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Material characterization and material model development for simulating elastomeric parts in diaphragm pumps.

Number: 1155

Author(s) : SWIENTY A., EBERLEIN R., THIERRIN R., DIAS VIDAL DE CASTRO N.

Summary

A diaphragm pump is a reciprocating positive displacement pump. It works according to the principle that a volume (working chamber) is periodically increased and decreased by a diaphragm. Due to this, a medium is sucked in and pushed out of the working chamber. Valves are used to prescribe the direction of flow and prevent back flow. The valves open and close automatically depending on the flow values or existing pressure differences. The diaphragm and, in many cases, the valves are made of a material which is capable of large reversible deformations such as elastomers (i. e. rubber). Such a material is necessary due to the diaphragm being stretched and compressed during its reciprocating movement. In addition, the flow domain is sealed off from the environment (this does not mean the sealing of the working chamber from the pressure or suction channels, but rather the prevention of leakage from the pump) by squeezing defined sealing surfaces on the diaphragm and the valves.
Numerical simulations with FEM are used to gain a deeper understanding of the movement, the strains and stresses that occur in the elastomeric part during operation. To achieve this, an adequate material model must first be created. A material model for elastomers differs substantially from a material model for steel, which in its simplest form consists only of a Young's modulus and a Poisson’s ratio. Elastomeric materials show a behavior that is nonlinear elastic (hyperelastic) and time dependent (viscoelastic).
The aim of this paper is to present two methods for measuring the nonlinear stress-strain relationship of EPDM with large strains, which is also affected by temperature and the strain rate at which the material is stressed. Firstly, a hyperelastic characterization method at low strain rates with dynamical mechanical analysis is introduced. Secondly, an advanced method is described that enables the examination of hyperelastic material properties at high strain rates. Furthermore, two viscoelastic material models are calibrated on the base of these measurements, the first is a Prony series approach and the second uses a Bergstrom-Boyce model.
Finally, simulation results are compared with measurements. Measured stress-strain curves of a cyclic simple tension experiment are available for this purpose. This experiment is reproduced numerically. Comparing the results provides a first assessment of the material models.

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  • Original title: Material characterization and material model development for simulating elastomeric parts in diaphragm pumps.
  • Record ID : 30033024
  • Languages: English
  • Subject: Technology
  • Source: 2024 Purdue Conferences. 27th International Compressor Engineering Conference at Purdue.
  • Publication date: 2024/07/18

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