Study On Roller Straightening Model For Strip Wave Defects

With the vigorous development of various industries such as defense,automobile,aerospace,and construction,the demand for strips in various industries is also increasing year by year,and the requirements for their quality are also increasing.In the process of production or processing,after rolling,forging,continuous annealing and other processing processes,uneven residual stress will be generated inside,showing different types of wave defects.In this paper,through finite element simulation,theoretical analysis and calculation,and finally the research idea of rolling and straightening experiments,the residual stress and residual curvature of the strip with medium wave shape defect before and after straightening are deeply studied.Through the ABAQUS finite element simulation software,the small deformation straightening scheme and the large deformation linearly decreasing straightening scheme are compared,which will pave the way for the selection of the straightening experimental scheme for the medium-wave corrugated strip.The distribution formula of residual stress along the width of the plate is theoretically derived for the plate with wave-shaped defects to be straightened.The residual stress of the strip before and after straightening was measured by the X-ray method and the blind hole method,respectively,and the distribution law of the residual stress of the strip with medium wave defect before and after straightening was obtained.The main research contents and conclusions of this paper are as follows:（1）After the finite element simulation of rolling and straightening of the strip,the residual stress is distributed parabolically symmetrically along the width direction of the strip,and the residual stress at the center of the strip reaches the maximum.And after straightening simulation,the residual stress at the center is reduced from 99 MPa before straightening to 63 MPa,and the residual stress at the edge of the strip is reduced from 65 MPa before straightening to 29 MPa.Whether it is the residual stress in the middle or the edge,after the straightening simulation,the residual stress is significantly reduced.（2）In the strip straightening experiment,the influence of the first pass and the second pass on the straightening of the strip with medium wave-shaped defects was studied by adopting the large deformation linear decreasing straightening scheme.After the second pass,the wave height of the overall warpage of the strip is 0.2 mm,and the curvature of the strip is 0.15×10^-2mm^-1.The strip has been well improved,which also shows the rationality of using the large-deformation linear decreasing straightening scheme to straighten the strip with medium-wave-shaped defects.（3）Using the X-ray method and the blind hole method to measure the residual stress of the strips with different specifications before and after straightening,it is found that the residual stress increases first along the width direction of the strip,and the wave shape of the strip is the highest.It peaks at,and then gradually decreases along the width of the plate,reaching a minimum at the edge of the wave.Moreover,the changes of residual stress are basically concentrated in the middle wave region,and the higher the wave shape,the larger the residual stress value.（4）By comparing and analyzing the error between the theoretical calculated value of the residual curvature after straightening of Cu-A,Cu-B,and Cu-C with the experimental mean value,the errors are 9.52%,11.11%,and6.67%,respectively.The errors of the Cu-1,Cu-2,Cu-3 straightening simulation values and the experimental measurement values are 14.23%,9.96%and13.04%,respectively,and the simulation results are basically consistent with the experimental measurement values.The correctness of the straightening simulation model and the theoretical calculation of residual curvature is verified.