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An impact test is a materials test to determine how well a material performs when subjected to a sharp impact. The goal is to determine how well the material will perform under real world conditions and to make sure it meets any standards set by regulatory agencies. Companies that perform materials testing usually offer several types of impact test, and companies can also perform their own if they have facilities and personnel for materials testing. One advantage of performing testing in-house is the ability to safeguard proprietary information.
In the course of routine use, objects can be subjected to a variety of impacts. They may be dropped, slammed against hard surfaces, or hit by flying projectiles. Their ability to absorb the stress of the impact determine whether they crack, pit, or shatter. For objects in a high impact setting like a car engine, resistance to impact also determines overall lifespan. It may not be enough for an object to survive a high pressure impact if it cannot repeat this feat over and over again.
During an impact test, precisely controlled conditions are necessary. A technician can use a test machine with carefully calibrated components to deliver a targeted impact with a known amount of strain. The machine may drop an object, hit it, or subject it to other kinds of impact, including repetitive strain. Materials can be locked in place to deliver impact to a very specific spot. In some forms of impact test, the material has a notch cut into it, and the test involves hitting the notch to see how the material responds.
Some materials are very brittle and may fail at relatively low impacts. Others are ductile and may deform before they fracture, or bend before breaking. They tend to be more forgiving of high impacts. It is not always possible to use ductile materials in construction, however, as sometimes the stiffness of brittle materials is necessary to meet the needs of a given manufacturing project. Materials scientists also need to think about how properties might change in response to environmental conditions; rubber, for example, can be brittle when frozen, but ductile at room temperature.
For a basic impact test during product and materials development, it is usually possible to use an internal lab. Some materials will need to be tested by an independent, verified lab before they can be released on the market. Regulators may insist on this for safety reasons. Companies can also use this and other materials testing in their quality control regimens. Employees can periodically pull and test random samples to confirm that they meet the company's standards.
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