內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓成形折疊缺陷機制研究
發(fā)布時間：2019-03-18 10:07
【摘要】：鎂合金內(nèi)筋殼體作為典型輕質(zhì)輕體結(jié)構(gòu)件廣泛應(yīng)用于航天、航空領(lǐng)域,傳統(tǒng)加工方法存在廢品率高、性能差、成本較大等缺點,無法滿足構(gòu)件輕量化與高性能的要求�；趦�(nèi)筋殼體結(jié)構(gòu)特點和鎂合金變形特性,提出旋轉(zhuǎn)擠壓成形方法以實現(xiàn)該類構(gòu)件整體塑性成形。旋轉(zhuǎn)擠壓成形具有降低載荷、改善成形性、細(xì)化晶粒、弱化各向異性和保證筋部流線完整等優(yōu)點,但由于加載方式的特殊性導(dǎo)致容易產(chǎn)生折疊缺陷。通過限元數(shù)值模擬與實驗相結(jié)合,研究了模具結(jié)構(gòu)參數(shù)及成形工藝參數(shù)對缺陷形成的影響,揭示了鎂合金內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓成形過程中折疊缺陷形成機理,為新工藝應(yīng)用奠定基礎(chǔ)。內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓分為旋轉(zhuǎn)軸向擠壓和旋轉(zhuǎn)徑向擠壓兩種模式,對成形過程中各區(qū)域應(yīng)力、應(yīng)變分布與金屬流動情況進行了分析。旋轉(zhuǎn)擠壓過程中,變形區(qū)金屬處于強壓剪應(yīng)力狀態(tài)能夠充分發(fā)揮鎂合金塑性;漸開式組合模具加載下產(chǎn)生微區(qū)累積劇塑性變形,有利于性能的提升;建立旋轉(zhuǎn)擠壓成形金屬速度場,為折疊缺陷研究提供了理論基礎(chǔ)。為深入了解內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓成形以進一步分析折疊缺陷的產(chǎn)生,利用數(shù)值模擬對某一內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓成形過程進行研究,該零件成形軸向載荷極值為57.1kN、徑向載荷極值為57.6kN以及成形扭矩極值為2867.1kN·mm;獲得等效應(yīng)力、應(yīng)變分布特點,其中壁部與內(nèi)環(huán)筋部分金屬等效應(yīng)變量大,有利于細(xì)化晶粒、提高構(gòu)件整體性能。對折疊缺陷進行研究,折疊缺陷分布于內(nèi)筋直筒件薄壁內(nèi)側(cè)。旋轉(zhuǎn)軸向擠壓過程中折疊缺陷產(chǎn)生是由于漸開式組合模間隙處凸起金屬徑向流動變形抗力過大,使凸起金屬內(nèi)側(cè)流動速度低于邊緣處金屬流動速度,最終使凸起金屬與薄壁內(nèi)側(cè)金屬匯流形成折疊缺陷。旋轉(zhuǎn)徑向擠壓過程中,由于瞬時擠壓量過大導(dǎo)致金屬向坯料空心處流動在凸模工作帶側(cè)面形成金屬堆積,在凸模作用下與未成形區(qū)金屬匯流產(chǎn)生折疊缺陷。確定模具結(jié)構(gòu)與工藝參數(shù)對折疊缺陷產(chǎn)生的影響,并繪制折疊極限圖,為實際生產(chǎn)與實驗避免折疊缺陷提供模擬依據(jù)。根據(jù)內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓成形過程中金屬流動特點以及折疊缺陷產(chǎn)生原因,設(shè)計實驗進行驗證。通過利用Gleeble-3500熱壓縮模擬實驗機進行熱模擬實驗,結(jié)果表明內(nèi)環(huán)筋直筒件旋轉(zhuǎn)擠壓成形中產(chǎn)生折疊缺陷,驗證了數(shù)值模擬結(jié)果可靠性。
[Abstract]:Magnesium alloy inner reinforcement shell is widely used in aerospace and aviation field as a typical lightweight structural component. The traditional machining method has the disadvantages of high waste rate, poor performance and high cost, and can not meet the requirements of lightweight and high performance of components. Based on the structural characteristics of the inner reinforcement shell and the deformation characteristics of magnesium alloy, the rotary extrusion forming method is proposed to realize the integral plastic forming of this kind of components. Rotary extrusion has the advantages of reducing load, improving formability, refining grain, weakening anisotropy and ensuring the integrity of rib streamline, but it is easy to produce folding defects due to the particularity of loading mode. Through the combination of finite element numerical simulation and experiment, the influence of die structure parameters and forming process parameters on the formation of defects was studied, and the forming mechanism of folding defects in the forming process of magnesium alloy inner ring stiffened straight tube parts was revealed. It lays a foundation for the application of the new process. The rotary extrusion of inner ring stiffened straight tube is divided into two modes: rotating axial extrusion and rotating radial extrusion. The stress, strain distribution and metal flow in each region during the forming process are analyzed. In the process of rotating extrusion, the metal in the deformation zone in the state of strong compressive shear stress can give full play to the plasticity of magnesium alloy, and the accumulative severe plastic deformation in the micro-region under the loading of the progressive composite die is beneficial to the improvement of the performance. The velocity field of rotating extrusion forming metal is established, which provides a theoretical basis for the study of folding defects. In order to understand the forming of inner ring stiffened straight tube by rotary extrusion to further analyze the forming of folding defects, the forming process of a inner ring stiffened straight cylinder was studied by numerical simulation. The extreme value of axial load of the part is 57.1kN, the maximum value of axial load of the part is 57.1kN, The extreme value of radial load is 57.6kN and the extreme value of forming torque is 2867.1kN mm;. The equivalent stress and strain distribution characteristics are obtained, in which the metal equivalent variables of the wall and inner ring bars are large, which is beneficial to refine the grain and improve the overall performance of the component. The folding defects were studied, and the folding defects were distributed on the inside wall of the inner stiffened straight tube. In the process of rotating axial extrusion, the folding defect is due to the excessive radial flow deformation resistance of convex metal at the gap of the involute composite die, which makes the flow velocity of the inner side of the raised metal lower than the metal flow velocity at the edge of the convex metal. Finally, a folding defect is formed between the bulge metal and the thin-walled inner metal confluence. In the process of rotating radial extrusion, due to the excessive amount of instantaneous extrusion, metal accumulation is formed on the side of the punch working belt, and folding defects are formed with the metal confluence in the unformed region under the action of the punch due to the excessive amount of instantaneous extrusion. The influence of die structure and process parameters on folding defects is determined, and the folding limit diagram is drawn, which provides a simulation basis for avoiding folding defects in practical production and experiment. According to the characteristics of metal flow and the reasons of folding defects during the rotary extrusion process of inner ring stiffened straight cylinder, the design experiment is verified. The thermal simulation experiment is carried out by using Gleeble-3500 hot compression simulator. The results show that folding defects occur in the rotary extrusion forming of inner ring stiffened straight tube, and the reliability of numerical simulation results is verified.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG379
本文編號：2442758
[Abstract]:Magnesium alloy inner reinforcement shell is widely used in aerospace and aviation field as a typical lightweight structural component. The traditional machining method has the disadvantages of high waste rate, poor performance and high cost, and can not meet the requirements of lightweight and high performance of components. Based on the structural characteristics of the inner reinforcement shell and the deformation characteristics of magnesium alloy, the rotary extrusion forming method is proposed to realize the integral plastic forming of this kind of components. Rotary extrusion has the advantages of reducing load, improving formability, refining grain, weakening anisotropy and ensuring the integrity of rib streamline, but it is easy to produce folding defects due to the particularity of loading mode. Through the combination of finite element numerical simulation and experiment, the influence of die structure parameters and forming process parameters on the formation of defects was studied, and the forming mechanism of folding defects in the forming process of magnesium alloy inner ring stiffened straight tube parts was revealed. It lays a foundation for the application of the new process. The rotary extrusion of inner ring stiffened straight tube is divided into two modes: rotating axial extrusion and rotating radial extrusion. The stress, strain distribution and metal flow in each region during the forming process are analyzed. In the process of rotating extrusion, the metal in the deformation zone in the state of strong compressive shear stress can give full play to the plasticity of magnesium alloy, and the accumulative severe plastic deformation in the micro-region under the loading of the progressive composite die is beneficial to the improvement of the performance. The velocity field of rotating extrusion forming metal is established, which provides a theoretical basis for the study of folding defects. In order to understand the forming of inner ring stiffened straight tube by rotary extrusion to further analyze the forming of folding defects, the forming process of a inner ring stiffened straight cylinder was studied by numerical simulation. The extreme value of axial load of the part is 57.1kN, the maximum value of axial load of the part is 57.1kN, The extreme value of radial load is 57.6kN and the extreme value of forming torque is 2867.1kN mm;. The equivalent stress and strain distribution characteristics are obtained, in which the metal equivalent variables of the wall and inner ring bars are large, which is beneficial to refine the grain and improve the overall performance of the component. The folding defects were studied, and the folding defects were distributed on the inside wall of the inner stiffened straight tube. In the process of rotating axial extrusion, the folding defect is due to the excessive radial flow deformation resistance of convex metal at the gap of the involute composite die, which makes the flow velocity of the inner side of the raised metal lower than the metal flow velocity at the edge of the convex metal. Finally, a folding defect is formed between the bulge metal and the thin-walled inner metal confluence. In the process of rotating radial extrusion, due to the excessive amount of instantaneous extrusion, metal accumulation is formed on the side of the punch working belt, and folding defects are formed with the metal confluence in the unformed region under the action of the punch due to the excessive amount of instantaneous extrusion. The influence of die structure and process parameters on folding defects is determined, and the folding limit diagram is drawn, which provides a simulation basis for avoiding folding defects in practical production and experiment. According to the characteristics of metal flow and the reasons of folding defects during the rotary extrusion process of inner ring stiffened straight cylinder, the design experiment is verified. The thermal simulation experiment is carried out by using Gleeble-3500 hot compression simulator. The results show that folding defects occur in the rotary extrusion forming of inner ring stiffened straight tube, and the reliability of numerical simulation results is verified.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG379
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