Towards accuracy improvement in single point incremental forming of shallow parts formed under laser assisted conditions
Towards accuracy improvement in single point incremental forming of shallow parts formed under laser assisted conditions
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DOI：
10.1007/s12289-014-1203-x
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发表时间：
2016
影响因子：
2.4
通讯作者：
A. Mohammadi;H. Vanhove;A. Bael;J. Duflou
中科院分区：
文献类型：
--
作者：
A. Mohammadi;H. Vanhove;A. Bael;J. Duflou
具有低壁角几何形状的单点增量成形部件通常表现出由于累积不必要的胀形变形而明显偏离设计表面的制造几何形状。零件底部凸起的发展可能导致在凸起区域的板料起皱，从而导致更高的成形力，甚至可以停止成形过程。本文采用有限元分析和锥形几何实验两种方法研究了小角度零件的几何误差。详细研究了浅倾角零件的变形机理，并对低角和高角几何形状的刀片接触面积进行了表征。在第二阶段，研究了激光辅助单点增量成形工艺及其提高精度的潜力。为了获得适合热成形条件的工艺参数，采用瞬态传热分析方法模拟了激光在锥体上的运动。在模拟和实验确定的刀片接触区域的基础上，采用了不同的激光光斑定位策略，同时测量了零件的精度和成形力。已观察到锥体壁的过成形是由于接触区外板材的持续变形引起的，这种变形在激光处理后转变为欠成形。通过选择合适的激光定位策略，可以观察到凸起高度降低42%。这表明了它在减小径向成形力方面的作用。
Single point incrementally formed parts with a low wall angle geometry typically exhibit a manufactured geometry that significantly deviates from the design surface due to accumulated unwanted bulging deformation. Development of the bulge on the bottom of the part might result in wrinkling of the sheet at the bulged region which leads to higher forming forces and can even cease the forming process. In this study, the geometric inaccuracy of low angled parts is investigated by means of both Finite element analysis and an experimental campaign on a conical geometry. Deformation mechanisms in shallow sloped parts have been studied in detail and the tool-sheet contact area has been characterized both for low and high angled geometries. In a second phase, the laser assisted single point incremental forming process and its potential for improving accuracy are investigated. To obtain suitable process parameters for a warm forming condition, a transient heat transfer analysis is developed to simulate the laser movement on the conical geometry. Based on the simulated and experimentally determined tool-sheet contact zone, different laser spot positioning strategies have been used while the accuracy of the part and forming forces were measured. It has been observed that overforming of the cone wall is due to the continuous deformation of the sheet outside the contact zone which changes into underforming upon laser treatment. By selection of a proper laser positioning strategy a reduction of 42 % in bulge height is observed. This shows its effect in reducing radial forming forces.