Answer:
The endurance strength for the rod is 434.6 MPa
Explanation:
Since the rod is used in rotating bending, we need to use Marin equation given by
Here S stands for the endurance strength for rotating bending, is the endurance strength, and are the parameters for Marin surface modification factor.
Endurance strength.
We can start finding the endurance strength, from the directions we know that the hardness was found to be 300 Brinell, thus for such value we can find the ultimate tensile strength using
Replacing the hardness we get
Now since the ultimate tensile strength has a value less than 1400 MPa, we can find the endurance strength using
Replacing the tensile strength we get
Parameters for Marin surface modification factor.
From the directions we know that the drill rod has a ground surface finish, so then from tables we get
Thus the surface factor will be
Replacing values and the ultimate tensile strength
Then we can find the rotating shaft factor, for a diameter of 10 mm, we can use the equation
Replacing the diameter we get
Estimating endurance strength for rotating shaft.
We can replace now all values we have found in Marin equation.
Thus the endurance strength for the rod is 434.6 MPa