小型轧钢机(工作原理+设计手册+外文文献翻译+CAD图纸) 第4页
The range of σθ is 0>=σθ>=-σγ.When σθ=-σγ, then εθ>0,εγ <0, and εθ=-εγ;when σθ=0, then εθ>0,εγ <0, and εθ=-εγ/2. Such deformation is in the region DOF of the diagram of the stamping strain (see Fig.1.1), and in the region BOC of the diagram of the stamping stress (see Fig.1.2).
The four deformation conditions are related to the corresponding stamping forming methods. Their relationships are labeled with letters in Fig.1.1 and Fig.1.2.
The four deformation conditions analyzed above are applicable to all kinds of plane stress states, that is, the four deformation conditions can sum up all kinds of stamping forming in to two types, tensile and compressive. When the stress with the maximum absolute value in the deformation zone of the stamping blank is tensile, the deformation along this stress direction must be tensile. Such stamping deformation is called tensile forming. Based on above analysis, the tensile forming occupies five regions MON, AON, AOB, BOC and COD in the diagram of the stamping stain; and four regions FOG, GOH, AOH and AOB in the diagram of the stamping stress.
When the stress with the maximum absolute value in the deformation zone of the stamping blank is compressive, the deformation along this stress direction must be compressive. Such stamping deformation is called compressive forming. Based on above analysis, the compressive forming occupies five regions LOM, HOL, GOH, FOG and DOF in the diagram of the stamping strain; and four regions EOF, DOE, COD and BOC in the diagram of the stamping stress.
MD and FB are the boundaries of the two types of forming in the diagrams of the stamping strain and stress respectively. The tensile forming is located in the top right of the boundary, and the compressive forming is located in the bottom left of the boundary.
Because the stress produced by the plastic deformation of the material is related to the strain caused by the stress, there also exist certain relationships between the diagrams of the stamping stress and strain. There are corresponding locations in the diagrams of the stamping stress and strain for every stamping deformation. According to the state of stress or strain in the deformation zone of the forming blank, and using the boundary line in the diagram of the stamping stress MD or the boundary line in the diagram of the stamping strain FB, it is easy to know the properties and characteristics of the stamping forming.
The locations in the diagrams of the stamping stress and strain for various stress states and the corresponding relationships of the two diagrams are listed in Table 1.1.It shows that the geometrical location for every region are different in the diagrams of the stamping stress and strain, but their sequences in the two diagrams are the same. One key point is that the boundary line between the tensile and the compressive forming is an inclined line at 45°to the coordinate axis. The characteristics of the stamping technique for tensile and compressive forming are listed in Table 1.2.
Table 1.2 clearly shows that in the deformation zone of the blank, the characteristics of the force and deformation, and the patterns relevant to the deformation for each stamping method are the same. Therefore, in addition to the
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