User:FuzzyMagma/Ultrasonic high cycle fatigue

History
Ultrasonic high cycle fatigue (UHCF) is a field of material science that deals with the study of the behavior of materials under cyclic loading in the high-frequency regime. The first use of ultrasonic frequencies to study fatigue was in the early 20th century when ultrasonic waves were used to study the fatigue behavior of materials. However, it wasn't until the 1950s and 1960s that researchers began to focus on the development of UHCF testing techniques. Since then, UHCF has emerged as a critical field of study, with extensive research being conducted on its various aspects.

Over the years, researchers have made significant progress in understanding the mechanics of UHCF. For example, researchers have found that the frequency of the ultrasonic waves can affect the fatigue life of a material, with some materials exhibiting higher cyclic strength at ultrasonic frequency due to plastic strain rate effects. Other researchers have used UHCF testing to investigate the properties of materials under very.

Historically, fatigue has been separated into regions of high cycle fatigue that require more than 104 cycles to failure where stress is low and primarily elastic and low cycle fatigue where there is significant plasticity. Experiments have shown that low cycle fatigue is also crack growth. (VHCF) conditions, where the cycle number ranges from 107 to 1012 cycles.

Very High Cycle Fatigue (VHCF)

Recently, UHCF testing has been used to investigate the behavior of materials under conditions that simulate real-world operating conditions. For example, researchers have conducted UHCF testing on austenitic steels at elevated temperatures and found that the material exhibited relatively lower fatigue strength compared to room temperature testing. Additionally, the method has been developed to perform cyclic compression tests with concrete, allowing time-saving investigations in the VHCF regime.

Ultrasonic high cycle fatigue (UHCF) is a phenomenon in which a material fails due to cyclic loading at frequencies higher than 20 kHz and a very high number of cycles, typically exceeding 108. UHCF testing machines are designed to operate at these frequencies and can significantly reduce the time needed to complete a test of 10^9 cycles to just a few hours. The principle of action of an ultrasonic fatigue machine is the excitation at a working frequency that corresponds to the fatigue specimen's first longitudinal mode.

UHCF testing has been used to investigate the fatigue behavior of various materials, including copper, duplex steel, mild steels, high-strength steels, and high-alloy steels. Studies have shown that higher cyclic strength of mild steels can be measured at ultrasonic frequency because of plastic strain rate effects. In addition, UHCF testing has been further developed to perform cyclic compression tests with concrete, allowing time-saving investigations in the VHCF regime.

Applications
UHCF testing is now widely used to investigate the behavior of materials under high-frequency cyclic loading conditions and has found applications in various fields, including aeronautics, hypersonic technology vehicles, and high-speed trains.

Ultrasonic impact treatment is another technique that has been used to improve the high cycle and very high cycle fatigue strength of welded joints. After being treated by ultrasonic impact, the stress concentration factor of the weld toe is decreased by 19.1%.

The main benefit of ultrasonic fatigue testing is the ability to complete a large number of cyclic loads in a reasonable timeframe, which allows for efficient testing of very high cycle fatigue domains [1]. Ultrasonic fatigue testing is particularly useful in detecting internal inclusions through actual fatigue testing and has been used to investigate the fatigue behavior of lightweight metallic alloys.

The objective of ultrasonic high cycle fatigue testing is to identify the highest stress that will produce a fatigue life beyond ten million cycles, also known as the material's endurance limit. This stress value is critical in the design of gas turbines, where engine components are designed to ensure that the stresses do not exceed this value, including an additional safety factor.

https://files.asme.org/igti/knowledge/articles/13048.pdf