Study On Basic Straightening Theory And Straightening Model Of Extreme Strip

Straightening machine is an important equipment to perfect the plate shape,decrease the irregularity,enhance the plate mechanical properties,eliminate the internal residual stress.The straightening model as the theoretical basis of straightening has a great optimization in straightening process.Nevertheless,it is extremely hard to set the straightening population parameters and the straightening effect is unproductive in the current straightening process of extreme thickness plates.On the one hand,there are some problems in the theoretical model of straightening is a difficult nut to crack.During the stretch-bending straightening method of extremely thin strip,tension bending is the major deformation modality.However,there are few researches on relevant theories which are too idealized.The results between the straightening theory and the actual straightening situation are not in agreement,so that it cannot be applied to practical straightening production.Even more,some problems in the actual straightening process have not been paid attention.For example,the determination of the distance between the pad and the amount of the pressing of the extra thick plate defects has long been determined by experience.Therefore we still need to fundamentally study of stretch bending straightening tension bending theory and construct a model of stretch bending straightening thin belt.At the same time for pressing of plate straightening procedure,setting up the model of the pressure straightening for determining the shim distance and head reduction.The ultimate objective is to provide available and rounded project for practical straightening process and meet the high quality of the extreme strip flatness requirement.The main research contents and results of this paper are as following:(1)The deformation behavior and energy change of linearly reinforced strip during the whole process of elastic-plastic bending were studied.It was found that the theoretical deflection was less than the practical deflection along with the increase of mid-span pressure.Therefore,the mid-span deflection formula was modified based on the experiment.(2)The deformation behavior and energy change of linearly reinforced strip during the whole process of elastic-plastic tension bending were studied.The eccentricity,bending curvature,deflection,elongation during loading and the elastic complex curvature,deflection and plastic elongation after unloading were analyzed and calculated.(3)We have independently designed the very thin band tension bending equipment and the very thin band tension bending equipment.Taking the stainless-steel thin strip as the experimental material,the mechanical properties of the thin strip were analyzed.It was found that the thin strip was easy to fold in the stretching process,which was caused by the material properties and the inhomogeneous force in the stretching process.At the same time,the tension-bending experiment was in progress to compare the theory.The bending fatigue test was in progress to observe the bending fatigue behavior of the thin strip in a great number of bending processes.(4)A method combining curvature analysis and energy calculation was proposed.An optimal process model was established to eliminate the protrusion defect of extra thick plate by using a flattening machine based on the principle of minimum deformation energy.And the optimal distance of the cushion iron and the reduction amount were determined.It not only provides a theoretical basis for pressure straightening of extra thick plate,but also provides an effective and energy saving fattening scheme for actual production.