Question

What are the differences between bulk deformation processes and sheet metal processes?

Answer 1

Bulk deformation processes:

In this process the workpiece actually  undergoes very large plastic deformation. This also means that large change in shape as well as the cross section will happen 
The piece of the permanent plastic deformation is generally quite large as compared to the  elastic deformation.

Sheet metal process:
Although there is large deformation  changes occur in the  shape in this case but this does not happen in the case of cross section.
There may be significant elastic recovery which does not happen in the case of bulk deformation.

Answer 2

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In bulk deformation processes the more important point are shape change. On the word we can say the shape changes are significant. In bulk deformation processes part of the work have low volume to area ratio on the other hand in sheet metal processes part of the work have a high volume to area ratio in sheet metal processes term press working often used for sheet metal processes.