Research On The Cutting Performance And Kinematic Synthesis Of The Rolling Shear Mechanism

In this paper,a novel and effective method for kinematic design of a planar mechanism based on the relative saddle point programming model is presented,under the support of the National Natural Science Foundation of China(51275067).The proposed method,which tends to promote the upgrade of the rolling shear length cutter machines,is applied to design a pure-rolling cutting mechanism based on the analysis of the shearing properties and motion characteristics of shear blade.By introducing the relative saddle point and the relaxation coefficient method,the relative saddle point programming model of the rigid body discrete multi-position synthesis is established.The dimensional synthesis of the linkage can be obtained by solving the model using proper optimization method.This provides the theoretical support for the independent research and development of the rolling shear equipment in our country.The ultimate goal of product design is to meet the needs of the operating requirement,especially in terms of performance requirements.Therefore,this paper begins with the research on the shearing performance and the factors of influence of the rolling shear mechanism.The finite element method is used to simulate the deformation,fracture and separation process of the steel plate at each stage of the shearing process.And a test system of the oblique cutting shears,which consists of the loading,demarcating and measuring modules,is designed to monitor the characteristics of the shearing force,deformation of the steel plate and displacement of the shear blade during cutting process.Then the cutting deformation and the factors of influences of the shearing performance are extracted by means of comparison and verification of the FEA simulation and experiment.Then,based on the analysis of the mechanical properties of the cutting process of the steel plate and the process action of the shearing process,the motion characteristics of upper shear blade with optimal cutting performance is obtained.Incorporation with the relative motion relations of the shear blades,the motion conditions of the pure-rolling kinematic synthesis of the rolling shear mechanism can be given as the known conditions.In accordance with the interrelation between the moving and fixed centrodes and the contacting line of the relative motion of two rigid bodies,the kinematical model of the continuous motion of a seven-bar linkage is established.Thus,the design requirements of the mechanism can be given incorporating with the dimensional parameters of the upper and lower shear blades.Considering the kinematic synthesis of the mechanism is a multi-peak and non-linear optimization problem,the dimensional synthesis problem of the rolling shear mechanism is transformed to the discrete multi-position synthesis problem of the rigid bodies for convenience of solving in this paper.The relationship between the arc track point and the saddle point,and the relationship between the two-link dyad trajectory point and the relative saddle point are established respectively by means of mechanism splitting,coordinate transformation and mechanism reversal.Then the problem of searching the hinge point and the lengths of the links can be transformed to saddle point planning and relative saddle point planning problems.The relaxation coefficient method is introduced to deal with the initial discrete position sets,which are transformed to a serial of floating discrete position sets.The discrete multi-position synthesis model of the relative saddle point programming method with relaxation coefficients,which can be solved directly,is established then.Finally,the optimal design example of a type of seven-bar linkage rolling shear mechanism with biaxial double eccentric cranks is presented.The optimal solution is obtained and the analysis results show that,the horizontal slipping and standard deviation of lowest moving points of the upper shear blade have been reduced by 80.1%and 78.0%,and the peak value of shear stress decreases by 29%,which indicate better cutting performance and long service life.The cutting performances of the new design are improved dramatically comparing with the initial design,which certified the effectiveness and practicability of the proposed method of this paper.