本文關(guān)鍵詞： 可降解鎂合金 力學(xué)環(huán)境 數(shù)值模擬 體外降解實驗　出處：《天津理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：目前臨床上常用的骨折內(nèi)固定修復(fù)材料多為不銹鋼、鈦合金等惰性材料,這些材料強度雖高但在愈合過程中由于彈性模量遠大于人骨,故存在應(yīng)力遮擋效應(yīng);另外這些材料在骨愈合后存在不吸收、難降解、需二次手術(shù)的缺點,而采用鎂合金材料修復(fù)骨折可以有效降低骨折愈合過程中應(yīng)力遮擋效應(yīng)和避免患者二次手術(shù)痛苦。以往的研究表明力學(xué)環(huán)境對鎂合金的降解有一定的影響且多為定性研究,本研究通過對有限元分析軟件ABAQUS中vusdfld用戶定義場變量子程序的編寫,實現(xiàn)在力學(xué)環(huán)境下對鎂合金材料降解過程的模擬預(yù)測,以便與體外降解實驗進行比較分析從而達到定量分析的目的。研究篩選了總體性能較好的鎂合金AZ31,對單一軸向壓力下的鎂合金降解過程進行了有限元仿真模擬,根據(jù)實驗要求設(shè)計制備鎂合金試件、鎂合金接骨板、接骨釘及其體外降解的實驗裝置,進行與仿真對應(yīng)的驗證實驗,探究鎂合金材料在不同力學(xué)環(huán)境下的降解規(guī)律。主要研究內(nèi)容如下:(1)闡述可降解鎂合金的國內(nèi)外研究現(xiàn)狀,提出課題研究的意義和重要性,確定課題的研究思路。(2)闡述連續(xù)損傷理論,編寫ABAQUS\EXPLICIT 6.13.1軟件中VUSDFLD用戶定義場變量子程序,實現(xiàn)降解過程中產(chǎn)生的氫氣體積、質(zhì)損及有效應(yīng)力的定量式輸出。建立有限元分析模型,包括:三種鎂合金試件模型及鎂合金接骨板固定羊脛骨中段斷骨的模型,在ABAQUS\EXPICITE軟件中進行數(shù)值模擬。(3)對數(shù)值模擬結(jié)果進行了研究與分析。結(jié)果表明:各組鎂合金試件模型降解過程氫氣體積與質(zhì)損均具同一性變化規(guī)律,軸向壓縮載荷大小對模型表面形貌特征、有效應(yīng)力分布、失效方式以及失效時間起著調(diào)控作用,且骨折固定模型中鎂合金的降解平緩。(4)設(shè)計鎂合金試件體外降解實驗,研究在單一軸向壓力下鎂合金試件(常規(guī)圓孔)降解行為特點。結(jié)果表明鎂合金的降解行為,包括氫氣體積、質(zhì)損及pH、最大壓縮位移、最大壓力及壓縮時間均與載荷值有關(guān),一定的軸向載荷會加快鎂合金的降解;各組實驗軸向載荷越大,pH波動相對較小;在軸向壓縮實驗過程中,軸向載荷對試件的最大抗壓性能有著調(diào)控的作用。(5)對仿真結(jié)果與實驗結(jié)果進行對比分析。結(jié)果表明:由于常溫(25℃)下模擬體液中空氣的溶解度大于體溫(37℃),導(dǎo)致實驗中收集的氫氣體積往往略大于仿真結(jié)果,但是均可說明在降解過程中一定的軸向載荷將加快鎂合金的降解速度;從質(zhì)損的仿真結(jié)果與實驗結(jié)果可以得出無機降解產(chǎn)物可以強化合金表面,而軸向載荷的大小可以通過調(diào)節(jié)降解產(chǎn)物的附著與脫落來控制鎂合金的降解行為。
[Abstract]:At present, the commonly used internal fixation materials are stainless steel, titanium alloy and other inert materials. Although the strength of these materials is high, the modulus of elasticity is much larger than the human bone during the healing process, so there is stress shielding effect. In addition, these materials have the disadvantages of no absorption, no degradation and the need for secondary surgery after bone healing. Using magnesium alloy to repair the fracture can effectively reduce the stress shielding effect during fracture healing and avoid the pain of secondary operation. Previous studies have shown that the mechanical environment has a certain impact on the degradation of magnesium alloy and most of them are qualitative research. In this study, the subprogram of vusdfld user-defined field variables in finite element analysis software ABAQUS was written to predict the degradation process of magnesium alloy under mechanical environment. In order to compare and analyze the degradation experiment in vitro and achieve the purpose of quantitative analysis, the magnesium alloy AZ31 with good overall performance was selected, and the degradation process of magnesium alloy under single axial pressure was simulated by finite element method. According to the requirements of the experiment, the magnesium alloy specimen, the magnesium alloy plate, the bone nail and the degrade device in vitro were designed and prepared, and the corresponding verification experiments were carried out. The main contents of this paper are as follows: (1) expound the domestic and international research status of degradable magnesium alloy, and put forward the significance and importance of the subject research. This paper describes the theory of continuous damage, compiles the VUSDFLD user-defined subprogram of field variables in ABAQUS\ EXPLICIT 6.13.1 software, and realizes the quantitative output of hydrogen volume, mass loss and effective stress in the process of degradation. The finite element analysis model is established. There are three kinds of magnesium alloy specimen models and the model of fixing the middle tibia of sheep with magnesium alloy plate. The numerical simulation results are studied and analyzed in ABAQUS\ EXPICITE software. The results show that the hydrogen volume and mass loss in the degradation process of each magnesium alloy model have the same change rule. Axial compression load plays an important role in controlling the surface morphology, effective stress distribution, failure mode and failure time of the model, and the degradation of magnesium alloy in fracture fixation model is gentle. 4) the in vitro degradation experiment of magnesium alloy specimen is designed. The degradation behavior of magnesium alloy specimens (conventional round holes) under single axial pressure is studied. The results show that the degradation behavior of magnesium alloys, including hydrogen volume, mass loss, pH, maximum compression displacement, maximum pressure and compression time, are all related to the loading values. A certain axial load will accelerate the degradation of magnesium alloys, the larger the axial load in each group, the smaller the pH fluctuation; in the process of axial compression test, The axial load has a regulating effect on the maximum compressive performance of the specimen. (5) the simulation results are compared with the experimental results. The results show that the solubility of air in the simulated body fluid is higher than that in the body temperature of 37 鈩，

本文編號：1538480