bow and twist. The critical forming limit (FLC0) is the
minimum value of a major strain when a minor strain is
zero and can be described by a function of n-value
(work hardening exponent) and strip thickness of different
steel types and grades [30].
Thus, the quality characteristic for major strains can be
formulated as:
FLC0 "1 ð6Þ
Edge cracking could be predicted in the course of
monitoring the strains in thickness direction. Such
strains should not surpass the ultimate elongation point
of the material, since they cause edge splitting. Thus,
the quality characteristic of thickness reduction can be
formulated as:
0 < "peak
3 < "UEP ð7Þ
Dimensional stability of the final cross section is another
critical quality issue for the cold roll forming process. Dimensional
error could be defined as the absolute difference
of target value (design) from the actual predicted value with
springback (FEM), as:
Derror ¼ jTarget Actualj ð8Þ
For maintaining the desired quality characteristics of the
produced profile, the dimensional error should be within the