本文選題：高分辨率CT + 圖像配準�。� 參考：《南昌航空大學》2015年碩士論文

【摘要】：2A50鋁合金由于其塑性好、強度高,因此在航空工業(yè)中得到了大量的應用。飛機結構在飛行過程中受彎曲載荷作用易產(chǎn)生疲勞裂紋,對飛機安全飛行帶來嚴重威脅。裂紋信息的確定是裂紋擴展分析的前提,而裂紋擴展具有典型的三維特征,常規(guī)無損檢測方法無法獲取裂紋的三維信息。因此,本文以2A50鍛鋁材料作為研究對象,提出采用高分辨率CT研究彎曲載荷作用下材料三維裂紋擴展行為和損傷表征。通過2A50鍛鋁三點彎曲試驗得到不同裂紋擴展階段的疲勞試樣,通過掃描電鏡分析表面裂紋擴展信息。利用高分辨率顯微CT對疲勞試樣進行掃描與重建獲取不同階段的裂紋擴展CT演化圖像。對不同擴展階段裂紋CT演化圖像進行了圖像配準,根據(jù)配準圖像對不同疲勞擴展階段二維CT裂紋圖像進行了對比分析。利用區(qū)域提取法成功提取裂紋特征,并通過三維可視化方法獲得裂紋三維形態(tài)。利用液態(tài)鎵滲入到裂紋體內,提高了裂紋圖像對比度,得到了增強顯示的裂紋CT圖像,通過三維可視化獲得了液態(tài)鎵的三維分布。將4個疲勞階段裂紋圖像投影在二維平面上,通過計算平面上裂紋前沿裂紋長度研究二維平面上裂紋擴展特性。提出了一種單像素厚度的裂紋擴展曲面提取算法,可用于提取裂紋體的中曲面,將4個疲勞階段裂紋投影到該中曲面上獲得了單像素厚度裂紋擴展曲面增量圖形,根據(jù)單像素厚度裂紋擴展曲面分析了裂紋擴展長度和裂紋擴展速率,并計算得到單像素厚度裂紋擴展曲面的表面粗糙度為2.2206個像素點,可用于反映裂紋在厚度方向上擴展的劇烈程度。提出了裂紋擴展危度因子計算模型,計算得到當前危險度因子為0.25,當前裂紋擴展處于危險階段。結果表明,高分辨率CT技術可用于檢測材料中存在的疲勞裂紋,三維可視化得到的裂紋三維信息可用于分析裂紋的三維擴展行為。
[Abstract]:2A50 aluminum alloy has been widely used in aviation industry because of its good plasticity and high strength. The fatigue crack of aircraft structure is easy to be caused by bending load during flight, which is a serious threat to the flight safety of aircraft. The determination of crack information is the premise of crack growth analysis, and crack propagation has typical three-dimensional characteristics. Conventional nondestructive testing methods can not obtain three-dimensional crack information. Therefore, in this paper, high-resolution CT is used to study the three-dimensional crack propagation behavior and damage characterization of 2A50 wrought aluminum material under bending load. The fatigue specimens of different crack growth stages were obtained by three-point bending test of 2A50 wrought aluminum. The surface crack propagation information was analyzed by scanning electron microscope (SEM). Fatigue specimens were scanned and reconstructed with high resolution microCT to obtain the evolution images of crack propagation CT at different stages. In this paper, the CT evolution images of cracks in different growth stages are registered, and the 2D CT crack images of different fatigue growth stages are compared and analyzed according to the registration images. The crack feature is extracted successfully by region extraction method, and the 3D shape of crack is obtained by 3D visualization method. Using liquid gallium to infiltrate into the crack body, the contrast of the crack image is improved, the enhanced CT image of the crack is obtained, and the three-dimensional distribution of liquid gallium is obtained by 3D visualization. Four fatigue phase crack images were projected on a two-dimensional plane, and the crack propagation characteristics on the two-dimensional plane were studied by calculating the crack front length of the crack front in the plane. A single pixel thickness crack propagation surface extraction algorithm is proposed, which can be used to extract the middle surface of the cracked body. Four fatigue stage cracks are projected onto the middle surface to obtain the incremental figure of the crack propagation surface with single pixel thickness. According to the single pixel thickness crack propagation surface, the crack growth length and crack growth rate are analyzed, and the surface roughness of the single pixel thickness crack propagation surface is calculated to be 2.2206 pixels. It can be used to reflect the intensity of crack propagation in the thickness direction. A model for calculating the risk factor of crack growth is proposed. The current risk factor is 0.25, and the current crack growth is at a dangerous stage. The results show that the high resolution CT technique can be used to detect the fatigue crack in the material, and the 3D visualization of the crack can be used to analyze the three-dimensional propagation behavior of the crack.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG146.21;TP391.41

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相關期刊論文 前1條

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