Testing rig - modal analysis
Testing rig - modal analysis
Solution:
- Obtain a 3D CAD model
- Natural frequencies evaluation
- Proposed new design
- Validation of new design
Figure 1 shows the structure model supplied by the customer. The frame serves for testing of the car hoses and hoses are tested at 60Hz. Therefore the first natural frequencies of the frame must be higher than 60Hz to avoid affecting the results. Thus, analysis is performed of the current frame to obtain natural frequencies. The frame is made of AA 6061.
Fig. 1 – Customer CAD model
The meshing procedure is applied to the CAD model, i.e. a regular mesh of elements is created. In this case, quadratic tetrahedron elements with 10 nodes are used. The tetrahedron has 4 vertices, ie. that it has 4 nodes as a linear element. These 4 nodes then form one tetrahedron element. The quadratic tetrahedron also contains nodes between vertices and thus the total number of nodes is equal to 10.
Fig. 2 – Mesh model
Fig. 3 – Tetra element (left – linear, TETRA4, right – quadratic, TETRA10)
After defining the material properties and determining the contacts between the profiles, modal analysis is performed. The first natural frequency is 105 Hz. This is more than the 60 Hz test frequency for hose testing.
Conclusion: Increasing the rigidity of the frame ensures that there is no impact on the measurement results.