基于细观尺度的钢纤维混凝土损伤破坏数值模拟研究

发布时间：2019-07-04 20:13

【摘要】：本文针对以钢纤维混凝土损伤破坏问题,从细观角度出发,采数值计算方法,建立钢纤维混凝土细观数值模型,对钢纤维混凝土的损伤破坏过程进行模拟计算,从宏观和细观的角度对破坏过程进行深入分析,获得了钢纤维混凝土力学性质同各影响因素之间的关系,揭示了钢纤维混凝土细观损伤破坏规律。首先,依据混凝土配合比理论和实际钢纤维混凝土配合比,利用MATLAB数学软件,建立钢纤维混凝土二维几何模型;针对建模过程中钢纤维与钢纤维相交判断和钢纤维与骨料相交判断问题,引入矢量算法,减少了计算工作量,提高了建模质量和速度;将矢量相交判断方法与扫描排序算法相结合,提高了骨料、钢纤维投放数量和投放速度;依托MATLAB中的GUI平台,编制了钢纤维混凝土二维建模软件,依托界面操作窗口,能够简洁、迅速地生成钢纤维混凝土平面模型;在骨料与钢纤维满足随机分布的几何模型上,依据随机力学参数模型,建立了力学参数满足Weibull分布的钢纤维混凝土细观数值模型。其次,开展了钢纤维拔出物理试验,获得了不同长度、不同形状钢纤维的荷载-位移曲线,在此基础上依据弹脆性损伤本构模型,对钢纤维拔出过程进行数值模拟;引入界面破坏量阀值,认为当界面的破坏量超过此值后钢纤维进入滑移阶段,对滑移阶段界面单元的弹性模量进行重新赋值,依据实际拔出试验中钢纤维滑移段的荷载曲线,用界面单元的弹性变形模拟钢纤维的刚体滑移,用弹性力模拟滑动摩擦力,取得了较好的模拟效果;开展了不同长度的单根钢纤维拔出试验的数值模拟研究,获得了钢纤维界面应力传递规律;将钢纤维拔出物理试验获得的位移-荷载曲线与数值模拟得到的位移-荷载曲线进行对比分析,结果表明,无论从峰值荷载、滑移荷载还是荷载变化规律上,数值计算结果均与物理试验结具有很好的一致性,验证了本文提出数值模型的准确性。第三,以钢纤维水泥砂浆数值模型为基础,依据弹脆性损伤本构模型,开展了钢纤维砂浆试件单轴拉伸、单轴压缩数值模拟。在此基础上研究了端部摩擦约束、钢纤维几何形状、钢纤维含量对模拟结果的影响。从宏观力学特性、细观裂纹演化、细观单元损伤破坏发展三个方面进行深入分析,建立了钢纤维砂浆试件在典型荷载下的宏观力学响应与细观单元损伤之间的联系,揭示了钢纤维在试件损伤破坏过程中的内力变化规律,获得了钢纤维对试件增强、增韧、阻裂效果与钢纤维角度、钢纤维尺寸和钢纤维含量之间的关系。最后,以骨料、钢纤维位置随机分布的钢纤维混凝土二维数值模型为基础,应用随机力学参数模型,基于弹脆性损伤本构理论,模拟了钢纤维混凝土试件在典型单轴拉伸、单轴压缩荷载作用下损伤破坏的全过程。分别模拟了不同基体强度、不同骨料形状以及含孔隙的钢纤维混凝土试件的单轴压缩全过程。结果表明,在几何参数不变的情况下,随着基体强度的提高,钢纤维混凝土试件的抗压强度随之提高,试件在破坏时的脆性特性越明显,骨料的损伤破坏量越大;在满足钢纤维分布情况相同,骨料投放面积相同的情况下仅改变骨料的形状,表明对CF80高强钢纤维混凝土而言,骨料形状对试件力学特性的影响较小;含有孔隙缺陷的钢纤维混凝土试件的损伤破坏过程更加复杂,抗压强度下降较为明显,裂纹发展不再遵循简单顺序,随机性更强,更符合实际钢纤维混凝土特点。研究表明,本文建立的细观数值模型能够有效地模拟钢纤维混凝土试件的损伤破坏过程,实现了从细观角度研究钢纤维混凝土裂纹萌生、演化、发展,为研究钢纤维混凝土损伤破坏问题提供了一种新的手段。
文内图片：

图片说明：骨料切面示意图
[Abstract]:In this paper, based on the damage of steel fiber concrete, the numerical calculation method of steel fiber concrete is set out from the micro-point of view, and the damage and destruction process of steel fiber concrete is simulated. The relationship between the mechanical property of the steel fiber concrete and the influence factors is obtained from the macroscopic and the micro-scale angle, and the damage rule of the steel fiber concrete meso-damage is revealed. First, according to the concrete mix ratio theory and the actual steel fiber concrete mix ratio, the two-dimensional geometric model of the steel fiber concrete is established by using the MATLAB mathematical software, and the vector algorithm is introduced aiming at the intersection judgment of the steel fiber and the steel fiber and the intersection judgment of the steel fiber and the aggregate during the modeling process, the calculation workload is reduced, the modeling quality and the speed are improved, the vector intersection judgment method and the scanning sequencing algorithm are combined, the quantity and the throwing speed of the aggregate and the steel fiber are improved, and the two-dimensional modeling software of the steel fiber concrete is prepared on the basis of the GUI platform in the MATLAB, Based on the interface operation window, the steel fiber concrete plan model can be generated in a simple and rapid manner; on the geometric model of the random distribution of the aggregate and the steel fiber, the micro-numerical model of the steel fiber concrete satisfying the Weibull distribution is established according to the random mechanical parameter model. Secondly, the physical test of steel fiber pull-out is carried out, and the load-displacement curve of steel fiber with different lengths and different shapes is obtained. Based on the constitutive model of the elastic brittle damage, the numerical simulation of the steel fiber pull-out process is carried out, and the threshold value of the interface failure amount is introduced. it is considered that when the damage amount of the interface exceeds this value, the steel fiber enters the sliding stage, the elastic modulus of the interface unit of the sliding stage is re-assigned, the rigid body of the steel fiber is simulated by the elastic deformation of the interface unit according to the load curve of the steel fiber sliding section in the actual extraction test, The elastic force is used to simulate the sliding friction force, and a good simulation effect is obtained; the numerical simulation of the single steel fiber pull-out test with different lengths is carried out, and the stress transmission law of the steel fiber interface is obtained; The displacement-load curve obtained by pulling out the steel fiber out of the physical test and the displacement-load curve obtained by the numerical simulation are compared and analyzed, and the results show that no matter the peak load, the slip load or the load change rule, The numerical results are consistent with the physical test, and the accuracy of the numerical model is verified. Thirdly, based on the numerical model of steel fiber cement mortar, the uniaxial tension and single-axis compression of steel fiber mortar test piece are simulated according to the constitutive model of the elastic brittle damage. The effects of end friction, steel fiber geometry and steel fiber content on the simulation results are studied. The relationship between the macro-mechanical response of the steel fiber mortar test piece under the typical load and the damage of the micro-unit is established from the three aspects of the macro-mechanical property, the micro-crack evolution and the damage development of the micro-unit. The relationship between steel fiber and steel fiber angle, steel fiber size and steel fiber content is obtained. At last, based on the two-dimensional numerical model of the steel fiber concrete which is randomly distributed at the position of the aggregate and the steel fiber, a random mechanical parameter model is applied to simulate the typical uniaxial tension of the steel fiber concrete test piece based on the elastic brittle damage constitutive theory. The whole process of damage damage under the action of uniaxial compression load. The whole process of uniaxial compression of steel fiber concrete specimen with different base strength, different aggregate shape and pore-containing steel fiber was simulated respectively. The results show that, with the change of the geometric parameters, with the increase of the strength of the matrix, the compressive strength of the steel fiber concrete test piece is increased, the more obvious the brittle character of the test piece when the test piece is damaged, the more the damage and the damage amount of the aggregate are, and in the case that the steel fiber distribution is satisfied, the shape of the aggregate is changed only under the condition that the aggregate throwing area is the same, indicating that the influence of the aggregate shape on the mechanical property of the test piece is small for the CF80 high-strength steel fiber concrete, and the damage and destruction process of the steel fiber concrete test piece containing the pore defect is more complicated, The compressive strength is obviously lower, and the crack development is no longer in the simple sequence, the randomness is stronger, and the concrete characteristics of the steel fiber concrete are more practical. The study shows that the micro-numerical model established in this paper can effectively simulate the damage and damage process of the steel fiber concrete specimen, and the crack initiation, evolution and development of the steel fiber concrete are studied from the micro-angle. In order to study the damage of steel fiber concrete, a new method is provided.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528.572

【参考文献】