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AFGROW (Air Force Grow) is a Damage Tolerance Analysis (DTA) computer program that calculates crack initiation, fatigue crack growth, and fracture to predict the life of metallic structures. Originally developed by the Air Force Research Laboratory , AFGROW [ 1 ] is mainly used for aerospace applications, but can be applied to any type of ...
Crack growth equations are used to predict the crack size starting from a given initial flaw and are typically based on experimental data obtained from constant amplitude fatigue tests. One of the earliest crack growth equations based on the stress intensity factor range of a load cycle is the Paris–Erdogan equation [2]
English: Geometrical representation of crack growth with respect to the alternate stress intensity, along with the representation of Paris' curve in the linear region of Regime B. Other information More information on this crack propagation curve can be found in Ritchie, R. O. "Near-threshold fatigue-crack propagation in steels."
In a 1961 paper, P. C. Paris introduced the idea that the rate of crack growth may depend on the stress intensity factor. [4] Then in their 1963 paper, Paris and Erdogan indirectly suggested the equation with the aside remark "The authors are hesitant but cannot resist the temptation to draw the straight line slope 1/4 through the data" after reviewing data on a log-log plot of crack growth ...
Crack deflection and twist occurs due to osteons, the structural unit of cortical bone. Osteons have a cylindrical structure and are approximately 0.2 mm in diameter. As the crack tip reaches an osteon, crack propagation is deflected along the lateral surface of the osteon slowing crack growth.
In fracture mechanics, a crack growth resistance curve shows the energy required for crack extension as a function of crack length in a given material.For materials that can be modeled with linear elastic fracture mechanics (LEFM), crack extension occurs when the applied energy release rate exceeds the material's resistance to crack extension .
The width of a striation indicates the local rate of crack growth and is typical of the overall rate of growth over the fracture surface. The rate of growth can be predicted with a crack growth equation such as the Paris-Erdogan equation. Defects such as inclusions and grain boundaries may locally slow down the rate of growth.
The stress intensity factor at the crack tip of a compact tension specimen is [4] = [() / / + / / + /] where is the applied load, is the thickness of the specimen, is the crack length, and is the effective width of the specimen being the distance between the centreline of the holes and the backface of the coupon.