See also: Impact strength

In Physical, the impact strength is the capacity of a material to resist attacks or to find its integrity after the aforementioned attacks.

The term is also employed in several other fields, as in Biologie, Psychologie (see the article Résilience (psychology)), in the Industrie or the Informatique where one speaks in English about system resiliency , which corresponds to the fault-tolerance.

In connection with the impact strength of steels

The test Charpy, that everyone continues to call the impact test, was 100 years old in 2001. Right from the start it was a question of characterizing the behavior of metals in a deflection test per shock on notched bars. Georges Charpy contributed to make the test quantitative and reproducible and developed the corresponding testing machine. The current pendulum hammers are always built on the model describes by Charpy in 1904, with some alternatives it is true. Officially the term of impact strength is reserved for the energy of rupture obtained with a test-tube with notch out of U and divided by the section under notch. After being expressed in kg.m/cm, it was noted KCU and expressed in J/cm. Currently, this concept and this notation are completely abandoned with the profit of the concept of energy of rupture , a manner shortened to indicate the energy absorptive by failure under bending by shock on test-tube Charpy . Certain purists wanted to reserve Charpy name with the test-tube with notch out of U, but the current standards consider as this name applies as well to the test-tubes with notch out of U as out of V. In spite of that, speech of impact strength when it is about a value in Joules obtained with a notched sample out of V is an abuse language. To avoid any misunderstanding it is thus to better give up employing the term of impact strength . It is far from being the case in practice, where because of generalization of the test on test-tube with notch out of V, one speaks still much about test of impact strength Charpy V and impact strength Kv . To reconcile the “old hand” and the “modern ones”, one can consider that the impact strength is a grade of the steel, whose synonym was the tenacity before the advent of the breaking process, and which its measurement is the energy of rupture .

Which is the standard currently in force for the impact strength ?

For a long time, there were in France two standards distinct for the impact test Charpy from steel and the test deflection per shock of steel on Bi-supported test-tube (notch out of V) . Since October 1990, there is nothing any more but only one standard, valid in all the European Union, Metallic materials - deflection Test per shock on test-tube Charpy . At the time of the periodic procedure of revision, this standard was confirmed recently. Its text is at the base of the ISO international standard 148-1. One can also quote the standard ASTM E23-96 which, in addition to the traditional Charpy test, described the impact test Izod. Figure 1 represents the geometry of these two types of test. In the Izod test, the test-tube has length a 75 mm (instead of 55 mm for the Charpy test-tube) and notches it out of V is practiced to 28 mm of the one of the ends. The other end is embedded vertically up to the level of the notch (from where the designation of cantilever-beam ). A knife of special shock comes to strike the face notched at the loose lead. This test is not practiced in Europe.

Measure impact strength of a material

See also: Test deflection per shock on notched sample Charpy

The characterization of the impact strength of a material is carried out thanks to a sheep pendulum of Charpy.

A notched sample is placed on two supports. The pendulum is released a given height in order to strike the test-tube with a speed between 1 and 4 m/s. The height of wound pendulum after the shock makes it possible to determine energy necessary to break the test-tube.

See too

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