A Study On Key Issues Of Frame Cold-Bending Ability

Bending capacity refers to the difficulty Level that frame is processed to bends with no defects and certain curvature. Bending capacity is determined by the geometric dimensioning, material properties and the bending degree of the frame. During the process of frame cold bending forming, the important basis to determine feed length is plastic forming interval length, which is the key to realize frame NC cold bending forming. During the process of recurvation Cold-Bending of the Frame, the web easily appears to wrinkle because of the combined action of pulling and pressing. Therefore, the prediction and control of the wrinkling is the key issues of the frame member workability. This dissertation studies some key issues of Frame Cold-Bending Ability mainly including plastic forming range and instability wrinkling through the combination of analytical method, FEM numerical simulation and experiment method.With the elastic-plastic theory, this dissertation deduces the theory analysis formula of critical effective forming range of T-section. The result shows that T-selection’s plastic forming range and the two sides’fulcrum spacing, panel width, panel thickness are in positive correlation; T-selection’s plastic forming range and web height, web thickness are in negative correlation; From the numerical simulation for Cold-Bending process of T-section with the Plastic Finite Element Method, it shows that the theoretical analysis is right. It further shows that T-selection’s plastic forming range and bending radius are in negative correlation. From the analysis above, this dissertation finds out the main factors and influence rules of plastic forming range.Based on the elastic-plastic theory, this dissertation deduces the critical buckling radius calculation formula of steel flat and T-section, and gets factors of influencing T-section’s instability, which includes fulcrum spacing, Material section size, etc. This dissertation makes the numerical simulation for the Cold-Bending process of T-section, Angle steel and flat-bulb steel. During the process of calculation, the buckling critical state of frame is expressed with Cold-Bending linear curvature radius. The main conclusions above are as follows: (1) T-selection’s buckling critical radius and the two sides’fulcrum spacing, web height, panel width, panel thickness are in positive correlation; T-selection’s critical relative buckling radius and web thickness are in negative correlation;(2) Angle steel’s critical buckling radius and the two sides’ fulcrum spacing are in positive correlation; Angle steel’s critical relative buckling radius and web thickness are in negative correlation;(3) Flat-bulb steel’s critical buckling radius and the two sides’ fulcrum spacing are in positive correlation; Flat-bulb steel’s critical relative buckling radius and web thickness are in negative correlation.At last, the dissertation makes experiment on Cold-Bender of Angle Steels with the testing machine, the SKJXS-100type cold bending machine. From the analysis, as for critical buckling, the experiment results is close to the results of FEM numerical calculation; the influences of fulcrum spacing and other factors on critical buckling radius are in consistent trend.