發(fā)布時間：2018-07-23 17:46

【摘要】：構件失效通常是導致設備無法正常運轉的主要原因,主要表現(xiàn)為應力分布不均與裂紋擴展,針對于大型設備的應力應變檢測以及裂紋擴展監(jiān)測一直是工程領域面臨的重大問題。量子點作為一種納米半導體材料,具有獨特的熒光性能,廣泛的應用在生物探針、太陽能電池以及發(fā)光二極管等方面。近年來,由于量子點納米晶在受力條件下展現(xiàn)出熒光性能改變的特性,利用量子點的熒光性能制備的熒光納米晶應力應變計得到了關注。本文基于核殼結構的熒光量子點,混合環(huán)氧樹脂制備了量子點環(huán)氧樹脂復合材料。以此為研究對象,在金屬緊湊拉伸基底上覆膜,可動態(tài)監(jiān)測金屬裂紋擴展情況�？疾炝孔狱c添加量濃度和裂紋區(qū)域熒光強度、裂紋寬度與裂尖、膜裂紋與金屬裂紋同步性等變化的影響,分析了可視化熒光信號出現(xiàn)的機理。研究了拉伸下金屬應力應變與膜熒光強度變化的響應,通過分析拉伸條件下金屬應力和膜應力的大小、量子點樹脂空白樣在循環(huán)拉伸下應力應變/應力松弛/量子點濃度變化等因素的影響,提出了應力應變熒光強度響應機理,利用中間帶圓孔的板材試樣考察了殘余應變分布。論文主要獲得了以下研究結果：(1)量子點環(huán)氧樹脂復合材料制備工藝優(yōu)化及拉伸熒光響應通過對不同種類環(huán)氧樹脂與量子點的混合測試研究,確定了6002型環(huán)氧樹脂與593固化劑的混合搭配可最大程度降低環(huán)氧樹脂對量子點熒光性能的影響,同時保持較好的混合成模性能。在同等體積下的環(huán)氧樹脂中添加不同濃度的量子點溶液,發(fā)現(xiàn)以1：4為標準量子點添加量時,實驗樣品可以較好地在線性變化區(qū)間�；诹孔狱c環(huán)氧樹脂復合材料的拉伸性能及熒光響應,確定了量子點環(huán)氧樹脂材料屬于非線性粘彈性材料,在拉伸后會產(chǎn)生較大的殘余應變,同時獲得了隨應變增大會,熒光強度整體呈現(xiàn)下降,但在小應變區(qū),熒光強度會有不同程度上升的熒光響應變化趨勢。通過溫度穩(wěn)定性的考察,獲得了量子點環(huán)氧樹脂材料的溫度適用范圍在30℃到100℃溫度變化區(qū)間。確定了溫度上升到150℃時,環(huán)氧樹脂的老化現(xiàn)象使得量子點的熒光現(xiàn)象消失。(2)金屬I型裂紋擴展的檢測開發(fā)了量子點環(huán)氧樹脂膜檢測金屬I型裂紋擴展的方法,實現(xiàn)了熒光信號的快速響應,可精確描述微米級寬度的裂紋生長狀態(tài)。對涂覆量子點環(huán)氧樹脂膜的金屬緊湊拉伸試樣的疲勞拉伸,確定了熒光信號出現(xiàn)的先決條件,并動態(tài)可視化地追蹤了裂紋擴展過程,同時,確定了拉伸后裂紋區(qū)域的熒光強度要高于未出現(xiàn)裂紋區(qū)域的熒光強度。通過對比膜裂紋與金屬裂紋的寬度及位置、裂尖形態(tài)的考察,獲得了寬度為1-100μm的裂紋檢測的適用范圍及薄膜裂紋形成的過程,實現(xiàn)了靈敏度為1μm、精度為0.1μm的裂紋尖端檢測,并提出控制薄膜厚度可更好的描述裂尖的形態(tài)。(3)膜裂紋與金屬裂紋同步性考察及熒光響應機理研究通過對量子點環(huán)氧樹脂膜的各添加劑比例的控制,確定了環(huán)氧樹脂/氯仿/固化劑的體積比為3：1：1-4：1：1區(qū)間為最佳的配比,其固化后的產(chǎn)物維氏硬度相對較高。同時選用體積比為3：1：1做為反應配比,通過改變固化溫度從50到80℃的變化,考察氯仿的揮發(fā)程度及固化產(chǎn)物的維氏硬度變化,避免了膜裂紋與金屬裂紋偏移、裂尖位置相差較大以及樹脂膜在拉伸過程中裂紋處薄膜剝離的發(fā)生,提高了樹脂膜裂紋與金屬裂紋的同步性,確保了裂紋的同步生長。最后,對量子點環(huán)氧樹脂膜熒光響應機理進行了分析,研究認為在膜裂紋斷裂處出現(xiàn)的收縮使得裂紋兩側的量子點相對濃度增加,同時由于膜裂紋的開裂,使得更多的量子點暴露于紫外激發(fā)光源下,導致了熒光信號的產(chǎn)生。(4)量子點環(huán)氧樹脂膜監(jiān)測金屬應力應變建立了量子點環(huán)氧樹脂復合材料檢測金屬應力應變的方法,新型的應力應變-熒光傳感器可以較好的描述金屬在線彈性區(qū)間內(nèi)拉伸條件下的應變變化。通過對涂覆量子點環(huán)氧樹脂的金屬試樣變應力循環(huán)拉伸,驗證了膜結構的變化導致了熒光強度變化的結論。對量子點環(huán)氧樹脂空白樣的拉伸應力應變曲線、應力松弛、應力回彈變化的考察進一步驗證了多次循環(huán)下熒光強度的累積來自于量子點環(huán)氧樹脂循環(huán)拉伸后應變累積,同時其熒光變化幅度與量子點樹脂每次循環(huán)的應變增量的呈對應關系。對比了拉伸前后量子點的分布濃度和應變變化,提出了熒光強度的上升和下降主要來源于拉伸前后單位范圍內(nèi)的量子點濃度的變化以及聚集的量子點間的距離增大導致更多量子點受到激發(fā)。對中間帶圓孔的薄板試樣拉伸測試,獲得熒光強度的變化與薄板試樣的應力分布及應變變化的對應關系。
[Abstract]:The failure of the component is usually the main cause of the failure of the equipment to operate normally. It is mainly manifested in the uneven distribution of stress and crack propagation. The stress and strain detection and crack propagation monitoring for large equipment have been a major problem in the field of engineering. As a nanomo semiconductor material, the quantum dots have a unique fluorescence performance. The ubiquitous applications are in biological probes, solar cells and light emitting diodes. In recent years, the fluorescence nanocrystalline stress-strain gage prepared by the fluorescence properties of quantum dots has been paid attention to because of the characteristics of the change in the fluorescence properties of the quantum dots nanocrystals under the force conditions. A quantum dot epoxy resin composite was prepared by epoxy resin. As a study object, film covered on a metal compact tensile substrate can dynamically monitor the expansion of metal cracks. The effects of quantum dots addition concentration, crack region fluorescence intensity, crack width and crack tip, membrane crack and metal crack synchronism are investigated. The mechanism of the appearance of the fluorescence signal was observed. The response of the stress strain and the change of the film fluorescence intensity under tension was studied. The stress strain and the stress relaxation of the quantum dot resin were influenced by the factors such as stress strain / stress relaxation / quantum dot concentration change under cyclic stretching. The distribution of residual strain was investigated by the plate specimen with round holes in the middle. The main results were as follows: (1) the optimization of the preparation technology of the quantum dots epoxy resin composite and the tensile fluorescence response of the epoxy resin and the quantum dots were determined by the mixing of different kinds of epoxy resin and quantum dots. The 6002 epoxy resin was determined. The mixing with 593 curing agent can minimize the effect of epoxy resin on the fluorescence properties of quantum dots, while maintaining a better mixing model performance. Adding different concentration of quantum dots solution at the same volume of epoxy resin under the same volume, it is found that the experimental sample can be well linearly changed when 1:4 is added as the standard quantum dot. Based on the tensile properties and fluorescence response of the quantum dots epoxy resin composite, it is determined that the quantum dots epoxy resin material belongs to the nonlinear viscoelastic material, which will produce large residual strain after stretching. At the same time, the fluorescence intensity as a whole decreases as the strain increases, but the fluorescence intensity will have different distances in the small strain zone. Through the investigation of temperature stability, the temperature range of the temperature applicable range of quantum dots epoxy resin materials was obtained at 30 degrees C to 100 C. The aging phenomenon of epoxy resin was determined to disappear the fluorescence image of the quantum dots at 150 C. (2) detection and development of the crack growth of the metal I type. The method of detecting the crack growth of the metal I type by the quantum dot epoxy resin film is used to realize the rapid response of the fluorescence signal, which can accurately describe the crack growth state of the micron width. The precondition of the appearance of the fluorescence signal is determined by the fatigue stretching of the compact tensile specimen of the metal coated with the quantum dots epoxy resin film, and the dynamic visual tracing is made. The crack propagation process is traced, and the fluorescence intensity of the crack region is determined to be higher than that of the uncracked region. By comparing the width and position of the crack to the metal crack and the shape of the crack tip, the suitable range of crack detection and the formation process of the crack in the crack are obtained by the investigation of the width and position of the crack and the crack tip. The sensitivity is 1 mu m and the precision of the crack tip is 0.1 M, and the control film thickness can better describe the shape of the crack tip. (3) the investigation of the synchronism of the crack and the metal crack and the mechanism of the fluorescence response are studied. The volume ratio of the epoxy resin / chloroform / curing agent is determined by the control of the ratio of each additive to the epoxy resin film of the quantum dots. The 1:1-4:1:1 interval is the best ratio, and the hardness of the cured product Vivtorinox is relatively high. At the same time, the ratio of the volume ratio is 3:1:1 as the reaction ratio. By changing the curing temperature from 50 to 80 C, the volatilization degree of chloroform and the change of the hardness of the cured product of the cured product are investigated, and the film crack and the metal crack offset and the crack tip are avoided. There is a large difference in position and the occurrence of film stripping at the crack of the resin film during the tensile process, which improves the synchronism of the crack of the resin film and the metal crack, and ensures the synchronous growth of the crack. Finally, the fluorescence response mechanism of the quantum dots epoxy resin film is analyzed. The study holds that the shrinkage of the crack at the crack of the membrane causes the two sides of the crack. The relative concentration of the quantum dots increases and the crack of the membrane cracks causes more quantum dots to be exposed to the ultraviolet light source, which leads to the production of the fluorescence signal. (4) the quantum dots epoxy resin membrane is used to monitor the metal stress and strain of the quantum dot epoxy resin composite to detect the stress and strain of the metal, and the new stress and strain. The fluorescence sensor can describe the strain change under the tensile condition of the metal on line. Through the cyclic stretching of the strain of the metal specimen coated with the quantum dots epoxy resin, the conclusion that the change of the membrane structure leads to the change of the fluorescence intensity is verified. The tensile stress strain curve and the stress on the blank sample of the quantum dots epoxy tree fat are stressed. The investigation of relaxation and stress rebound changes further verifies that the accumulation of fluorescence intensity in multiple cycles is derived from the strain accumulation after the cyclic tensile of quantum dots, and the amplitude of the fluorescence is corresponding to the strain increment in each cycle of the quantum dots, and the distribution of the quantum dots and the strain changes before and after the extension are compared. It is proposed that the rise and decrease of fluorescence intensity is mainly due to the change in the concentration of quantum dots within the unit range before and after stretching and the increase of the distance between the quantum dots, which leads to the excitation of more quantum dots. The tensile test of thin plate specimen with a round hole in the middle is used to obtain the change of the fluorescence intensity and the stress distribution and strain variation of the thin plate specimen. The corresponding relationship.
【學位授予單位】：華東理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG115

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