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第46卷第9期2010年5月

机械工程学报

JOURNAL OF MECHANICAL ENGINEERING

Vol.46 No.9

May 2010

DOI：10.3901/JME.2010.09.107

压头曲率半径对单晶硅径向纳动损伤的影响*

张赜文余家欣钱林茂

(西南交通大学牵引动力国家重点实验室成都 610031)

摘要：采用纳米压痕仪，研究了不同曲率半径的金刚石压头在单晶硅表面的径向纳动运行行为和损伤特征。结果表明，相对于尖端名义曲率半径，压头在一定压入深度下的等效曲率半径是决定材料纳动损伤的更有效参数。在50 mN的峰值载荷下，曲率半径20 μm的球形压头在单晶硅表面的径向纳动以弹性变形为主，未观察到明显的纳动损伤；尽管Berkovich压头尖端曲率半径仅为150 nm，但其在单晶硅表面产生的纳动损伤却比2 μm球形压头轻微。分析其原因，Berkovich压头的等效半锥角为70.32°，远大于2 μm球形压头的半锥角42.50°。因此，Berkovich压头在高载下具有更大的等效曲率半径，产生更轻微的纳动损伤。研究结果还表明，在纳动循环初期，2 μm球形压头和Berkovich压头在硅表面的接触刚度升高较快，单晶硅表面的加工硬化现象明显；而20 μm球形压头基本不引起硅的加工硬化。

关键词：纳动径向纳动纳米摩擦学单晶硅压头曲率半径

中图分类号：TH117

Effect of Curvature Radius of Indenter on the Radial Nanofretting

Damage of Monocrystal Silicon

ZHANG Zewen YU Jiaxin QIAN Linmao

(Traction Power State Key Laboratory, Southwest Jiaotong University, Chengdu 610031)

Abstract：A nanoindenter is adopted to study the radial nanofretting behaviors of diamond indenters of different curvature radii on the monocrystal silicon surface and the damage characteristic. It is found that compared to the tip nominal curvature radius, the equivalent curvature radius of indenter at a certain identation depth plays a much more important role in the nanofretting damage of material. Under a peak indentation load of 50 mN, no obvious damage is observed on Si<100> after 200 nanofretting cycles by 20 μm spherical indenter. Even with a relatively smaller curvature radius, 150 nm Berkovich indenter induces the weaker nanofretting damage than 2 μm spherical indenter on Si<100>. Analysis indicates that the equivalent half cone angle of Berkovich indenter is 70.32°，which is much larger than that of 2 μm spherical indenter, 42.50°. As the indentation depth is larger than 300 nm, the equivalent curvature radius of Berkovich indenter is larger than that of 2 μm spherical indenter. As a result, the contact area of Berkovich indenter will be larger and nanofretting damage will be weaker. The results also indicate that the contact stiffness of both 2 μm spherical indenter and Berkovich indenter increases sharply in the initial nanofretting cycles, which induces an obvious work-hardening process of material. However, no work-hardening process is found during the nanofretting by 20 μm spherical indenter.

Key words：Nanofretting Radial nanofretting Nanotribology Monocrystal silicon Curvature radius of indenter

0 前言

随着微机电系统(Micro electro-mechanical systems, MEMS)的快速发展，相关的纳米摩擦学问题已成为其实用化进程的巨大障碍[1-2]。针对MEMS

* 国家自然科学基金资助项目(90923017, 50625515, 50821063)。20090517收到初稿，20100111收到修改稿接触界面间往复运动幅值在纳米量级的特殊摩擦运动方式，我国学者率先提出了“纳动”的概念[3]。由于表面效应和尺寸效应的影响，纳动不应该是微动在纳米尺度的简单延伸，其损伤可能具有更强的隐蔽性，在运行规律和损伤机制等方面都可能表现出其独有特点[4-8]。

例如，QIAN等[4]通过对镍钛合金切向纳动的研究指出，由于纳动为单点接触，微动为多点接触，