Distribution of Pressure on Carton Board Packages : An Objective Analysis

Abstract: Biomimetic tactile sensing was previously mostly performed in medical situations, such as when locating tumors in patients’ bodies. This thesis examined the effectiveness of using a biomimetic tactile sensory equipment for examining pressure distribution throughout carton board packages, made in two different carton board qualities. The purpose was to examine to what extent biomimetic tactile sensing was able to mimic the results of a group of human test subjects evaluations. Eight packages, made from two different materials, were tested. There were four packages of each of the materials. Each package had four points where displacement measurements with a force of 6N were conducted. The packages were then measured twice on a single point on the edge of the package, with the force of 12N.  The packages at disposal were compressed using a uniaxial-tensile-testing machine alongside with the aforementioned equipment. The pressure sensitive film was placed on top of the packages and a limit on the maximum force to be applied was set on the testing machine. Two limits on the applied forces were set, the first to see the distribution of pressure within the range of elastic deformation, so that no lasting deformation would have occurred. The second force limit was set to see the moment where the elastic deformation area transformed into the plastic deformation area, to see whether or not there was a difference in the distribution of pressure pre- or post-plastic deformation. From the results from compression tests, it was clear that there was a difference in pressure distribution before and after the plastic deformation had occurred. The experimental diagrams showed that the curves were vastly different in both cases. It was also clear that there was a significant difference in the distribution of pressure, depending on if the pressure was applied closer to the middle compared to closer to the center of the package (single vs multiple concentration of forces, respectively). Inspecting results from packages made in both carton board qualities, there were no clear results as the same trends could be seen throughout the tests.  It was concluded that the BioTac could be used to accurately identify concentrations of forces, differences in pressure distribution and the location of deformation. This means that the BioTac will be useful in future experiments, when objectively evaluating and defining grip stiffness, with the help of methods such as the finite-element method.