2022 年 26 巻 1-2 号 p. 25-38
In 2008, the authors created a system to quantify plasticity from image analysis of impressions of clay dough samples prepared under predetermined conditions, deformed using a drop weight device similar to the Pfefferkorn method, in order to improve the functionality of a computer programmed tool to support the design of ceramic bodies. This system was intended to evaluate the plasticity of clay dough for potter’s wheel molding, however it was also used to evaluate ceramic dough for casting and extrusion molding. Although good results were obtained for the clay dough for potter’s wheel molding made mainly of feldspar, silica stone, pottery stone, and clay, the plasticity index became negative in the evaluation of porous clay dough, causing a problem that deviated from the evaluation of the clay craftsman. The purpose of this study is to solve this problem. In order to compare the evaluation of the clay craftsman with the evaluation of the computer program, clay dough samples containing gairome clay, kaolin with two levels of particle size, bentonite, polyvinyl alcohol and diatomaceous earth were prepared. Each sample was further processed into samples with four levels of moisture content and deformed using a drop weight device. The deformed samples were subjected to image processing and binarized to calculate the deformation rate. The binarized image was processed into a line image by analyzing the binary vector. Vector analysis of contour shapes such as cracks was performed from the line image, and from the pass rate, the moisture content region where good plasticity can be obtained was estimated. In the calculation of plasticity index, the change of setting of plasticity potential plane and the application of curved surface were considered. Through these considerations, the problem of negative plasticity index was solved, and it was possible to roughly agree with the evaluation of the clay craftsman.
