Impact testing of materials for toughness and sensitivity is an important process in various fields. There are various standardized methods to perform this task and identify toughness. Two such processes are the Izod Method and the Charpy Method.
Both of these methods are used widely for determining the strength, toughness and sensitivity of the material. In both methods, a hammer is made to strike on the material under test and the difference in height before and after hitting is measured and the strength or toughness is calculated.
In the Izod and Charpy methods, a pendulum of known mass and length is adjusted to drop from a particular height.
Izod vs Charpy Methods
The main difference between Izod and Charpy Methods is that in the Izod method, the sample notch is always facing the pendulum vertically and the striking point is on the upper tip of the given sample. In the Charpy method, the notch is kept facing away from the pendulum horizontally and the striking point is in the middle of the sample.
Comparison Table Between Izod and Charpy Methods
| Parameter of Comparison | Izod Method | Charpy Method |
| What is it? | Izod method or Izod impact strength test is one of the standard methods to determine the impact resistance of various materials in which an arm is raised to a specific height and then released, the arm moves down to hit a sample to break it and this sample is used to calculate the notch sensitivity and energy, this energy, in turn, determines the toughness of the material. | The Charpy method or sharply impact test is a high strain rate standardized test to determine the energy absorbed by the sample material during hitting. This energy is used to determine the notch toughness of the material. It is an important method to understand fracture problems. |
| Striking point | In the Izod method, the striking point is on the upper tip of the given sample. | In the Charpy method, the striking point is in the middle of the given sample. |
| Types of notches | The Izod method has only one notch, named as V notch. | The Charpy method has two notches, namely, U notch and V notch. |
| Adjustments of the equipment | In the Izod method, the notch is always facing towards the pendulum vertically. | In the Charpy methods, there is a pendulum for which the mass and length is known which is dropped from a particular height, the notch is kept facing away from the pendulum horizontally. The size and mass of the notch sample tend to affect the results obtained. |
| Materials that can be tested | Plastics and metals can be tested using the Izod methods. | Only metals can be tested using Charpy methods. |
What is the Izod Method?
The Izod method is an impact testing method given by Gilbert Izod in 1903. The method is used to test the impact of strain which is important in determining the life time of the material.
In the Izod method, the notch is kept vertical and facing towards the striker. The striking point in the Izod method is on the upper tip of the material. It has only a V notch. The Izod method can be used to test metals as well as plastics.
What is the Charpy Method?
In 1901, Georges Charpy devised an improved and standardized method for impact testing using spring-loaded machines which came to known as the Charpy Impact testing method.
In this method, the equipment is adjusted in such a way that the hammer strikes the material under test, the material is further used to determine the notch sensitivity and the energy absorbed by the material is used to calculate the strength and toughness of the material.
The notch in the Charpy method is kept horizontal and facing away from the pendulum. The striking point of it is in the middle of the sample. The Charpy method has U notch and V notch.
Main Differences Between Izod and Charpy Method
- The Izod and Charpy methods are the impact testing methods, in both methods, a hammer is made to strike on the material from a particular height, the energy absorbed by the material is used to calculate the toughness of the material and the material is used to determine sensitivity.
- In the Izod method, the notch is kept facing towards the pendulum vertically whereas, in the Charpy method, the notch is kept facing away from the pendulum horizontally.
- In the Izod method, the material under test is placed vertically whereas in the Charpy method, the material under test is placed horizontally.
- In the Izod method, the striking point is on the upper tip of the material, on the other hand, in the Charpy method, the striking point is in the middle of the material.
- The Izod method has only a single notch which is named as V notch whereas in the Charpy method, there are two notches named as U notch and V notch.
- In the Izod method, the hammer used for striking is a farming hammer whereas in the Charpy method, the hammer used is a ball pin hammer.
- The Izod method is used for testing both metals and plastics whereas the Charpy method is used for testing metals.
- The common dimensions of the equipment of the Izod method are 64*12.7*3.2 mm for plastics and 127*11.43 mm round bar for metals whereas the dimension of equipment in the Charpy method is 55*10*10 mm.
- Some of the common specifications used in the Izod method are ASTM D256, ASTM E23 and ISO 180 whereas the common specifications in the Charpy method are ASTM E23, EN 10045-1, etc.
Conclusion
In the Izod and Charpy method, the adjustment of the equipment is different but both the processes are used for the same purpose. In these methods, the energy is absorbed by the sample and this energy is used to calculate the toughness of the material and the sample is used to find the sensitivity of the notch sample. These methods play an important role in understanding the fracture problems of various materials such as metals and plastics.
References
- https://link.springer.com/chapter/10.1007/978-3-319-72484-3_19
- https://link.springer.com/content/pdf/10.1007/BF03378353.pdf