Research On Forming Mechanism And Influence Law Of Stagnant Region In Mechanical Ruling

Mechanical ruling technology is widely used in the processing and manufacturing of micro structures because of its low cost,green,large area and high-precision processing.The processing quality of the microstructure determines its performance,so how to manufacture high-quality microstructures has become an urgent problem in the field of manufacturing science.There will be a stagnant region in the formed groove surface in mechanical ruling with a diamond wedge scratching tool.The boundary between the plastic flow region and the stagnant region is clear,and the stagnant region will affect the forming groove quality and tool wear.Meanwhile,there are few related researches on stagnant region in mechanical ruling now.Therefore,research on the forming mechanism and influence law of the stagnant region in mechanical ruling is of great significance for perfecting mechanical ruling forming theory,guiding mechanical ruling technology,and improving the quality of mechanical ruling.In this paper,a theoretical model of mechanical characterization of stagnant region is established based on the characterization of plastic flow characteristics and stagnant phenomenon of materials,and then the formation mechanism of stagnant region is revealed by combining its formation process and characteristics.Base on the theoretical model of the stagnant region and the ruling experiment,the influence of the processing parameters on the stagnant region is studied.According to the characteristics of the stagnant region,the influence of the stagnant region on the material processing method,the quality of the groove shape and the tool wear is studied.The main research contents are as follows:Research on the plastic flow characteristics of material in mechanical ruling has been carried out in this paper.First,a mathematical model of the unit plastic flow vector was established based on the characterization of the three-dimensional force balance equation and the vector method,and further deduced the mathematical expressions of the negative working rake angle and chip flow angle of the ruling tool,so as to obtain the mathematical relationship among the unit plastic flow vector,the negative working rake angle,the chip flow angle,the normal vector of the contact surface and the equivalent cutting edge.Then,the mechanical ruling experiment was carried out to investigate the change law of the projection angle of the unit plastic flow vector and the chip angle under the influence of the processing parameters,the applicability of the unit plastic flow vector and the chip angle was analyzed as well.Investigation on the formation mechanism of the stagnant region has also been conducted.First of all,based on the contact friction zoning mechanism and slip line field theory,the theoretical calculation model of geometric parameters of mechanical scratch stagnant region was established to obtain the mathematical relationship among the length of the stagnant region of the forming groove surface l B-sg,the length of the stagnant region l V-sg in top view,the ratio of the stagant region to the groove length (?)lsg,the length of the stagnant region in the plastic flow plane lp-sg and the transformation parameters.Then,the forming process and characteristics of the stagnant region were studied through the orthogonal cutting simulation with the negative rake angle tool in the plastic flow plane and the mechanical ruling experiment.The results show that the stagnant region is the plastic extrusion deformation region formed by the over-extrusion and restriction of the negative rake face of the ruling tool and the internal friction effect of the ruling material.Therefore,the microstructure of the material in the stagnant region becomes finer and dense,and the boundary has the characteristics of high frequency declining.Both the peak hardness and the depth of the hardened layer of the stagnant region are smaller than those of the plastic flow region,and the surface roughness of the stagnant region is significantly better than the plastic flow region.The influence of the processing parameters on the stagnant region is studied as well.Firstly,combining the mathematical model of unit plastic flow vector,the theoretical calculation model of the geometric parameters of the mechanical ruling stagnation zone and the simulation of mechanical ruling,the influence of the processing parameters on the theoretical value of the geometric parameters of the stagnation zone is studied.The results show that the lp-sg is the dominant influencing factor of the geometric parameters l B-sg,l V-sg,and (?)lsg of the stagnant region of the forming groove,and the hydrostatic pressure PI/k at point I in the plastic flow plane is the dominant influencing factor of the lp-sg when the geometry parameters of the ruling tool,the rotation angle around the Y axis of the ruling tool,the ruling speed,the friction coefficient and the ruling material changed.Then,the change law of geometric parameters of the stagnant region was analyzed through the experiment,and the processing parameters which can adjust and control in the stagnant region are determined.Based on the critical criterion of cutting and plowing extrusion processing,namely critical negative rake angle,the influence of stagnant region on material processing mode is studied.First,based on the characteristics of the stagnant region,the minimum energy approach and the infinite shear strain approach were used to establish the critical negative rake angle theoretical model,and the mathematical relationship between the critical negative rake angle and the adhesive friction angle was determined.Secondly,through the orthogonal cutting simulation of the negative rake angle tool,the influence of the processing parameters on the shear angle and the critical negative rake angle was studied.Combined with the theoretical model,the effect of the stagnant region on the critical negative rake angle is studied,which determined that the stagnant region is the main cause of the deviation between the critical negative rake angle and the effective critical negative rake angle.The adhesion friction coefficient is proportional to the stagnant region,which further reveals the adhesion internal friction forming mechanism of the stagnant region.Finally,the influence of material processing methods on surface quality was studied through the orthogonal cutting experiments with negative rake angle tools.A study on the effect of the stagnant region on the groove quality and the tool wear is carried out.First,based on the characteristics of the stagnant region and the nonlinear deformation of the groove surface,the critical mechanical criterion and the theoretical calculation model of the critical point were established.Combined with the ruling simulation,the influence of the length of the back groove stagnant region on the critical point of the front groove nonlinear deformation under the influence of the engraving processing parameters is studied,and the range of the engraving processing parameters which can inhibit the groove nonlinear deformation is determined,which provides the basis for the regulation of the groove nonlinear deformation.Then,through the ruling tool wear simulation,the wear process of the ruling tool and the influence of the ruling processing parameters on the extreme value of the ruling tool wear depth were studied.Combined with the study of the influence of the stagnant region and the EDS experimental analysis of the formed groove surface material,the adhesive wear mechanism of the ruling tool is revealed.