Relationship between Sharply Notched Fracture Strength and Fracture Surface Marks in a Brittle Plastic in Tension : In the case of an Inside Loading : Series A : Solid-Mechanics, Strength of Materials

The fracture strength was varied by changing an inter-grip distance (which we call a gage length here) of a sharply center-notched tensile sheet specimen of unsaturated polyester resin, where the specimen width, thickness, crack length and loading method were kept constant. The loading method is such that the main load works on a central-line parallel to the axis of loading which crosses perpendicularly the central crack length. We call this an inside loading in contrast to an outside loading (1). The number, density, area ratio of fracture surface marks vary with the fracture strength of the material. The total number of marks increases with the fracture strength. The density and area ratio marks increase at each different rate with respect to fracture strength. These results are discussed with the analytical relations of the fracture strength, the dynamic stress-intensity factor and the dynamic strain-energy-release rate by employing the reported relations. The fracture surface marks are examined by the two-dimensional equation of fracture surface marks, and the analytical area ratio of the marks is also calculated.