發(fā)布時(shí)間：2018-06-01 03:19

  本文選題：大鍛件 + 孔洞演化�。� 參考：《燕山大學(xué)》2015年碩士論文

【摘要】：大型鍛件制造是重型機(jī)械制造業(yè)的基礎(chǔ),其在國(guó)民經(jīng)濟(jì)建設(shè)、國(guó)防裝備發(fā)展和現(xiàn)代尖端科學(xué)重大裝置的建立中,發(fā)揮著至關(guān)重要的作用。眾所周知大型鋼錠內(nèi)部不可避免的會(huì)存在孔洞型缺陷,這類缺陷嚴(yán)重破壞了材料的連續(xù)性,容易在服役期間形成應(yīng)力集中并導(dǎo)致裂紋損傷。對(duì)消除大型鍛件內(nèi)部孔洞缺陷的很多研究都依賴于有限元數(shù)值模擬技術(shù)來分析孔洞缺陷的演化行為和規(guī)律,但是由于孔洞尺寸遠(yuǎn)小于大鍛件的輪廓尺寸,現(xiàn)有的數(shù)值模擬方法存在著模型建立困難、模擬計(jì)算復(fù)雜等問題。因此提出了一種大鍛件孔洞缺陷演化過程跨尺度數(shù)值模擬的體胞法,并利用MSC.Marc有限元軟件二次開發(fā)功能,開發(fā)了相應(yīng)的有限元軟件及其分析模型。大鍛件孔洞缺陷演化過程數(shù)值模擬的體胞法由宏觀、體胞模型兩部分組成,單元節(jié)點(diǎn)的數(shù)據(jù)信息從宏觀模型傳遞到體胞模型是聯(lián)系這兩層模型的關(guān)鍵,對(duì)大鍛件鍛造成形和內(nèi)部孔洞缺陷演化分別在宏觀與細(xì)觀尺度上進(jìn)行分析。在此基礎(chǔ)上對(duì)體胞法進(jìn)行應(yīng)用,對(duì)一具體鍛件的孔洞缺陷演化行為進(jìn)行了模擬計(jì)算,得到孔洞演化的結(jié)果與已公開發(fā)表的研究成果和實(shí)驗(yàn)數(shù)據(jù)進(jìn)行對(duì)比,驗(yàn)證了體胞法分析結(jié)果的準(zhǔn)確性。確定了體胞模型中邊長(zhǎng)比、孔洞表面節(jié)點(diǎn)密度和體胞表面節(jié)點(diǎn)密度這三個(gè)影響孔洞缺陷演化模擬結(jié)果的關(guān)鍵因素,采用單因素輪換法對(duì)它們的影響規(guī)律進(jìn)行了數(shù)值模擬研究,在此基礎(chǔ)上確定了一套較佳的體胞模型參數(shù)。以鉛作為模擬材料,在鉛試件內(nèi)設(shè)置孔洞,通過鐓粗實(shí)驗(yàn)來研究孔洞缺陷的演化情況,并將其與體胞法數(shù)值模擬結(jié)果進(jìn)行對(duì)比,證明了本文提出的體胞法是正確的,能夠準(zhǔn)確地反應(yīng)孔洞的演化規(guī)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.
【學(xué)位授予單位】：燕山大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG316.2

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