Sharp tipped V-shaped notches are often used in standard fracture toughness testing for ductile materials, polymers and for the characterization of weld strength. For all notch types, a key parameter in governing stress concentration and failure in notched materials is the notch tip curvature or radius.
NOTCHED UP DEF ISO
For standardized testing of fracture toughness by the Charpy impact method, specimen and notch dimensions are most often taken from American standard ASTM E23, or British standard BS EN ISO 148-1:2009. The type of notch introduced to a specimen depends on the material and characterization employed. Notched specimens are used in other characterization protocols, such as tensile and fatigue tests. Charpy testing is conducting with U- or V-notches whereby the striker contacts the specimen directly behind the notch, whereas the now largely obsolete Izod method involves a semi-circular notch facing the striker. The Izod impact strength test uses a circular notched vertical specimen in a cantilever configuration. The height of its subsequent swing-through is used to determine the energy absorbed during fracture. The most common is the Charpy impact test, which uses a pendulum hammer (striker) to strike a horizontal notched specimen. Notches are commonly used in material impact tests where a morphological crack of a controlled origin is necessary to achieve standardized characterization of fracture resistance of the material. Notches are used in materials characterization to determine fracture mechanics related properties such as fracture toughness and rates of fatigue crack growth. In structural components, a notch causes a stress concentration which can result in the initiation and growth of fatigue cracks. In mechanical engineering and materials science, a notch refers to a V-shaped, U-shaped, or semi-circular defect deliberately introduced into a planar material.
0 kommentar(er)
