微型管件軸向補料液壓成形工藝研究
發(fā)布時間：2018-10-22 17:55
【摘要】：在微機電、醫(yī)療器械等領域,對微型異形管件的需求正逐漸上升。液壓成形能夠高效生產微型異形管件,成為研究的重點。由于零件尺寸與晶粒大小接近,微型管件產生了尺度效應問題,成形能力降低,制約了其發(fā)展。軸向補料工藝能夠提高管件成形能力,已在常規(guī)異形管件生產中廣泛應用。為了提高微型管件成形能力,本文將軸向補料工藝引入微型管件液壓成形中,進行了相關研究。首先,對微型管件液壓成形導向區(qū)內的摩擦特性進行了研究。采用自行開發(fā)的實驗裝置,通過測定初始摩擦力與總推力,并根據(jù)內壓大小以及其它尺寸參數(shù),即可計算出摩擦系數(shù)。分別對外徑2mm與1mm的304不銹鋼微型管件進行實驗,結果發(fā)現(xiàn)隨著尺寸縮小,摩擦系數(shù)顯著上升。造成微型管件摩擦尺度效應的主要原因在于管件外表面為曲面,曲率半徑的縮小導致模具表面相對凹凸不平程度減低,使液體潤滑劑存儲困難,摩擦力增大。其次,對軸向補料工藝進行了數(shù)值與實驗分析。利用GTN細觀損傷模型,直接將外徑2mm,壁厚0.15mm的304不銹鋼微型管件的流動應力引入到材料屬性當中,對微型管件進行建模;同時,基于大量的軸向補料自由脹形實驗,通過在線性加載路徑條件下獲得的破裂點壓力值,考察補料量對成形能力的影響。模擬與實驗結果表明,軸向補料工藝能夠提高微型管件液壓成形能力,但由于尺度效應問題,實際成形能力受到多種因素影響,從而表現(xiàn)出顯著的工藝分散性。最后,為了考察微型管件實際成形能力,對不同尺寸的304不銹鋼微型管件,在不同補料量的條件下,進行了 30%脹形率的成形實驗以及等徑T形三通管液壓成形實驗。成形實驗的結果發(fā)現(xiàn),兩種管件在不同補料量條件下都能實現(xiàn)成形。T形管液壓成形實驗發(fā)現(xiàn),兩種管件成形后支管最大高度過低,不足以形成完整的支管,這是由于尺度效應使材料的應變延伸率下降。數(shù)值模擬的結果則表明,增大補料量能夠改善壁厚減薄,提高成形能力,但由于摩擦力的影響,導致管件兩端壁厚顯著增厚。
[Abstract]:In the field of micro-electromechanical, medical devices, the demand for micro-shaped pipe fittings is increasing gradually. Hydroforming has become the focus of research because it can efficiently produce miniature special-shaped pipe fittings. Because the size of the parts is close to the grain size, the miniature pipe fittings have the problem of scale effect, and the forming ability is reduced, which restricts their development. Axial feeding technology can improve the forming ability of pipe fittings and has been widely used in the production of conventional special-shaped pipe fittings. In order to improve the forming ability of micro tube fittings, this paper introduces the axial feeding technology into hydroforming of micro pipe fittings. Firstly, the friction characteristics in the hydroforming guide zone of micro tube fittings are studied. The friction coefficient can be calculated by measuring the initial friction force and the total thrust force and according to the internal pressure and other dimension parameters. The experimental results show that the friction coefficient of 304 stainless steel pipes with external diameters 2mm and 1mm increases significantly with the reduction of size. The main reason for the friction scale effect of micro pipe fittings is that the outer surface of the pipe fittings is curved surface. The reduction of curvature radius leads to the reduction of the relative uneven degree of the die surface, which makes the storage of liquid lubricant difficult and the friction force increase. Secondly, the numerical and experimental analysis of axial feeding process is carried out. Using the GTN damage model, the flow stress of 304 stainless steel tube fittings with external diameter of 2 mm and wall thickness of 0.15mm is directly introduced into the material properties to model the micro tube fittings. At the same time, based on a large number of free bulging experiments of axial feeding, the flow stress of 304 stainless steel micro-tube fittings with external diameter of 2 mm and wall thickness of 0.15mm is directly introduced into the material properties. The influence of feeding amount on the forming capacity was investigated by the fracture point pressure value obtained under the linear loading path condition. The simulation and experimental results show that the axial feeding process can improve the hydroforming ability of micro pipe fittings, but due to the scale effect, the actual forming ability is affected by many factors, thus showing a remarkable process dispersion. Finally, in order to investigate the actual forming ability of micro tube fittings, the forming experiments of 30% bulging rate and equal diameter T-shaped three-way tube hydroforming experiments were carried out for 304 stainless steel micro-tubes with different sizes under different feeding quantities. The results of forming experiments show that the two kinds of pipe fittings can be formed under the condition of different recharge amount, and the hydroforming experiment of T-shaped tube shows that the maximum height of the branch pipe is too low to form a complete branch tube after the forming of the two kinds of pipe fittings. This is due to the reduction of the strain elongation of the material due to the scale effect. The results of numerical simulation show that the wall thickness can be improved and the forming ability can be improved by increasing the amount of feedstock, but due to the influence of friction, the wall thickness at both ends of the pipe is significantly increased.
【學位授予單位】：南京理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG306
本文編號：2287888
[Abstract]:In the field of micro-electromechanical, medical devices, the demand for micro-shaped pipe fittings is increasing gradually. Hydroforming has become the focus of research because it can efficiently produce miniature special-shaped pipe fittings. Because the size of the parts is close to the grain size, the miniature pipe fittings have the problem of scale effect, and the forming ability is reduced, which restricts their development. Axial feeding technology can improve the forming ability of pipe fittings and has been widely used in the production of conventional special-shaped pipe fittings. In order to improve the forming ability of micro tube fittings, this paper introduces the axial feeding technology into hydroforming of micro pipe fittings. Firstly, the friction characteristics in the hydroforming guide zone of micro tube fittings are studied. The friction coefficient can be calculated by measuring the initial friction force and the total thrust force and according to the internal pressure and other dimension parameters. The experimental results show that the friction coefficient of 304 stainless steel pipes with external diameters 2mm and 1mm increases significantly with the reduction of size. The main reason for the friction scale effect of micro pipe fittings is that the outer surface of the pipe fittings is curved surface. The reduction of curvature radius leads to the reduction of the relative uneven degree of the die surface, which makes the storage of liquid lubricant difficult and the friction force increase. Secondly, the numerical and experimental analysis of axial feeding process is carried out. Using the GTN damage model, the flow stress of 304 stainless steel tube fittings with external diameter of 2 mm and wall thickness of 0.15mm is directly introduced into the material properties to model the micro tube fittings. At the same time, based on a large number of free bulging experiments of axial feeding, the flow stress of 304 stainless steel micro-tube fittings with external diameter of 2 mm and wall thickness of 0.15mm is directly introduced into the material properties. The influence of feeding amount on the forming capacity was investigated by the fracture point pressure value obtained under the linear loading path condition. The simulation and experimental results show that the axial feeding process can improve the hydroforming ability of micro pipe fittings, but due to the scale effect, the actual forming ability is affected by many factors, thus showing a remarkable process dispersion. Finally, in order to investigate the actual forming ability of micro tube fittings, the forming experiments of 30% bulging rate and equal diameter T-shaped three-way tube hydroforming experiments were carried out for 304 stainless steel micro-tubes with different sizes under different feeding quantities. The results of forming experiments show that the two kinds of pipe fittings can be formed under the condition of different recharge amount, and the hydroforming experiment of T-shaped tube shows that the maximum height of the branch pipe is too low to form a complete branch tube after the forming of the two kinds of pipe fittings. This is due to the reduction of the strain elongation of the material due to the scale effect. The results of numerical simulation show that the wall thickness can be improved and the forming ability can be improved by increasing the amount of feedstock, but due to the influence of friction, the wall thickness at both ends of the pipe is significantly increased.
【學位授予單位】：南京理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG306
【參考文獻】
相關期刊論文 前10條
1 李萍;趙賓;薛克敏;;銅合金微塑性成形力學性能及其本構關系[J];固體力學學報;2015年05期
2 李金陽;鄭志鎮(zhèn);吳曉;李建軍;;Zr55塊體非晶合金在低頻振動場下的微成形能力[J];塑性工程學報;2015年05期
3 王國峰;李優(yōu);劉奇;趙相禹;;納米材料微陣列超塑微成形機理與尺度效應[J];精密成形工程;2015年03期
4 孫慧敏;王國珍;軒福貞;劉長軍;;焊接接頭延性裂紋擴展的數(shù)值模擬[J];焊接學報;2010年08期
5 郭斌;王春舉;單德彬;周健;;基于微塑性成形的微型零件批量制造技術[J];功能材料與器件學報;2008年01期
6 雷濵;張凱鋒;;金屬微成形過程中微尺度效應與相似評估[J];機械工程學報;2007年07期
7 趙亞西;童國權;李凡國;;尺寸效應對黃銅鐓粗微成形影響規(guī)律的研究[J];電加工與模具;2006年06期
8 雷潂;張凱鋒;;金屬微成形中微尺度效應新分類及評估分析[J];哈爾濱工程大學學報;2006年01期
9 趙迎紅;雷麗萍;曾攀;;微塑性成形技術及其力學行為特征[J];塑性工程學報;2005年06期
10 申昱,于滬平,阮雪榆;微成形中材料非均勻流動研究[J];鍛壓技術;2005年05期
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