Posted by: Jon - 09-28-2021, 04:38 AM - Forum: MYSTRAN
- Replies (4)
I came across and issue with the RBE3 element. I have already emailed Bill about the issue, but I thought I would post here for the benefit of the rest pf the community.
I am using a RBE3 to distribute load at a bolted joint. The joint is in thin sheet metal structure so I do not want the fasteners to take out of plane load. I used the following RBE3 to accomplish this.
When I run this through MYSTRAN the SPC forces are not equal and opposite the applied loads. The SPC forces in the Y and Z directions are half of what they should be. It appears that the RBE3 is incorrectly calculating the weighted average when one or more independent nodes are not effective in all three translational DOF. To check this I changed the RBE3 to have Ci = 123 for every independent node. I also ran my original model through NXNASTRAN. In both cases the SPC forces were equal and opposite to the applied loads.
I have attached copies of the BDF and F06 files for the original run and the run with Ci = 123.
attached two simple cantilever analysises. One runs the other with slighlty greater cross section does give all zero. I do not know why nor can I really read the logs. What do I need to look for? Can someon confirm the problem an may be give some hints what went wrong.
I've recently added code to MYSTRAN for buckling/differential stiffness for the 6 solid elements: HEXA (8 and 20 node), PENTA (6 and 15 node) and TETRA (4 and 10 node). Attached are the results of a study of the accuracy of the code. A beam of dimensions 1"x1"x40" was modeled with each of the 3D solid elements and results are shown for the convergence to the beam critical buckling load vs mesh size. It is seen that all 6 elements are quite accurate, even for a fairly coarse mesh. I would appreciate anyone trying out these elements, especially with some element distortion, to see if the accuracy holds up
Writing a FEMAP neutral parser, I met some some quirks with the file generated by MYSTRAN (v12.1). This thread aims to collect them. Please tell me if I need to split this thread per subject or question!
I'll begin with this a simpleCBAR + CBUSH model. The attached archive provides the following files:
* "bulk_model_TC3.nas": the BULK file
* "mystran_00.NEU": the MYSTRAN output
* "FEMAP_v8.2.neu": the FEMAP v8.2 output
* "FEMAP_v2020-1-0.neu": the FEMAP v2020.1 output
First remark: Block451 is used by both MYSTRAN and FEMAP8.2 to collect results, but is deprecated in later versions in favor of block 1051.
Block451: titles used by MYSTRAN do not match FEMAP titles. This makes harder to write "solver-agnostic" parsers. From the uploaded files, here is the list with mismatch and missing :
That's all for now! thanks for reading and happy MYSTRANning !
Code:
| FEMAP vector Title | FEMAP vector ID | MYSTRAN vector Title | MYSTRAN vector ID |
|---------------------------+-----------------+--------------------------+-------------------|
| Total Translation | 1 | RSS translation | 10001 |
| T1 Translation | 2 | T1 translation | 10002 |
| T2 Translation | 3 | T2 translation | 10003 |
| T3 Translation | 4 | T3 translation | 10004 |
| Total Rotation | 5 | RSS rotation | 10005 |
| R1 Rotation | 6 | R1 rotation | 10006 |
| R2 Rotation | 7 | R2 rotation | 10007 |
| R3 Rotation | 8 | R3 rotation | 10008 |
| Total Applied Force | 41 | RSS applied force | 20001 |
| T1 Applied Force | 42 | T1 applied force | 20002 |
| T2 Applied Force | 43 | T2 applied force | 20003 |
| T3 Applied Force | 44 | T3 applied force | 20004 |
| Total Applied Moment | 45 | RSS applied moment | 20005 |
| R1 Applied Moment | 46 | R1 applied moment | 20006 |
| R2 Applied Moment | 47 | R2 applied moment | 20007 |
| R3 Applied Moment | 48 | R3 applied moment | 20008 |
| Total Constraint Force | 51 | RSS SPC force | 30001 |
| T1 Constraint Force | 52 | T1 SPC force | 30002 |
| T2 Constraint Force | 53 | T2 SPC force | 30003 |
| T3 Constraint Force | 54 | T3 SPC force | 30004 |
| Total Constraint Moment | 55 | RSS SPC moment | 30005 |
| R1 Constraint Moment | 56 | R1 SPC moment | 30006 |
| R2 Constraint Moment | 57 | R2 SPC moment | 30007 |
| R3 Constraint Moment | 58 | R3 SPC moment | 30008 |
| Total MultiPoint Force | 151 | na | na |
| T1 MultiPoint Force | 152 | na | na |
| T2 MultiPoint Force | 153 | na | na |
| T3 MultiPoint Force | 154 | na | na |
| Total MultiPoint Moment | 155 | na | na |
| R1 MultiPoint Moment | 156 | na | na |
| R2 MultiPoint Moment | 157 | na | na |
| R3 MultiPoint Moment | 158 | na | na |
| Total Summed GPForce | 161 | na | na |
| T1 Summed GPForce | 162 | na | na |
| T2 Summed GPForce | 163 | na | na |
| T3 Summed GPForce | 164 | na | na |
| Total Summed GPMoment | 165 | na | na |
| R1 Summed GPMoment | 166 | na | na |
| R2 Summed GPMoment | 167 | na | na |
| R3 Summed GPMoment | 168 | na | na |
| Total Applied GPForce | 171 | na | na |
| T1 Applied GPForce | 172 | na | na |
| T2 Applied GPForce | 173 | na | na |
| T3 Applied GPForce | 174 | na | na |
| Total Applied GPMoment | 175 | na | na |
| R1 Applied GPMoment | 176 | na | na |
| R2 Applied GPMoment | 177 | na | na |
| R3 Applied GPMoment | 178 | na | na |
| Total Constraint GPForce | 181 | na | na |
| T1 Constraint GPForce | 182 | na | na |
| T2 Constraint GPForce | 183 | na | na |
| T3 Constraint GPForce | 184 | na | na |
| Total Constraint GPMoment | 185 | na | na |
| R1 Constraint GPMoment | 186 | na | na |
| R2 Constraint GPMoment | 187 | na | na |
| R3 Constraint GPMoment | 188 | na | na |
| Bar EndA Plane1 Moment | 3000 | BAR EndA Plane1 Moment | 50201 |
| Bar EndA Plane2 Moment | 3001 | BAR EndA Plane2 Moment | 50203 |
| Bar EndB Plane1 Moment | 3002 | BAR EndB Plane1 Moment | 50202 |
| Bar EndB Plane2 Moment | 3003 | BAR EndB Plane2 Moment | 50204 |
| Bar EndA Pl1 Shear Force | 3004 | BAR EndA Pl1 Shear Force | 50205 |
| Bar EndA Pl2 Shear Force | 3005 | BAR EndA Pl2 Shear Force | 50207 |
| Bar EndA Axial Force | 3008 | BAR EndA Axial Force | 50209 |
| Bar EndA Torque | 3010 | BAR EndA Torque | 50211 |
| Bar EndA Pt1 Bend Stress | 3075 | BAR EndA Pt1 Comb Stress | 60301 |
| Bar EndA Pt2 Bend Stress | 3076 | BAR EndA Pt2 Comb Stress | 60303 |
| Bar EndA Pt3 Bend Stress | 3077 | BAR EndA Pt3 Comb Stress | 60305 |
| Bar EndA Pt4 Bend Stress | 3078 | BAR EndA Pt4 Comb Stress | 60307 |
| Bar EndB Pt1 Bend Stress | 3083 | BAR EndB Pt1 Comb Stress | 60302 |
| Bar EndB Pt2 Bend Stress | 3084 | BAR EndB Pt2 Comb Stress | 60304 |
| Bar EndB Pt3 Bend Stress | 3085 | BAR EndB Pt3 Comb Stress | 60306 |
| Bar EndB Pt4 Bend Stress | 3086 | BAR EndB Pt4 Comb Stress | 60308 |
| Bar EndA Axial Stress | 3107 | na | na |
| Bar EndA Max Comb Stress | 3109 | BAR EndA Max Stress | 60309 |
| Bar EndA Min Comb Stress | 3110 | BAR EndA Min Stress | 60311 |
| Bar EndB Max Comb Stress | 3111 | BAR EndB Max Stress | 60310 |
| Bar EndB Min Comb Stress | 3112 | BAR EndB Min Stress | 60312 |
| Bar Tension M.S. | 3113 | na | na |
| Bar Compression M.S. | 3114 | na | na |
| Bush X Force | 3774 | na | na |
| Bush Y Force | 3775 | na | na |
| Bush Z Force | 3776 | na | na |
| Bush X Moment | 3777 | na | na |
| Bush Y Moment | 3778 | na | na |
| Bush Z Moment | 3779 | na | na |
| Bush TX Stress | 3780 | na | na |
| Bush TY Stress | 3781 | na | na |
| Bush TZ Stress | 3782 | na | na |
| Bush RX Stress | 3783 | na | na |
| Bush RY Stress | 3784 | na | na |
| Bush RZ Stress | 3785 | na | na |
| Elem C1 T1 GPForce | 85000 | na | na |
| Elem C1 T2 GPForce | 85001 | na | na |
| Elem C1 T3 GPForce | 85002 | na | na |
| Elem C1 R1 GPMoment | 85003 | na | na |
| Elem C1 R2 GPMoment | 85004 | na | na |
| Elem C1 R3 GPMoment | 85005 | na | na |
| Elem C2 T1 GPForce | 85010 | na | na |
| Elem C2 T2 GPForce | 85011 | na | na |
| Elem C2 T3 GPForce | 85012 | na | na |
| Elem C2 R1 GPMoment | 85013 | na | na |
| Elem C2 R2 GPMoment | 85014 | na | na |
| Elem C2 R3 GPMoment | 85015 | na | na |
| na | na | BAR EndB Pl1 Shear Force | 50206 |
| na | na | BAR EndB Pl2 Shear Force | 50208 |
| na | na | BAR EndB Axial Force | 50210 |
| na | na | BAR EndB Torque | 50212 |
