Complete Machine Control And Application Expansion Of Nanoindentation Test Instrument

The nanoindentation test technique has become one of the mainstream methods for the characterization of the micromechanical properties of materials due to its simplicity of specimen preparation,high measurement resolution,ease of operation and rich test content.A number of foreign companies have successfully developed commercial nanoindentation testers,but China has not yet fully mastered the technology,resulting in domestic researchers relying on foreign instruments for relevant scientific research and applications.Foreign indentation instruments are not only expensive and less capable of being applied,but are also at risk of being embargoed in the context of a growing embargo on high-end technology in the US and other Western countries.Therefore,it is necessary to develop a nanoindentation test instrument that is technologically autonomous and can support the expansion of multifunctional applications.Based on a comprehensive analysis of the progress in the development and application of nanoindentation testing instruments at home and abroad,the following work has been carried out in this thesis.(1)The Oliver-Pharr classical nanoindentation test data analysis method was reviewed;the flexibility calculation method for flexible hinges was derived;the Oliver-Pharr proposed self-calibration method for instrument frame flexibility and indenter area function and its advantages and disadvantages were analyzed,and a new method for indenter area function calibration was proposed based on the reference mapping method,and its feasibility was verified through experiments.(2)The design and integration of the mechanical structure of the nanoindentation tester,including the three-degree-of-freedom macro-motion module,precision drive module and precision detection module,was carried out;the structural strength of the flexible mechanism was verified through finite element simulation analysis;the sweep test of the whole machine was carried out under the test environment;the indentation test process under the hybrid drive mode of stepper motor and direct-acting piezoelectric driver was proposed,and the control system of the whole machine was built on this basis;the control program of the nanoindentation tester was developed based on the PID closed-loop control algorithm.(3)The analysis of the resolution,noise and linearity test of the force sensing and displacement sensor in the instrument was carried out,and the results show that the noise of the force sensor is less than 25μN and the resolution is less than 10μN,and the noise of the displacement sensor is less than 1.8 nm and the resolution is less than1 nm.The resolution is less than 1nm.In order to verify the closed-loop control characteristics of the program,closed-loop force,closed-loop displacement and cyclic indentation tests on fused silica surfaces were carried out;methods to reduce assembly errors and improve the regularity of the load-displacement curve were analyzed and proposed;based on the reference mapping method and the new method of calibrating the indenter area function proposed in this paper,the calibration of displacement,frame flexibility and indenter area function was carried out;several indentation tests with different loads were carried out on the surface of standard fused silica samples,and the results showed that the test instrument has good repeatability and testing accuracy.(4)The control program of a home-made nanoindentation test apparatus was improved,a rapid indentation processing method was proposed,and rapid indentation tests were carried out under different indentation heads,sample materials and maximum load conditions;furthermore,a process for processing microarray structures on the material surface was proposed,and the feasibility and applicability of the process was verified experimentally;using this method,a 40 x 40 indentation array was processed on the surface of 1015 Al,and the functional properties of the indentation microarray structure in regulating the reflective properties of the material surface were tested experimentally.(5)Based on the nanoindentation method,a measurement method for the stiffness of the flexible mechanism was proposed,and the measurement principle of the method was elucidated;based on this method,the stiffness of three typical flexible mechanisms was measured experimentally,and the feasibility of the method was verified by comparing the results with the finite element simulation analysis and the theoretical calculation of the flexibility matrix;the analysis showed that the error of the measurement method was mainly caused by the paraffin between the sample and the flexible mechanism,while The greater the stiffness of the smoothing mechanism,the smaller the relative measurement error.