Collapse Pressure Analysis in Torsion of a Functionally Graded Thick-walled Circular Cylinder under External Pressure

A hollow thick-walled cylinder made of functionally graded material subjected to twist has been analyzed. The objective of this paper is to provide the guidance to design the torsion of thick-walled cylinder made of functionally graded material so that collapse of cylinder due to external pressure can be avoided. The concept of transition theory based on the concept of Lebesgue strain measure has been used to simplify the constitutive equations. Results have been analyzed theoretically and discussed numerically. From the discussion, we can conclude that highly non-homogeneous cylinder is on the safer side of the design as compared to lesser non-homogeneous cylinder. This is because of the reason that percentage increase in pressure required for initial yielding to become fully plastic is very high for non-homogeneous cylinder whose non-homogeneity increases radially as compared to lesser non-homogeneous cylinder. Also, non-homogeneous cylinder whose thickness is very high is on the safer side of the design as compared to less thick-walled cylinders because percentage increase in pressure required for initial yielding to become fully plastic is very high for highly thick-walled cylinders as compared to other cases.