The CAD model of the office chair was downloaded from grabCad (https://grabcad.com/library/office-chair-5-3) and simplified on Fusion360. The simplification process consisted of removing the wheels and adding a hole on the bottom of the seat’s back rest to allow a simpler bonded contact constraint later.
A Tet-dominant meshing algorithm with automatic element sizing was used to create 3 meshes with Very Coarse, Coarse and Moderate mesh fineness for comparison reasons. Material properties of aluminum were imported from the SimScale library and assigned to the legs, seat and back of the chair. Wood properties were also imported and assigned to the seat padding and back padding.
Various bonded contact constraints were assigned to the chair. The 2 paddings were bonded to their respective seat and back, the back to the seat, the seat to the leg pole and the leg pole to the legs. The 5 points of contact that the legs made with the ground (facing downward) were constrained on all degrees of freedom.
A pressure load was assigned to the back of the chair, to its seat and to the 2 arm rests. The amount of pressure used was calculated based on a 2x safety factor of a 100kg person sitting down. This total pressure was then divided 80% for the seat, 10% for the back rest and 10% for the arm rests.
Various simulations were run with 2x, 4x, 6x and 10x safety factors. These views were then placed side by side using the transform filter in the post-processing tab. The results of the simulation with 2x, 4x and 6x safety factors showed that this office chair doesn’t reach the yielding strength of aluminum of 276 MPa under those forces.