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

a) omax=125 MPa

omin=75 MPa

b) Temperature = 1289.6°F

Step-by-step explanation:

a) The mean stress is:

`mean stress=(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