Study On Friction And Wear Characteristics Of TBM Disc Cutters’ Cuter Rings Based On The Similarity Theory

TBM is widely used in tunnel construction because of its advantages of fast tunneling speed and high comprehensive benefit.During TBM tunneling,the disc hob mounted on the cutter head(hereinafter referred to as the hob)contacts and breaks the rock,and often encounters extreme geological conditions such as "three high"(high confining pressure,high rock strength and high quartz content),and bears huge leap cutting load.This leads to serious hob wear failure and low rock breaking efficiency,which reduces the tunnelling efficiency of TBM and increases the construction cost.Therefore,prolonging the wear life of hob has become an urgent problem in TBM field.At present,in view of the existing hob friction and wear test apparatus and its test methods,which have much difference with the engineering practice,this paper has carried out based on the similarity principle of hob-rock for grinding experiment design and experimental verification,to study the different lithology,blade width,injection speed,cutting speed and medium environment factors such as the influence law of friction and wear mechanism of cutter ring were investigated.The main research work of this paper is as follows:(1)According to the similarity theory,the design parameters of the hob scale scale test platform were obtained;Based on the contact stress similarity of cutter rock,the size of cutter ring was designed,and the numerical simulation of cutter ring rock breaking by rolling was carried out by ABAQUS software.The similarity design scheme of hob material physical properties,cutting depth and speed of cutter ring sample,cutting mode of cutter ring sample is put forward.(1)Based on the similarity theory,the main parameters and dimensions affecting the knife-rock interaction are selected;Based on dimensional analysis method,the similarity design criterion of cutter rock grinding test bed is derived.Based on the similarity of the contact stress between the cutter and rock,the numerical simulation of rock breaking with different reduced size ratio of the hob ring was carried out with the help of the transient dynamics numerical simulation technology,and the optimal reduction ratio of the hob ring was determined to be 1:8.The numerical simulation results of rock breaking with the cutter ring samples under the condition of cutting depth of 0.6mm were analyzed in depth,and the change rules of rock breaking morphology,contact stress and rock breaking load of the cutter ring samples during rock breaking were determined,which provided a reference for the selection of appropriate hob parameters and cutting parameters for the subsequent cutter rock grinding test bed test.Based on the similarity of the relative movement mode of the cutter rock,the shaper was selected as the main body of the test bed,and the similarity scheme was put forward from the aspects of the material physical properties of the cutter ring,the cutting depth and the cutting speed of the cutter ring sample.(2)according to the identified hob cutter ring to reduce the size of the scale,the preparation of the similar to hob material physical and mechanical performance of the knife ring sample,further carry out the knife ring sample as opposed to a knife rock cutting ways of verification test,the test results show that: under the periodic rotary rolling cutting way,knife ring rolling rock sample of vertical force is relatively stable;In the rolling cutting mode of all grooves for many times,the vertical force decreases first in a straight line and then becomes stable.Through the analysis of the two cutting methods,the same groove multiple rolling cutting method is similar to the actual TBM hob cutting method.The relationship between slip rate and cutting depth of 17 inch hob ring and hob sample and the theoretical prediction model of wear amount of hob sample were established,and the theoretical value of slip rate was compared with the measured value.The results show that the slip rate of cutter ring sample is in the range of0.008～0.29.It is verified that there is sliding of the cutter ring sample in the cutter rock grinding test,and the variation law of the slip rate is consistent with the theoretical model.(3)A single factor test was carried out to study the effects of different lithologies,blade width,penetration velocity and cutting velocity on the wear quantity and macroscopic and microscopic wear morphology of the cutter ring samples.A method for analyzing the microwear of the cutter ring sample matching with the cutter rock grinding test bed was proposed.The practicability of measuring the microwear of the cutter hob by atomic absorption spectrometer was verified by experiments.The test results show that the wear amount of cutter ring samples does not change significantly with the increase of rock sample strength,but increases linearly with the increase of rolling distance,cutting speed and blade width,and increases exponentially with the increase of penetration speed.The wear removal mechanism of cutter ring samples with sandstone,rust stone and granite in the grinding process is mainly micro-cutting.The chemical composition of rock powder samples is basically the same as that of cutter ring samples,and the content of metal elements increases with the increase of rolling distance.(4)In order to study the friction and wear mechanism of cutter ring samples under geological conditions,the influence of Na Cl solution at different p H values and different concentrations on the corrosion resistance of cutter ring materials was discussed.In the wet and dry cutting environment,distilled water and Na Cl solution with different p H values were used in the wet cutting environment.The experimental results show that the above wear conditions have a significant effect on the wear behavior of the cutter ring samples.The wear of the cutter ring samples is significantly increased under the dry conditions compared with the wet conditions,but the Na Cl solution has little effect on the wear behavior of the cutter ring samples.In acidic and alkaline Na Cl solution conditions,the surface of the cutter rim samples appeared microscopic cutting and corrosion phenomena,which aggravated the quality loss of the cutter rim samples.