Non-Uniform Sliding Behavior Of Contact Friction Sliding Surface And Spatial Evolution Characteristics Of Stick-Slip

The stick-slip instability of contact friction is directly related to many contact slip phenomena in nature and practical engineering,such as earthquake and machinery.The nonuniform sliding evolution characteristics of sliding surfaces during the initiation and development of stick-slip instability is a key and fundamental problem to understand stickslip instability.At present,the research of stick-slip instability mainly focuses on the evolution process of the global average quantity,but the evolution characteristics of the sliding surface are not fully understood.In this article,a test platform will be designed and built to conduct detailed experimental observation on the sliding evolution characteristics of the sliding surface,providing support and direct basis for understanding the process and principle of stick-slip.The experimental methods and devices for monitoring the sliding evolution process of the sliding surface are designed and built.The sliding process of PMMA material was systematically observed and analyzed by DIC numerical speckle correlation technique.The direct observation of the sliding evolution process of the fault contact surface is realized.Through the comparative analysis of the evolution characteristics of the key parameters of force,displacement,velocity and acceleration under different loading speeds,the detailed development process and characteristics of the instability sliding are analyzed.The spatial non-uniform characteristics of sliding parameter time history are analyzed in detail,and the spatial distribution characteristics of sliding displacement,sliding velocity and sliding acceleration are clarified.The experiments illustrate the spatial development characteristics of pre-slip and the spatial development process of the instability process,and reveal the spatial evolution characteristics of the stick-slip start-up and the spatial non-uniform distribution of the instability.Based on the design of each component measurement,the loading force and friction force are decouple,thus realizing the detailed analysis of the whole sliding and instability process.The development characteristics of the whole mechanical process from static contact to pre-slip,destabilizing transition,destabilizing sliding development,and then back to static friction at the end of the destabilizing sliding are analyzed.The evolution characteristics of sliding and deformation of the contact surface after multiple stick-slip instability are revealed.The main research results are as follows:The spatial and temporal distribution of the displacement of the contact friction sliding surface is different in the stick-slip process.During the stick-slip instability sliding process of the contact surface,the starting time is different at different positions,and the phenomenon of accelerating and decelerating sliding will occur simultaneously,which is a non-uniform starting process.The stick-slip evolution characteristics are different at different locations of the contact surface.The displacement,velocity and acceleration of different positions vary at the same time,and the sliding state of different positions on the fault slip surface is different.In the stick-slip process,the deformation of the contact friction sliding surface is characterized by non-uniform evolution.The positive strain region of the strain field is distributed horizontally along the sliding direction of the test block in a gully shape on the contact surface.The negative strain zone and the positive strain zone mainly show a striplike staggered distribution.With the development of the stick-slip process,the difference between the positive strain and the negative strain distribution is gradually obvious.