Moment load
Moment load
(OP)
Hello,
I need to apply moment load on my whole body (1200 Nm) about some reference point.
first option, make analytical rigid body and linked with reference point. It leads to contact analysis and makes it difficult. Does not converge.
second option, kinematic coupling. But it removes boundary conditions whcih exists in original part.
Solver is abaqus. Any idea.
Thanks for your replies.
feaplastic
I need to apply moment load on my whole body (1200 Nm) about some reference point.
first option, make analytical rigid body and linked with reference point. It leads to contact analysis and makes it difficult. Does not converge.
second option, kinematic coupling. But it removes boundary conditions whcih exists in original part.
Solver is abaqus. Any idea.
Thanks for your replies.
feaplastic





RE: Moment load
RE: Moment load
feaplastic
RE: Moment load
In short, it has some loading features that make things like this very easy. You basically apply a pressure load to a face, but you can designate that pressure in a variety of ways including telling the software to distribute a load. A simple calculation will tell you what that load needs to be.
Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
Magnitude The Finite Element Analysis Magazine for the Engineering Community
RE: Moment load
I gone through the website. But, What about the methods which i explained in my original post. Is it possible to achieve what i want to do using those methods.
feaplastic
RE: Moment load
Is the lack of convergence due to this moment, or because its a contact analysis. One has to be careful to avoid rigid body modes (including torsion) and get the contact faces orientations etc correct.
RE: Moment load
I haven't worked with Abaqus, but I believe the input and output of Roshaz is fairly seamless. I've used it with Calculix, Nastran (a little), and used it's internal solvers, but the internal solvers are for static analyses.
crisb points out another method. The easy way to handle the DOF issues is simply to make your rigid beams tie from your single point to several nodes on the surface of your model and then either penetrate into interior nodes with the beams or tie them to adjacent surface nodes. You can't use the Nastran formulation of "Rigid" for this because it generally requires a Master node and a Slave node, but a standard beam formulation with a high modulus (E), high inertia (I), etc. should work.
RE: Moment load
I understand abt the ability of Roshaz. Hope, you know the influence of engineers in any organisation. Straight away i cant ask for a new facility. So, I am trying to do with abaqus.
Abt other method, i am little confused with beam connection which you explained. Moreover, is it possible to calculate pressure value equivalent to my moment by hand calculation or by some other means. Approximate would be enough for initial calculation.
Crisb,
Samething i have done. Created a reference point. analytical surface is linked with ref point as rigid body. Constrained ref point in 5 DOF except x axis, abt which i want to apply moment. But, no success so far.
Let me try further and reply. Hope, users can guide me to find equivalent pressure value.
Thanks for your time and replies.
feaplastic
RE: Moment load
Its a while since I did this and remember it was easy to mess up the rigid link by having wrong degrees of freedom and not apply the loads (especially moments and torsion) you think are applying. All software is different and I do not know Abaqus. In my program this method works fine and its not necesary to use a dummy beam or penetrate to internal nodes.
I think I had the loads/moments applied to a point which was the master of a rigid link with the slave as a surface/face on the body. I think you need all 6 degrees of freedom active otherwise the moments dont get transferred down the rigid link. Also if the model is all 3D elements make sure you havent turned off the rotational degrees of freedom.
RE: Moment load
pressure = moment/section modulus
look in any structures book
RE: Moment load
Method which u suggested works fine. My rigid surface rotates as wanted and contacts my original model. But, i get very less displacment and stress. To explain, i simplified geometry and did it as follows.
1. Original part - Flat 400*400*50 mm
2. Rigid surface - 100*100 mm - Tie constrained with original model (to avoid contact converg. problem)and positioned at top center of original model.
3. Ref point - 50 mm away from bottom middle point of original model.
4. Moment applied - 1200000 Nmm
Material: youngs modulus 25000 MPa. Poisson Ratio :0.35
Result :
Displacement: in the range of 10^-4 mm
von mises Stress: in the range of 10^-5 MPa
IS my load very less? i expected a lot of stress. Same case with my original model which has some curved, bent surfaces with more or less same dimension.
Where i have done a mistake. How to calculate amount of force on my rigid plate due to moment on ref point. How it is distuibuted.
Thanks for your time.
feaplastic