- 學位論文
鋁合金高速艇之結構疲勞強度與極限強度分析
Fatigue and ultimate strength analysis of Aluminum alloy high speed craft
摘要
鋁合金材料之密度約為鋼材之1/3，也有較高之抗腐蝕性，常應用於高速艇之材料。高速艇結構在鋼材有完整的設計資料，採用鋁合金結構時，其結構設計常從現有鋼材結構設計，以等效降伏強度比例為依據而轉換為鋁合金結構設計，鋁合金結構除了考慮降伏強度外，必須檢討鋁合金電銲結構熱效應區(Heat affected zone,HAZ)，材料強度下降對疲勞強度及極限強度之影響。本文針對一高速三體船結構進行局部疲勞壽命評估。採用Palmgren-Miner 疲勞損害累積法假設去推算結構的疲勞壽命，並探討材料產生初始裂紋時，經過海上航行之循環變動外力作用下，裂紋之擴展速度，以檢視船舶局部構件能否達到疲勞壽命規範之需求，檢討高速三體船之結構設計所需改良之處。並針對船舶之甲板結構受壓縮應力、彎曲力矩下進行極限強度之分析，以及探討壓擠成型三明治甲板結構與傳統肋骨甲板結構之強度差異，評估採用壓擠成型甲板所能減輕結構之重量等。
並列摘要
Recently Aluminum alloy has been applied for high speed vessel because its density is 1/3 of steel, and has good corrosion resistance. For aluminum structure not only the equivalent yield strength need be considered, the strength reduction due to heat affected after welding, and relative lower fatigue strength should be taken account, if the design of aluminum structure member is based on the exsisted desing of steel structure, the fatigue life and the ultimate strength of structure member should be assessed. In this work the Palmgren-Miner rule was used to predict the fatigue life of aluminum of structure member, the crack length within specified time period by the crack growth speed method was also predicted for member with initial crack. After assessment of fatigue strength, the structural member should be modified if its fatigue life is shorter than required service life. Comparrision study of ultimate strength for deck structure between lightweight extrusion deck panel and traditional deck structure by applied displacement control and bending moment control.