Use the knowledge of material mechanics to design your own chair. Several key parts need to be evaluated from the aspects of strength or deformation. For example, (1) the joint components should be calculated and evaluated by using the theory in terms of shearing deformation; 

(2) the link bars should be evaluated by using the tension and compression deformation theory; 

(3) the legs should be evaluated from the following knowledge points such as the compression deformation, bending deformation, and combined deformation; 

(4) the seat can be evaluated by simplifying it as an overhanging beam.