基于内聚力模型非均质材料损伤与失效的数值研究

发布时间：2019-01-06 08:22

【摘要】：非均质材料通常是由不同材料或相组成的复合材料,由于它具有高强度、耐高温、耐腐蚀、高韧性、抗氧化等优点而被广泛应用于建筑、机械、电子以及航空航天等领域。该种材料往往有多相成分组成,因而其研究方法不同于均质材料。非均质材料的数值模型主要有宏观模型、细观模型和多尺度模型。细观模型能真实地反映材料内部的损伤与失效现象而被广泛采用。建立能够客观反映其细观结构特性及损伤演化关系的数值模型,是进行细观数值研究的前提和基础。国内外很多学者提出了不少损伤模型,但是大部分模型较为复杂或者参数较多,实际的工程应用非常困难。内聚力模型由于其较为简洁,又能够准确地模拟许多工程断裂问题而成为一个研究的热点。然而真正利用内聚力模型来研究非均质材料的损伤与破坏,模拟其任意裂纹的扩展,目前国内外还是相对少见,还有很多问题有待完善或者解决。针对上述问题,本文基于三种数值建模方法实现了两种典型非均质材料(混凝土和非均质焊锡合金材料)细观模型的构建。改进了常用建模方法中存在的模型过于简化和建模流程过于繁琐的缺点,提高了建模的效率。同时,采用改进的内聚力模型对非均质材料损伤与断裂失效进行了研究,得到了和实验较为吻合的模拟结果。针对内聚力模型参数难以确定的问题提出了一种基于卡尔曼滤波算法的反演优化方法,并采用两种反演方案确定了相关的内聚力模型参数。本文的主要研究工作包含以下几个方面:(1)基于图像处理方法(图像法)和随机骨料自动生成程序(程序法)对非均质材料细观模型的建模方法开展了研究。提高了原有图像法中骨料轮廓的识别效率,简化了其建模流程,改善了现有程序法中存在的模型过于简化的问题。同时,提出了图像法和程序法相结合的建模方法,从而能够更加精确地表征非均质材料的真实细观结构。(2)采用改进的双线型内聚力模型,编写了ABAQUS用户单元自定义子程序(VUEL),对混凝土材料和非均质焊锡材料的损伤和失效进行了模拟分析。同时,提出了一套内聚力单元自动植入的程序实现方法,在提高计算效率的同时也大大简化了建模工作。最后通过典型的算例验证了上述方法的合理性。(3)提出了一种基于卡尔曼滤波算法的反演优化方法,采用分步优化法和能量法两种反演方案确定了指数型内聚力模型参数。首先,针对不同的载荷模式分别采用DCB试样和SLJ试样研究了无铅焊锡/铜界面层的破坏情况。然后,采用伪实验数据从不同的角度对反演方法的有效性和可靠性进行了验证。最后,结合实验数据和模拟数据对两种不同载荷模型下的内聚力模型参数进行反演识别。(4)鉴于非均质材料数值建模过程过于繁琐的缺点,本文开发了一套基于C语言的具有交互界面的非均质材料数值建模系统。该系统整合了多种数值建模方法和内聚力单元的植入方法,非常方便地实现了非均质材料有限元模型的构建。
[Abstract]:The non-homogeneous material is usually a composite material composed of different materials or phases, and is widely used in the fields of building, machinery, electronics and aerospace, due to the advantages of high strength, high temperature resistance, corrosion resistance, high toughness, oxidation resistance and the like. This kind of material often has multi-phase composition, so its research method is different from the homogeneous material. The numerical model of the non-homogeneous material mainly has the macro-model, the micro-model and the multi-scale model. The micro-model can truly reflect the damage and failure phenomenon inside the material and is widely used. The numerical model, which can objectively reflect the relationship between the microstructural characteristics and the damage evolution, is the premise and foundation of the mesoscopic numerical study. Many scholars at home and abroad have put forward many damage models, but most of the models are more complex or more parameters, and the practical engineering application is very difficult. The cohesive force model has become a hot spot of a study because of its simple and accurate simulation of many engineering fracture problems. However, using the cohesive force model to study the damage and damage of the non-homogeneous material, and to simulate the expansion of any crack, it is still relatively rare at home and abroad, and there are still many problems to be perfected or solved. In view of the above problems, the micro-model of two typical non-homogeneous materials (concrete and non-homogeneous solder alloy material) is constructed based on three numerical modeling methods. The defect that the model of the common modeling method is too simplified and the modeling process is too complicated is improved, and the modeling efficiency is improved. At the same time, an improved cohesive force model was used to study the damage and fracture failure of non-homogeneous material. An inversion optimization method based on the Kalman filter algorithm is proposed in order to determine the parameters of the cohesive force model, and the relevant cohesive force model parameters are determined by the two inversion schemes. The main research work of this paper includes the following aspects: (1) The modeling method of the non-homogeneous material meso-model is studied based on the image processing method (image method) and the random aggregate automatic generation program (procedural law). the identification efficiency of the aggregate profile in the original image method is improved, the modeling process is simplified, and the problem that the model existing in the prior art law is too simplified is improved. At the same time, the modeling method of the combination of the image method and the procedural law is put forward, so that the real micro-structure of the non-homogeneous material can be more accurately characterized. (2) Using the improved double-wire cohesion model, the ABAQUS User-Defined Subprogram (VULEL) was written, and the damage and failure of the concrete and the non-homogeneous solder material were simulated and analyzed. At the same time, a method for realizing the automatic implantation of the cohesive unit is proposed, and the modeling work is also greatly simplified while the calculation efficiency is improved. Finally, the rationality of the above method is verified by a typical example. (3) An inversion optimization method based on the Kalman filter is proposed, and the parameter of the index type cohesion model is determined by the two inversion schemes of the step-by-step optimization method and the energy method. First, the damage of lead-free solder/ copper interface layer was studied by using DCB and SLJ samples for different load modes. Then, the validity and the reliability of the inversion method are verified by using the pseudo-experimental data. Finally, the cohesive force model parameters under two different load models are identified by combining the experimental data and the simulation data. (4) In view of the disadvantage that the non-homogeneous material numerical modeling process is too complicated, this paper develops a set of non-homogeneous material numerical modeling system with interactive interface based on Clanguage. The system integrates a number of numerical modeling methods and an implantation method of the cohesive unit, and the construction of the non-homogeneous material finite element model is realized very conveniently.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33

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