本文關(guān)鍵詞：基于晶體塑性的鋁合金韌性斷裂細(xì)觀力學(xué)研究　出處：《哈爾濱工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 晶體塑性 孔洞增長(zhǎng) 孔洞聚合 應(yīng)力三軸度 韌性斷裂

【摘要】：韌性斷裂是金屬材料的重要的非線性行為,加深對(duì)韌性斷裂的理解在實(shí)際工程中有重要意義,如改善金屬塑性成型工藝,提高結(jié)構(gòu)完整性評(píng)估精度等。眾所周知,韌性斷裂與微孔洞的形成,增長(zhǎng),聚合的過(guò)程有關(guān)。材料的韌性斷裂受應(yīng)力狀態(tài),孔洞體積分?jǐn)?shù),孔洞幾何尺寸,基體本構(gòu)響應(yīng)及溫度等眾多參數(shù)的影響,其中,應(yīng)力狀態(tài)對(duì)韌性斷裂的影響至關(guān)重要。目前,已有的韌性斷裂研究大都以唯象本構(gòu)代表材料的非線性行為,對(duì)材料韌性斷裂過(guò)程中微觀晶體變形和孔洞擴(kuò)展的機(jī)理缺乏明確考慮。本文對(duì)5083-H116鋁合金材料提出一個(gè)基于晶體塑性力學(xué)的細(xì)觀有限元模型以明確考慮材料中的非線性晶相滑移與孔洞擴(kuò)展之間的相互作用。有限元分析中,本文選取含單一孔洞的代表性胞元對(duì)其施加周期性邊界條件,并采用結(jié)構(gòu)化的網(wǎng)格進(jìn)行有限元離散。本文基于Taylor平均場(chǎng)均勻化方法模擬多晶基體材料的力學(xué)響應(yīng),將其與實(shí)驗(yàn)對(duì)比標(biāo)定了本構(gòu)模型的材料參數(shù),并將該模型應(yīng)用于基體材料中。為研究多軸載荷作用下應(yīng)力狀態(tài)對(duì)單晶含孔洞胞元力學(xué)行為的影響,本文發(fā)展了一種控制胞元應(yīng)力三軸度和洛德參數(shù)的方法。在三維胞元模型中,本文加入剛硬斜桿來(lái)控制代表性胞元總體應(yīng)力分量之間的比值,進(jìn)而實(shí)現(xiàn)對(duì)胞元應(yīng)力三軸度以及洛德參數(shù)的控制。本文在有限元軟件中開(kāi)發(fā)了相應(yīng)的用戶子程序并分析了相關(guān)參數(shù)的影響,最終實(shí)現(xiàn)應(yīng)力狀態(tài)的控制。在此基礎(chǔ)上,本文定量分析了應(yīng)力三軸度,晶體取向以及洛德參數(shù)對(duì)孔洞擴(kuò)展以及孔洞聚合的影響規(guī)律,有以下發(fā)現(xiàn):應(yīng)力三軸度的提高可降低孔洞聚合應(yīng)變,并改變孔洞擴(kuò)展趨勢(shì);晶體取向?qū)Π獞?yīng)力應(yīng)變分布有重要影響;隨著應(yīng)力三軸度的提高,晶體取向的影響減弱;同時(shí),洛德參數(shù)對(duì)單晶孔洞聚合行為產(chǎn)生重要影響。本文進(jìn)一步發(fā)展了Taylor-Reuss平均場(chǎng)均勻化方法獲得含孔洞多晶體材料的力學(xué)響應(yīng),并將預(yù)測(cè)結(jié)果與傳統(tǒng)的采用宏觀唯象本構(gòu)的細(xì)觀力學(xué)模型所得結(jié)果以及廣為應(yīng)用的G-T本構(gòu)模型對(duì)比。對(duì)比結(jié)果驗(yàn)證了本文模型的可靠性,同時(shí)這些模型結(jié)果之間的區(qū)別顯示出在分析多晶體材料孔洞擴(kuò)展行為時(shí)對(duì)材料的塑性滑移與孔洞之間的相互作用予以明確考慮是很必要的。
[Abstract]:Ductile fracture is an important nonlinear behavior of metal materials. It is of great significance to deepen the understanding of ductile fracture in practical engineering, such as improving metal plastic forming process. It is well known that ductile fracture is related to the formation, growth and polymerization of microvoids. The ductile fracture of materials is subjected to stress state, pore volume fraction, and pore geometry size. The effect of matrix constitutive response and temperature on ductile fracture is very important. At present, most of the researches on ductile fracture represent the nonlinear behavior of materials. The mechanism of microscopic crystal deformation and pore propagation during ductile fracture of materials is not considered clearly. A meso-finite element model based on crystal plastic mechanics is proposed for 5083-H116 aluminum alloy in this paper. The interaction between the nonlinear crystal phase slip and the pore propagation in the material is taken into account. In the finite element analysis. In this paper, periodic boundary conditions are applied to representative cells with a single pore. Based on the Taylor mean field homogenization method, the mechanical response of the polycrystalline matrix is simulated, and the material parameters of the constitutive model are compared with the experimental results. The model is applied to the matrix material. In order to study the effect of stress state on the mechanical behavior of single crystal porous cells under multiaxial loading. In this paper, a method to control the triaxial degree of cellular stress and the Lod parameter is developed. In the three-dimensional cell model, the ratio between the stress components of the representative cell population is controlled by adding rigid and hard skew bars. In this paper, the user subprogram is developed in the finite element software and the influence of the related parameters is analyzed. Finally, the stress state is controlled. On this basis, the effects of stress triaxiality, crystal orientation and Lod parameters on the pore propagation and pore polymerization are quantitatively analyzed. It is found that the increase of stress triaxiality can reduce the pore aggregation strain and change the trend of pore expansion. The crystal orientation has an important effect on the stress and strain distribution of the cell. With the increase of stress triaxiality, the effect of crystal orientation is weakened. At the same time, the Lod parameters have an important effect on the pore polymerization behavior of single crystal. In this paper, the Taylor-Reuss mean field homogenization method is further developed to obtain the mechanical response of porous polycrystalline materials. The prediction results are compared with the results obtained from the traditional meso-mechanical model using macrophenomenological constitutive model and the widely used G-T constitutive model. The comparison results verify the reliability of the model. At the same time, the differences between the results of these models show that it is necessary to consider the interaction between the plastic slip and the pore in the analysis of the pore propagation behavior of polycrystalline materials.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG146.21
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本文編號(hào)：1437193