## General Mechanical

#### N-S of the element with the hole

• momidor
Subscriber

Hi,

Having a cuboid with a hole in it, I wonder how to determine the N-S curve for the whole element ? Let say the primary load is pure stretching.

How can I obtain graph the stress in function of the number of cycles ?

• mattw
Subscriber

Hello momidor,

The "Fatigue Sensitivity" in the "Fatigue Tool" can calculate stress life from a range of load values based on the primary loading conditions you set. See a picture below:

See this ANSYS documentation for more help.

There are some considerations you might want to consider for the analysis.

1. Do you have empirical N-S data for the given material or are you going to approximate the fatigue life from Goodman, Gerber, or other fits.

2. Is the stress cyclic? What is the stress ratio, R = Min_stress/Max_stress, and mean stress for the given setup? If the cuboid experiences cyclic stretching (also known as tension) but no compression (i.e. the stress varies from zero to a positive value) then the mean stress will be positive.

3. If the loading is random, there is added complexity to the post processing of the fatigue.

• momidor
Subscriber

Hi mattwallingford,

ad 1) Material is the typical low carbon steel, let say A 106 A but I haven't fatigue data yet.

ad 2) It's constant amplitude fatigue with the mean stress let say 150 MPa, and the ratio is  150 + 30 = 180 MPa and 150 - 30 = 120 MPa. The type of the load is the pure streting by mean stress 150 MPa

ad 3) It is simple excercise with no random phenomenon.

In this excercise I asked myself: what is the fatigue strenght of this element with (1) and without (2) the hole inside for 1x10exp+6 numers of cycles ?