What Is an Impact Test?
An impact test is a test to determine the degree to which a material can withstand an impact load applied to the material under test.
Usually, the test sample is fixed and then a pendulum hammer is swung down to the sample to apply the impact.
This impact test also reveals the strength of the material itself, which is useful for material selection in the case of a material base, and for quality assurance of the product in the case of a product state.
Uses of Impact Test
Impact tests can measure the impact resistance of the material itself or the product. Therefore, products that are prone to impact need to be evaluated by applying a shock that is appropriate for the environment in which they will be used.
Mobile products such as smartphones and tablets are most likely to be subjected to a drop impact during use, so impact tests are conducted under all conditions to ensure that they can withstand high impacts.
In addition, the products are also tested for impact during transportation to prevent damage caused by drop impact before they reach the consumer’s hands.
Principle of Impact Test
A drop test is similar to the impact test, but the drop test confirms the impact of a product dropped freely. The impact test is a hammer blow to a single point, which is a different type of impact test. Also, in an impact test, a high-speed load is applied to the test sample as it is struck at or above the velocity that occurs during a free fall.
Such impact tests can be performed by swinging a hammer on a pendulum down on a normally stationary test sample. The specific machines used for impact testing are the Izod impact testing machine and the Charpy impact testing machine.
1. Izod Impact Test Machine
In the Izod impact tester, one side of the test piece is fixed and is struck with a hammer from the unfixed side to measure the impact value.
2. Charpy Impact Test Machine
In the Charpy impact test machine, the left and right sides of the specimen are fixed, and the specimen is struck from the rear side with a hammer to fracture it and measure the impact value.
How to Choose an Impact Test
1. Izod Impact Test
The Izod impact test is used to check toughness, much like a golf tee shot. A small incision is made in the specimen and struck from a notched direction. The angle at which the hammer is lifted and the angle at which it is lifted can be measured. Measurements may be compared with notched and unnotched results.
In the Izod impact test, the movement of the hammer after breaking the specimen is important. If the specimen does not absorb the impact test, the hammer will swing up high; if the specimen absorbs the impact test, the hammer will swing down low. The test can be performed on a variety of materials, such as plastics and metals. Plastics have different impact strength at different temperatures, so it may be done at low and high temperatures.
2. Charpy Impact Test
Charpy impact tests can test for brittleness and strength based on the energy used during fracture. A specimen is placed in the testing machine and struck to the center with a pendulum, or, in the notched case, with a pendulum against the opposite side of the notch.
After swinging down, the hammer will swing up to the opposite side. The toughness can be checked by comparing the angle of swing up with and without the specimen. If the specimen does not absorb the impact test, the hammer swings up to a high place, and if the specimen absorbs the impact test, the hammer does not swing up so much. The test is performed on all kinds of products, such as plastic, wood, and metal.
Types of Impact Tests
1. Falling Ball Impact Test
In a falling ball impact test, a steel ball is dropped from a specified height onto a product or material to determine its toughness.
2. DuPont Drop Impact Test
The DuPont drop impact test is a test to determine the strength of plastic sheets and coatings. Since plastics and coatings can peel or crack due to impact, a simulated impact is applied to determine the fragility of the product.
3. Dirt Impact Test
Dirt impact test is a test to determine if a specimen is destroyed when a dart is dropped onto a plastic board, glass, or building board.