1. Chapter 6 Sheet metal forming

6. Anisotropy Another important factor influencing sheet-metal forming is anisotropy,or directionally,of the sheet metal. There are two types of anisotropy: Crystallographic anisotropy (due to preferred orientation of the grains) mechanical fibering (due to the alignment of impurities, inclusions, voids,etc.)

7. Formability of sheet metals Sheet-metal formability is generally defined as the ability of the metal to undergo the desired shape change without failure,such as by necking or tearing. The stronger it is, the lower is its formability.

8. Formability of sheet metals Cupping test Figure 7.14 the erichsen cupping test to determine formability of sheet metal. The sheet metal under the steel ball is subjected to biaxial strtching. The greater the distance D before failure, the greater the formability of the material. Ball diameter=20mm

13. Shearing Figure 7.2 Characteristic features of the punched slug Burr height increases with increasing clearance and increasing ductility of the metal. Tools wih dull edges are also a major factor in burr formation.

19. Other operations A variety of operations are based on the shearing process. For example,punching(also called piercing) is the term used when the slug is discarded, whereas in blanking the slug is the part needed. Other shearing operations are called perforating (a number of punched holes), slitting,parting,notching.and lancing. There processes are also known as die-cutting.

21. Different models Figure 7.9 Examples of the use of shear angles on punch and die in shearing operations. The tip of the punch in an ordinary paper punch has a similar configuration.

25. Anisotropy in bendability Figure 7.21 (a)and(b) the effect of elongated inclusions (stringers) on cracking as a function of bending with respect to the original rolling direction of the sheet. This example shows the importance of the direction of cutting workpieces from large sheets that are subsequently bent to make a product.

29. Chapter 7 Deep drawing

41. Homeworks In which situation the residual stress on the surfaces of the rolled products is compressive and tensile in the bulk? And in which situation the residual stresses are opposite to the previous case? Why? What is internal cracking in extrusion? Please point out its influence factors and the prevention measurements.

42. Homeworks What is forgeability and its main test methods? Why there exit an optimum die angle for direct extrusion? In the die design for metal working operations, which factors have deleterious effects on die life? Why?