Final answer:
To estimate the fatigue life of the steel rotating beam test specimen, use the stress-life method. Calculate the fatigue life using the given stress amplitude and material properties. The estimated fatigue life is approximately 0.896 cycles.
Step-by-step explanation:
To estimate the fatigue life of the steel rotating beam test specimen, we can use the stress-life method. The completely reversed stress amplitude is 900 MPa. First, we need to determine the fatigue strength coefficient and fatigue exponent for the steel material. Then, we can use these values to calculate the fatigue life.
Let's assume the fatigue strength coefficient for steel is 0.5 and the fatigue exponent is -0.1 for the given material. The fatigue life can be calculated using the equation:
N = (Smax / (K * Δσ))^b
Where:
N = fatigue life
Smax = stress amplitude (900 MPa)
K = fatigue strength coefficient (0.5)
Δσ = stress range (Smax / 2)
b = fatigue exponent (-0.1)
Substituting the values into the equation, we get:
N = (900 MPa / (0.5 * (900 MPa / 2)))^-0.1
Simplifying the equation:
N = (900 MPa / (0.5 * 450 MPa))^-0.1
N = (2)^-0.1
N = 0.896
Therefore, the estimated fatigue life of the specimen is approximately 0.896 cycles.