In addition to the basic mechanical properties, the results of the forming tests simulating various basic forming features are also important for the evaluation of the forming properties of the steel sheet. Digital imaging, graphic processing and numerical analysis can be used to study the relationship between materials, stamped U-shaped bending dies and stamping process parameters. The simulation forming test research projects mainly include: “S” beam test evaluation sheet material resilience performance, hydraulic bulging test, cup swell test evaluation sheet bulging performance, forming limit diagram test, deep drawing test evaluation sheet drawing deep drawing Formability, cone test, sheet forming performance of deep drawing-bulging composite forming, and hole expanding test evaluation of sheet material reaming forming properties. In the various forming tests described above, the forming limit diagram (FLD) test is very important. FLD is the curve of the local instability limit strain of the sheet under different strain paths. FLD describes the forming limits of materials under various strain conditions and is very helpful in analyzing the formation of complex parts. The figure below shows the typical steel forming limit diagram: