A test in which in which a numerous specimens are tested until fatigue failure to determine the fatigue characteristics. Fatigue tests fall into two categories (depending on the test specimens) —
- Specimens with a simple shape so that the fatigue characteristics of the test material may be determined. Different specimens may be tested at different stresses so that an S‑N curve can be developed. Alternately, all specimens may be tested at a single stress so that different materials can be compared. Ultrasonic fatigue tests of this type use specially designed fatigue test horns.
- Specimens with a complex shape (e.g., a complete part such as an application horn). These tests are used to compare different designs. Because of the cost of the specimens, these fatigue tests are often conducted at only a single stress level.