Heat Generation around Fracturing Point during the Tearing Process of Paper

A tearing test method by using tensile tester was employed to investigate local deformation process of paper by the change in temperature distribution images during the course of Elmendorf tearing test. Thermography successfully aIlowed the successive and detailed observation of heat generation around the notch tip tracing the tearing line. The zone being stressed in softwood pulp sheet, which appears around the tearing point as a high-temperature zone, is somewhat bigger than that of hardwood pulp sheets. Behavior of the area and maximum temperature rise of high-temperature zone with an increase in beating degree is similar to that of tear strength. Thus, the maximum temperature rise and area decrease after passing an early peak as beating proceeds for softwood pulp sheets, while these increase as beating proceeds for hardwood pulp sheets. The decrease in area of the zone refers to an enhanced stress concentration, and the increase in the maximum temperature rise by Iightly beating refers to a large amount of work including a pulIing fibers out of the paper done at the tip of tearing point.