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Different results in linear static analysis between SimLab and HyperWorks (all version 2022.1)

User: "James Lewis"
Altair Community Member
Updated by James Lewis

Hi,

 

I did a simple linear static analysis in both SimLab and HyperWorks.

They are same with all BCs, but there a significant difference in Von mises stress.

Any can help explaining with this issue?

 

Many thanks!

image

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    User: "Adriano_Koga"
    Altair Employee
    Updated by Adriano_Koga

    Hi,

     

    have you checked the total reaction forces in both models?

    Are you sure the loads are the same?

    In HW, for exxample, you could be applying the total load multiple times, in each node, instead of applying the load divided by the node count.

    SimLab by default distributes the force in all the face equally.

     

    I would start checking reaction forces (SPCF) to make sure you have the correct loading, first.

    User: "Jason_Craanen"
    Altair Employee
    Updated by Jason_Craanen

    Also make sure you are comparing the same results (average or not. Element stress or nodal stress)...

    Each run should have a fem file and out file. Compare those as well.

    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    Hi,

     

    have you checked the total reaction forces in both models?

    Are you sure the loads are the same?

    In HW, for exxample, you could be applying the total load multiple times, in each node, instead of applying the load divided by the node count.

    SimLab by default distributes the force in all the face equally.

     

    I would start checking reaction forces (SPCF) to make sure you have the correct loading, first.

    Hi,

    Thank you, I got the problem.

    In SimLab by default, loads are distributed to each nodes by shape function.

    And in HW, by default, loads applied to each nodes equally, so that make the this difference.

    image

    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    Hi,

     

    have you checked the total reaction forces in both models?

    Are you sure the loads are the same?

    In HW, for exxample, you could be applying the total load multiple times, in each node, instead of applying the load divided by the node count.

    SimLab by default distributes the force in all the face equally.

     

    I would start checking reaction forces (SPCF) to make sure you have the correct loading, first.

    Hi,

    Could I ask you one more question?

    When I compare the stress concentration factor between: looking up at table and using SimLab linear static analysis, there is difference.

    1. With parameters of the model as below:

    image

    The stress concentration factor = 1.5, according this table:

    image

    reference link to the table: https://topdogengineer.com/stress-concentration-factors-a-fundamental-example/

    2. When using SimLab, I've received different Kt

    image

    If you have free time, please give me a look, I attached model below.

    User: "Adriano_Koga"
    Altair Employee
    Accepted Answer
    Updated by Adriano_Koga

    Hi,

    Could I ask you one more question?

    When I compare the stress concentration factor between: looking up at table and using SimLab linear static analysis, there is difference.

    1. With parameters of the model as below:

    image

    The stress concentration factor = 1.5, according this table:

    image

    reference link to the table: https://topdogengineer.com/stress-concentration-factors-a-fundamental-example/

    2. When using SimLab, I've received different Kt

    image

    If you have free time, please give me a look, I attached model below.

    Hi,

     

    in order to get the Kt closer to the analytical value, you would need to refine the mesh at the fillet region to get a better representation of stresses.

    I've done it roughly in Inspire, as you can see below.

    0.02MPa as far field stress and close to .03MPa at the fillet area.

    image

     

    In Inspire you can also choose the meshless SimSolid solver, and get similar results.

    The advantage is that you don't need to worry about the mesh. :)

    image

    User: "Adriano_Koga"
    Altair Employee
    Updated by Adriano_Koga

    Hi,

     

    in order to get the Kt closer to the analytical value, you would need to refine the mesh at the fillet region to get a better representation of stresses.

    I've done it roughly in Inspire, as you can see below.

    0.02MPa as far field stress and close to .03MPa at the fillet area.

    image

     

    In Inspire you can also choose the meshless SimSolid solver, and get similar results.

    The advantage is that you don't need to worry about the mesh. :)

    image

    in Inspire, with refined mesh, running with second order tetra mesh, I got stresses around 0.034MPa at the fillet.

    User: "Adriano_Koga"
    Altair Employee
    Updated by Adriano_Koga

    in Inspire, with refined mesh, running with second order tetra mesh, I got stresses around 0.034MPa at the fillet.

    reference model

    User: "James Lewis"
    Altair Community Member
    OP
    Updated by James Lewis

    reference model

    Hi,

     

    You've really widen my mind, thank you very much.