Definition - What does Striation mean?
A striation is usually found on crack surfaces, which serve as standard signs of a condition known as fatigue fracture. This is usually found in materials that are constantly exposed to fluctuating stress levels that are far below the critical tensile strength.
Striations are normally caused by the instantaneous actions of tensile and cyclic stress, as well as plastic strain. The presence of striations indicates a serious issue, such as fatigue corrosion.
Corrosionpedia explains Striation
This corrosion pattern of striations looks similar to stretch marks, and necessitates extra attention during inspection through ultrasonic techniques, because corrosion surfaces that are striated can have a negative effect on ultrasonic signals.
Striations are usually a signal of fatigue corrosion, which is the overall action of cyclic stresses along with corrosion. These usually begin as irregularities, pits or defects on the surface. The profile of striations is usually wedge shaped, and depends on several factors such as stress frequency. Fine cracks are brought on by high-frequency stresses, while wide cracks are the result of low-frequency stresses.
Striations are not usually visible to the naked eye. Hence, there is a need for high magnification through the aid of an electron microscope to view striations.
Being able to identify striations can be very helpful in evaluating crack profiles. By identifying the crack causes, the materials involved and the atmosphere that is leading to cracking, proper intervention can be applied.