Study On Wrinkles Phenomenon On Tensile And Bending Fatigue Characteristic Of The Ultra-thin Stainless Steel Strip

As a new type of high precision material,the stainless steel thin strip is widely used in aerospace,mobile phone and other fields,but the stainless steel thin strip in its tensile deformation will often produce the phenomenon of wrinkling instability,resulting in structural and functional failure,affecting the surface smoothness and service life,and may even cause safety problems.Therefore,it is of great theoretical and practical value to investigate the causes of the wrinkling in the process of tensile deformation of stainless steel wafers.As a new kind of foldable mobile phone screen material,the bending fatigue performance of stainless steel thin strip is one of the key parameters.Therefore,it is of great significance to study the change of metallographic structure in the process of fatigue bending to improve the bending fatigue performance.In this paper,the causes of longitudinal folds and transverse folds of 304 stainless steel ultra-thin strip during tensile process are discussed,and the evolution process of folds is analyzed by combining the stress-strain parameters collected,which provides help for the formation of later tensile deformation folds.At the same time,the bending fatigue experiment of 304 stainless steel thin strip was carried out to study the microstructure change of the thin strip under different bending radius and bending times.The main contents and research results of this paper are as follows:(1)Based on DIC technology,the tensile test of SUS304 0.02 mm stainless steel ultra-thin strip was carried out.Longitudinal folds on the surface of SUS304 stainless steel ultra-thin strip were predicted by strain during the tensile process,and the correlation between strain and fold generation was established.It provides a reference for predicting the longitudinal folds of 304 stainless steel thin strip in the later tensile deformation process.(2)Based on DIC technology,the tensile test of SUS301 0.02 mm stainless steel ultra-thin strip was carried out,and the correlation between strain and fold generation was discussed.The cause of lateral fold on the surface of SUS301 stainless steel ultra-thin strip during tensile process was analyzed,and the evolution of movement state during lateral fold generation was deeply analyzed.(3)The bending fatigue properties of SUS304 0.02 mm stainless steel ultra-thin strip were experimentally studied.The influence of different bending times and bending radius on the microstructure of ultra-thin strip was established,and the ultimate bending times of stainless steel ultra-thin strip under different bending radius were obtained.The process of microstructure change of ultra-thin strip under the same bending radius is analyzed,which provides basic guidance for further improving the bending fatigue performance of SUS304 ultra-thin strip.The research results of this paper have a positive and beneficial effect on the later prediction of longitudinal and transverse folds in the tensile deformation of stainless steel extremely thin strip.There are still many problems to be solved for further improving the tensile properties of extremely thin strip and eliminating the generation of folds.Through the bending fatigue test of SUS304 stainless steel ultra-thin strip,the process of microstructure change with the increase of bending times under the same bending radius is analyzed,which provides reference for further improving the fatigue bending performance of ultra-thin strip in the later period.