本文選題：生物分層結(jié)構(gòu) + 牙釉質(zhì)��； 參考：《華東理工大學(xué)》2014年博士論文

【摘要】：分層結(jié)構(gòu)廣泛存在于牙齒、骨骼等生物材料和結(jié)構(gòu)中,表現(xiàn)為優(yōu)異的機械與力學(xué)性能。對其宏/微觀結(jié)構(gòu)-性能-功能之間關(guān)系的深入理解和認識,不僅使人們更好地認識生物材料和結(jié)構(gòu)的進化規(guī)律,而且有助于設(shè)計、制造出擁有更佳性能的仿生結(jié)構(gòu)和器件,相關(guān)研究一直是機械、材料、力學(xué)和醫(yī)學(xué)領(lǐng)域共同關(guān)注的熱點。本文以典型天然生物分層結(jié)構(gòu)材料-牙釉質(zhì)層(牙齒最外層材料)為實驗研究對象,利用微納米壓/劃痕實驗、有限元模擬和理論分析等方法,系統(tǒng)研究了其微觀摩擦磨損機理、微觀力學(xué)性能表征以及循環(huán)接觸行為。主要的研究工作和結(jié)論如下： (1)納米尺度下牙釉質(zhì)的各向異性摩擦行為。采用球錐形壓頭的納米壓痕儀,進行了不同載荷下釉質(zhì)層在單個釉柱層級的咬合面和軸剖面上原位劃痕實驗,基于表面粗糙度、劃痕深度和殘余深度,分析了劃痕過程中的彈性回復(fù)和非彈性變形行為。結(jié)果表明：釉柱咬合面上的彈性回復(fù)和非彈性變形明顯小于軸剖面,且咬合面更加耐磨損。納米尺度上牙釉質(zhì)的摩擦系數(shù)表現(xiàn)為載荷相關(guān)性與位置相關(guān)性,摩擦系數(shù)的載荷相關(guān)性源于劃痕過程中的犁溝效應(yīng),而位置相關(guān)性是由于正向加載、劃痕方向與細長狀羥磷灰石晶粒方向的夾角差異導(dǎo)致。 (2)圓柱/包圍層微結(jié)構(gòu)單元壓痕力學(xué)分析�？紤]到富蛋白質(zhì)的釉柱鞘對硬質(zhì)的釉柱壓痕可能產(chǎn)生的影響,建立了圓柱/包圍層結(jié)構(gòu)的理論模型,得到了壓痕載荷-位移關(guān)系的彈性理論解,結(jié)合有限元討論了包圍層的厚度和圓柱/包圍層的彈性模量對壓痕曲線的影響；此外,討論了儀器化壓痕測試圓柱/包圍層結(jié)構(gòu)彈性模量時所采用的Oliver-Pharr方法的局限性,提出了門檻壓入深度參數(shù),當(dāng)壓痕深度小于該門檻值時,測試模量的誤差在±10%內(nèi)。研究表明：對于可壓縮彈性包圍層,產(chǎn)生相同的壓痕位移所需的載荷會隨著模量的增加而降低；而不可壓縮層對圓柱的彈性壓痕響應(yīng)影響不明顯。另外,門檻壓入深度與模量、包圍層厚度和圓柱半徑比密切相關(guān),該結(jié)果對如何使用Oliver-Pharr方法測試類似釉柱/釉柱鞘結(jié)構(gòu)的彈性模量有指導(dǎo)意義。 (3)微、納尺度下牙釉質(zhì)循環(huán)壓痕行為的各向異性分析。利用Berkovich壓頭在釉質(zhì)和釉柱兩個層級上分別進行循環(huán)壓痕實驗,基于壓痕位移曲線,分析了循環(huán)壓痕過程中的變形行為和能量耗散。研究發(fā)現(xiàn)：壓頭在循環(huán)載荷作用下會連續(xù)壓入材料,深度變化經(jīng)歷瞬態(tài)并達到準(zhǔn)穩(wěn)態(tài)。在準(zhǔn)穩(wěn)態(tài)時,每周壓入深度和每周塑性能耗散與最大壓痕載荷無關(guān),但與循環(huán)載荷幅值成正比,并且軸剖面的壓痕深度幅值和每周壓入深度要大于咬合面。進一步提出,利用釉柱上的單循環(huán)和多循環(huán)載荷-位移曲線之間的偏差來描述咬合面和軸剖面的循環(huán)響應(yīng)差異,發(fā)現(xiàn)在咬合面上,晶粒和蛋白質(zhì)的界面剝離以及蛋白質(zhì)分子循環(huán)過程中的不完全折疊是其疲勞損傷的主要原因,而在軸剖面上,除了與咬合面相同的損傷形式外,細長狀晶粒因彎曲發(fā)生的斷裂以及晶粒末端剝離對失效有影響。 (4)循環(huán)壓痕作用下牙釉質(zhì)變形模擬分析的雙層結(jié)構(gòu)模型�；谖⒓{尺度下內(nèi)、外層釉質(zhì)不同的釉柱排列形式,提出了循環(huán)壓痕有限元分析的雙層結(jié)構(gòu)模型,以模擬其結(jié)構(gòu)重復(fù)接觸的問題。研究結(jié)果表明,外層釉質(zhì)因其更大地抵抗接觸變形的能力,承擔(dān)了主要載荷,循環(huán)過程中的內(nèi)層釉質(zhì)上產(chǎn)生更大的等效塑性應(yīng)變和較低的應(yīng)力,內(nèi)層釉質(zhì)擁有更好的抵抗斷裂的能力。 (5)生物/仿生材料廣義錯列結(jié)構(gòu)的熱-機應(yīng)力分析�；谘烙再|(zhì)結(jié)構(gòu)的微觀分析,提出表征承載生物分層結(jié)構(gòu)材料的錯列微觀結(jié)構(gòu),通過修正經(jīng)典的“剪滯模型”,從應(yīng)力解和位移解的角度分別討論結(jié)構(gòu)在熱-機載荷作用下的應(yīng)力分布和等效熱膨脹系數(shù)。與有限元計算結(jié)果對比表明：應(yīng)力模型能更好地預(yù)測應(yīng)力分布；當(dāng)硬組織小板的縱橫比和體積分?jǐn)?shù)超過臨界值時,結(jié)構(gòu)的等效熱膨脹系數(shù)會達到常數(shù)；兩個理論模型的相對誤差會隨著兩個小板錯列程度的增加而增加。
[Abstract]:In this paper , we study the micro - friction wear mechanism , micro - mechanical property characterization and cyclic contact behavior of typical natural biological layered structure material - dental enamel layer ( the outermost layer of tooth ) . The main research work and conclusion are as follows :

The results show that the elastic recovery and inelastic deformation of the enamel layer on the occlusal surface of the enamel column are obviously smaller than those of the axial section and the occlusal surface is more wear - resistant . The results show that the elastic and inelastic deformation of the enamel on the occlusal surface of the enamel is obviously smaller than that of the axial section , and the occlusal surface is more resistant to wear . The friction coefficient is caused by the plow groove effect in the scratch process , and the positional correlation is caused by the difference of the forward loading , the scratch direction and the direction of the elongated hydroxyapatite grain .

( 2 ) The indentation mechanical analysis of the microstructure unit of the cylindrical / surrounding layer . The theoretical model of the structure of the cylinder / surrounding layer is established in consideration of the possible influence of the rich protein glaze sheath on the indentation of the hard glaze column , and the elastic theoretical solution of the indentation load - displacement relationship is obtained . The influence of the thickness of the surrounding layer and the elastic modulus of the cylindrical / surrounding layer on the indentation curve is discussed in combination with the finite element method .
In addition , the limitation of the Oliver - Pharr method used in the testing of the elastic modulus of the cylindrical / surrounding layer of the instrumented indentation is discussed , and the threshold pressure - in depth parameter is proposed . When the indentation depth is less than the threshold value , the error of the test modulus is within 鹵 10 % . The study shows that the load required for generating the same indentation displacement for the compressible elastic surrounding layer decreases with the increase of modulus ;
In addition , the threshold press - in depth is closely related to the modulus , the thickness of the surrounding layer and the ratio of the radius of the cylinder . The results are of great significance to how to use the Oliver - Pharr method to test the elastic modulus of the similar glaze / enamel structure .

The deformation behavior and energy dissipation in the process of cyclic indentation are analyzed by using the results of cyclic indentation experiments at two levels of enamel and glaze . The results show that the interfacial peeling of grains and proteins and incomplete folding in the process of molecular cycling are the main causes of fatigue damage .

( 4 ) The double - layer structure model of the simulated analysis of the tooth enamel deformation under the action of cyclic indentation is presented . The double - layer structure model of cyclic indentation finite element analysis is proposed based on the different patterns of enamel columns in the inner and outer layers of the micro - nano - scale . The results show that the outer enamel has higher equivalent plastic strain and lower stress on the inner enamel due to its greater resistance to contact deformation , and the inner enamel has better resistance to fracture .

( 5 ) The thermal - mechanical stress analysis of the generalized staggered structure of biological / bionic material . Based on the microscopic analysis of the tooth enamel structure , the stress distribution and the equivalent thermal expansion coefficient of the structure under the action of heat - machine load are discussed from the angles of the stress solution and displacement solution based on the microscopic analysis of the tooth enamel structure .
When the aspect ratio and the volume fraction of the hard tissue panel exceed the critical value , the equivalent thermal expansion coefficient of the structure can reach constant ;
The relative error of the two theoretical models increases with the increase of the error of the two small plates .

【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TH117.1;TB302

【參考文獻】

相關(guān)期刊論文 前1條

1 ;EFFECTIVE ELASTIC MODULUS OF BONE-LIKE HIERARCHICAL MATERIALS[J];Acta Mechanica Solida Sinica;2007年03期

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本文編號：1759194