engleski

Influence of the thread profile on the fatigue damage and lifetime of threaded connections

Fatigue damage and lifetime assessments of threaded connections were evaluated on metric normal, metric fine and trapezoidal thread profiles. In most of the cases on threaded connec- tions fatigue cracks initiate in first engaged thread root. This fact shows a need for models with local geometry of thread profiles and appropriate preload forces as well as fatigue in- fluencing factors. For the same nominal diameter, thread profiles have a different root radi-us, pitch and minor diameters among others. Therefore, multitude of geometry parameters, contact mechanics, and fatigue influencing factors results with complex and uncertain fa-tigue assessments. Local approach for fatigue of threaded connections is capable to describe the local stress and strain fields in thread root. In order to consider multiaxial stress field in thread root with high notch effect, multiaxial fatigue stress criterion based on a critical plane theory was applied for fatigue damage assessment. Bolt finite element model corresponds to model class IV from VDI 2230 Part 2. Assessments were done with preload forces from 10% to 90% of force at bolt yield point.

fatigue damage ; critical plane theory ; thread profile ; bolted connections ; bolt preload force

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