【作者】 张传敏；

【导师】 李明哲；

【作者基本信息】 吉林大学 ， 材料加工工程， 2006， 硕士

【摘要】 蒙皮多点拉形是采用很多基本体构成工件成形面,利用基本体高度的调整实现成形面变化的板类件三维曲面柔性成形技术,在航天航空领域有着广阔的应用前景。压痕和起皱是蒙皮多点拉形时典型的成形缺陷;在工件和基本体之间放置弹性垫可实现薄板三维曲面蒙皮件的无缺陷成形。本文采用有限元方法对薄板件蒙皮多点拉形过程进行数值模拟研究,并对使用弹性介质的成形方法和无弹性介质的重叠拉形方法的蒙皮多点拉形过程进行了研究,得出两种成形方法均能有效抑制压痕,明显改善工件成形质量的结论。本文对成形过程中压痕和起皱缺陷的产生原因及抑制方法进行了探讨,通过选择不同的水平拉力、材质、成形尺寸、板料厚度和不同厚度的弹性介质以及重叠成形方法对蒙皮多点拉形过程进行了模拟。通过与实际蒙拉工艺经验公式的对比,验证了模拟结果与经验公式吻合较好。研究工作表明,通过薄板蒙皮多点拉形的数值模拟研究,可以为蒙皮多点拉形工艺参数的确定以及成形性的判断提供重要依据。更多还原

【Abstract】 Multi-point forming (MPF) is a flexible manufacturing technology for three-dimensional surface part of thin sheet metal. Its main idea is dividing the curvedsurface of the traditional stamping dies into rule arrange, high adjustable elementgroup, and then the three-dimensional shape of sheet metal is formed by thecurved surface of elements(element group forming surface). MPF controls thedisplacement and speed of elements through computer, to change the curvedsurface of elements and complete flexible manufacturing. Currently MPF isextensively applied in many realms, such as shipbuilding, orbit passenger car,medical science engineering and the large stadium building construction...etc. thereis extensively applied foreground in the aviation aerospace realm.Numerical analysis technology of sheet metal forming is an essential tool tooptimize die design, forecasting forming defects and analyzing forming quality.Finite element technology is the most valid method in the simulation methods. Inrecent decades, Finite element technology is applied more and more extensivelyin blank forming. Numerical analysis technology is not only used to typicalforming analysis and simulation , but also used to forecasting wrinkling ,dimpling defects , calculating spring and the original blank design. Because thecontact between the elements and blank is changing all the time, and thecomplicated applying load condition, adoptoing dynamic explicit finite elementcalculation has apparent advantage on the process of multi-point stretching foraircraft skin. Therefore, making numerical simulation analysis on the on theprocess of multi-point stretching for aircraft skin by dynamic explicit finite elementcalculation.The main contents are as follows:1)Building up finite element model of multi-point stretching for aircraft skinwith thin blank, simulating the wrinkling defect of the blank under differentHorizontal pulling force. By contrast with analysis on the practical stretching forceverified the accuracy of the calculating way indirectly without experiment.2)Building up finite element model of multi-point stretching with elasticcushion for aircraft skin and simulating the process. Simulation results show that,using elastic cushion on the process of multi-point stretching can suppress thedimpling defect effectively, and can improve the forming quality on the basis ofmeeting the accuracy request.3)Building up finite element model of repeated multi-point stretching foraircraft skin and simulating the process. Simulation results show that, repeatedmulti-point stretching can uppress the dimpling defect effectively . By contrastwith using elastic cushion , repeated multi-point stretching can improve theforming accuracy and efficiency doubly4)Simulating the wrinkling defect on the process of multi-point stretching,discussing the causes and solutions of the wrinkling defect. through horizontalpulling force, blank size and material etc. Simulation results show that, thewrinkling trend is decling as the blank thickness and horizontal pulling forceincrease, but too large horizontal pulling force can result in cracking defect.Make use of the hard aluminum plank of LY12 takes better result than usingindustry of L2Y2 aluminum plank and wrinkle appear easier as the stretchingcoefficient increase.5)Simulating the dimpling defect on the process of multi-point stretching,discussing the causes and solutions of the dimpling defect. Comparing the differentthickness of the elastic cushion effection to the dimpling defect. Simulation resultsshow that, the thickness of the elastic cushion does not affect the dimpling defectapparently. But when the thickness of the elastic cushion increases, the formingaccuracy decreases.Studying the multi-point stretching for aircraft skin systematically ,simulating the factors affecting the blank forming quality on the process of multi-point stretching, especially discussing and analyzing the influence of horizontalpulling force, blank thickness , different material and blank size etc on theblank forming quality.Putting forward the influence regulation of techniquefactors to the blank forming quality.更多还原