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200 Ovidiu Niţă et al.
aluminium presents the highest sensibility to lamination direction. Basically, the
breaking of aluminium specimen, cut at 90 0 to the lamination direction,
occurred in the mid-range elongation obtained for the specimen orientated after
rolling direction.
a b
Fig. 2 – Characteristic diagrams obtained by tensile test:
a – aluminium; b – brass.
It should be noted that, the steel specimens recorded the lower sensitivity
regarding deformation capacity to the lamination direction. This phenomenon is
illustrated in Fig. 3, where the characteristic diagram obtained for steel blanks is
shown.
Fig. 3 – Characteristic diagrams obtained for steel specimens.
3.2. Mathematical Relations between Roughness and Tensile Strain
After the accomplish of experimental tests, it was found that the
transition from lower to higher levels, of the considered influencing factors,
determine a noticeable variation in surface roughness. Both influencing factors
consider have a direct influence on the roughness, but only increasing the
tensile force leads to a significant increase in roughness. Varying the lamination
direction orientation also produces a fluctuation of roughness values but this
variation occurs randomly and not after a predictable pattern.
The nest step after the acquisition of surface roughness values was to
draw the roughness evolution diagrams depending of specimen elongation. For