【摘要】：多點拉形是一種新的板料柔性成形技術,能夠節(jié)省模具制造成本,縮短零件制造周期。但由于多點拉形與傳統(tǒng)拉形存在相似的局限性,在成形過程中板料變形并不均勻,容易出現(xiàn)拉裂、滑移線、起皺等缺陷。因此,需要探討新的加載方法提高板料變形均勻性。隨著多點技術的發(fā)展,多點模具的基本體沖頭能夠在承受一定壓力的條件下主動調整各自沖頭的高度,對板料施加載荷,迫使板料漸進成形。本文基于上述基本體沖頭的特點,將其應用到拉形中,研究了多點沖頭主動加載路徑對板料成形質量的影響。在這種成形方式中多點模具始終與板料處于貼合狀態(tài),能夠提高板料變形均勻性,避免成形缺陷,獲得合格的零件。本文主要內容和結論如下:1.板料受力分析及有限元模型建立對板料的變形條件做了基本假設,采用解析方法對板料的拉形過程進行了力學分析,得出板料在成形過程中應力、應變和厚度減薄的表達公式。同時建立了有限元模型,確定了邊界條件。2.多點沖頭主動加載拉形與加載路徑設計介紹了多點沖頭主動加載拉形的特點,分析了它與普通多點拉形的異同點。闡述了多點沖頭主動加載拉形的路徑設計原則,根據沖頭運行時間、速度和板料變形曲率設計了三種加載路徑,分別為等時沖頭主動加載、等速沖頭主動加載和等差曲率沖頭主動加載。同時對多點拉形與等差曲率沖頭主動加載拉形中板料的受力特點進行了分析,表明等差曲率沖頭主動加載能夠提高板料變形均勻性。3.多點沖頭主動加載拉形的數值模擬分析基于多點沖頭主動加載拉形與多點拉形,分別對球面件和鞍面件進行數值模擬分析,研究了不同加載路徑對板料成形效果的影響規(guī)律。結果表明:與多點拉形相比,多點沖頭主動加載拉形中的等時沖頭主動加載、等速沖頭主動加載和等差曲率沖頭主動加載均能減小板料鉗口處應力集中,提高成形件有效區(qū)域的應力分布、應變分布、厚度分布和延伸率分布的均勻性,對回彈的抑制作用比較明顯。4.多點沖頭主動加載拉形工藝參數研究通過數值模擬研究了工藝參數對鞍面件成形質量的影響,主要涉及到的工藝參數有板料預拉量、彈性墊厚度、過渡區(qū)長度、拉伸速率和基本體參數。研究結果表明,合理的工藝參數組合能夠使板料變形更加均勻,提高零件的整體成形質量。
[Abstract]:Multi-point drawing is a new flexible forming technology for sheet metal, which can save the manufacturing cost of die and shorten the manufacturing cycle of parts. However, due to the similar limitation between multi-point drawing and traditional drawing, the sheet metal deformation is not uniform in the forming process, and the defects such as tensile crack, slip line and wrinkle are easy to appear. Therefore, it is necessary to explore a new loading method to improve the uniformity of sheet metal deformation. With the development of multi-point technology, the basic punch of multi-point die can adjust the height of their punches under certain pressure, and apply load to the sheet metal, forcing the sheet metal to form gradually. Based on the characteristics of the basic punch, this paper applies it to the drawing, and studies the influence of the active loading path of the multi-point punch on the forming quality of the sheet metal. In this way, the multi-point die is always fit with the sheet metal, which can improve the uniformity of sheet metal deformation, avoid forming defects, and obtain qualified parts. The main contents and conclusions of this paper are as follows: 1. The stress analysis of sheet metal and the establishment of finite element model have made the basic hypothesis to the deformation condition of the sheet metal. The mechanical analysis of the drawing process of the sheet metal has been carried out by using the analytical method, and the expression formula of stress, strain and thickness thinning of the sheet metal in the forming process has been obtained. At the same time, the finite element model is established, and the boundary condition is determined. Design of active loading and loading path for multi-point punch the characteristics of multi-point punch active loading and drawing are introduced and the similarities and differences between multi-point punch and common multi-point tension are analyzed. This paper expounds the principle of path design for active loading and drawing of multi-point punch. According to the running time, speed and deformation curvature of sheet metal, three loading paths are designed, which are isochronous punch active loading. Active loading of constant speed punch and active loading of isometric curvature punch. At the same time, the mechanical characteristics of sheet metal in active loading of multi-point tension and isodyne curvature punch are analyzed. It is shown that active loading of isometric curvature punch can improve the uniformity of sheet metal deformation. Numerical simulation analysis of multi-point punch active loading and drawing based on multi-point punch active loading and multi-point drawing respectively numerical simulation analysis was carried out on spherical parts and saddle surface parts. The influence of different loading paths on sheet metal forming effect was studied. The results show that the isochronous punch active loading, the constant velocity punch active loading and the isodyne curvature punch active loading can reduce the stress concentration at the clamp of sheet metal compared with the multi-point drawing, the multi-point punch active loading, the isochronous punch active loading and the isokinetic curvature punch active loading can reduce the stress concentration at the clamp of sheet metal. Increasing the uniformity of stress distribution, strain distribution, thickness distribution and elongation distribution in the effective zone of forming parts, the inhibition of springback is obvious. The influence of process parameters on the forming quality of saddle surface was studied by numerical simulation. The main process parameters involved included sheet metal pretension thickness of elastic pad length of transition zone. Tensile rate and basic body parameters. The results show that the reasonable combination of process parameters can make the sheet metal deformation more uniform and improve the integral forming quality of the parts.
【學位授予單位】：吉林大學
【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 朱漸昌;李曉星;張偉;;超厚復雜蒙皮的拉形工藝及回彈補償自動實現(xiàn)[J];機械工程與自動化;2016年06期

2 李曉星;畢研華;葛宇龍;;飛機蒙皮拉形工藝輔助設計系統(tǒng)開發(fā)[J];航空制造技術;2016年17期

3 王志成;何桃;王旭;李小強;李東升;;鋁合金復雜變截面蒙皮拉形有限元仿真與試驗研究[J];鍛壓技術;2016年08期

4 王德亮;王輝;高霖;張浩;安傳海;;拉形輔助的數控漸進成形試驗研究[J];機械科學與技術;2016年01期

5 劉凱;王成軍;方代正;陳孝U，

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