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How hair deforms steel
Science ( IF 56.9 ) Pub Date : 2020-08-06 , DOI: 10.1126/science.aba9490
Gianluca Roscioli 1 , Seyedeh Mohadeseh Taheri-Mousavi 1, 2 , Cemal Cem Tasan 1
Affiliation  

A hair-splitting way to get dull Razors eventually become dull after shaving even though the blade is about 50 times harder than the hair. Whereas edge rounding and brittle cracking of a blade's hard coating were thought to be responsible, a detailed microstructural investigation by Roscioli et al. shows a different mechanism. A combination of out-of-plane bending, microstructural heterogeneity, and asperities—microscopic chips along the smooth edge—sometimes caused fracture to occur if the conditions lined up. This fracture originated at the hair-edge asperity interface and created chipping that dulled a blade faster than other processes. Science, this issue p. 689 A combination of out-of-plane deformation, asperities, and grain heterogeneity cause blades to dull from shaving hair. Steels for sharp edges or tools typically have martensitic microstructures, high carbide contents, and various coatings to exhibit high hardness and wear resistance. Yet they become practically unusable upon cutting much softer materials such as human hair, cheese, or potatoes. Despite this being an everyday observation, the underlying physical micromechanisms are poorly understood because of the structural complexity of the interacting materials and the complex boundary conditions of their co-deformation. To unravel this complexity, we carried out interrupted tests and in situ electron microscopy cutting experiments with two micromechanical testing setups. We investigated the findings analytically and numerically, revealing that the spatial variation of lath martensite structure plays the key role leading to a mixed-mode II-III cracking phenomenon before appreciable wear.

中文翻译:

头发如何使钢变形

一种让头发变得无光泽的分裂方式 剃须刀在剃须后最终会变得无光泽,即使刀片的硬度约为头发的 50 倍。尽管认为刀片硬涂层的边缘倒圆和脆性开裂是原因,但 Roscioli 等人的详细微观结构研究。显示了不同的机制。平面外弯曲、微观结构异质性和凹凸不平(沿着光滑边缘的微观碎片)的组合有时会导致在条件一致时发生断裂。这种断裂起源于毛边粗糙界面,并产生碎屑,比其他工艺更快地使刀片变钝。科学,这个问题 p。689 平面外变形、粗糙和颗粒异质性的组合导致刀片因剃须而变钝。用于锋利边缘或工具的钢通常具有马氏体微观结构、高碳化物含量和各种涂层,以表现出高硬度和耐磨性。然而,在切割人发、奶酪或土豆等柔软得多的材料时,它们实际上无法使用。尽管这是日常观察,但由于相互作用材料的结构复杂性及其共同变形的复杂边界条件,人们对潜在的物理微观机制知之甚少。为了解开这种复杂性,我们使用两种微机械测试装置进行了间断测试和原位电子显微镜切割实验。我们对这些发现进行了分析和数值研究,
更新日期:2020-08-06
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