from  the following  eijuat ions:

Hole hanging, expanding, bulg'•6

n here,  z is the inward moving coefficient  of  neutral line。

As shown  in  Eqs。(IS)  (18),  the  forming  limits  of  ten- sile stamping operations can be calculated with deformation length L。 As a result, the geometrical dimension  of  blank  is th‹。 vital parameter to  determine  the forming  limits。  In order to avoid tedious calculations, the forming limit nomogram of tensile stamping operations (shown in Fig。1) is established to apply  to engineering。

In Fig。1, the curves of  ‹I =  J(L)  for several  materials  are di awn on the left, and the coefficients of forming limits re the maximum strain curves (Eqs。(1)  (4))  are drawn  on the right。 As the graph is used, the length L should be calculated and found on the horizontal axis。 Then, a vertical  line  is drawn from the point to the d cs L curve of corresponding material。 Afterwards, a horizontal  line is drawn from the meeting  point to the corresponding forming limit curve, the horizontal coor- dinate of this meeting point is the coefficient of forming limit Uist  is needed。

3。Physical  Experiments

lii order to verify tlie correctness of  this  nomogram,  a series of experiments on tensile stamping operations are per- formed。 The comparisons between experiments and calcula- tions  are shown  in  Table 2。

4。Conclusions

(1)The method advanced in this paper realized the idea that using analytic method to determine forming limits of tensile stamping operations。

(2)For a certain material, the geometrical dimension of blank is the vital factor to determine the forming limits of ten- sile stamping operations, and the forming limits can be cal- culated by the parameter i which comes from uniaxial tensile test。

(3)To avoid tedious calculations, the forming limit nomo- gram of tensile stamping operations  is established  in this pa- per  to apply to  engineering。

(4)There should be noted that this nomogram is only ap- plied to tensile stamping operations including hole Hanging, expanding, bulging, bending, because they share the same mechanical features that the stress-strain  state at  the criti- cal section can be considered as uniaxial tensile stress-strain state。

基于可塑性理论和物理实验，给出了通过单轴拉伸获得的伸长率δ和拉伸冲压操作的形成极限之间的定量关系，这主要解决了简单拉伸试验可形成成形极限的问题。拉伸冲压操作的成形极限列线图也适用于工程中。

关键词：列线图，拉伸试验，成型极限，拉伸冲压

1。介绍

    成形极限系数是表示冲压操作成型能力的主要参数，通常通过实验和错误中获得。它是否能够通过分析的方法确定，在理论和实践中有着重大的意义。一个苏联的学者通过伸长获得孔法兰的系数δ[1]，而用δ的孔径验证误差不是常数。拉伸冲压操作包括孔的法兰，膨胀，凸出，弯曲（外层），它们共享相同的机械特性。因此影响其成形极限的因素是相似的，主要因素是材料的塑性[2~3]。因此，可以通过单元化分析方法获得拉伸冲压操作的成形极限。而如何实现这个想法正是本文所要考虑的。来-自~优+尔=论.文,网www.youerw.com +QQ752018766-

2。理论分析

    如上所述，拉伸冲压操作共享相同的机械特性，其中最大应变发生在主导和强制拉伸主应力下，并且决定成形极限的临界截面处的应力 - 应变状态可以被认为是单轴拉伸应力 - 应变状态。因此可以通过简单的拉伸试验获得的参数来表示拉伸冲压操作的成形极限。