Study Of Calibration Models For Nano-indentation Instrument And Application In Definite Value Of Sapphire Standard Substance

Nano indentation instrument because of its high force and displacement resolution,high positioning accuracy,has been more and more widely used in the thin film new materials and MEMS micro devices and other fields.The tip of the instrument will wear out due to the use of indentation,and the calibrated nano indentation will have a significant effect on the test results,In this paper,the calibration model of nanometer indentation instrument is studied and a new calibration model is applied to calibrate the load factor,frame compliance and the tip area function of the indenter in the calibration of nanometer indentation.On the basis of calibration,Sapphire standard set value.After the completion of the value of the sapphire standard sample can be used as a nano indentation standard sample.To achieve the accuracy of non-nano indentation measurement results and the equivalent of comparable.Firstly,a calibration model was established for the load factor of the nanoindentation instrument.The nanoindentation test was carried out by selecting 20 force values between0.5 mN and 10 mN.Using the weighing module of the electromagnetic force balance and the indentation to achieve the load unloading process,measured on the balance of the actual loading force value,each loading process nano indentation instrument will give a load force value,for the two force values of the linear fitting,fitted out of the straight line is the load factor which is calibrated.After the calibration of the load factor,the indentation test was carried out.It was found that the hardness and elastic modulus of standard fused silica measured by the nanoindizer after the load factor calibration were more accurate than before calibration.Based on the completion of the load factor calibration,four different calibration methods were used to calibrate the frame compliance and tip area functions of the nanoindentation machine using the AFM direct method and the iterative method.After the calibration was completed,The results of the four methods to calibrate the frame compliance and area of the machine are applied to the indentation instrument.At the shallow indentation depth,the compliance and area functions obtained by calibration of the single-crystal tungsten and fused-silica iterative methods were more accurate than theother three calibration methods;When the depth of indentation is getting larger,the frame compliance and the area functions obtained by the four calibration methods are all close to the exact value.In the horizontal comparison,the calibration of frame compliance with the single-crystal tungsten is better than that of the fused silica.For the calibration of the area function,the AFM direct method is more accurate for the calibration of the instrument than the indirect method at the depth of the shallow pressure;When the depth is below 60 nm,the radius of curvature of the tip has a great influence on the accuracy of the test result.At the very shallow penetration depth,the needle tip with small radius of curvature will get more accurate test data.Finally,the calibrated load factor and the optimal selection calibration model which to calibrate the frame compliance and area function were used into the nanoindentation instrument.Using the TriboIndenter-900 nano indentation instrument,the uncertainty introduced by uniformity,stability,repeatability in the indentation text and the uncertainty introduction by the instrument will be evaluated.The total uncertainty of the synthesis and the extended uncertainty required for the setting are calculated.Then the flexural modulus and hardness values of the sapphire standard sample candidates were valued.