General Mechanical

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,


      Thanks for reply. 


      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 ? 



       

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