New Strength Theory and Its Application to Determine Burst Pressure of Thick-Wall Pressure Vessels

The classical Tresca and von Mises strength theories have been utilized extensively for pressure vessel and pipeline design. For pressure vessel design, ASME B&PV code was developed using both Tresca and von Mises strength theories, where the yield strength (YS) was used for an elastic design and the ultimate tensile strength (UTS) was used for an elastic-plastic design. For pipeline design, ASME B31.3, B31G, or other codes were developed using the Tresca strength theory coupled with the YS or a flow stress. The flow stress was introduced to reduce over conservatism from the YS and avoid overestimation from the UTS for many steels. It has been widely accepted that the burst strength of pipelines depends on the UTS and strain hardening rate, n, of the ductile steel. The average shear stress yield theory was thus developed, and the associated burst pressure solution was obtained as a function of UTS and n. Experiments showed that the Zhu-Leis solution provides a reliable prediction of the burst pressure for defect-free thin-wall pipes. In order to extend the Zhu-Leis solution to thick-wall pressure vessels, this work modified the traditional strength theories and obtained new burst pressure solutions for thick-wall pressure vessels. Three new flow stresses were proposed to describe the tensile strength and plastic flow response for a strain hardening material. The associated strength theories were then developed in terms of the Tresca, von Mises and Zhu-Leis yield criteria. From these new strength theories, three burst pressure solutions were obtained for thick-wall cylinders, where the von Mises solution is an upper bound prediction, Tresca solution is a lower bound prediction, and the Zhu-Leis solution is an averaged prediction of burst pressure for thick-wall vessels. Subsequently, the proposed burst solutions were validated by a large dataset of full-scale burst tests.