A cylindrical rod of copper originally 16.0 mm in diameter is to be cold worked by drawing; the circular cross section will be maintained during deformation. A cold-worked yield strength in excess of 250 MPa and a ductility of at least 12% EL are desired. Furthermore, the final diameter must be 11.3 mm. Explain how this may be accomplished: (1) show why it cannotbe realized by single drawing and (2) suggest proper procedures to fulfill the requirements. You will need to use following figuresto solve the problem.

Solution :

Given data:

Diameter of the copper cylindrical rod = 16 mm

Yield strength  = 250 MPa

Calculating the percent cold work

                                  = 50% CW

Therefore, at , the yield strength of copper will be of the order of 330 MPa.

The ductility will be 4% elongation (EL).

Rather than performing drawing in single operation, we draw some of the fraction of total deformation, and then the anneal them to recrystallize and also finally w do cold work on the material  for the second time to achieve its final diameter, ductility and yield strength.

is required for a yield strength of . Similarly, a maximum of is required for.

The average of the two values is . To achieve both the the copper should be deformed to. The after the first drawing and the initial diameter for the second drawing is , then

answer:

50 vo; ts

explanation: