Fracture surface digitizing of specimen from drop-weight tear

Abstract

There is always a need to determine a fraction of the ductile, and respectively, brittle fracture on the fracture surface of specimen examined using a drop-weight tear test (DWTT). Determination of the percentage of ductile fracture (PDF) in accordance with valid national and international recommendations is not entirely unambiguous. Results of evaluation show a large scattering for each criterion, and depend on the subjective view of the evaluator. Criteria are complex in nature and are independent of the fracture morphology. The dimensionless areas ratio criterion has been newly proposed for the evaluation of the DWTT specimens. This criterion is given by the ratio of the fracture surface projection into a base plane to the scanned fracture surface. The fracture surface of the DWTT specimen is scanned using a 3D-Cam scanner into a network of discrete points. A fracture surface area is calculated from the sum of the areas of triangles constructed above the element of the projection of fracture surface. A dimensionless areas ratio criterion is sensitive to a change of the size of fracture surface evaluated and its value depends on the proportion of PDF in the specimen. An application of the proposed assessment of fracture surfaces in the DWTT specimens in engineering practice will contribute to the objectivity of DWTT test results and to improve equipment reliability, in which the DWTT test result is a part of attestations in materials used.