| With the development of science and technology,more and more MEMS devices and biological devices are subjected to small load alternating stress.Its main failure form is fatigue failure.At present,the most effective means to prevent fatigue failure is fatigue testing.The fatigue testing machine is an important tool for testing the mechanical properties of materialsand at the same time,our demands for it is gradually improving.Compared to the traditional electromagnetic and electro hydraulic fatigue testing machine,piezoelectric drive fatigue testing machineis more suitable for fatigue testing of specimen which is subjected to high frequency force and small loadas it has such advantageas small volume,high response speed,high precision and no electromagnetic interference.In order to solve small load fatigue test problem such as load acting on the specimen is less than gravity clamp,on the basis of the research on piezoelectric driving fatigue testing machine which has been carried out in the project team,this paper present a kind of piezoelectric driven horizontal small load high frequency fatigue testing machine.Compared with the traditional vertical fatigue testing machine,its load occurs only in the horizontal direction,avoiding the effect of gravity of the clamping apparatus on the load.This method greatly improves the accuracy of detection and makes up for the shortage of traditional testing machine.The main contents of this paper is as follows:1.Through the relevant literature reading and Monographs review,I understand the principle and research status of the traditional fatigue testing machine,the research history and current situation of the research on the piezoelectric driving technology in the field of fatigue detection,and the content and significance of this study are clarified.2.Piezoelectric vibrator which is the core driving part is analyzed in detail during this paper.This paper elaborate the piezoelectric effect from microcosmic nature,the performance evaluation parameters of piezoelectric ceramics are defined and the fabrication process and the driving mechanism of piezoelectric vibrator is introduced.Completing production of two types of circular bimorph piezoelectric vibrator and impedance and center point displacements were tested by experiment which provides the basis for the design of the prototype.3.In this paper,the working principle of the piezoelectric driven horizontal small load fatigue testing machine is analyzed and the structural design of the whole machine which include pre load loading module,Load amplifier module,frame,clamping apparatus etc is carried out.According to the proposed size parameters,the prototype is assembled in the three-dimensional design software and the modal analysis is carried out in ANSYS.The results show that the fourth order mode is the mode we need,and its natural frequency is 218.3Hz.4.The fatigue detection software system based on LabVIEW is designed,and the force reading of the sensor is realized by calling the dynamic link library.Many functions such as interface switching,triggering,parameter presetting,information archiving,numerical storage,load cycle display,waveform display,system time display and so on has been realized.5.The dynamic model of the system is established.The differential equations of motion are listed according to Newton's second law and the steady-state response of the equation is solved.At the same time,the expression of natural frequency and phase angle of the system is obtained,and the influence factors are analyzed.The amplitude frequency characteristic curve and phase frequency characteristic curve are plotted respectively,and many conclusions are obtained.In this paper,the numerical expression of the relevant part is given.The actual processing and assembly of prototype has been completed and the performance test is also carried out.The standard specimen was made with H62 brass strip,and the tensile fatigue test was carried out.The experimental results verify the reliability and accuracy of the device. |
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