**2. Applications and limitations of sheet hydroforming process [9-16]**

Each of the sheet hydroforming mentioned above has its own limitations and applications. Sheet hydroforming process would be useful in reducing weight and cost simultaneously by

improving structural integrity, strength and rigidity. In addition, this process satisfies these requirements with utilizing the common and available material efficiency.

Developments in Sheet Hydroforming for Complex Industrial Parts 61

2. There is a sharp edge on the workpiece that is specified in Figure 7(a). This is the most

3. The flange area of the workpiece that is shown in Figure 7(b), should be produced with

**Figure 7.** Case study 1; The part of lightning industry (after trimming and coating): (a) internal view,

(a) (b)

Drawing of conical parts is considerably more difficult than the deep drawing of cylindrical cups. Conical shape forming through conventional deep drawing is shown in Figure 8. As it is shown in the figure, due to small contact area of the punch tip with the blank at initial stages of deformation, high stresses are applied to this area of the sheet. This may cause bursting in the sheet. In addition, when forming conical cups through conventional deep drawing, wrinkling occurs on the sheet wall because the blank is free between the punch and the die [18, 19]. Thus, conical parts are normally formed by multi-stage deep drawing

Because of the large radial tensile stresses, small drawing ratios must be used in each stage when making conical components in multi-stage deep drawing. In addition, the ratio of the sheet thickness to the initial blank diameter influences the limiting drawing ratio to a greater extent than when drawing cylindrical parts. The limiting drawing ratio also depends on the

In all the hydroforming processes a universal testing machine (Figure 9(a)) and a hydraulic unit (Figure 9(b)) are used. In addition, the hydraulic unit was used as the pressure medium to form the workpiece. A control valve with a maximum pressure of 50MPa regulated the

Figure 10 illustrates the schematic illustration of the new tool set-up proposed for this part. Figure 11 shows the photograph of the punch used for the part. The manufactured die-set is

cone angle and the ratio of the largest to the smallest cone diameter [18].

complex region of the workpiece to be formed.

good accuracy and with no wrinkle.

[18], spinning [20] or explosive forming [21].

liquid flow to maintain the required pressure.

(b) external view

*Case study II [17]* 

*Experimental set-up* 

*Tool set-up: Case study I* 

Saving in tooling, material, design, production and assembly will altogether contribute reducing the overall cost of a sheet hydroforming part. Elimination or decrease of welds and welding operations is an additional of the overall cost.

A reduction in number of production steps and components in an assembly will be obtained with this process. This would reduce dimensional variations, and facilitate assembly operations.

Following is a list of potential advantages gained with the use of sheet hydroforming technology:


In contrast, longer process cycle and higher tool cost are limitations of this process.
