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The Electrochemical Fatigue Crack Sensor. In 1992, Dr. Campbell Laird and Dr. Yuanfeng Li invented the EFS™. The EFS™ relies on a patented electrical test [2] [3] method, which monitors the current flow at the surface of a metal while it is being mechanically flexed. The output current resembles a heart’s EKG pattern and can be ...
Scanning electron microscope image of fatigue striations produced from constant amplitude loading. The crack is growing from left to right. Striations are marks produced on the fracture surface that show the incremental growth of a fatigue crack. A striation marks the position of the crack tip at the time it was made.
It is the result of the process of fatigue due to rolling/sliding contact. [2] [3] The RCF process begins with cyclic loading of the material, which results in fatigue damage that can be observed in crack-like flaws, like white etching cracks. [2] These flaws can grow into larger cracks under further loading, potentially leading to fractures ...
White etching cracks (WEC), or white structure flaking or brittle flaking, is a type of rolling contact fatigue (RCF) damage that can occur in bearing steels under certain conditions, such as hydrogen embrittlement, high stress, inadequate lubrication, and high temperature. WEC is characterised by the presence of white areas of microstructural ...
In true corrosion fatigue, the fatigue-crack-growth rate is enhanced by corrosion; this effect is seen in all three regions of the fatigue-crack growth-rate diagram. The diagram on the left is a schematic of crack-growth rate under true corrosion fatigue; the curve shifts to a lower stress-intensity-factor range in the corrosive environment.
The oil and whiting method used in the railroad industry in the early 1900s was the first recognized use of the principles of penetrants to detect cracks. The oil and whiting method used an oil solvent for cleaning followed by the application of a whiting or chalk coating, which absorbed oil from the cracks revealing their locations.
Crack closure is a phenomenon in fatigue loading, where the opposing faces of a crack remain in contact even with an external load acting on the material. As the load is increased, a critical value will be reached at which time the crack becomes open .
A crack arrestor (otherwise known as a rip-stop doubler) is a structural engineering device. Being typically shaped into ring or strip, and composed of a strong material, it serves to contain stress corrosion cracking or fatigue cracking, helping to prevent the catastrophic failure of a device.