Expression And Evaluation Of The Distribution Characteristics Of Undeformed Chip Thickness In The Grinding Process

The material removal in grinding process is realized by the interactions between a large number of cutting grains and workpiece.High-efficiency and high-quality grinding requires understanding and mastering the mechanisms of abrasive micro-interactions with the workpiece to actively control the process.However,at present,the conventional model for maximum undeformed chip thickness of single grain,which are based on an idealized grinding wheel situation,has always been used to evaluate and regulate the grinding process by researchers.In modeling,such as assumption was made that the abrasive grains uniformly distributed over the wheel surface,that is,the abrasive grains have equal spacing and protrude uniformly.As a result of this assumption,all grains in the grinding contact zone would take part in chip formation and have an identical chip thickness.In the actual surface situation of grinding wheel,the abrasive grains have different size and spacing and do not protrude uniformly,which causes the large variations in the interference situation between the grains and workpiece and in the cut depth of each single grain.The undeformed chip thicknesses produced by single grains are distributed over an interval and are not single valued.Obviously,it is not appropriate to use the conventional undeformed chip thickness model based on an idealized grinding wheel situation to evaluate and regulate the actual grinding process.Based on the analysis,a new research idea has been proposed in the paper.The distributions of undeformed chip thickness were systematically studied through the combination methods of simulation and experiment,and were used to evaluate and regulate the grinding process.The main research contents of this thesis can be summarized as follows:?1?A model for the distribution of undeformed chip thickness has been established,and the validity of the model has been verified by experiments.Based on the established model,the mean value(h_mean)of the undeformed chip thickness distribution considering the practical grain distribution and grain protrusion conditions was compared with the value of h_max calculated by using the conventional grinding theoretical model for maximum undeformed chip thickness of single grain.It is found from the comparison that the conventional model for maximum undeformed chip thickness(h_max)of single grain is only a special case of the universal model established in this paper.The prerequisite to satisfy the special case is such as assumption that the grains uniformly distributed over the wheel surface,it is impossible in practical processing.This is also a proof of the significances of the research on the distribution of undeformed chip thickness.?2?The study on the distribution characteristics of abrasive grains with different interference states in grinding zone has been conducted.The results show that the quantity distribution of abrasive grains in various interference states?sliding,plowing,cutting?can be extracted from the undeformed chip thickness distribution by combining the material properties of workpiece and the depth of abrasive grain cutting into workpiece,which provides a theoretical basis for the analysis of the mapping relationship between the distribution characteristics of undeformed chip thickness and the specific grinding energy.?3?The study on the influences of surface conditions of grinding wheel and grinding parameters on the distribution characteristics of undeformed chip thickness has been conducted.The index system for the description of distribution characteristics of undeformed chip thickness has been constructed,and the parametric expression of distribution characteristics of undeformed chip thickness has been realized;the influences of surface condition of grinding wheel and grinding parameters on the distribution characteristics of undeformed chip thickness has been revealed,and the theoretical basis for regulation of the undeformed chip thickness distribution can be provided.The research results show that the disdribution charateristics of undeformed chip thickness can be actively controlled by the radial dressing of grinding wheel and the adjusting of the arrange distance of the grains in wheel circumferential direction and the optimizing of grinding parameter.?4?The research on the mapping relations between distribution characteristics of undeformed chip thickness and processing results has been conducted.The results show that the distribution characteristics of undeformed chip thickness have constraint effects on the processing results.Smaller undeformed chip thickness of single grains,lower distribution mean,more even and concentrated distribution characteristics of undeformed chip thickness can help to form a smooth workpiece surface and achieve a better surface quality.More concentration of active grains in the distribution interval with larger undeformed chip thickness can reduce proportion of the sliding grains and plowing grains and increase the proportion of cutting grains,which can reduce the specific grinding energy.?5?The above research results have been used to realize the active design of grinding wheel for meeting the double constraints of surface roughness and specific grinding energy.The design method and procedure have been proposed for inverse determination of surface condition parameters and grinding parameters from the desired grinding results.The effects of optimal design have been verified by an example.