Monitored indentation for the detection of inclusions in elastomer material

Abstract

The detection of inclusions in soft material is of great interest, especially in the medical field. Traditionally, a biopsy exam is performed after palpation, when necessary. In the present work, a potentially quantitative method, via monitored indentation, is used to mimic palpation. This method consists in investigating the relaxation and stress-free relaxation responses to an indentation test performed on a silicone block with an inclusion. The aim of the study is to evaluate how a difference in position, size and adhesion of the inclusion can influence the response of the samples to monitored indentation. A finite element model is constructed to conduct comparative studies. The hyper-viscoelastic parameters of the silicone have been identified experimentally. Results from the simulations showed that the indicators measured during monitored indentation, especially during the stress-free relaxation phase, are sensitive to adhesive inclusions, while they provide little information regarding their non-adhesive counterparts. Depths and sizes for which adhesive inclusions are more likely to be detected have been identified. These results are encouraging but are conducted on polymer material and a rigid inclusion; nevertheless, they suggest that the non-destructive measure of the stress-free relaxation response of a tissue may help practicians to quantitatively characterize the nature of a nodule.