Projects for Mechanics of Metal Forming Courses: A Look at User Subroutines for Formability Assessment

Dr. Lorenzo M. SmithOakland University, Rochester, MI

OBJECTIVE Describe how Marcs user

subroutine UACTIVE is currently being employed as an instrument for instruction in the area of sheet metal blanking modeling.

BACKGROUND

Lift Gate Outer

BACKGROUND

Failure originating from an edge remains a significant concern.

BACKGROUND

The sheet metal blanking process is similar to three- hole punching of a piece of paper.

COURSE PROJECT

M.E. 571: Theory of Plasticity

M.E. 578: Mechanics of Metal Forming

M.E. 678: Advanced Metal Forming

COURSE PROJECT

COURSE PROJECT

COURSE PROJECTMain Components of the Course

Classical Theory of Plasticity (Overview)

Failure Criteria

Stretching

Bending

Drawing

Stretch-Bend-Draw

COURSE PROJECT

How can Marc be used to help the students explore the modeling of sheet metal blanking?

COURSE PROJECT

50% True Effective Strain Failure Criterion

(One of many possible ductile fracture criteria)

COURSE PROJECT

COURSE PROJECTFar in excess of 50% effective strain

COURSE PROJECTStill.no separation! Another approach is needed.

COURSE PROJECTsubroutine uactive(m,n, mode, irststr, irststn, inc, time,

1timinc)c c implicit real*8 (a-h,o-z) dp

include '../common/implicit'dimension m(2), stress(1), strain(1), epten(6,28)include '../common/space'include '../common/elmcom'include '../common/heat'include '../common/strvar'

cc failure criterion for shearing of sheet metalc m(1) = element number, m(2) = master element number inc the adaptive analysis, n = internal element number,c inc = increment number, time = time at beginning ofc increment, timinc = incremental timec Also, nn = integration point number which is available c through include 'lass'c Also note key element info is available through include 'elmcom'c Required Output:c mode = -1 to deactivate elementc mode = 2 leave in current statusc mode = 1 activate elementc irststr - set to 1 to reset stresses to zeroc irststn - set to 1 to reset strains to zerocc

call elmvar(7, m, 1, 1, xx)

if (xx.gt.0.50)thenwrite(*,*) "Element Removed. Effective Strain = ", xx mode = -1endif

If the effective strain exceeds 50%, then remove element.

UACTIVE Subroutine

COURSE PROJECT

COURSE PROJECT

COURSE PROJECT

CONCLUDING REMARKSThe automotive industry relies heavily upon numerical modeling of metal forming/cutting.

The use of Marc within the context of a graduate-level course at OU, has helped academia prepare engineers for the challenges associated with sheet metal blanking.

Dr. Lorenzo M. SmithEmail: L8smith@oakland.edu Tel. (248) 370-4629

Slide Number 1OBJECTIVEBACKGROUNDBACKGROUNDBACKGROUNDCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCOURSE PROJECTCONCLUDING REMARKSSlide Number 20