Multiaxial stress concentration in an externally pressurized cylinder with an external circumferential groove

Journal Article · Wed Nov 01 04:00:00 EST 1995 · Journal of Pressure Vessel Technology

DOI:https://doi.org/10.1115/1.2842144· OSTI ID:131635

Tipton, S M; Sorem, Jr, J R ^[1]; Hickey, K A; Rawson, M S ^[2]

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1. Univ. of Tulsa, OK (United States). Mechanical Engineering Dept.
2. Baker Oil Tools, Broken Arrow, OK (United States)

Downhole oil tools are often comprised of cylindrical sections with external, circumferential stress concentrations. Frequently, it is necessary to design locally thin walls that are just capable of sustaining rare applications of severe external pressure with little or moderate amounts of yielding. Here, a thick-walled cylindrical specimen containing an external circumferential groove was subjected to external pressure. To investigate the maximum pressure sustainable by the reduced wall thickness, strain gage measurements were taken during external pressurization tests. For comparison to experimental results, an elastic-plastic notch stress-strain analysis was conducted based on Neuber`s rule. The analysis utilized multiaxial elastic finite element results along with elastic-plastic tensile test data for the cylinder material. It is demonstrated that the boundary conditions used to model the specimen had a substantial effect on the finite element results, even though the boundary was somewhat removed from the region of concentrated stress. Biaxial strain measurements are presented versus pressure over the elastic and into the plastic regime, and deformation plasticity theory was used to compute stress and radial strain components corresponding to measured strains. It is demonstrated that in order to apply a multiaxial Neuber`s rule to accurately estimate the elastic-plastic stress-strain response (using elastic stress concentration information and elastic-plastic material data), it is necessary to utilize an experimental observation that the ratio of the hoop to radial strain remains invariant from the elastic to the elastic-plastic regime. This differs from published assumptions about invariant hoop-to-axial strain ratios based on analysis of circumferentially grooved solid shafts. The predictions are accurate for moderate plastic strains, but correlation breaks down for bulk plastic deformation.

• Sponsoring Organization: USDOE
• OSTI ID: 131635
• Journal Information: Journal of Pressure Vessel Technology, Journal Name: Journal of Pressure Vessel Technology Journal Issue: 4 Vol. 117; ISSN JPVTAS; ISSN 0094-9930
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
CYLINDRICAL CONFIGURATION
DEFORMATION
EXPERIMENTAL DATA
FIELD PRODUCTION EQUIPMENT
MATERIALS TESTING
PLASTICITY
STRESS ANALYSIS
THEORETICAL DATA