Researchers have devised a new testing method to pinpoint the mechanism that leads to crack initiation in metals at a microscopic scale.
A crack in metallic components in aircraft, bridges, and other structures can lead to catastrophic damage to both properties as well as life. Metals in these applications undergo a constant change in load and stress. This cyclic loading induces slips in the internal molecular structure of the metal until a crack occurs.
According to El-Awady, “Fatigue failure plagues all metals and mitigating it is of great importance. It is the leading cause of cracks in metallic components of aircraft.“
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The current tests to understand the origins of crack initiation focus on the moments just before or after a crack occurs to determine what happened in the makeup of the metal. These tests also use larger samples, making it almost impossible to track the damage initiation, which is a sub-micrometer level feature.
Now researchers from the Johns Hopkins University researchers have found a new method to test metals at a microscopic scale, which allows them to rapidly impose repetitive loads on materials and record how the resulting damage evolves into cracks. These new tests are more reliable and predict the vulnerabilities earlier than the current tests. The details of the test are published in Science.
The airline industry adheres to regular replacement schedules for many parts. The life expectancy of these parts and hence the replacement schedules can be accurately determined by better understanding the origins of crack initiation. Sometimes the component could be fine and never fail, but it gets replaced due to statistical arguments, leading to increased maintenance expenditures.
El-Awady added, “We’re able now to have a more fundamental understanding of what leads up to cracks. The practical implication is that it will allow us to understand and predict when or how the material is going to fail.“
The new testing method narrows down to finer details feasible. It begins evaluating starting from when the metals are exposed to loads for the first time, leading to localized damage that could become cracks.
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