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Inelastic effects in bulge formation of inflated polymer tubes
Fatemeh Rouhani1, Jack Wurster Pazin1, Brian A Young2
1Department of Mechanical Engineering and Material Science, University of Pittsburgh, Pittsburgh, PA 15261, USA. velankar@pitt.edu.
Soft Matter
|May 13, 2024
Summary
Polyurethane tubes exhibit unique inflation behaviors not seen in hyperelastic materials. Viscoelasticity explains phenomena like pressure maxima without bulging and gradual pressure drops during inflation.
Area of Science:
- Materials Science
- Solid Mechanics
- Polymer Physics
Background:
- Bulge instability in soft tubes is well-understood for hyperelastic materials.
- Polyurethane tubes display complex deformation patterns during inflation that deviate from hyperelastic predictions.
Purpose of the Study:
- To investigate the inflation behavior of polyurethane tubes, which are not strictly hyperelastic.
- To identify and explain the unique deformation modes and pressure responses observed.
Main Methods:
- Experimental inflation of polyurethane tubes at a constant rate.
- Observation and documentation of various deformation shapes (e.g., multiple bulges, propagating bulges).
- Comparison of experimental results with existing hyperelastic tube theory and finite element simulations.
Main Results:
- Observed diverse shapes including irregular axisymmetric forms, single propagating bulges, and homogeneous cylinders.
- Noted pressure maxima can occur without bulging, unlike in hyperelastic materials.
- Documented gradual pressure reduction over extended periods (up to an hour) and permanent deformation upon deflation.
Conclusions:
- Existing hyperelastic theory fails to capture the observed behaviors in polyurethane tubes.
- Viscoelastic properties, particularly slow material response, are suggested to explain the prolonged high pressure and multi-bulge formation.
- The study highlights the importance of considering viscoelasticity in soft tube inflation mechanics.
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