Izod and Charpy Impact Test
The instant force or shock that is applied over a body when another body collide with it for a short period of time is known as impact.
Impact test: These test are basically used to study the mechanical properties of materials as the result of impact produced by instant high loading. The purpose of these test is to measure the ability of a material to absorb energy as the result of the instant loading. This energy leads to further study of mechanical properties (toughness, impact strength, fracture resistance, impact resistance etc.). Furthermore these properties help in the selection of material for different applications.
Types of Impact Test There are three types of impact test that are commonly used…show more content… The standard size of the specimen is 64mm X 12.7mm X 3.2mm with a V shaped notch in the middle. Occasionally specimen without notch can also be used.
Prepare the specimen as specified above. Place the specimen in the position clamped it upright in an anvil (vertically) , with a V notch at the level of the top of the clampfacing the striker (Pendulum). Now record the initial height. Remove the pendulum which is allowed to fall freely to strike the specimen with a specified energy. Now use the data points for further calculations.
Izod impact test and Temperature This test is performed at different temperatures to more closely evaluate the service conditions as most of the properties of the material are temperature dependent such as ductility or yield behavior
Charpy test It is also known as Charpy V_notch test. Most commonly it is used for measuring the relative toughness or impact resistance of a material (polymer, ceramic, metals) this test is quite common due to its fast results. It is a comparative test rather than a definitive test…show more content… The standard size of the specimen is 10mm X 10mm X 55mm.
Types of notch:
V-notch is a V shaped notch of depth 2mm, 0.25mm base and 45 angled.
U-notch is a key-hole type notch of 5mm depth, 1mm radius at the base of notch
Take a specimen as describe above. Now fixe the specimen from both ends at the base. Set free the striker, it will strike the specimen immediately behind a machined notch. Use the resultant energy (obtained by material failure) for further calculations.
The amount of energy absorbed by the specimen when it breaks is known as breaking energy. It is related to the height from which the load strikes the specimen. This energy calculations are same for both Izod and Charpy test. It is usually written as:
E = mg (h0-hf)
This breaking energy leads to further studies of properties of a material such as impact resistance, toughness etc.
Impact energy (Breaking energy) vs Temperature When a graph is plotted between impact energy and temperature the resulting curve shows a rapid decrease in energy as the temperature decreases. A very sharp drop in energy can be used to evaluate the transition temperature
Factors effecting Izod and Charpy impact energy
• Yield strength and