LIFE ASSESSMENT OF HIGH STRENGTH STUDS FOR GENERAL FLANGED CONNECTIONS PWR NUCLEAR POWER PLANTS

摘要

A most high reliability and maximum serviceability ofthreaded connections of fasteners are thought to be achieved bythe creation of a certain above zero temperature margin which isthe difference between operating and fracture assessmenttransition temperature (FATT) of fasteners including the maindisengagement pressure vessel.In such circumstance the application of fasteners of generalmechanical engineering purpose with specific requirements toproduction processing provides a necessary service life ofthreaded connections of fasteners. However, when it isimpossible for high loaded fasteners PWR to sustain above zerotemperature margin, then a sufficient brittle fracture resistanceoff threaded connection can be ensured only by check brittlestrength calculation and estimation of permissible FATT ofproducts with the criteria of linear fracture mechanics. For thispurpose we must possess information of the character of stressstate in fastener thread with a screw crack as well as localfracture criteria under conditions of complex stress state. Thewhole complex of these data permits to link fastener transitiontemperature with fastener geometry and material resistance tobrittle and low cycle fatigue failure.