Izod impact strength testing
is an ASTM standard method of determining impact strength. A notched sample is generally used to determine impact strength.
The test is named after the English engineer Edwin Gilbert Izod (1876–1946), who described it in his 1903 address to the British Association, subsequently published in Engineering
Impact is a very important phenomenon in governing the life of a structure. For example, in the case of an aircraft, impact can take place by a bird hitting a plane while it is cruising, or during take off and landing the aircraft may be struck by debris present on the runway, and as well as other causes.
An arm held at a specific height (constant potential energy
In physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
) is released. The arm hits the sample and breaks it. From the energy absorbed by the sample, its impact strength is determined.
The North American standard for Izod Impact testing is ASTM D256. The results are expressed in energy lost per unit of thickness (such as ft-lb/in or J/cm) at the notch. Alternatively, the results may be reported as energy lost per unit cross-sectional area at the notch (J/m² or ft-lb/in²). In Europe, ISO 180 methods are used and results are based only on the cross-sectional area at the notch (J/m²).
The dimensions of a standard specimen for ASTM D256 are 63.5 x 12.7 x 3.2 mm (2.5" x 0.5" x 1/8"). The most common specimen thickness is 3.2 mm (0.125"), but the width can vary between 3.0 and 12.7 mm (0.118" and 0.500").
The Izod impact test differs from the Charpy impact test
The Charpy impact test, also known as the Charpy v-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's toughness and acts as a tool to study temperature-dependent...
in that the sample is held in a cantilevered beam configuration as opposed to a three-point bending configuration.
This test can also be used to determine the notch sensitivity.
Impact tests are used in studying 'toughness' of material , that is the ability of material to absorb
energy during plastic deformation because of high toughness the material have strength and at the
same time large durability . Brittle materials have low toughness means they have low plastic
deformation . The impact value of material used also change. The temperature of the material is
directly proportional to impact value and size of specimen is inversely proportional to the impact
nature.so at lower temperature durability of the material is decreased . Also with the increase in
dimension of specimen .the impact value decreases because the probability of heavy imperfection
increases It's value .
Standard impact of same material are given below :
- Mild steel at 20°C = 60 J
- Ductile iron at 30°C = 50 J
- Wrought iron at 30°C = 50-100 J
- BS EN ISO 180:2001 - "Plastics. Determination of Izod impact strength"
- BS EN ISO 13802:2006 - "Plastics. Verification of pendulum impact-testing machines. Charpy, Izod and tensile impact-testing"