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HighPa-Shock - Increasing reproducibility of the spring-back angle of thin metal sheets by inducing residual compressive stress with laser shock

HighPa-Shock - 通过激光冲击诱导残余压应力，提高薄金属板回弹角的可重复性

基本信息

批准号：
399930874
负责人：
Professor Dr.-Ing. Frank Vollertsen
金额：
--
依托单位：
BIAS - Bremer Institut für Angewandte Strahltechnik GmbH
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/399930874?language=en
关键词：
HighPa Shock Increasing reproducibility spring

项目摘要

Metallic micro components can be found in many products of daily life such as in smartphones, tablets or laptops. A majority of these micro parts are fabricated by cold forming operations as these allow low cycle times and generally a high reproducibility. However, when it comes to bending of thin metallic sheets, the reproducibility of the bending angle is rather low. This is due to the fact that the spring-back suffers large scatter. It is found that the scatter in spring-back is caused by a scatter in residual stress state of the work piece. The residual stresses are brought in the material for example by manufacturing processes prior to the bending process such as casting or rolling.Own experimental results show that the resulting bending angle can be influenced by a laser shock process prior to bending operation. Within this laser shock process, a laser shock wave is generated by an ultra-short-pulse laser and this shock wave induces residual compressive stress within the work piece. The specific mechanism behind this complex process interaction is not understood yet and therefore cannot be used industrially. It is the long term goal of this project to fully understand the influence of the laser shock process on the reproducibility of the bending process. In the first part of the priority programme it is investigated if a reproducible residual stress state can be generated by laser induced shock waves. For that, the residual stress state of commercially available steel sheets with a thickness of 0,2 mm are examined and mapped. Subsequently the stress state that can be induced by a single laser shock pulse in an annealed sheet is investigated by varying the pulse parameters. This knowledge is enhanced to evaluate if a maximum compressive stress state is achievable independent of number of applied pulses. Finally it is aimed to achieve a planar stress state by applying multiple allocated laser shock pulses.

在智能手机、平板电脑或笔记本电脑等许多日常生活产品中都可以找到金属微元件。这些微型零件中的大多数都是通过冷成形操作制造的，因为这些操作允许较短的周期时间和通常较高的再现性。然而，对于金属薄板的弯曲，弯曲角度的重现性相当低。这是因为回弹受到了很大的散布。结果表明，回弹过程中的离散性是由工件残余应力状态的离散性引起的。材料中的残余应力是在弯曲过程之前的制造过程中产生的，如铸造或轧制。几个实验结果表明，在弯曲操作之前，激光冲击过程可以影响所产生的弯曲角度。在激光冲击过程中，超短脉冲激光产生激光冲击波，在工件内部产生残余压应力。这种复杂过程相互作用背后的具体机制尚不清楚，因此不能用于工业。充分了解激光冲击工艺对弯曲工艺重现性的影响是该项目的长期目标。在优先方案的第一部分，研究激光诱导冲击波是否能产生可重复的残余应力状态。为此，研究并绘制了厚度为0.2 mm的商用钢板的残余应力状态图。随后，通过改变脉冲参数，研究了单个激光冲击脉冲在退火板中所能引起的应力状态。该知识被增强以评估最大压缩应力状态是否可独立于施加脉冲的数目而实现。最后，通过施加多个分配的激光冲击脉冲来实现平面应力状态。