A System for Measuring Dynamic Viscoelasticity ofa Small Irregularly Shaped Sample

Abstract

A new system for measuring dynamic viscoelasticity has been developed. It is now possible to measure rapidly the properties of a small irregularly shaped sample such as a grain of cooked rice or a piece of noodle. The time dependence can also be investigated, because the sample is not destroyed. The sample is sandwiched between two plates which are a constant distance apart and vibrated in the shear direction by moving one of the plates. The other plate detects the response through the sample. To obtain the value of viscoelastici-ty independent of the sample size, one of the plates is made of a transparent acrylic board and the contact area between the sample and the transparent plate is measured by an imageprocessing device with a monitor camera. Viscoelastic moduli G' and G″ can be calculated from vibration applied and response of the sample, the sample thickness and the contactarea. As an application to quality evaluation, the viscoelasticity of three kinds of cookedrice was measured in this. system. The results of the measurement showed a tendencysimilar to those of sensory evaluation.