**6. Conclusions**

Based upon the experimental, theoretical and numerical approaches used in this research the following conclusions could be drawn for forming titanium sheet alloys at room temperature:


### **Nomenclature**

Although the forming behavior of materials can be well expressed through uni-axial tensile tests, the theoretical prediction of FLD may still lie in large deviations from the experimentally determined FLDs. This finding proves that suitable theoretical approaches depend not only on the thorough understanding of the forming behavior of materials, but also on the suppo‐

Based upon the experimental, theoretical and numerical approaches used in this research the following conclusions could be drawn for forming titanium sheet alloys at room

**1.** Several approaches were used to generate true stress strain data based on thebulge test. Equations based on Kruglov and Panknin gave the most accurate results comparing to

**2.** Tensile tests showed that Ti-6Al-4V sheet alloy has large plastic strain ratio (r) values. Generally higher strain-hardening exponent (n) delays the onset of instability and this delay, enhances the limiting strain (i.e. better stretchability is achieved with higher n-

**3.** Investigation of the influence of material anisotropy showed that increase in normal anisotropy would result in lower thickness thinning when drawing is the deformation mode and higher n-value would bring about higher bulge height, lower bulge radius and

**4.** The comparison between uniaxial and balanced biaxial bulge tests indicates that, in bulge test the flow stress curve can be determined up to larger strains than in the tensile test. This is an advantage of the bulge test, especially for metal forming processes in which the state of stress is almost biaxial; using bulge test is a more suitable method for obtaining the flow stress of the above sheet materials for use as an input to Finite Element (FE)

**5.** It was shown that the percent difference for maximum plastic strain obtained from bulge

**6.** For Ti-6Al-4V alloy, the best agreement between experimental and theoretical approaches is achieved when the M-K with Hill'93 yield criteria is used. As a result, the overall comparison shows a well agreement between FE results and data obtained from the

**7.** The small deviation between numerical and experimental results may be the conclu‐ sion of frictional effects between hemispherical punch (in FE simulation) and the sheet

lower thickness thinning when stretching is the deformation mode.

and tensile test is as high as 504% (for Ti-6Al-4V).

sitions for yield surfaces as well as material specifications.

the step-wise experimental measurements.

**6. Conclusions**

106 Titanium Alloys - Advances in Properties Control

temperature:

value).

simulation models.

experiments.

metals.


