AISI 304不銹鋼管材是一種應用非常廣泛的工程構件,管材在使用中由於
熱應力或振動等負載的交替作用, 很容易在環向方向起始穿透式裂縫,當
裂縫起始後便開始穩定成長,直到無法承受外加負載時發生斷裂行為。本
文針對管材在裂縫起始後,裂縫穩定成長,斷裂二個階段提出三種研究方法
。首先,為準確預估含穿透式環向裂縫管材的疲勞壽命,必須先求得正確的
應力強度因子。接著探討可能使裂縫減速的方法。最後,探討管材的斷裂
現象。首先利用相似原理及應變計量測方法,量測具穿透式環向裂縫管材
的應力強度因子,以供能準確的預測疲勞壽命。試驗發現由相似原理所得
的結果與Sanders為架構發展所得的理論解最接近;應變計量測所得的結果
則因僅取描述裂縫尖端應力場函數係數中的前四項,而有明顯低估。其次,
分別利用鑽孔法,高峰應力減速及異物填充裂縫法修補裂縫。試驗結果發
現,鑽孔法中,若裂縫能確實長入孔內,則引起之減速循環數最多;異物填充
法中則需視填充是否確實決定減速效應。最後,以現有的三種工程評估法
評估管材承受單調加載與變動加載的能力。結果發現承受單調負載時均能
得到保守的評估,其中又以J積分估算法可預測整個負載及位移關係,最能
掌握整個斷裂行為;在變動負載中除淨截面塑性破壞法以降伏應力為依據
可得保守評估外,其餘幾乎均為不保守,有發展新的工程估算法之必要。

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.