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Both Izod and Charpy tests are used to measure the impact strength of materials, but the main difference lies in the direction of the impact force. The Izod test involves a single impact from a swinging pendulum on a notched specimen, while the Charpy test involves a swinging pendulum striking a notched specimen in a horizontal position. Charpy tests are more common due to their simplicity and reproducibility, but both tests provide valuable information about a material's toughness.
In a charpy impact test, the purpose of the notch is to provide a point of fracture at the same point for each material, to make it a fair test.
because in charpy test we uplace it in as simply supported beam
A U-notch is used in the Charpy impact test to create a specific stress concentration that promotes fracture in the material being tested. The U-shaped notch helps to standardize the impact test by ensuring that the fracture occurs at a predetermined location, allowing for consistent comparison of materials' toughness. Additionally, the notch simulates real-world conditions where materials may have defects or flaws, providing insight into their performance under dynamic loading conditions.
1) The test notches for the impact specimens for the tests have different dimensions. The Izod test is a V-notch; the Charpy test has three different specimen types: Key-hole, U-notch, and V-notch. However, other specimen types may be specified as required for both tests.2) The specimens are held differently. The Izod specimen is held in a cantilevered manner; the Charpy test is held such that the specimen rests against two supports on either side of the test notch.3) The impact location is different. The Izod test impact is against the end of the exposed cantilever; the Charpy test is struck directly behind the test notch such that the specimen undergoes three point bending.4) The test specimens have different dimensions. The basic Izod test specimen is 75 x 10 x 10mm (2.95" x 0.394" x 0.394"); the basic Charpy test specimen is 55 x 10 x 10mm (2.165" x 0.394" x 0.394")It's really a stretch to give 4 points of difference, particularly as these tests may be altered as required depending on the material performance characteristic being investigated.Source(s):Degarmo, E. Black, J. Kohser, R. 2003, Materials and Processes in Manufacturing: Ninth Edition. John Wiley and Sons Inc. pp. 40 - 41
It shows the fracture toughness of materials. higher the brittleness lower the fracture toughness and also lower will be the impact value and vice verse.
To convert Charpy impact energy to impact strength, you divide the impact energy by the cross-sectional area of the specimen. Impact strength is typically expressed in units of energy per unit area, such as J/m^2 or ft-lbf/in^2. This conversion allows for a more standardized comparison of materials' impact resistance.
The Charpy test involves striking a suitable test piece with a striker, mounted at the end of a pendulum. The test piece is fixed in place at both ends and the striker impacts the test piece immediately behind a a machined notch. While most commonly used on metals, it is also used on polymers, ceramics and composites. The Charpy test is most commonly used to evaluate the relative toughness or impact toughness of materials and as such is often used in quality control applications where it is a fast and economical test. It is used more as a comparative test rather than a definitive test.
Georges Charpy died on 1945-11-25.