本文選題：混凝土 + 裂縫擴(kuò)展　； 參考：《遼寧工程技術(shù)大學(xué)》2015年碩士論文

【摘要】：尺寸效應(yīng)作為準(zhǔn)脆性材料的固有屬性,在混凝土中表現(xiàn)尤為明顯,如何準(zhǔn)確、合理的通過研究小尺寸試件的斷裂參數(shù)來分析大尺寸混凝土結(jié)構(gòu)的斷裂破壞是廣大科研工作者需要解決的問題。而研究混凝土的斷裂參數(shù)建立混凝土斷裂破壞準(zhǔn)則首先要研究混凝土斷裂過程中裂縫擴(kuò)展規(guī)律。目前對于混凝土裂縫擴(kuò)展路徑規(guī)律的研究很少涉及而且大多數(shù)只是從混凝土試件的表面觀測裂紋的擴(kuò)展。因此混凝土斷裂破壞過程中裂縫擴(kuò)展規(guī)律以及其斷裂參數(shù)的尺寸效應(yīng)問題仍具有重要的研究價(jià)值。針對以上問題本文通過數(shù)字圖像相關(guān)方法研究了混凝土楔入劈拉試件的斷裂全過程,分析混凝土裂縫的擴(kuò)展全過程并在對得到的荷載—裂縫張開口位移曲線尾部進(jìn)行擬合分析的基礎(chǔ)上計(jì)算分析了混凝土斷裂能和斷裂韌度的尺寸效應(yīng)。在對比物理試驗(yàn)的基礎(chǔ)上進(jìn)一步做了數(shù)值模擬研究,通過Matlab建立反映混凝土內(nèi)部結(jié)構(gòu)的隨機(jī)骨料模型并在Ansys中進(jìn)行網(wǎng)格單元的劃分,并最終導(dǎo)入FLAC3D對數(shù)值模型進(jìn)行計(jì)算分析。通過物理實(shí)驗(yàn)和數(shù)值模擬的對比進(jìn)一步研究了混凝土裂縫擴(kuò)展規(guī)律和斷裂參數(shù)的尺寸效應(yīng)規(guī)律。通過物理試驗(yàn)和數(shù)值模擬結(jié)果的對比研究發(fā)現(xiàn)：(1)數(shù)字圖像相關(guān)方法能真實(shí)的反映混凝土斷裂破壞中裂縫的擴(kuò)展過程,混凝土破壞時(shí)其裂縫尖端附近存在應(yīng)變局部化帶,裂縫的擴(kuò)展過程中存在著亞臨界擴(kuò)展。數(shù)字圖像相關(guān)方法研究混凝土裂縫的擴(kuò)展對評價(jià)混凝土構(gòu)件的穩(wěn)定性和控制裂縫擴(kuò)展方向具有指導(dǎo)意義。(2)在混凝土斷裂過程中其斷裂能和斷裂韌度存在著尺寸效應(yīng),混凝土的斷裂能和斷裂韌度有隨著混凝土試件高度的增大而增大的趨勢,但當(dāng)試件高度超過500mm時(shí),混凝土的斷裂韌度與試件尺寸無關(guān)。(3)數(shù)值試驗(yàn)結(jié)果與物理試驗(yàn)的結(jié)果具有一致性,因此數(shù)值試驗(yàn)為解決土木、水利等工程中由于實(shí)驗(yàn)室中大尺寸試件制作及實(shí)驗(yàn)困難這一難題提供了一個(gè)有效途徑。
[Abstract]:As the inherent property of quasi-brittle material, the size effect is especially obvious in concrete. It is necessary to solve the problem of analyzing the fracture failure of large size concrete structures by studying the fracture parameters of small size concrete structures. In order to establish the fracture failure criterion of concrete, it is necessary to study the crack propagation law in the process of concrete fracture. At present, the research on crack propagation path of concrete is seldom involved, and most of them are only observed from the surface of concrete specimen. Therefore, it is of great value to study the crack propagation law and the size effect of fracture parameters during the fracture failure of concrete. In view of the above problems, the whole fracture process of concrete wedge wedge tensile specimen is studied by digital image correlation method. The whole process of crack propagation is analyzed and the size effect of fracture energy and fracture toughness of concrete is calculated and analyzed on the basis of fitting and analyzing the load-crack opening displacement curve. On the basis of comparing the physical experiments, the numerical simulation is done. The random aggregate model reflecting the internal structure of concrete is established by Matlab, and the mesh element is divided in Ansys. Finally, the numerical model is calculated and analyzed by introducing FLAC3D. Through the comparison of physical experiment and numerical simulation, the law of crack propagation and size effect of fracture parameters of concrete are further studied. By comparing the results of physical test and numerical simulation, it is found that the digital image correlation method can truly reflect the crack propagation process in concrete fracture failure, and there is a strain localization zone near the crack tip of concrete. There is subcritical propagation in the process of crack propagation. The digital image correlation method is helpful to evaluate the stability of concrete members and control the crack propagation direction.) there is a size effect on the fracture energy and fracture toughness of concrete in the process of fracture. The fracture energy and fracture toughness of concrete increase with the height of concrete specimen, but when the height of concrete specimen is higher than 500mm, The fracture toughness of concrete has nothing to do with the size of the specimen.) the results of the numerical test are consistent with the results of the physical test, so the numerical test is to solve the problem of civil engineering. In water conservancy engineering, an effective way is provided because of the difficulty of making large scale specimen in laboratory and the difficulty of experiment.
【學(xué)位授予單位】：遼寧工程技術(shù)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528

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