Dreyer, Jason

• Mechanical Engineering
• Stiffness coupling
• Beam structures
• Damping calculations
• Asymmetric coupling
• Joint identification
• Experimental dynamics
• Elastomer properties

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1364809438

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1364809438