Impact Test

Definition - What does Impact Test mean?

An impact test is a technique for determining the behavior of material subjected to shock loading in:

  • Bending
  • Tension
  • Torsion

This test is designed to determine how a specimen of a known material will respond to a suddenly applied stress. The test ascertains whether the material is tough or brittle.

It is mostly used to test the toughness of metals, but similar tests are used for polymers, ceramics and composites. Metal industry sectors that use the impact test include:

  • Oil and gas
  • Aerospace
  • Power generation
  • Automotive
  • Nuclear

Impact testing is also known as ASTM E23.

Corrosionpedia explains Impact Test

The impact test is a method for evaluating the toughness, impact strength and notch sensitivity of engineering materials.

Engineers test the ability of a material to withstand impact to predict its behavior under actual conditions. Many materials fail suddenly under impact, at flaws/cracks or notches. The most common impact tests use a swinging pendulum to strike a notched bar; heights before and after impact are used to compute the energy required to fracture the bar. In the Charpy test, the test piece is held horizontally between two vertical bars. In the Izod test, the specimen stands erect, like a fence post.

The notched test specimen is broken by the impact of a heavy pendulum or hammer, falling at a predetermined velocity through a fixed distance. The quantity usually measured is the energy absorbed in breaking the specimen in a single blow, as in the Charpy impact test and Izod impact test.

Impact tests are also performed by subjecting specimens to multiple blows of increasing intensity, as in the drop ball impact test and the repeated blow impact test. Impact resilience and scleroscope hardness are determined in nondestructive impact tests.

The impact resistance of a part is, in many applications, a critical measure of its service life. More importantly, it affects product safety and liability. Factors affecting impact performance include:

  • Molded-in stresses
  • Polymer orientation
  • Weak spots (weld lines or gate areas)
  • Part geometry

Impact properties can also change when additives, such as coloring agents, are added to plastics.

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