Mechanical Characterization Of Bovine Gels By Depth-Sensing Indentation: Inverse Approach And Dimensionless Equations

L. SANCHEZ FELLAY; M. CZEMER; L. FASCE; PATRICIA FRONTINI

AVEIRO

Conferencia; 5th International Conference on Polymer Behavior; 2012

Bovine gelatin gels are widely used in food industry as additives. Gelatin gels influence the food’s macroscopic structure and hence its mechanical behavior. In this work, the feasibility of extracting the stress-strain material parameters from an indentation test was investigated for gels that obey the Ogden constitutive model. Indentation experiments were carried out using a flat ended tip similar to the one used in quality control tests in food industry. In FEM simulations, the indenter tip was assumed as an axisymmetric rigid body while the test sample was modeled using quadrilateral linear elements. The contact between the indenter and the material was assumed frictionless. FEM computational experiments were first performed considering Ogden material parameters obtained from conventional uniaxial compression tests. Then, by varying the constitutive parameters, a set of finite element simulations were computed and used as input for an optimization algorithm in order to fit the true material parameters. Once the methodology was optimized, physical indentations were conducted on bovine gelatin gels and the Ogden equation was calibrated. Finally, in order to simplify the methodology and make it easy to implement in practical situations, dimensionless equations were developed in which the force versus displacement curve was fitted with the Ogden constitutive parameters.