Huge different in stress result in RADIOSS
Huge different in stress result in RADIOSS
(OP)
Hi there,
Currently I am fully use Hyperworks product in strength analysis. Start from pre-processing (HyperMesh), Solving (RADIOSS non-linear) and post-processing (HyperView & HyperGraph).
For comparing purpose, I also run same FE model (in terms of mesh model, load & BCs, material properties, stress-strain data) in ABAQUS and NASTRAN.
The stress that I look for is Maximum principal stress and nodal based result. NASTRAN and ABAQUS gives similar maximum principal stress while RADIOSS stress result is lower ~250 MPa which is considered very big in strength analysis and will drive to wrongly interpret the fatigue life cycle.
Can anybody suggest why this huge stress different occur and how can I resolve this problem. I have asked this issue to the support team and currently there is no solution yet.
An analogy:
If we go to the market and ask 5kg of fish, suppose it will shows 5kg in the mass scale. Either with seller A, B, C, D and E.
Suddenly we go to the seller H and ask for 5kg of fish. In the mass scale shows 3kg but the seller H strongly said that is 5kg. ---Is that make sence?![[ponder] ponder](https://www.tipmaster.com/images/ponder.gif)
Note1: 5kg fish= stress result. seller = software.
Note2: Definitely it will be a different, maybe mass scale at seller A shows 4.9kg, seller B 4.86kg, seller C 5.1kg, seller D 4.88kg and so on... It doesn't matter since it close to the 5kg that we require. We can not accept the 5kg fish with 3kg indicator at mass scale.
Lets discuss.
Thanks.
KN.
Currently I am fully use Hyperworks product in strength analysis. Start from pre-processing (HyperMesh), Solving (RADIOSS non-linear) and post-processing (HyperView & HyperGraph).
For comparing purpose, I also run same FE model (in terms of mesh model, load & BCs, material properties, stress-strain data) in ABAQUS and NASTRAN.
The stress that I look for is Maximum principal stress and nodal based result. NASTRAN and ABAQUS gives similar maximum principal stress while RADIOSS stress result is lower ~250 MPa which is considered very big in strength analysis and will drive to wrongly interpret the fatigue life cycle.
Can anybody suggest why this huge stress different occur and how can I resolve this problem. I have asked this issue to the support team and currently there is no solution yet.
An analogy:
If we go to the market and ask 5kg of fish, suppose it will shows 5kg in the mass scale. Either with seller A, B, C, D and E.
Suddenly we go to the seller H and ask for 5kg of fish. In the mass scale shows 3kg but the seller H strongly said that is 5kg. ---Is that make sence?
![[ponder] ponder](https://www.tipmaster.com/images/ponder.gif)
Note1: 5kg fish= stress result. seller = software.
Note2: Definitely it will be a different, maybe mass scale at seller A shows 4.9kg, seller B 4.86kg, seller C 5.1kg, seller D 4.88kg and so on... It doesn't matter since it close to the 5kg that we require. We can not accept the 5kg fish with 3kg indicator at mass scale.
Lets discuss.
Thanks.
KN.





RE: Huge different in stress result in RADIOSS
what happens if you compare linear results instead?
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Huge different in stress result in RADIOSS
Since current trend requires an ultimate optimize spring design, so the stress level set to be ~1000 MPa (SUP12 or SAE 9254). Based on tight maximum stress target, we also need to include material non-linear properties to be aware of yielding and stress fatigue limit.
I have compared along the spring dispalcement between RADIOSS and ABAQUS, and RADIOSS stress result is lower along the displacement.
Beside spring comparison, I also compared the stress result of knuckle between NASTRAN and RADIOSS. Still RADIOSS gives lower stress result. This knuckle analysis also included material non-linear properties.
As a conclusion, definition of non-linear applies for material and also geometry.
rgds,
KN
RE: Huge different in stress result in RADIOSS
Beside spring comparison, I also compared the stress result of knuckle between NASTRAN and RADIOSS. Still RADIOSS gives lower stress result. This knuckle analysis also included material non-linear properties.
I also run knuckle analysis using ABAQUS and the stress result between ABAQUS and NASTRAN is close to each other. while RADIOSS is lower than these 2 software.
RE: Huge different in stress result in RADIOSS
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Huge different in stress result in RADIOSS
Here I attached some capture view of the stress result. In this example, the stress different is ~150 MPa which is considered huge also.. If we refer back to analogy, suppose it would not differ in that huge.
The stress concentration area at the same place. The differrent only the value.
Both result were read at same displacement, stress of Maximum principal, nodal based (simple averaging method in RADIOSS and banded in ABAQUS).
Since the FE model setup is same, what is the possible mistake I done cause my stress result in RADIOSS differ.?
RE: Huge different in stress result in RADIOSS
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Huge different in stress result in RADIOSS
By the way this problem is resolved.
Let me explain...
RADIOSS are using purely element based result as their stress result. So the stress value is at the middle of the solid element. ABAQUS also has the element based stress result.
Right now the only different between ABAQUS and RADIOSS is the method of averaging the stress value between the element at the shared node. The averaging method in ABAQUS will represnt the stress at the surface while RADIOSS can't gives this types of averaging.
So, to get stress value at the surface in RADIOSS solver, skin element need to be applied on the part. The stress result at the skin element are now similar with ABAQUS.
Problem resolved..