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.

金属微型元件存在于许多日常生活产品中，例如智能手机、平板电脑或笔记本电脑。大多数这些微型零件是通过冷成型操作制造的，因为这样可以缩短循环时间，并且通常具有较高的再现性。然而，当涉及薄金属板的弯曲时，弯曲角度的再现性相当低。这是因为回弹分散较大。研究发现，回弹的分散是由于工件残余应力状态的分散造成的。残余应力是由弯曲过程之前的制造过程（例如铸造或轧制）引入材料中的。我们自己的实验结果表明，最终的弯曲角度可能会受到弯曲操作之前的激光冲击过程的影响。在该激光冲击过程中，超短脉冲激光产生激光冲击波，该冲击波在工件内引起残余压应力。这种复杂过程相互作用背后的具体机制尚不清楚，因此无法在工业上使用。该项目的长期目标是充分了解激光冲击工艺对弯曲工艺再现性的影响。在优先计划的第一部分中，研究是否可以通过激光诱导冲击波产生可再现的残余应力状态。为此，对厚度为 0.2 mm 的市售钢板的残余应力状态进行了检查和绘制。随后，通过改变脉冲参数来研究退火板中由单个激光冲击脉冲引起的应力状态。该知识得到增强，以评估是否可以实现最大压应力状态，而与所施加的脉冲数量无关。最后，目的是通过应用多个分配的激光冲击脉冲来实现平面应力状态。