混凝土构件裂缝动态扩展数值仿真

发布时间：2018-02-14 08:38

本文关键词： 动态裂纹扩展损伤模型 ANSYS/LSDYNA 偏置裂纹三点弯曲梁　出处：《广西科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：混凝土在内拉应力作用下由于其抗拉强度较低会产生裂纹,混凝土基本都是带裂纹工作。而混凝土动态裂纹扩展由于其复杂的应变率和惯性效应,其与静态裂纹扩展相比具有较大的差异性。且动态裂纹扩展问题的理论还不完善,实验的离散性也较大。因此数值模拟含偏置裂纹混凝土在冲击荷载作用下的裂纹扩展对实际工程的安全和设计具有重要的实际意义。基于此,本文在动力分析有限元软件LSDYNA的基础上,所做的主要工作如下:一、在损伤模型和弹塑性模型的基础上,实现了含偏置裂纹三点弯曲梁的两种典型破坏过程。通过将数值模拟结果同已有的实验及数值计算结果相比较,验证了此方法的准确性。二、研究了不同位置的偏置裂纹对构件动态裂纹扩展的影响。研究发现:当荷载P值不变、偏置裂纹在横向不同位置时,裂纹倾角随着偏置裂纹距加载点距离的增大先增大后减小;构件破坏时间随着偏置裂纹位置距加载点距离的增大先增大后减小;当偏置裂纹在纵向不同位置处移动,偏置裂纹的位置越靠近加载点时,试样的破坏时间越大,但对裂纹扩展倾角没有影响。三、研究了纵向偏置裂纹不同长度对构件动态裂纹扩展的影响,研究发现:当偏置裂纹在纵向位置固定且荷载P值一定时,纵向不同长度的偏置裂纹扩展路径基本相同且都是垂直向加载点处扩展;当偏置裂纹在纵向位置固定且荷载P值一定时,纵向不同长度偏置裂纹对试样的破坏时间基本没有影响。四、研究了偏置裂纹不同宽度对构件动态裂纹扩展的影响。研究发现:当偏置裂纹位置、荷载P值不变时,偏置裂纹的不同宽度对构件的裂纹扩展路径有影响,偏置裂纹的宽度越大,裂纹扩展的倾角也越大,对构件的最终破坏时间没有影响。五、研究了偏置裂纹不同高度对构件动态裂纹扩展的影响。研究发现:当偏置裂纹的位置、荷载P值不变时,偏置裂纹的不同高度对构件的裂纹扩展路径有影响且随着偏置裂纹高度的增加,裂纹扩展的倾角逐渐减小,试样最终破坏的时间逐渐减小。六、研究了不同弹性模量对构件动态裂纹扩展的影响。研究发现:当偏置裂纹的位置、荷载P值一定时,不同弹性模量对试样的裂纹扩展路径没有影响,即裂纹扩展倾角基本不变;随着弹性模量的增大,试样最终破坏的时间逐渐增大。
[Abstract]:Under the action of internal tensile stress, cracks will occur in concrete due to its low tensile strength, and the concrete is basically working with cracks, while the dynamic crack propagation of concrete is due to its complex strain rate and inertia effect. Compared with the static crack propagation, the theory of dynamic crack propagation is not perfect. Therefore, numerical simulation of crack propagation of concrete with bias crack under impact load is of great practical significance to the safety and design of practical engineering. Based on the finite element software LSDYNA, the main work of this paper is as follows: 1. Based on the damage model and elastic-plastic model, Two typical failure processes of three-point bending beams with bias cracks are realized. The accuracy of this method is verified by comparing the numerical simulation results with the existing experimental and numerical results. The effect of the bias crack at different positions on the dynamic crack propagation of the member is studied. It is found that when the load P value is constant, the crack inclination increases first and then decreases with the increase of the distance between the bias crack and the loading point. With the increase of the distance from the position of the bias crack to the loading point, the failure time of the member first increases and then decreases, and when the offset crack moves at different longitudinal positions, the more the position of the offset crack is near the loading point, the larger the failure time of the specimen is. But it has no effect on the crack growth angle. Thirdly, the influence of longitudinal bias crack length on the dynamic crack growth is studied. It is found that when the bias crack is fixed in the longitudinal position and the load P value is constant, The propagating path of the biasing crack with different longitudinal lengths is basically the same and all of them are propagated vertically at the loading point, when the bias crack is fixed in the longitudinal position and the load P value is fixed, The influence of different widths of biasing crack on dynamic crack propagation is studied. It is found that when the position of bias crack is constant, the load P value is constant. The different widths of the offset crack have an effect on the crack growth path of the member. The larger the width of the offset crack, the greater the dip angle of the crack growth, which has no effect on the ultimate failure time of the member. The influence of different height of bias crack on dynamic crack growth of member is studied. It is found that the load P value is constant when the position of bias crack is constant. The different height of the bias crack has an effect on the crack growth path of the member. With the increase of the height of the biased crack, the dip angle of the crack propagation decreases gradually, and the time of the ultimate failure of the specimen decreases gradually. The effect of different elastic modulus on dynamic crack propagation of member is studied. It is found that when the position of the biased crack and the load P value are fixed, the different elastic modulus has no effect on the crack growth path of the specimen, that is, the crack growth inclination angle is basically unchanged. With the increase of elastic modulus, the time of final failure increases gradually.
【学位授予单位】：广西科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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