Ing. Aponte
Mechanical
- Jan 7, 2024
- 5
Good evening dear specialists, I writing today because I have a question regarding yield criterions. A minimum of background: I have a simple filter, already evaluated by ASME VIII div. 2 par 5. The exercise is evaluate legs and attaching points with only weight + pressure.
I have ANSYS and here the standard criterion is Von Mises. A final Client asked for an evaluation by EN13445 and this code states to use Tresca criterion, instead of Von Mises. I remember from university that area of yield of Tresca is smaller is smaller than Von Mises. I checked the worst point - considering the distance between Von Mises border and Tresca border and found root(3)/2.
EN13445 is based on limit load method. Also ASME has this procedure. In material properties, with ASME, I prepare a first straight line considering a slope like module of Young - till to yield value - and after a second line not perfectly horizontal - because it create problems with convergences - with a slope of 1 MPa.
What to do with EN13445? I suspect that here the material property is same for the first part of the line (except for the Young module, where I have to consider at temperature instead of cold but we have 80 °C so no differences ) but correct yield point - considering that ANSYS will develop the calculation aways considering Von Mises - has to be root(3)*yield/2. Second part of the material curve will remain same. Is that correct?
Last point: when I will read the total deformation ( not the plastic one! ) I have to stay under 5% but what i will read on ANSYS - always based on von mised criteria - need to be multiplied again by root(3)/2 - to be compliant with Tresca criterion, right?
Added to previous issue: 5% appears as very high deformation. It is correct?
Thanks, Francisco
I have ANSYS and here the standard criterion is Von Mises. A final Client asked for an evaluation by EN13445 and this code states to use Tresca criterion, instead of Von Mises. I remember from university that area of yield of Tresca is smaller is smaller than Von Mises. I checked the worst point - considering the distance between Von Mises border and Tresca border and found root(3)/2.
EN13445 is based on limit load method. Also ASME has this procedure. In material properties, with ASME, I prepare a first straight line considering a slope like module of Young - till to yield value - and after a second line not perfectly horizontal - because it create problems with convergences - with a slope of 1 MPa.
What to do with EN13445? I suspect that here the material property is same for the first part of the line (except for the Young module, where I have to consider at temperature instead of cold but we have 80 °C so no differences ) but correct yield point - considering that ANSYS will develop the calculation aways considering Von Mises - has to be root(3)*yield/2. Second part of the material curve will remain same. Is that correct?
Last point: when I will read the total deformation ( not the plastic one! ) I have to stay under 5% but what i will read on ANSYS - always based on von mised criteria - need to be multiplied again by root(3)/2 - to be compliant with Tresca criterion, right?
Added to previous issue: 5% appears as very high deformation. It is correct?
Thanks, Francisco
