Date of Award

8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Member

Dr. Georges Fadel, Committee Chair

Committee Member

Dr. Nicole Coutris

Committee Member

Dr. Gang Li

Abstract

Operational wear and hysteretic heat loss frequently affect the rubber components of the M1 Abrams main battle tank, leading to deterioration of the material and laborious replace and repair efforts in tactical situations. In previous work at Clemson University, meta-material backer pads had been designed and optimized using the Unit Cell Synthesis method and the Modified Unit Cell Synthesis method to match the characteristic deformation behavior of current elastomer backer pads on the M1 Abrams battle tank. In this case, a meta-material is a periodic, unit cell based, material that exhibits global mechanical properties that differ from the mechanical properties of the constitutive material. After successful optimization results were obtained, physical parts were manufactured using an Electron Beam Melting additive manufacturing process and a Ti-6Al-4V powder, however the behavior of the physical pads was never tested. The work in this research begins here, with the experimental testing and performance comparison of the titanium backer pads against the respective finite element model. Using compressive and high cycle fatigue testing, the behavior of one backer pad was observed, showing a desired nonlinear behavior but larger than expected strain values. Fatigue testing, in turn, resulted in a critical failure prior to meeting the desired and expected number of cycles. To search for causation for these discrepancies, three potential sources for performance deviation were identified through literature and FE model review. A sensitivity analysis was employed to analyze the influence of manufacturing tolerances and material property variation on final performance, which showed significant performance error could be feasibly expected. In tandem with testing, expressed interest in replacing additional rubber track system components led to the design and optimization of a meta-material system. Using MUCS methodology, a circular meta-material for use on the road wheel was designed and optimized. Inadequate results encouraged the introduction of layer multipliers. The multipliers altered the design space and provided several significantly improved design options to choose from. The system design was then carried out, utilizing both a single level and multi-level optimization approach to compare against one another, based on several criteria. Finally, research questions are answered, conclusions are discussed, and the path to future work is provided.

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