In materials science, fatigue damage refers to the initiation and growth of cracks in a device as repeated stress or movement leads to the emergence of microscopic cracks. It is one of the main reasons why a machine wears out and ultimately breaks.
The idea of self-healing metals has already been conceptualized in a 2013 study led by Michael Demkowicz. Using computer simulations, he argued that metals could repair cracks caused by wear and tear when exposed to certain conditions. Although scientists have successfully created self-healing materials such as plastics, developing a self-healing metal seemed impossible since their cracks were only expected to get bigger, not smaller.
Remarkable Discovery
For the very first time, this stunning phenomenon was witnessed by a team of researchers from Sandia National Laboratories and Texas A&M University. They observed pieces of metal that crack but fuse back together without human intervention. Although the disappearing fissures they kept were only at the nanoscale level, they are indeed consequential fractures.
The research team discovered r evidence of the self-healing metal hypothesis was e evaluating the formation and spread of cracks through a nanoscale piece of platinum. They used a specialized microscopic method where the ends of the metal can be repeatedly pulled 200 times per second.
They were surprised that after almost 40 minutes, the damage in one spot was suddenly reversed, with one end of the fracture merging without any trace of the previous crack. After that, the fissure started growing in a different direction.
Materials scientist Brad Boyce from Sandia describes the stunning experience of watching this phenomenon first-hand. From their observation, the scientists have confirmed that metals possess an intrinsic, natural tendency to heal themselves, at least at the nanoscale level of fatigue damage.
According to scientists, further experiments are needed to determine if the self-healing process can be used as a practical manufacturing tool. If this property is harnessed, it can lead to a breakthrough in engineering that allows the construction of self-healing engines, airplanes, and bridges. The experts are also confident that such structures can reverse the damage from wear and tear and thus become safer and longer lasting.
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What is Fatigue Damage?
Many engineering structures experience high cycle loading or the continuous application of stress, strains, or forces in a material. Such load can cause damage to a material which, when accumulated, could result in fatigue. The accumulation of damage changes the properties of an object leading to the appearance of cracks.
For objects exposed to cyclic loading, the development of fissures begins with microcracks which nucleate and grow at the initial stage of the process. As the macrocracks form and propagate, the entire material gets fractured.
Traditionally, fatigue has been connected with the failure of metal components and separated into high-cycle and low-cycle fatigue. Both high and low cycles follow the stages of crack initiation and crack growth.
Fatigue damage is considered the most delicate yet most dangerous type of failure in metals. Even though metal fatigue can result from excessive shear load, impact load, and tensile load, this failure type can go unnoticed until it is too late.
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