Incremental Solution Of Internal Stress In Coiling Process Of Cold Rolled Strip

The radial pressure and circumferential tension between layers of cold rolled strip will be produced due to the effect of tension in the coiling process.The distribution of radial pressure and circumferential tension in the coil is related to many factors,such as coiling tension,material quality,shape and coiling weight.For a certain size of steel coil,there exists an internal stress range to stabilize the coil.If the radial compressive stress is too large,it may cause inner convexity,and if the radial compressive stress is too small,it may cause coil collapse.Therefore,it is necessary to further study the variation of the radial pressure and circumferential stress in the coil during tension coiling,so as to establish a coiling tension system which is suitable for the finished products of strip without collapse and convexity.In this paper,the incremental method is used to calculate the internal stress of the strip coil.The radial elastic modulus of the strip coil is treated as a variable,the anisotropy of the strip coil is considered,the shrinkage of the drum is considered,and the stress change after the strip is unloaded is considered.Based on the thickness center of each layer of strip coil and the axisymmetric theory of elasticity,the equations of the increment of radial displacement and stress between layers of strip coil are presented.The radial pressure and circumferential stress inside the strip coil are calculated by solving the incremental calculation formulas of the internal stress of the strip coil without considering the shrinkage,the shrinkage and the unloading of the coil.Through theoretical calculation formula,VC++ software programming and MATLAB software,the simulation diagram of the calculation results is drawn.The effects of coiling parameters such as strip thickness,initial coiling tension and critical pressure of drum diameter reduction on the internal stress distribution of strip coil and the properties of strip steel are studied.The effects of different initial coiling tension,different coiling layers and different strip thickness on the radial pressure on the drum were tested by a laboratory 20-high rolling mill with pressure sensitive paper.Using strain gauge,the radial pressure on the drum of strip with different initial coiling tension and strip thickness was measured by laboratory 20-high rolling mill.The experimental results are close to the theoretical results and can be used in design calculation.