【摘要】：針對(duì)球墨鑄鐵QT600,設(shè)計(jì)了一系列不同尺寸和幾何形狀的圓棒、薄壁圓管、板狀及缺口試樣,對(duì)光滑實(shí)心圓棒、缺口實(shí)心圓棒、缺口平板和中心孔板試樣進(jìn)行單軸拉伸試驗(yàn)以及對(duì)薄壁圓管試樣進(jìn)行扭轉(zhuǎn)試驗(yàn),獲得了試樣的荷載-位移曲線,并測(cè)試了材料在不同應(yīng)力狀態(tài)下的斷裂應(yīng)變;通過對(duì)試樣變形過程的觀測(cè),用光學(xué)顯微鏡確定了試樣的啟裂位置。結(jié)合觀測(cè)球墨鑄鐵金相組織,采用Matlab編寫程序?qū)η蚰T鐵金相進(jìn)行了定量金相分析,針對(duì)球墨鑄鐵金相組織的不同因素討論其球墨鑄鐵力學(xué)性能的影響;使用光學(xué)顯微鏡和掃描電鏡系統(tǒng)對(duì)試樣斷口形貌進(jìn)行觀測(cè),根據(jù)試樣宏微觀斷口討論不同試樣的斷裂形式,為研究材料在復(fù)雜應(yīng)力狀態(tài)下破壞提供依據(jù)。然后采用ABAQUS有限元分析軟件進(jìn)行彈塑性大變形數(shù)值模擬計(jì)算分析,結(jié)合數(shù)值模擬與顯微觀測(cè)結(jié)果,確定了不同試樣啟裂點(diǎn)位置的應(yīng)力狀態(tài)參數(shù),進(jìn)一步探討了斷裂應(yīng)變與應(yīng)力三軸度之間的關(guān)系。通過研究,得到的主要結(jié)論有:(1)根據(jù)拉伸和扭轉(zhuǎn)試驗(yàn)與數(shù)值模擬分析,拉伸和扭轉(zhuǎn)的等效應(yīng)力應(yīng)變曲線基本相同。(2)根據(jù)本文的試驗(yàn)與數(shù)值模擬結(jié)果可知,缺口實(shí)心圓棒試樣斷裂應(yīng)變隨著應(yīng)力三軸度的升高而降低,與GTN模型描述由孔洞模型韌性材料破壞規(guī)律相符合,而缺口平板試樣和中心孔板試樣的破壞規(guī)律與GTN模型描述的斷裂應(yīng)變與應(yīng)力三軸度的規(guī)律不相符。(3)對(duì)斷裂應(yīng)變相同而應(yīng)力三軸度不同的情形,發(fā)現(xiàn)Lode參數(shù)相差較大,可判定Lode參數(shù)是影響材料斷裂的重要因素。
[Abstract]:A series of round rods, thin-wall tubes, plates and notched specimens with different sizes and geometric shapes are designed for nodular cast iron QT600,. For smooth solid round rods and notched solid round rods, The load-displacement curves of notched plate and central orifice plate were obtained by uniaxial tensile test and torsional test of thin-wall circular tube specimen, and the fracture strain of the material under different stress conditions was tested. Through the observation of the deformation process of the sample, the crack opening position of the sample is determined by optical microscope. Combined with the observation of the metallographic structure of nodular cast iron, the metallographic analysis of nodular cast iron was carried out by Matlab program, and the influence of the mechanical properties of nodular cast iron was discussed according to the different factors of the metallographic structure of nodular cast iron. The fracture morphology of the sample was observed by optical microscope and scanning electron microscope system. According to the macro and micro fracture of the sample, the fracture forms of different samples were discussed, which provided the basis for the study of the failure of the material under complex stress state. Then the elastic-plastic large deformation numerical simulation analysis is carried out by using ABAQUS finite element analysis software. Combined with the numerical simulation and microscopic observation results, the stress state parameters of different crack opening points of the specimen are determined. The relationship between fracture strain and stress triaxiality is further discussed. Through the study, the main conclusions are as follows: (1) according to the tensile and torsional tests and numerical simulation analysis, the equivalent stress-strain curves of tensile and torsional are basically the same. (2) according to the experimental and numerical simulation results of this paper, The fracture strain of notched solid rod decreases with the increase of stress triaxiality, which is consistent with the failure law of ductile material described by GTN model. However, the failure law of notched plate specimen and central orifice plate specimen is not consistent with the law of fracture strain and stress triaxiality described by GTN model. (3) for the case of the same fracture strain and different stress triaxiality, it is found that the Lode parameters are quite different. It can be determined that Lode parameters are an important factor affecting the fracture of materials.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG143.5

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本文編號(hào)：2486077