| Summary: | 碩士 === 國立臺灣大學 === 機械工程研究所 === 81 === AISI 304 stainless steel pipe has been widely used in
engineering structures. A crack may initiate in the
circumferential direction due to the action of thermal and
vibratory stresses. It will propagate under the cyclic load.
Eventually, the pipe will fracture when the residual ligament
is too small to bear the external load. In this thesis, three
aspects about pipe integrity have been studied. Firstly, a
correct stress intensity expression is established to ensure
accurate fatigue life prediction for circumferentially cracked
piping. Then, the possibility of retarding such a crack was
investigated. Finally, the fracture behaviour of cracked piping
was studied. In the first part of work, the similarity
principle and strain gage method was used to measure stress
intensity factor for pipe with circumferential through-crack.
The result of using principle was very closed to the analytic
solution derived by Sanders. It was found that the strain gage
method underestimates. The possible reason is that only four
coefficients were used in the description of crack tip stress
distribution. Secondly, the drill hole method, overload
retardation and vacuum-infiltrating material into the crack
flanks had been used to repair crack. It was found that the
hole drilling method induced maximun retardation if the crack
propagates into the hole. The degree of retardation for the
vacuum-infilrating material method was dependent on whether the
infilration was successful or not.
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