小型轧钢机(工作原理+设计手册+外文文献翻译+CAD图纸) 第5页
research on the detail stamping method, it is feasible to study stamping systematically and comprehensively. The characteristic of the systematic research is to study the common principle of all different types of stamping methods. The results of the systematic research are applicable to all stamping methods. The research on the properties and limit of the sheet metal stamping has been carried out in certain extent. The contents of the research on the stamping forming limit by using systematic method are shown in Fig.1.3.
State of stress Location in the diagram of the stamping strain Location in the diagram of the stamping stress  
Types of deformation
Stress  Strain 
Biaxial tensile stress state
σθ>0,σγ>0 σγ> σθ AON GOH +        + Tensile
 σθ>σγ AOC AOH +        + Tensile
Biaxial compressive stress state
σθ<0,σγ<0 σγ< σθ EOG COD —       — Compressive
 σθ<σγ GOL DOE —       — Compressive
Stateof stress with opposite signs
σγ>0,σθ<0 |σγ|>|σθ|  MON FOG +        + Tensile
 |σθ|>|σγ| LOM EOF —       — Compressive
State of stress with opposite signs
σθ>0,σγ<0
 |σθ|>|σγ| COD AOB +        + Tensile
 |σγ|> |σθ| DOE BOC —       — Compressive
Table 1.1 Comparison between states of stress and strain in stamping   
Table 1.2 Comparison between tensile and compressive forming
Item      Tensile forming
    Compressive forming
Representation of the quality problem in the deformation zone Fracture in the deformation zone due to excessive deformation Instability wrinkle caused by compressive stress
Forming limit 3． Mainly depends on the plasticity of the material, and is irrelevant to the thickness
4． Can be estimated by extensibility or the forming limit DLF 4． Mainly depends on the loading capability in the force transferring zone
5． Depends on the anti-instability capability
6． Has certain relationship to the blank thickness
Variation of the blank thickness in the deformation zone        Thinning      Thickening
Methods to improve forming limit 4． Improve the plasticity of the material
5． Decrease local deformation, and increase deformation uniformity
6． Adopt an intermediate heat treatment process 4． Adopt multi-pass forming process
5． Change the mechanics relationship between the force transferring and deformation zones
6． Adopt anti-wrinkle measures
Fig.1.1 Diagram of stamping strain                  　　　Fig.1.2 Diagram of stamping stress

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