Research Of High Frequency Micro-load Fatigue Testing Machine Drived By Piezoelectric Actuator

Since the Industrial revolution of 19 th century,various small scale devices in the fields of MEMS,biomedicine,new energy and bionics have been emerging,and these small scale devices have been subjected to alternating loads,and the fatigue damage is the main failure form.At present,the main way to deal with fatigue failure in China and abroad is to fatigue test the material,draw the fatigue curve,and calculate the fatigue life.Fatigue testing machine is an important tool for fatigue testing,the traditional fatigue testing machine has four kinds of driving modes: mechanical,pneumatic,electro-hydraulic servo and electro-magnetic resonance.Among them,mechanical and pneumatic fatigue tester loading frequency is low,electro-hydraulic servo type and electro-magnetic resonance type is the application of high frequency loading mode,but they have a loading load greater than 500 N and are expensive.Therefore,it is of great significance to design a kind of fatigue testing machine which is applied to the work under the condition of alternating micro-load.The paper is based on the National Natural Science Foundation Project named ?The structure design and performance research of piezoelectric high frequency fatigue testing machine?.A new type of piezoelectric fatigue tester(hereinafter referred to as ?piezoelectric micro-load fatigue machine? or ?fatigue machine?)is designed for a high-frequency,micro-load bearing force device using a piezoelectric ceramic as a driving element.It conducts mechanical structural design,dynamic analysis,modal analysis,prototyping and experimental testing.The main contents are as follows:1.After reading relevant literatures and consulting relevant monographs,this paper makes clear the classification,application and research status of traditional fatigue testing machines,and discusses the application of piezoelectric driving technology in the field of fatigue detection,and puts forward the significance and application prospect of this topic.2.The driving source-piezoelectric vibrator used in this paper is described in detail,and the parameters related to the performance evaluation of piezoelectric ceramics are clarified.The rectangular two-chip piezoelectric vibrator(piezoelectric vibrator)is determined as the driving element of the fatigue machine,and its fixing mode,wiring form and vibration mode are discussed.The piezoelectric oscillator is made and the impedance characteristic is analyzed,which lays a foundation for the design of the fatigue machine.3.The working principle of the fatigue machine is analyzed in detail,the design principle and function of each module of the fatigue machine preload adjustment module,the elastic swinging beam,the base and the guide pillar are defined,and the dimensions and material requirements of each part are completed,and the structure of the whole machine is designed.The micro-cantilever load sensor is selected for the load characteristics of this paper,The testing module of fatigue machine is designed to realize real-time monitoring,recording and processing of the applied alternating load.4.Using three-dimensional software SolidWorks assembly model,the modal simulation analysis is carried out by Ansys software,the mechanical structure of the fatigue machine is simplified,the dynamic model is established,and the dynamic differential equation is given.The amplitude magnification ratio of the vibration system and the theoretical expression of the dynamic load applied during the experiment are obtained,and the influencing factors and the changing laws are clarified.5.Actual processing and assembly of the fatigue machine were conducted to test the output displacement and output force of the fatigue machine,and the effect of the externally applied excitation frequency and magnitude on their impact was investigated;a test piece was made and the test piece was subjected to the cycle characteristics.For a tensile fatigue test of the specimens are R=0.1,the test data was processed and analyzed,and the SN curve was plotted.The fatigue characteristics of the specimen under symmetric cycles were obtained,which further verified the feasibility and accuracy of the fatigue machine.