Center notched test piece

There are two principle methods for measuring impact and notched impact strength, which in practice differ only in the way in which the test bar is held. In the Charpy method the test piece is suspended at both ends and is struck in the center by a weighted pendulum. In the Izod method the test piece is clamped at one end only and is struck at the free end by the pendulum. 

The Izod test is notionally very similar to the Charpy test, except that the test piece is clamped at one end below the notch, or at the center of the specimen if it is unnotched, and struck by a pendulum close to the other end. It is therefore a cantilever bending test (Fig. 14). Traditionally the Izod test has been more favoured in North America, while the Charpy test has been more popular in Europe. The test details arc given in ISO 180 [73], BS 2782. Method 350 74] (which is identical to it), and ASTM D256, Method A [67] (also methods C. D, and E). 

Standard test methods for the determination of Charpy impact strength are Usted in Table 10.11. For example, BS 2782 (Method 351A) uses a rectangular, notched or unnotched, bar supported at both ends in such a position that the pendulum strikes it in the center, directly behind the notch. The energy absorbed in the impact is read directly by means of a pointer from a scale calibrated to allow for frictional and windage errors. Three standard test pieces are defined - the preferred being 120 x 15 x 10 mm with a span of 70 mm. The standard impact energies are 0.5, 1,4, 15, and 50 J. 

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