Theoretical And Experimental Study On Straightening Of Workpiecewith Irregular Section Based On Curvature Description

The straightness of shaft parts is an important parameter to ensure their processing,assembly and service performance.However,bending deformation often occurs due to external force,internal force and temperature.Therefore,straightening is an unavoidable process.The current domestic straightening process still has a big gap with the developed countries in terms of straightening efficiency and straightness accuracy and so on.In order to improve the advancement of current domestic straightening equipment,this paper establishes straightening models for various profiled workpieces based on curvature description,and experiments are carried out to verify the proposed model,which provides a theoretical basis for the realization of intelligent precision straightening.At the same time,the curvature description model provides a new research idea for the precise straightening of other profiled sections,and the related research can be further enriched and expanded on this basis.The research contents of this paper are as follows:1.Based on elastic-plastic theory,the law of pressure straightening process is analyzed.The expressions of bending moments are established from two perspectives of internal stress and external deformation,and the feasibility of curvature straightening model is theoretically demonstrated.Based on the elastic-plastic double-linear stress-strain model of materials,curvature calibration models of shaft parts with circular section,tubular section,side-cut D-section and flat-cut D-section are established respectively after dimensionless treatment,and the relationship between flattening rate and residual curvature of tubular section workpiece is emphatically discussed.The curvature straightening model breaks through the limitations of the traditional pressure straightening process and reveals the essential laws in the process of straightening the three-point bend.2.Aiming at the calculation of mechanical parameters in the process of straightening,the analytical relationship between bending curvature,deformation and bending moment is established and the numerical calculation of different pressure points is carried out.Meanwhile,the analytical relationship between dimensionless curvature and dimensionless pressure is established,and the workpieces with different pressure point position,pressure and section shape are numerically calculated.The general rules of mechanical parameters during the three-point bending straightening process are summarized.In the process of straightening,the relevant mechanical parameters can be calculated and predicted,the overpressure crack and fracture in the straightening process can be reduced,and the scrap rate can be reduced.3.According to the functional requirements of the experiment,the experimental testing system was designed and built.The structure design,hardware selection,measurement and control program development and electromagnetic shielding were carried out.At the same time,curvature conversion methods are studied and evaluated from three points of view: three-point circle,three-point parabola and fitting parabola.It lays the hardware foundation and method foundation for the experimental verification of curvature straightening model.4.Two experimental schemes of one-way repeated bending and reverse bending straightening are designed respectively.Experiments are carried out on workpieces of different materials and cross-section types,and data calibration,denoising and regression analysis are carried out to verify the proposed curvature straightening model.At last,two practical GUI interfaces are developed based on MATLAB software to calculate straightening process parameters and straightening mechanics parameters.The straightening model can be directly applied to existing equipment,which can improve straightening efficiency and accuracy without increasing cost.