CARLETON FORMULA ELECTRIC / SOLIDWORKS + ANSYS / IN PROGRESS
Rear suspension
pushrod.
From tube geometry to a checked structural baseline.
I modeled a normalized 4130 steel tube and investigated its response to a team-supplied 1500 lbf axial load. The study covers tension, compression and ideal elastic buckling, with force-balance and mesh-sensitivity checks.
27–30 OCTOBER 2026 / DOCUMENTED 1 NOVEMBER 2026
My role and team inputs
I built the tube CAD, checked the dimensions and imported material assignment, configured the supports and loads, reviewed solver messages, and interpreted the stress, displacement and buckling outputs. I used guided assistance to learn the workflow and organize the evidence. The team supplied the material, tube size and approximate load; those were constraints for my study rather than dimensions I optimized independently.
01 / GEOMETRY
Check the model
before the solve.
The team specified a 0.750 in outside diameter and 0.049 in wall. I checked that the sketch’s 0.326 in inner radius gave the required 0.652 in inner diameter. The modeled 354 mm length remains provisional.
Method and assumptions
Building and checking the CAD
I created a SolidWorks part with a cylindrical extrusion and an axial cut to form the hollow tube, retaining V1 and V2 files and STEP exports. I checked the hollow end face, dimensions and mass properties. Increasing display precision showed a volume of 1.50395 cubic inches and a mass of 0.42652 lb, approximately 0.19347 kg. The CAD was a simple baseline tube rather than a full pushrod assembly.
Material transfer difficulty
The imported geometry initially showed generic Structural Steel. I learned that a SolidWorks material selection should not be assumed to carry through a geometry export as a usable ANSYS material definition. I checked the assigned body material and imported a custom Engineering Data XML for AISI 4130 normalized at 870 C in standalone Mechanical. I did not substitute a nearby alloy such as 4140 simply because it was available.
Material assumptions
The entered properties were density 7850 kg/m3, Young’s modulus 205 GPa, Poisson’s ratio 0.285, tensile yield strength 460 MPa and tensile ultimate strength 731 MPa. The model was linear elastic and isotropic. Yield and ultimate strength entries provide comparison limits; they do not themselves create a plasticity, fracture or fatigue simulation. The 870 C value describes heat treatment, not service temperature. Actual purchased tubing properties still need confirmation.
02 / SUPPORTS AND LOADING
Make the assumptions
explicit.
I applied 6672.33 N along the tube axis, reversing its sign for tension and compression. One end locates the tube; the other can move axially. The simplified restraints allow tilting rather than treating both ends as fully clamped.
Method and assumptions
Defining the supports
I named the annular end faces End_A and End_B. The tube axis was global Z, with End_A at Z = 0.354 m and End_B at Z = 0. End_A used a deformable remote displacement with X, Y and Z translations set to zero, X and Y rotations free, and Z rotation zero. End_B restrained X and Y translation, left Z translation free, and left all rotations free. The setup approximated ends that can tilt while preventing whole-body translation and axial spin.
Applying and checking the force
I applied a distributed force to End_B. A negative global Z load pulled that end away from End_A for tension; reversing the sign to positive Z produced compression. Entering -1500 lbf directly did not commit in the force field and reverted to zero. I corrected this by entering the converted numerical value in the field’s newton units and checking that the load updated.
03 / STATIC CHECKS
Read the result.
Check the physics.
The original model gave 95.857 MPa equivalent stress and 0.16553 mm displacement magnitude in both load directions. Stress magnitude alone cannot distinguish tension from compression, so I checked reaction force and directional motion separately.
Method and assumptions
Investigating the warning
Mechanical displayed a warning that the model might not have enough constraints to prevent rigid-body motion. I reviewed the solver output instead of adding restraints solely to remove the warning. It completed with zero errors, no spring elements and no reported small-pivot warning. The intended remote-node restraints appeared in the log. Two solver warnings concerned inactive element shape checking and a material notice on a surface-load element. These observations supported continuing the preliminary review, but did not replace checking mesh quality.
Verifying equilibrium
I added a force reaction probe at End_A. The Z reaction was approximately +6672.3 N, opposing the applied -6672.3 N, while X and Y reactions were near zero. This verified axial force balance for the tension case. It did not by itself validate the geometry, material condition or end-connection assumptions.
Compression and motion direction
I saved a compression copy and reversed the force to +6672.332423 N. The original compression equivalent stress was also 95.857 MPa and the total displacement magnitude remained about 0.16553 mm. Since these magnitude plots cannot identify tension versus compression, I checked directional deformation. End_B moved in positive Z by about 0.16553 mm, confirming shortening toward the held end.
Yield comparison
Dividing the entered yield strength of 460 MPa by 95.859 MPa gives a refined yield ratio of approximately 4.80. This is a preliminary ratio against first yielding for the idealized tube under the stated load. I did not present it as the complete pushrod’s approved safety factor or as a guarantee against buckling, fatigue or connection failure.
04 / BUCKLING AND REFINEMENT
Compare the meshes.
Qualify the conclusion.
Refinement changed the first buckling multiplier from 6.6254 to 6.6252, approximately 0.0030%. The maximum compression stress changed from 95.857 to 95.859 MPa, approximately 0.0021%.
The multiplier corresponds to an ideal elastic estimate of 9937.8 lbf (44.21 kN). The entered yield-strength comparison is approximately 4.80, below the elastic multiplier. Plasticity, imperfections and real connections could therefore change the actual response.
Method and assumptions
Elastic buckling estimate
For this linear reference case, multiplying 1500 lbf by 6.6252 gives an ideal elastic buckling estimate of 9937.8 lbf, approximately 44.21 kN. I did not treat that as actual failure capacity. The approximately 4.80 yield ratio is lower than the 6.6252 elastic multiplier, so the elastic prediction extends beyond the first-yield estimate. Initial imperfections, residual stresses, plasticity and actual connections may change the real instability response.
Refinement comparison
After refining the mesh, maximum compression stress changed from 95.857 to 95.859 MPa, approximately 0.0021 percent. The first buckling multiplier changed from 6.6254 to 6.6252, approximately 0.0030 percent. These are small changes across the two meshes for these outputs. Higher modes were less stable: modes 5 and 6 changed from 53.963 to 52.414, about 2.87 percent. I therefore limited the low-sensitivity conclusion to the stress and first buckling mode.
What this check establishes
The comparison suggests that those selected outputs were not materially affected by this refinement. It is a two-mesh sensitivity check, not proof that every local stress is converged, that the supports match the completed assembly, or that the design is ready to manufacture.
05 / ENGINEERING DEVELOPMENT
What comes
next.
The next inputs are the actual rod-end part numbers, inserts or bungs, attachment method, thread engagement and final cut length. The assembly should then be assessed for its real load path and mounting behavior, including bending from eccentricity. Fatigue, weld or thread details, material certification and any needed nonlinear imperfection-sensitive compression study remain outstanding. The team must confirm the load basis and required design margins.
Method and assumptions
What I learned
I learned that a credible analysis depends on the assumptions and checks surrounding the solve. I distinguished radius from diameter, force from mass, stiffness from strength, and equivalent stress from directional motion. I checked material assignment after CAD transfer, verified equilibrium with a reaction probe, investigated solver warnings and tested the effect of mesh refinement. I also learned that a dramatic color plot or buckling animation needs a numerical and physical explanation.