Study of the relationship between the drawing coefficient and hardening ratio.(Report)

1. INTRODUCTION

Knowledge of the conditions under which the material passes during processing from the status of elastic state to plastic presents importance in the analysis of the deformation processes.

In the case of traction--uniaxial tensile, the passage from the elastic state to the plastic state occurs when strain exceeds the limits of the material's flow.

The appreciation of the ability of deformation for thin steel plates can be carried out on the basis of their mechanical properties: yield limit [R.sub.e], breaking strength [R.sub.m], breaking elongation, necking ratio, properties determinted by tensile tests.

For the plastic deformation process a specific tensile strain is necessary in the structure of the material. During the tensile test, this is possible if the strains have values between [R.sub.e] and breaking strength [R.sub.m].

Generally, as the Romanian literature mentions, (Gadea & Petrescu, 1983), (Teodorescu et al, 1987), (Teodorescu, 1992), it can be appreciated that a material, which has a large breaking elongation, a small yield point and great tensile strength, has also the mechanical properties that are favorable for a good behavior deformation. A small value of the ratio between yield limit [R.sub.e] and breaking strength [R.sub.m] indicates also a good behavior for the thin sheet during the deformation process.

The hardening process increases the yield point to a greater extent than the tensile strength (Cao et al., 2000). The difference between these two factors ([R.sub.m] - [R.sub.e]) determines the decreasing of the material deformation capability.

The breaking strength is a representative factor that …