本文選題：混凝土 + 細(xì)觀層次��； 參考：《昆明理工大學(xué)》2013年碩士論文

【摘要】：混凝土是一種典型的多相非均質(zhì)復(fù)合材料,它的力學(xué)性能主要依賴(lài)于其內(nèi)部各相材料的力學(xué)性能。在一定的試驗(yàn)基礎(chǔ)上,采用數(shù)值模擬方法不僅可以直觀地反映混凝土細(xì)觀斷裂破壞的全過(guò)程,還可以反映骨料的形狀、含量及界面過(guò)渡區(qū)(ITZ)等對(duì)混凝土宏觀力學(xué)性能的影響。在確保計(jì)算模型可靠和有效的前提下,可以替代部分試驗(yàn),避開(kāi)試驗(yàn)條件的限制及人為操作誤差等對(duì)結(jié)果的影響。 本文依據(jù)細(xì)觀力學(xué)理論,將混凝土看作由骨料、砂漿及兩者之間的粘結(jié)界面組成的三相復(fù)合材料,用MATLAB自編程序生成隨機(jī)分布的骨料顆粒幾何模型,從中選取代表性體積單元作為混凝土試樣,并運(yùn)用有限元分析軟件ABAQUS對(duì)其在單軸拉伸、壓縮荷載作用下的破壞全過(guò)程進(jìn)行了數(shù)值模擬研究,并對(duì)試件的細(xì)觀損傷與宏觀破壞之間的聯(lián)系進(jìn)行了分析探討。 采用ABAQUS有限元分析軟件對(duì)混凝土試樣中的骨料、砂漿和界面分別賦予各自的材料屬性并分別進(jìn)行網(wǎng)格劃分。對(duì)混凝土試樣施加隨時(shí)間變化的位移荷載來(lái)進(jìn)行數(shù)值模擬研究。計(jì)算結(jié)果表明：界面過(guò)渡區(qū)是混凝土的薄弱環(huán)節(jié),首先在界面單元上出現(xiàn)微裂紋,而后向相鄰的砂漿單元擴(kuò)展,微裂紋不斷擴(kuò)展,延伸,合并,最終導(dǎo)致試樣破壞。這說(shuō)明,混凝土的宏觀力學(xué)性能受細(xì)觀結(jié)構(gòu)的制約�；炷良�(xì)觀結(jié)構(gòu)的損傷和破壞是引起宏觀破壞的內(nèi)因和基礎(chǔ)。數(shù)值模擬結(jié)果和試驗(yàn)結(jié)果一致,證明了所建模型的有效性和可行性。 通過(guò)本文研究可知,界面過(guò)渡區(qū)是混凝土的薄弱環(huán)節(jié),混凝土的損傷斷裂最先發(fā)生在界面區(qū),隨著界面微裂縫的不斷擴(kuò)展,延伸,合并,最終導(dǎo)致試件破壞。即混凝土的細(xì)觀損傷是宏觀破壞的內(nèi)因和基礎(chǔ),而試件的宏觀破壞是細(xì)觀損傷不斷積累和發(fā)展的結(jié)果。本文具體工作如下： 1、對(duì)混凝土材料在細(xì)觀層次上損傷斷裂的理論進(jìn)行了研究,對(duì)混凝土材料的破壞機(jī)理和斷裂損傷的物理機(jī)制進(jìn)行了研究。 2、利用MATLAB程序化設(shè)計(jì)語(yǔ)言首先生成滿(mǎn)足給定區(qū)間上隨機(jī)分布的骨料顆粒的圓心坐標(biāo),再根據(jù)圓心坐標(biāo)合格的判別條件進(jìn)行判定,最終生成圓形及橢圓形骨料顆粒的混凝土試件的幾何模型。 3、介紹了有限單元法的基本原理,等參單元的力學(xué)分析及等參單元在本文中的應(yīng)用。 4、對(duì)幾何數(shù)值模型選取代表性體積元作為混凝土試樣,對(duì)其在單軸受拉、受壓荷載作用下進(jìn)行數(shù)值模擬研究,找出混凝土內(nèi)部裂紋的擴(kuò)展規(guī)律。對(duì)所得到的曲線進(jìn)行分析得出相關(guān)結(jié)論。 5、對(duì)界面的厚度取值進(jìn)行研究,從而找出界面厚度不同對(duì)混凝土力學(xué)性能的影響規(guī)律,為混凝土數(shù)值模擬時(shí)界面厚度的選取提供依據(jù)。
[Abstract]:Concrete is a typical heterogeneous composite material. Its mechanical properties mainly depend on the mechanical properties of each phase material. On the basis of certain tests, the numerical simulation method can not only directly reflect the whole process of microfracture failure of concrete, but also reflect the influence of aggregate shape, content and interface transition zone (ITZ) on the macroscopic mechanical properties of concrete. On the premise of ensuring the reliability and effectiveness of the calculation model, the partial test can be replaced, and the influence of the limit of test conditions and the error of artificial operation on the results can be avoided. In this paper, according to the theory of mesomechanics, the concrete is regarded as a three-phase composite composed of aggregate, mortar and the bond interface between them, and the random distribution of aggregate particle geometry model is generated by MATLAB program. The representative volume element is selected as the concrete specimen and the finite element analysis software Abaqus is used to simulate the whole failure process of the concrete under uniaxial tensile and compression loads. The relationship between meso-damage and macro-damage is analyzed and discussed. Abaqus finite element analysis software is used to divide the aggregate, mortar and interface of concrete samples into their own properties and mesh. A numerical simulation study was carried out on concrete specimens subjected to displacement loads varying with time. The results show that the interfacial transition zone is the weak link of concrete. At first, there are microcracks on the interface elements, but then on the adjacent mortar elements. The microcracks continue to expand, extend and merge, resulting in the failure of the specimens. This shows that the macro-mechanical properties of concrete are restricted by the mesoscopic structure. The damage and failure of concrete meso-structure is the internal cause and foundation of macro-damage. The numerical simulation results are in agreement with the experimental results, which proves the validity and feasibility of the proposed model. Through the study of this paper, it can be seen that the interface transition zone is the weak link of concrete, and the damage and fracture of concrete first occur in the interface area. With the continuous expansion, extension and merging of the micro-cracks in the interface, the ultimate failure of the specimen is caused. That is, the meso-damage of concrete is the internal cause and foundation of macroscopic damage, while the macroscopic damage of specimen is the result of the accumulation and development of meso-damage. The specific work of this paper is as follows: 1. The theory of damage and fracture of concrete material at meso level is studied. The failure mechanism of concrete material and the physical mechanism of fracture damage are studied. 2. Firstly, the center coordinates of aggregate particles which meet the random distribution in a given interval are generated by MATLAB programming language. Then the geometric model of concrete specimen with circular and elliptical aggregate particles is formed according to the criterion conditions of the center coordinates. 3. The basic principle of the finite element method is introduced. The mechanical analysis of isoparametric element and the application of isoparametric element in this paper. To find out the law of crack propagation in concrete. By analyzing the obtained curves, the relevant conclusions are drawn. 5. The thickness of the interface is studied to find out the influence of the thickness of the interface on the mechanical properties of concrete. It provides a basis for the selection of interface thickness in numerical simulation of concrete.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類(lèi)號(hào)】：TU528

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