What is Coffin-Manson model?
The Coffin-Manson model considers the effects of dwell time and ramp time using frequency of usage f. It cannot tell the difference between dwell time and ramp time. Dwell time and ramp rate are critical factors in temperature cycle test. Dwell time is important for creep development, especially at high temperature.
Under what conditions is the coffin-Manson law applied?
1992] proposed a theory, which is based on the observation of the “mesoscopic” grain scale, intermediate between the dislocation scale and the macroscopic crack scale. Well known, that under ex- tremely low cycle fatigue conditions the Coffin-Manson law tends to over-predict the cyclic life. …
How do you find acceleration factor?
If we write t_f = G(S), with G(S) denoting the model equation for an arbitrary stress level S, then the acceleration factor between two stress levels S_1 and S_2 can be evaluated simply by AF = G(S_1) / G(S_2).
What is low and high cycle fatigue?
High cycle fatigue require more than 104 cycles to failure where stress is low and primarily elastic. Low cycle fatigue is characterized by repeated plastic deformation (i.e. in each cycle) and therefore, the number of cycles to failure is low.
What is the limit for low cycle fatigue?
3. What is the limit for low cycle fatigue? Explanation: Fatigue which occurs below 104 or 105 cycles is low cycle fatigue. Thermal conditions are considered here.
What is accelerated factor?
An Acceleration Factor is the constant multiplier between the two stress levels. When there is true acceleration, changing stress is equivalent to transforming the time scale used to record when failures occur.
What are acceleration factors?
The acceleration of an object depends on the mass of the object and the amount of the force applied to it. It states that the acceleration of an object increases with increased force and decreases with increased mass.
How do you calculate period to failure?
D=N/Nf. For example, if a component could sustain 1000 loading cycles until failure, then one loading cycle has exhausted 1/1000 of its fatigue life. Failure occurs if N = N f, that is if D = 1 (in this case, D = 1 for N = 1000). Note the difference between N and N f !
What is fatigue strength?
Fatigue strength is the highest stress that a material can withstand for a given number of cycles without breaking. Fatigue strength is affected by environmental factors, such as corrosion. The maximum stress that can be applied for a certain number of cycles without fracture is the fatigue strength.