大锻件孔洞缺陷演化过程的跨尺度数值模拟方法研究

发布时间：2018-06-01 03:19

本文选题：大锻件 + 孔洞演化　；参考：《燕山大学》2015年硕士论文

【摘要】：大型锻件制造是重型机械制造业的基础,其在国民经济建设、国防装备发展和现代尖端科学重大装置的建立中,发挥着至关重要的作用。众所周知大型钢锭内部不可避免的会存在孔洞型缺陷,这类缺陷严重破坏了材料的连续性,容易在服役期间形成应力集中并导致裂纹损伤。对消除大型锻件内部孔洞缺陷的很多研究都依赖于有限元数值模拟技术来分析孔洞缺陷的演化行为和规律,但是由于孔洞尺寸远小于大锻件的轮廓尺寸,现有的数值模拟方法存在着模型建立困难、模拟计算复杂等问题。因此提出了一种大锻件孔洞缺陷演化过程跨尺度数值模拟的体胞法,并利用MSC.Marc有限元软件二次开发功能,开发了相应的有限元软件及其分析模型。大锻件孔洞缺陷演化过程数值模拟的体胞法由宏观、体胞模型两部分组成,单元节点的数据信息从宏观模型传递到体胞模型是联系这两层模型的关键,对大锻件锻造成形和内部孔洞缺陷演化分别在宏观与细观尺度上进行分析。在此基础上对体胞法进行应用,对一具体锻件的孔洞缺陷演化行为进行了模拟计算,得到孔洞演化的结果与已公开发表的研究成果和实验数据进行对比,验证了体胞法分析结果的准确性。确定了体胞模型中边长比、孔洞表面节点密度和体胞表面节点密度这三个影响孔洞缺陷演化模拟结果的关键因素,采用单因素轮换法对它们的影响规律进行了数值模拟研究,在此基础上确定了一套较佳的体胞模型参数。以铅作为模拟材料,在铅试件内设置孔洞,通过镦粗实验来研究孔洞缺陷的演化情况,并将其与体胞法数值模拟结果进行对比,证明了本文提出的体胞法是正确的,能够准确地反应孔洞的演化规律。
[Abstract]:The manufacture of large forgings is the foundation of heavy machinery manufacturing, which plays an important role in the construction of national economy, the development of national defense equipment and the establishment of modern advanced scientific equipment. It is well known that there are void defects in large steel ingots, which seriously destroy the continuity of materials and lead to stress concentration and crack damage during service. Many researches on eliminating the internal cavity defects of large forgings depend on finite element numerical simulation technology to analyze the evolution behavior and law of the cavity defects, but the size of the holes is much smaller than the outline size of the large forgings. The existing numerical simulation methods are difficult to establish models and complicated in simulation. In this paper, a volume cell method is proposed to simulate the evolution process of large forgings' hole defects, and the corresponding finite element software and its analysis model are developed by using the secondary development function of MSC.Marc finite element software. The cellular method for numerical simulation of the evolution process of large forgings' hole defects is composed of two parts: macroscopic model and cellular model. The key to connect these two models is to transfer the data information of the unit node from the macroscopic model to the volume cell model. The forging forming and internal cavity defect evolution of large forgings are analyzed in macro and meso scale respectively. On the basis of this, the cavity defect evolution behavior of a specific forgings is simulated and calculated, and the results of pore evolution are compared with the published research results and experimental data. The accuracy of the results was verified. Three key factors which affect the simulation results of cavity defect evolution are determined: side length ratio, hole surface node density and volume cell surface node density. The single factor rotation method is used to simulate the influence law of these three key factors. On this basis, a set of better cell model parameters are determined. Using lead as simulation material and setting holes in lead specimen, the evolution of pore defects was studied by upsetting experiment, and compared with the numerical simulation results of volume cell method, it was proved that the method proposed in this paper is correct. It can accurately reflect the evolution of holes.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG316.2

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