In Situ Investigation of Load-Dependent Nonlinearities in Tangential Stiffness and Damping of Spherical Contacts
Autor: | Melih Eriten, Shixuan Chen, Ahmet D. Usta, Karthik Yerrapragada |
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Rok vydání: | 2020 |
Předmět: |
Materials science
Deformation (mechanics) Mechanical Engineering Stiffness 02 engineering and technology Surfaces and Interfaces Mechanics Plasticity Dissipation 021001 nanoscience & nanotechnology Surfaces Coatings and Films body regions Stress (mechanics) 020303 mechanical engineering & transports 0203 mechanical engineering Mechanics of Materials medicine Displacement (orthopedic surgery) medicine.symptom Tangential stiffness 0210 nano-technology |
Zdroj: | Journal of Tribology. 143 |
ISSN: | 1528-8897 0742-4787 |
Popis: | Seemingly stationary (pre-sliding) interfaces between different materials, parts, and components are major sources of compliance and damping in structures. Classical pre-sliding contact models assume smooth elastic contact and predict that frictional slip leads to a well-defined set of stiffness and damping nonlinearities. However, reported data deviate from those predictions, and literature lacks a conclusive evidence leading to those deviations. In this work, the authors measure tangential stiffness and damping capacities inside a scanning electron microscope (SEM) while monitoring contacts between a rigid spherical probe and two materials (high-density polyethylene (HDPE) and polyurethane elastomer). Measured force, displacement, contact area, stiffness, and damping are then compared with predictions of classical models. In situ SEM images synchronized to the tangential force–displacement responses are utilized to relate the degree of plasticity and geometric alterations to stiffness and damping nonlinearities. In agreement with the classical models, increasing tangential loads cause softening in contacts under light normal preloads. In contrast, stiffness for HDPE increases with increasing tangential loads at heavy normal preloads due to plasticity and pileups over the contact. Material damping is prevalent for all loading cases in polyurethane samples thanks to nearly fully adhered contact, whereas for only light tangential loads in HDPE. With increasing tangential loading, specific damping capacity of HDPE contacts increases tenfold. This nonlinear increase is due to plastic shearing and frictional losses induced by tangential loading. Those findings suggest that predictive interface models should include geometric alterations of contact, plasticity, and material damping. |
Databáze: | OpenAIRE |
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