A 2-DOF Testing Device For Material Micro-mechanics Properties

With the development of science and technology,high-tech products become more and more accurate,integral and miniature.Microstructure and nanostructure are widely used in MEMS/NEMS,information storage,precision optical lens,IC, composite film and novel semiconductor.Because the corresponding testing technology of material micromechanics properties is not mature and there are lack of fundamental data about micro-structure's mechanics properties,it hasn't been establish that an effective design criteria about micro-mechanical reliability.This situation has seriously hampered the design and development on MEMS/NEMS, micro-components,information storage and so on.Therefore,the testing technology of material micro-mechanics properties is becoming the research priorities in the world academia and industry.Because of the piezoelectric elements' advantages such as small bulk,large generated force,high frequency response and high resolution of displacement,and flexible hinge's advantage such as no mechanical friction,gapless,compact structure,quick response and high resolution,this paper put forward a 2-DOF testing device for material micromechanics properties based on piezoelectric driving.First,the basic characteristics of flexible hinge are analyzed in this paper.It is established that the spatial mechanics model of flexible hinge on the situation of bending load.It is discussed that the deformation under the situation of pure torsion and the spatial mechanics model of flexible hinge is made out.This paper analyze the basic characteristics of piezoelectric material and the electromechanical coupling of piezoelectric stack,give a piezoelectric equation and derive the output characteristics of piezoelectric stack among driving voltage, output force and output displacement..Subsequently,utilizing the flexible hinge theory,piezoelectric straight drive theory and designing thought of monomer with more multiple freedoms,to design a 2-DOF testing device for material micromechanics properties.The device can conduct multiscale non-invasive measurement to sample and consists of indentation unit,transmission unit in scratch direction,self-detection unit of deformation-load,preload unit and piezoelectric stack.In the testing,the piezoelectric stack in indentation unit reacts firstly and pushes the indentation unit contact with sample.The imposing load value is measured by multiplying displacement with stiffness of self-detection unit of deformation-load and indentation depth is the difference of indenter's displacement and displacement of self-detection unit of deformation-load.If the piezoelectric stack in self-detection unit of deformation-load works,the device will start scratching.This paper puts forward a method of self-detection of deformation-load and establishes the theoretical model of self-detection unit of deformation-load by means of designing and analyzing the each unit of the device.This paper analyzes the spatial mechanics model of self-detection unit of deformation-load and carries on modal analysis of subject structure in software ANSYS.The results show that the natural frequency of the subject structure is higher than working frequency,there is no resonance.Last the paper establishes the kinetics model of subject structure.The experimental researches contain resolution,loading capacity,the stiffness of self-detection unit of deformation-load,output characteristics of testing device in open loop.Experimental results indicate that the resolution of indentation unit is 20nm,the biggest load is 201mN,the stiffness of self-detection unit of deformation-load is 15.955KN/m,the maximum stroke of indentation unit is 13.24μm and the maximum stroke of scratching unit is 16.5μm.The test device has a good repeatability during loading and transmission unit in scratch direction maintains good linear.The thesis analyzes the experimental error of testing device and puts forward some measures to reduce the error.Last the paper make a scratching experiment on precision wafer grinder with the testing device that has been adjusted well and observe the scratching under the confocal laser scanning microscopy.Testing indicate that the testing device has a good precision and can conduct the scratching experiment.The 2-DOF testing device for material micro-mechanical properties uses the thought of monomer with more multiple freedom,can conduct multiscale non-invasive measurement to sample.The testing device is so miniature that the device can be used in precision instrument to realize online observation,such as SEM and TEM.The experimental analyses indicate that testing device possesses good comprehensive properties and resolution;the stroke and loading capacity achieve the application requirements.The testing device will provide a kind of effective instrument for testing material micromechanics properties if we can establish an experimental foundation theory matching with testing device.