摘要
Abstract
Objectives:Cf/SiC composite material is a kind of material difficult to be machined,and laser assisted grinding is a kind of composite processing method that can effectively improve the machining efficiency.Methods:In this work,a single diamond abrasive grain is used to carry out the quasi-static scratch experiment,the acoustic emission signals have been analyzed under different loads,and material removal behavior and scratch removal mechanism have been analyzed by combining with SEM.The experimental material is a cube Cf/SiC composite material with a side length of 10 mm.The material surface is polished to reduce the impact of surface defects and roughness.The material is divided into two groups,one of which uses a laser to create micro-grooves on the surface.Micro-grooves shall be kept away from holes.Laser process parameters are power 20 W,scanning times 50 times and scanning speed 200 mm/s.In the scratch test,the constant load is set as 2,4,and 6 N respectively,and the scratch length is set as 5 mm.In the experiment,data collector is used to collect acoustic emission signal and force signal respectively.Scratch patterns are photographed using different micro-grooves after the experiment.Results:The results show that a large amount of chips are distributed on both sides of the scratch after the material surface is scratched by the diamond indenter.When the scratch direction is parallel to the fiber direction,the material is mainly subject to brittle removal.The scratch edge is relatively smooth without obvious damage.There is a small amount of carbon fiber peeling at the scratch edge,leaving a semicircular groove on the SiC matrix.When the scratch direction is vertical to the fiber direction,the material is mainly removed by brittleness,and there is uneven fiber fracture at the scratch edge.In the case of laser-ablated grooves,the difference between the morphology of scratches and the absence of laser-ablated grooves is mainly concentrated near the grooves.When the indenter is scribed into the groove,the matrix at the edge of the groove is sunken,and the matrix at the inlet is torn in a triangular shape.Different acoustic emission signals are generated under different loads.At 2,4,and 6 N,the maximum AE signals produced by the grooveless surface are 2 167,1 814,and 2 883 Hz,respectively.The maximum AE signals generated by the grooved surface are 4 190,8 736,and 5 052 Hz,respectively.The greater the load,the greater the acoustic emission signal produced,and the greater the acoustic emission signal produced by the grooved surface,the more dense the acoustic emission signal.The micro-groove makes the force signal have obvious fluctuation.Conclusions:Based on the acoustic emission signal and scratch morphology,the material removal mechanism is obtained.The fibers in two directions are removed in different ways.Brittleness removal is the main method for the whole material,tensile fracture is the main method for the fibers in parallel direction,and shear fracture and bending fracture are the main methods for the fibers in vertical direction.The removal mechanism of materials varies significantly with fibers in different directions,and laser prefabricated micro-grooves have a certain impact on the removal mechanism of materials.Laser prefabricated micro-grooves cause more damage to the indenter under the same load,making the material easier to remove.关键词
Cf/SiC/单颗磨粒划擦/声发射信号/激光织构/材料去除机理Key words
Cf/SiC/single grit scratching/acoustic emission signal/laser texturing/material removal mechanism分类
机械制造
