Strength of Materials

1.8 ALLOWABLE STRESS

Most of the materials begin to exhibit some non-linearity between stress and strain when loaded beyond a certain limit. With this non-linear behaviour of the materials, the problem of assessing deformation and distribution of internal forces in structural members and machine element become much more complicated compared with a material with linear stress–strain behaviour. To have the structure in an elastic condition and to remove the possibility of permanent set, it is usual practice to keep the stress in the material in the elastic range such that permanent set is not caused.

With the knowledge of the limit of proportionality, the yield point and the ultimate stress of the material, it is possible to fix for a given field ...