Development of the On-Line Gravity-Induced Compression Test: “The Inverse Slugs Test”

A novel experimental method is developed that allows for on-line high-frequency measurement of the material’s yield stress and stiffness under compressive loading. This loading condition corresponds to the dominating condition directly after extrusion, and the obtained properties are thus essential to controlling the extruded material’s shape and stability. Since these measurements can be conducted at high frequency, they could also be used for quality control. A theory for the design of the experimental setup is developed and applied in a case study. In this case study, the material’s stiffness remains relatively stable after four seconds after the last moment of applied shear. Furthermore, its dependency on nozzle width correlates to the model estimation, which validates the measurement principle. It is concluded that the inverse slugs test is less suitable for measuring process variations since it is relatively labor-intensive. It can, however, be used for an in-depth analysis to quantify the effect of the nozzle design.