Thermally Induced Mechanical Response of Metal Foam During Laser Forming
Thermally Induced Mechanical Response of Metal Foam During Laser Forming
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DOI：
10.1115/1.4038995
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发表时间：
2018-04
影响因子：
4
通讯作者：
Tizian Bucher;Adelaide Young;M. Zhang;Changjun Chen;Y. Yao
中科院分区：
文献类型：
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作者：
Tizian Bucher;Adelaide Young;M. Zhang;Changjun Chen;Y. Yao
迄今为止，金属泡沫产品很少能超过原型阶段。原因是几乎没有方法将金属泡沫制造成工程应用中所需的形状。激光成形是目前唯一具有高几何灵活性的方法，能够成形任意尺寸的零件。然而，当用于金属泡沫时，该过程仍然知之甚少，并且关于泡沫的机械响应的许多问题尚未得到解决。在这项研究中，泡沫金属在激光成形过程中的力学行为进行了表征，通过测量其应变响应，通过数字图像相关（DIC）。由此产生的数据被用来验证是否温度梯度机制（TGM），以及建立在固体金属板材成形，是有效的金属泡沫，一直假设没有实验证明。此外，还研究了泡沫金属在大角度弯曲时的行为，以及激光诱导缺陷对其力学性能的影响。使用具有不同几何近似水平的模型对机械响应进行了数值模拟。结果表明，弯曲主要是由压缩引起的缩短，通过细胞破碎激光照射表面附近实现。由于这种机制不同于传统的TGM，其中弯曲是由激光照射表面附近的塑性压缩应变引起的，因此提出了修改的温度梯度机制（MTGM）。MTGM中发生的致密化局部改变了金属泡沫的材料性质，限制了可实现的最大弯曲角度，而不会显著影响其机械性能。[DOI：10.1115/1.4038995]
To date, metal foam products have rarely made it past the prototype stage. The reason is that few methods exist to manufacture metal foam into the shapes required in engineering applications. Laser forming is currently the only method with a high geometrical flexibility that is able to shape arbitrarily sized parts. However, the process is still poorly understood when used on metal foam, and many issues regarding the foam’s mechanical response have not yet been addressed. In this study, the mechanical behavior of metal foam during laser forming was characterized by measuring its strain response via digital image correlation (DIC). The resulting data were used to verify whether the temperature gradient mechanism (TGM), well established in solid sheet metal forming, is valid for metal foam, as has always been assumed without experimental proof. Additionally, the behavior of metal foam at large bending angles was studied, and the impact of laserinduced imperfections on its mechanical performance was investigated. The mechanical response was numerically simulated using models with different levels of geometrical approximation. It was shown that bending is primarily caused by compression-induced shortening, achieved via cell crushing near the laser irradiated surface. Since this mechanism differs from the traditional TGM, where bending is caused by plastic compressive strains near the laser irradiated surface, a modified temperature gradient mechanism (MTGM) was proposed. The densification occurring in MTGM locally alters the material properties of the metal foam, limiting the maximum achievable bending angle, without significantly impacting its mechanical performance. [DOI: 10.1115/1.4038995]