Experimental analysis of preload in threaded connections

F. P. Brennan, R. F. Kare

Research output: Chapter in Book/Report/Conference proceedingConference contribution book


Stress analysis of threaded connections has been a widely researched topic for many years. Recently full three dimensional finite element models have been used to determine the relationship between the nominal applied load and the resulting critical tooth root stress within threaded connections. However these require that the model is correct. Frequent assumptions made in these models are that the connections are not preloaded or that a constant preload is applied to the bolt head irrespective of externally applied axial, bending or indeed torsional loading. The level of preload applied during make-up of threaded connections will directly effect the stress distribution within the connection as a whole, and will also determine the level of mean stress of an oscillating fatigue stress. If large tensile mean stresses are not taken into account in fatigue analysis, unconservative fatigue life predictions can result. Stress corrosion cracking could also become a significant feature even without fatigue loading. For these reasons an experimental investigation of preload due to applied torque in threaded connections was carried out. Three very different connection types were studied, these were large diameter thick and thin walled connections and a regular ISO metric threaded bolt. The paper presents the results of the experimental stress analysis and observations made on the topic of preload with regard to fatigue. Conclusions arrived at are that large circumferential stresses may exist close to the rotary shoulder interface due to applied preload. Also fatigue analyses should consider whether packing material remains inert during service - otherwise the initial stress analysis may no longer be appropriate.

Original languageEnglish
Title of host publicationProceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE
Number of pages7
Publication statusPublished - 1 Jan 1994
EventProceedings of the 13th International Conference on Offshore Mechanics and Arctic Engineering - Houston, TX, USA
Duration: 27 Feb 19943 Mar 1994


ConferenceProceedings of the 13th International Conference on Offshore Mechanics and Arctic Engineering
CityHouston, TX, USA


  • fatigue of materials
  • fatigue testing
  • interfaces (materials)
  • mathematical models
  • stress analysis
  • tensile testing
  • connectors (structural)


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