Stresses in Thick-Walled Plane Pipe Bends

Abstract

The increasing use of high pressures in engineering requires the employment of thick-walled pipes, and consequently of thick-walled pipe bends. The behaviour of conventional pipe bends under bending loads and internal pressure has been understood for some time, and more recent work has been concentrated on thin-walled, short-radius bends. Experiments on two thick-walled pipe bends, having Λ values of 4·57 and 1·76 respectively are described; in-plane bending and internal pressure are considered, both separately and together. Bending stresses and flexibilities are satisfactorily described by existing theories (Turner and Ford, Barthélemy); no existing theory is adequate for the pressure stresses, but modifications to Thuloup's theory make it applicable to thick-walled pipe bends. Bending and pressure stress systems were found to be superposable. Maximum equivalent stresses calculated by the above theories were 20 per cent higher than those derived from the experiments, provided that the cross-section of the pipe bend was describable by a convergent Fourier series; random local flattenings can cause large stresses under internal pressure.