Question

In the results of afatigue test, themean stress was 100MPa and the stress amplitude was 50MPa.a) Determine themaximum and minimum stress levelsand the stress ratio.b) Ifthematerial is copper(which has a melting point of 1984 degrees F),at what temperature do considerations of creep become important?

Answer 1

Answer:

a) omax=125 MPa

omin=75 MPa

b) Temperature = 1289.6°F

Explanation:

a) The mean stress is:

$mean stress=\frac{o_{max}+o_{min} }{2} =100 MPa$

omax+omin=200 MPa

stress amplitude=50 MPa

omax-omin=50MPa

2omax=250 MPa

omax=125 MPa

omin=75 MPa

b) For copper, the creep is important at 0.65 of the melting point, thus:

Temperature = 0.65*1984°F=1289.6°F