Compression-Resilience Responses of Commonly Used Membrane Materials in Spiral Case Structures of Hydroelectric Power Plants: Experimental Investigation

Abstract

The compressive behavior of membrane materials used in spiral case structures (SCSs) is of interest because, to a large extent, it determines the structural performance of SCSs. Unfortunately, it has not been dealt with in depth and was routinely assumed to be linear and elastic in SCS structural design. The aim of this work is to further current knowledge of the compression-resilience responses of the two most commonly used membrane materials: the polyurethane (PU) cork and polyethylene (PE) foam. A lever-type consolidometer was employed for the current cyclic compression-resilience test. The compressive behavior of both materials was stabilized after six loading/unloading cycles (with maximum pressure of 1. MPa). Strong evidence of the nonlinearity and inelasticity of both materials was found. The relevance of cyclic loading/unloading to the permanent set of both materials is clearly supported by the current findings. This study has gone some way toward enhancing the community’s understanding of the nonlinearity and inelasticity of the two membrane materials and has highlighted the need to consider them in the structural design of SCSs.