Experimental Studies of Ratcheting of Pressurized Pipe

Abstract

In these studies, both dynamic and static tests were conducted on pressurized pipe. Dynamic tests were run on 1 in. Schedule 40 and Schedule 10 seamless 304 stainless steel pipe. Welded 1 in. Schedule 40 304 stainless steel pipe and seamless carbon steel (ASTM A106) pipe were tested statically. Internal pressures varied from 1000 psi to 3000 psi. In these tests, axial bending stresses from either inertial loads or static loads were superposed on to the initial pressure stresses. Strain gages were used to measure the cyclic strains on the outer walls of the pipe. Measurements indicated that ratcheting occurred primarily in the hoop direction and varied from a maximum at the top and bottom of the pipe that had the highest bending stresses to zero at the neutral axis. Though ratcheting occurred primarily in the hoop direction, some ratcheting in the axial direction was observed in 304 stainless steel pipe in both static and dynamic tests. Axial ratcheting was insignificant in the carbon steel pipe. Data obtained from these tests are presented. Measured ratcheting strains are compared to approximations of Beaney, Edmunds and Beer and to finite element computations.