油箱積水環(huán)境下航空鋁合金2E12-T3和7050-T7451疲勞性能實驗

油箱積水環(huán)境下航空鋁合金2E12-T3和7050-T7451疲勞性能實驗Contrasty Tests on Fatigue Properties of Aluminum Alloys 2E12-T3 and 7050-T7451 in Pooding Environment of Fuel Tank

典型腐蝕環(huán)境下的疲勞性能是航空金屬結(jié)構(gòu)疲勞壽命設(shè)計的前提，為此，實驗測定航空鋁合金2E12-T3和7050-T7451光滑試樣和缺口試樣在干燥大氣環(huán)境和油箱積水環(huán)境下的疲勞性能S-N曲線，觀測實驗現(xiàn)象，根據(jù)實驗數(shù)據(jù)結(jié)果進(jìn)行疲勞性能對比，并對試樣斷口進(jìn)行掃描電鏡（SEM）分析，研究油箱積水腐蝕環(huán)境和載荷聯(lián)合作用對疲勞性能的影響機(jī)理，結(jié)果表明：油箱積水環(huán)境對材料的疲勞性能產(chǎn)生不利影響，疲勞載荷的降低和試樣的缺口均加劇腐蝕環(huán)境對材料疲勞性能的不利影響；腐蝕引起的試樣表面粗糙狀況更容易萌生疲勞裂紋，裂紋尖端發(fā)生的電化學(xué)反應(yīng)和氫脆效應(yīng)加快裂紋擴(kuò)展，使得疲勞性能降低和疲勞壽命縮短。

Fatigue properties in typical corrosion environments are the premise of fatigue life design for metallic structures in aircraft. Therefore, fatigue tests were performed on smooth and notched specimens subjected to constant amplitude loading in two environments of dry air and fuel tank ponding respectively to determine pure and corrosion fatigue properties of aluminum alloys 2E12-T3 and 7050-T7451. Corrosion fatigue properties in the two environments were analyzed and compared with each other, and the interaction mechanisms between corrosion and fatigue were deduced from fractographical studies by using scanning election microscope (SEM). It is showed that fuel tank ponding has a detrimental influence on fatigue properties and the adverse effect increases with the decreasing stress level. In addition, the notch of specimen enhances the severity of corrosion effects. Fatigue crack is easily initiate from the corrosion pits on the rough fatigue surface, and crack propagation is enhanced by the corrosion products and the hydrogen embrittlement effects at crack tips, thus the degradation of fatigue properties and the reduction of fatigue life are caused.