Pattern formation on free surfaces via plastic buckling and periodic folding
Pattern formation on free surfaces via plastic buckling and periodic folding
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通过塑性屈曲和周期性折叠在自由表面上形成图案
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
S. Chandrasekar
中科院分区：
文献类型：
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作者：
A. Udupa;K. Viswanathan;S. Chandrasekar
表面图案的自发形成，如褶皱和折痕，在工程系统中广泛观察到，如薄膜和机械加工表面，以及在自然系统中，如花瓣和叶子。一种公认的形成它们的途径是通过表面弹性不稳定性。在这里，我们演示了它们形成的另一种途径--塑性屈曲和折叠--当延性材料受到大应变(>；1)变形时发生。利用聚丙烯简单剪切变形的原位成像，我们描绘了褶皱形成的机制和由此产生的表面形态。折叠图案显示了单一波长，该波长与塑性区的大小成线性关系。分析模型预测了塑性屈曲失稳的开始和褶皱的特征。除了在大面积可控地生成表面特征方面的明显应用外，我们的结果还表明了固体中表面粗糙度起源的一种贡献机制。
Spontaneous formation of surface patterns such as folds and creases is widely observed in engineered systems, such as thin films and machined surfaces, as well as in natural systems such as floral petals and leaves. A recognized route for their formation is via surface elastic instabilities. Here we demonstrate an alternate route for their formation —plastic buckling and folding—that occurs when ductile materials are subject to large-strain (>1) deformation. Using in situ imaging of simple-shear deformation of polypropylene, we delineate the mechanics underlying formation of folds and the resulting surface morphology. The fold pattern shows a single wavelength that scales linearly with the size of the plastic zone. An analytical model predicts onset of the plastic buckling instability and characteristics of the folds. Besides obvious applications for controllably generating surface features over large areas, our results suggest a contributing mechanism for origin of surface roughness in solids.