Multi-section strip element method for surface shape prediction and control of variable thickness rolling
Longitudinal variable thickness rolling is an effective technical means to achieve light weight and low loss of rolled products.Different from conventional rolling,the rolling gap changes continuously during longitudinal vari-able thickness rolling,resulting in the change of rolling force,friction force,length of deformation zone and other important rolling parameters,forming an unstable rolling state,which makes it difficult to accurately predict the plane shape of rolled parts.In order to solve the problem of plane shape prediction in the rolling process of variable thickness,a multi-stage steady-state processing method is proposed.The variable thickness rolling area is divided into several rolling stages along the longitudinal,and each stage is approximately stable rolling state,so that the plane shape prediction problem of variable thickness rolling is transformed into the plane shape prediction problem of multi-stage constant thickness rolling.Each stable rolling stage is divided into several strip elements along the trans-verse.According to the bar variation method,the transverse displacement of each strip element line is listed as the undetermined parameter in the deformation power function in the deformation zone.According to the principle of energy minimization and variational method,the transverse displacement function of rolling outlet of each element can be calculated.Then,the transverse displacement of the strip elements line after rolling can be obtained by the whole variational calculation of each steady rolling stage.It is proposed that the midpoint of the edge element is the feature point of the plane shape,and the feature points of the edge element are arranged according to the division order of the steady rolling stage,which can form the feature series of the plane shape of the rolled piece.Achieve the prediction of the edge shape of the rolled piece.Based on the principle of metal volume invariance,the longitudinal extension of each element after rolling can be calculated according to the width and thickness of each element.The longitudinal extension of each stage elements are arranged in order and summed to obtain the longitudinal length of each equivalent element.According to the metal flow characteristics in the forward area and backward area of the deformation zone,the longitudinal length distribution of the rolled strip element after variable thickness rolling is transformed into the feature series of the end plane shape,which can predict the end plane shape of the rolled piece.The correctness and feasibility of this method are verified by experiments.
rollingvariable thicknessplane shapestrip element variation methodlongitudinal length difference
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