Design Examination And Testing Verification Of Multi-functional Vibration Contact Tester

It is well known that there are many contact pairs in mechanical equipment,transportation and pantograph-catenary systems,such as the contact interfaces at machine tool guideway,gear teeth,wheel-rail pairs,pantograph-catenary pair,bearing components,etc.Increasingly higher requirements for the service performance of components have been put forward due to the rapid development of high-tech fields.Contact systems often serve under multi-direction impacts,cyclic load and other multi-coupling conditions.The contact stress field and failure mode of materials are much more complicated than those of quasi-static simplified model.Existing testers,however,rely fewer parameters and run for single contact geometry under impact or vibration conditions,it is difficult to use them to support researches on the behaviors of material under multi-condition coupling situations.Hence,it is necessary to develop a dynamic contact tester which integrates contact conditions with rotation and bidirectional vibrations capable of supporting the work on the researches of dynamic contact experiment,analysis of dynamic contact interface tribological behavior,establishment of scientific dynamic contact theories,design and optimization of dynamically loaded components,and the development of new materials and surface treatment processes.The research and design work reported in this thesis aim at developing a multi-functional vibration tester(MFV tester),containing a multifunctional sample stage,a set of dynamic loading mechanisms,an auto measurement and signal acquisition system and systematic examinations of this new instrument.The dynamic contact test of the tester was conducted by using three ball-on-flat and three ball-on-cone sliding contact pairs.The characteristics of the worn ball surfaces were analyzed with an optical microscope,SEM,and a white-light interferometer.The wear characteristics for two kinds of contact geometry specimens under different vibration conditions were investigated.The wear trend of the contact surface under different conditions was qualitatively analyzed from the worn surface morphology.The wear characteristics were quantitatively analyzed from the wear-scar shape,size,area,spherical cap height and volume.The main work and results are as follows:(1)A comprehensive examination of the MFV tester was conducted.The testing run results indicate that the test signals in real time can be collected by the sensors and signal analyzer;the spindle speed can reach all the major setting values and maintain good stability;the vertical independent loading module can provide the designed dynamic loading function;the vibration system can be effectively controlled by the function generator and power amplifier;The dynamic examinations of the whole system were conducted by using three ball-on-flat sliding contact pair;the method is proposed to explore of dynamic load fluctuation of the system by finishing the lower specimen installation disc with a cutting tool.(2)The influence of vibration direction under oil lubrication on the dynamic contact tribological characteristics of three ball-on-flat sliding contact samples based on GCr15 was investigated.The results indicated that the vibration load significantly changes the wear characteristics of contact interface in four different loading conditions(vertical loading,vertical loading coupled with vertical vibration,vertical loading coupled with transverse vibration,vertical loading coupled with bidirectional vibration).The degree of wear of steel balls under the vertical vibration condition is the most serious,that is,the wear volume is the largest,while the wear volume under bidirectional vibration is the smallest,which indicates that bidirectional vibration could help reduce the wear.(3)The influence of vibration direction under oil lubrication on dynamic contact tribological characteristics was investigated using three ball-on-cone sliding contact pair based on bearing steel GCr15.The results indicate that the wear condition of steel ball surface after applying vibration load is significantly different from that under vertical loading condition in four different load conditions(vertical loading,vertical loading coupled with vertical vibration,vertical loading coupled with transverse vibration,vertical loading coupled with bidirectional vibration).By comparing the vertical loading conditions with the vibration conditions,it is found that the all vibration conditions increase the wear of the steel ball surfaces.The degree of wear of steel balls is the most serious under the transverse vibration,and the wear volume under the bidirectional vibration is lower than that under the single vibration modes.