【摘要】：混凝土作為一種率敏感性材料,在強沖擊載荷作用下其材料特性會發(fā)生很大的變化。長期以來,混凝土動態(tài)力學(xué)性能研究多數(shù)是在宏觀層面上開展的,即將混凝土視為一種各向同性的均質(zhì)材料,且大多數(shù)研究都建立在試驗基礎(chǔ)上,試驗成果多偏離原型。為了清楚的掌握混凝土在沖擊荷載作用下的動態(tài)力學(xué)性能以及影響因素,本文從細觀層面上,將混凝土視為骨料、砂漿以及二者之間的界面層組成的非均勻復(fù)合材料,采用隨機骨料模型,借助富勒Fuller三維級配曲線計算出各個區(qū)間骨料的顆粒數(shù),利用MATLAB編程語言結(jié)合蒙特卡羅方法實現(xiàn)了混凝土細觀結(jié)構(gòu)三維球形骨料模型的自動生成。運用有限元軟件ANSYS/LS-DYNA對純砂漿、僅有一個骨料(骨料含量為3.35%)的混凝土試件、以及骨料含量為24%的單級配、二級配混凝土試件進行應(yīng)變率分別為10s-1、102s-1下的沖擊荷載下的動力分析,最后,對不同應(yīng)變率下相同骨料含量和不同骨料含量相同應(yīng)變率下的沖擊結(jié)果進行了對比。結(jié)果表明： (1)從細觀層次上對各相材料賦予不同的本構(gòu)模型是合適的。 (2)界面層是最薄弱、最需要加強的地方。 (3)在低應(yīng)變率下,試件碎成數(shù)塊,碎塊較大；在高應(yīng)變率下碎塊多為小塊。 (4)純砂漿在不同應(yīng)變率沖擊荷載作用下表現(xiàn)出的率敏感性沒有混凝土強烈。混凝土(骨料含量為24%)在應(yīng)變率為100s-1的沖擊荷載作用下的極限抗壓強度比應(yīng)變率為10s-1下的提高了80%,并且其應(yīng)力應(yīng)變曲線下降段很陡,表現(xiàn)出明顯的脆性。 (5)混凝土(骨料含量為24%)峰值壓應(yīng)變隨應(yīng)變率的增加有所增加,單級配和二級配的峰值壓應(yīng)變分別提高了21.2%和12.5%。 (6)沖擊荷載作用下,骨料含量相同時不同級配對力學(xué)性能的影響不大,且在高應(yīng)變率下不同骨料含量對力學(xué)性能的影響較大。
[Abstract]:Concrete, as a rate sensitive material, will change greatly under strong impact load. For a long time, the research on the dynamic mechanical properties of concrete has been carried out on the macroscopic level, that is to say, the concrete is regarded as an isotropic homogeneous material, and most of the studies are based on the experiment, and the experimental results deviate from the prototype. In order to clearly understand the dynamic mechanical properties of concrete under impact load and the influencing factors, this paper regards concrete as a nonuniform composite material composed of aggregate, mortar and interfacial layer between them from the meso level. Based on the random aggregate model and Fuller three-dimensional gradation curve, the particle number of each interval aggregate is calculated, and the automatic generation of three-dimensional spherical aggregate model of concrete meso-structure is realized by using MATLAB programming language and Monte Carlo method. The finite element software ANSYS/LS-DYNA is used to analyze the dynamic behavior of concrete specimens with only one aggregate (3.35% aggregate content) and single gradation (24% aggregate content) under impact load with strain rate of 10s-1102s-1. Finally, the impact results of the same aggregate content and different aggregate content under the same strain rate were compared. The results show that: (1) it is appropriate to assign different constitutive models to different phase materials at the meso level. (2) the interface layer is the weakest and most in need of strengthening. (3) at low strain rate, the specimens are broken into several pieces, and the fragments are large, and the fragments are mostly small at high strain rate. (4) the rate sensitivity of pure mortar under different strain rate impact load is not as strong as that of concrete. The ultimate compressive strength of concrete (aggregate content is 24%) under impact load with strain rate of 100s-1 is 80% higher than that under strain rate (10s-1), and its stress-strain curve decreases steeply, showing obvious brittleness. (5) the peak compressive strain of concrete (aggregate content is 24%) increases with the increase of strain rate, and the peak compressive strain of single grade and secondary distribution increases by 21. 2% and 12. 5%, respectively. (6) under impact load, different gradation of aggregate has little effect on mechanical properties when the content of aggregate is the same, and different aggregate content has great effect on mechanical properties at high strain rate.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU528.01

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