Research On Micro-nano Hardness Measurement Based On Indentation Work

Along with the widespread availability of micro-components and thin-film material, the measurement and evaluation of micro-components'surfacial mechanical property must be paid attention to. Hardness is a simple and efficient means in material's mechanical property measurement. However, hardness measuring results of material's micro-nano surface shows indentation size effect, what means hardness value gets larger as the indentation depth or load gets smaller. And different hardness evaluating methods get discrete calculating results with each other, so the real hardness value of material's micro-nano suface is impossible to be got. Then, research on micro-nano hardness measurement technique and theory makes sense and has use value.In this paper, a kind of micro-nano hardness measuring approach based on indentation work is proposed, and the prototype instrument is developed. Material micro-nano hardness measurement system based on indentation work can gain the load-depth curve and indentation 3D image, which can provide theoretic foundation and experimental means for getting material's micro-nano real hardness and understanding the sources of indentation size effect.The finite element simulation of aluminum sample is carried on by using finite simulation software, and the finite element simulation model is established. By using the simulation results of load-depth curve and indentation 3D image, different evaluating methods are used to obtain and analyze the sample's hardness value. A kind of hardness measuring approach based on indentation work is brought forward, and it is considered that the hardness value which is equal to the whole volume of plastic deformation divided by the plastic work gained from stepped fit and integration of load-depth curve, can reflect the real hardness of material and help to establish the relationship between microcosmic hardness and macroscopical hardness.In response to the demands of micro-nano hardness measuring approach based on indentation work, the probe device which has load drive and displacement measurement functions is designed. This device has an electro-magnetic force drive, which can meet the no mechanical friction, small size, high resolution and large force demands by optimizing the structure parameters. Capacitance sensor, which can meet the demands of small range and high resolution, is chosen to measure the displacement of the indenter. The force drive and displacement measurement controller is designed technically, and the environment disturbs are considered adequately, so that satisfactory experimental results are obtained. Then a kind of micro-nano superficial hardness measurement system composed of indentation preparation and image scan functions is proposed, and the prototype instrument is developed. This measurement system can obtain load-depth curve and indentation 3D image, which provide more information for getting material's micro-hardness value by using some different hardness calculating methods flexibly.On the basis of this micro-nano hardness measurement system, the load-depth curves and indentation 3D image with different depth of single crystal aluminum and single crystal silicon are obtained, then after processing these data by math operation software, some different hardness evaluating methods are used to obtain and analyze the hardness value. It is validated that the hardness value got from the calculating method on the basis of indentation work changes evenly with the minishing of indentation size, and can reflect the real hardness of material better than other measuring methods. The development of micro-nano hardness measurement system based on indentation work provides foundation for analyzing and studying the sources of indentation size effect. According to the experimental results, some theoretic models are analyzed, and a new HAV model is proposed based on energy balance approach, which can explain the indentation size effect well.Hardness measurement based on indentation work minishes influence of indentation size effect and can achieve the real hardness value of material in micro-nano size, which provides technical support for measuring material's micro-mechanical property and assurance for reliably using of micro-components.