BUILDING MATERIALS TESTING LABORATORY
Introduction:
The property of a material relating to the work required to cause rupture is designated as toughness. Toughness depends fundamentally upon strength and ductility and would appear to be independent of the type of loading. A measure of toughness and brittleness is obtained from impact tests.
The tests consist of breaking standard specimen by one blow from a swinging hammer under specified conditions. The energy absorbed by the specimen for rupture is then determined. In order to induce fracture to take place under a single blow, test specimens of ductile material are notched. The use of a notch causes high localized stress concentration, restricts the drawing out action, causes most of the energy of rupture to be absorbed in a localized region of the piece and tends to induce a brittle type of fracture. The tendency of a ductile material when it breaks in the form of a notched specimen is referred to as "notch sensitivity".
The most commonly used impact tests in India are the CHARPY and the IZOD tests.
Scope and Application of Impact Tests:
Many machines and machine parts are commonly subjected to impact loads. The energy absorption capacity of materials under impact load (impact value) helps a designer in the selection of material. The effect of stress, temperature, geometric discontinuity and notch can be evaluated by this test and the design of the structure can be made by avoiding the condition that tend to cause brittle fracture and also by selecting a steel appropriate for the application.
3 окт 2024
