Stigma (letter) sigma form ς never occurs inside a word and is never used as a numeral either. Uppercase forms of stigma as a numeral (Ϛ) are rare in practice; when they occur, they can often be confused with uppercase forms of another numeral symbol, koppa (Ϟϟ), which stands for 90. Stigma is encoded in Unicode as "Greek letter stigma" U+03DA (Ϛ) and "Greek small letter stigma" U+03DB (ϛ). Stigma (letter) Stigma (ϛ) is a ligature of the Greek letters sigma (Σ) and tau (Τ), which was used in writing Greek between the Middle Ages and the 19th century. It is also
Torque-to-yield fastener is therefore beneficial in high-frequency high-load situations with a higher risk of fatigue related failure, like a bolted down cylinder head, to use torque to yield bolts. Torque-to-yield fastener A torque to yield fastener (TTY) or stretch bolt is mounting hardware in the form of a fastener which is torqued beyond the state of elasticity and therefore undergoes plastic deformation, causing it to become permanently elongated. Torquing a fastener to yield results in a high preloading of the fastener which, depending on the load frequency and amplitude, can significantly increase the fatigue life of the fastener. When the applied load