Wrinkling Calculation And Analysis Of T Section In Cold Bending Process

Cold bending process is one forming technique widely used in shipbuilding industry to bend structural components. Being major component of flat sections, T section can provide high strength reasonably using less material, and maintain good symmetrical characteristic, which makes it more and more popular in the use of hull structural. Most T sections should be bent before assembling to meet a certain curvature requirement. The technique first welding together then bending for T sections can save a lot of material and labor cost, and has outstanding advantages. However, plastic instability and wrinkling may occur in web if excessive tangential compressive stress reached when T section under convex bending. Wrinkling is one of the major defects and may cause structural strength to sharply decrease. Thus the wrinkling mechanism and the influencing laws of dimensional parameters on wrinkling in the bending process have been investigated thoroughly by using FEM simulation technology. The achievements of the research have theoretical significance and reference value for the selection and optimization of T section dimensional parameters. The brief introduction and major results are as follows:Key technological problems of modeling in cold bending process of T sections are analyzed and solved. A three dimensional dynamic explicit FE model of the process has been established based on ANSYS/LS-DYNA software platform. Both computation accuracy and efficiency are taken into account. And then verify the reliability of the model by comparing the calculation result and experiment result in reference. The success of establishing the model makes a solid foundation for the research of wrinkling mechanism and the influencing laws of dimensional parameters on wrinkling in the bending process.For the mode established above, tangential stress and effective strain distributions of T section in bending process are obtained. The plastic deformation behavior and wrinkling mechanism have been analyzed, and stress, strain, and displacement of different element in compressive area have also been tracked. The result indicates that wrinkling occurs in the primary stage of bending, and wrinkling development has been precisely described, which provides a basis for systematic study on influencing parameters of wrinkling.Based on the FE model, nine series of calculation conditions with changing web thickness under uniform web height and seven series with different width-thickness ratio of web under same section modulus are simulated. The results show that it is more difficult for wrinkling when the web is thicker and the ratio is smaller. Then based on results, fitted formulas are obtained to reveal the maximum tangential stress and minimum relative bending radius at bifurcation points changing with thickness and the width-thickness ratio of web, and their curves are plot.