In furniture, often elements are used which essential feature is high pliability, much greater than the pliability of other elements. Most structural elements, due to the impact of load, change their dimensions; however, this is a very undesired side effect, since their main purpose is to preserve the designed stiffness and strength. The susceptible elements are by nature prone to strains and are used in those construction assemblages, which are to provide the feeling of comfort and convenience to the user. The most frequently used susceptible elements in furniture include springs, elastomer foams and wooden of plywood fittings (Fig. 4.51).
The main task of susceptible elements is given as follows:
• taking over external forces acting on the furniture piece or its elements, especially forces of shock nature,
• accumulation of energy in order to use it later and
• the even support of the human body in contact with a seat or bed.