**Author details**

26 Metal Forming – Process, Tools, Design

uncertainties can affect the probability of failure.

**Figure 20.** Thickness variation in an axial position

**6. Conclusion** 

**Table 8.** Statistical parameters of the extreme value distribution

area of the expanding zone not far from the weld zone.

The parameters that characterize these distributions are summarized in Table 8. Then we can simply assess the probability of failure of the potential failure modes to show how

Parameters μ σ k Gnecking 264.8466 54.1678 0 Gthinning 0.2223 0.0882 −0.0654

The first part of this work presents the results of a combined experimental/numerical effort that aims to assess the performance of different plastic stress flow in predicting the burst of welded steel tubes loaded under internal pressure. The prediction of the stress-strain characteristic with the anisotropic effect of tubular material has been proposed. Once the expanding diameter, the internal pressure and the wall thickness were obtained from the results of the bulge tests, the effective stress and effective strain could be calculated. The bulge tests carried out until bursting showed that all the fissures are initiated in the central

A. El Hami *LMR, INSA de Rouen, St Etienne de Rouvray, France* 

B. Radi *LMMI, FST Settat, Settat, Morocco* 

A. Cherouat *GAMMA3, UTT, Troyes, France* 

#### **7. References**

Asnafi, N. & Skogsgardh, A. (2000). Theoretical and experimental analysis of strokecontrolled tube hydroforming, *Materials Science and Engineering A279*, pp. 95-110

**Chapter 2** 

© 2012 Wang et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Wang et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Stamping-Forging Processing** 

Additional information is available at the end of the chapter

**1. SFP principle of thickening in axial direction** 

stop a further instability causing folding defect.

Xin-Yun Wang, Jun-song Jin, Lei Deng and Qiu Zheng

**1.1. Principle of stamping-forging processing (SFP) for sheet metal** 

SFP is a combined metal forming technology of stamping and forging for sheet metal parts. In an SFP, generally, stamping or drawing is used to form the spatial shape of the part first, and followed by a bulk forming employed to form the local thickened feature. It is suitable for making sheet metal parts which have local thickened feature, such as single or double layers cup parts with thickened inner or outer wall, disc-like parts with thickened rim, etc.

It is difficult to manufacture cup part whose wall thickness is greater than that of its bottom by general sheet metal forming technology. As is well known, on the one hand, making the thickness of sheet metal reduction by compression is almost impossible due to the great metal flow resistance. On the other hand, it is not able to obtain different thicknesses of wall and bottom by stamping, although it is very effective to form the spatial shape of sheet metal part. The SFP of thickening in axial direction is just feasible to manufacture this type

The SFP principle of forming this kind of parts is shown in Fig .1. Firstly, a disk blank is formed to a single or double layer cylinder cup by a conventional drawing or hole flanging process. And then the inner or outer wall is thickened by an axial upsetting process. In the thickening step, the non-freestyle upsetting process such as hydraulic pressure assistant upsetting and small gap upsetting with rigid support will be used. In the former upsetting, a hydraulic pressure is adopted to make the blank stick with the sidewall of die to ensure stability (see Fig.1 a). In the latter upsetting, a mandrel is placed in the center hole. When the wall comes with a slight local thickening, the other cavity wall will contact it immediately to

**of Sheet Metal Parts** 

http://dx.doi.org/10.5772/52710

**1. Introduction** 

part.


**Chapter 2** 
