chapter 3.9: break forming

8/14/2019 Chapter 3.9: Break Forming

1/16

Chapter 3.9: Break Forming

3.9 Break Forming

Summary 2

Chapter Overview 3

Detailed Session Description of Break Forming 4

Run Job and View Results 9

Discussion 13

Modeling Tips 14

Input Files 15

Animation 16


2/16

Marc Users GuideSummary

3.9-2

Summary

Title Break forming of a metal bracket

Problem features Contact and metal forming - clickhere for interactive preview

Geometry

Material properties E = 30x106 Psi, = 0.3,

Analysis type Static with elastic plastic material behavior

Boundary conditions Ux = 0 at center nodes, cylindrical rigid body bends metal sheet

Element type Plane strain element type 11

FE results Punch load verses stroke

u=1

v=0.4Grid Spacing 0.1 in

X

Y

Z

5x104 1 p0.6

+ =

job1

70696867666564636261

Pos Y cbody2 (x.1)

Force Y cbody2 (x1000)

-3 060

1.289

0 5957

4039

383736

35343332

3130

4142

4344

5655545352 5851

49

48

4746

45

50

292826

9

8

7654321

0

10111213

25

2423222120181716151419

27
http://www.mscsoftware.com/product_demos/Marc_Nonlinear_Analysis/player.htmlhttp://www.mscsoftware.com/product_demos/Marc_Nonlinear_Analysis/player.html


3/16

3.9-3CHAPTER 3.9Break Forming

Chapter Overview

A flat sheet is formed into an angled bracket by punching it though a hole in a table using thecontact option.

Figure 3.9-1 Punching Examples

The cylindrical punch drives the sheet down into the hole of the table to a total stroke of 0.3. The punch

then returns to its original position. The material is elastic plastic with workhardening.

Figure 3.9-2 (A) Vertical Punch Load versus Stroke (B) Stress versus Plastic Strain

At the bottom of the stroke, the total plastic strain is nearly 45%. The vertical punch force is plotted

versus its vertical position. This force rises quickly, hardens though about half of the stroke, then softens

near the end of the stroke. Upon lifting the punch, the punch force drops rapidly and the sheet has very

little springback.

The stress-plastic strain response of a point in the sheet under the punch is plotted and shown to overlay

the material data. This workshop problem exemplifies how every point in the sheet must follow the

materials constitutive behavior as well as being in equilibrium throughout the deformation. The vertical

line in the history plot to the right is the elastic unloading of this point in the sheet.

This is a break forming problem where a punch indents a sheet over a table to make an bracket.

The problem geometry is shown below:

X

Y

Z-2.149e-004

4.581e-002

9.184e-002

1.379e-001

1.839e-001

2.299e-001

2.759e-001

3.220e-001

3.680e-001

4.140e-001

4.600e-001

lcase1

Total Equivalent Plastic Strain

Inc: 50Time: 5.000e-001

X

Y

Z

1

-2.149e-004

4.581e-002

9.184e-002

1.379e-001

1.839e-001

2.299e-001

2.759e-001

3.220e-001

3.680e-001

4.140e-001

4.600e-001

lcase2


Inc: 70Time: 1.000e+000

X

Y

Z

1

job1

70696867666564636261

Pos Y cbody2 (x.1)


-3 060

1.289

0 5957

4039

383736

35343332

3130

4142

4344

5655545352 5851

49

48

4746

45

50

292826

9

8

7654321

0

10111213

25

2423222120181716151419

27

10.0 0.2 0.4 0.6 0.8 1.0

0

20000

40000

60000

80000

100000

Strength

Equivalent Von Mises Stress Node 63


Elastic Unload

A B


4/16

Marc Users GuideDetailed Session Description of Break Forming

3.9-4

Figure 3.9-3 Break Forming Geometry Problem

Detailed Session Description of Break FormingMESH GENERATION

COORDINATE SYSTEM SET: GRID ON

V DOMAIN

-.7 .4

FILLRETURN

CURVES ADD (pick indicated points on grid)POINT (1,0,0), POINT(.3,0,0)

POINT(.3,0,0), POINT(.3,-.6,0)

POINT(.3,-.6,0), POINT(-.3,-.6,0)

POINT(-.3,-.6,0), POINT(-.3,0,0)

POINT(-.3,0,0), POINT(-1,0,0)

CURVE TYPE

FILLET

RETURN

CURVES ADDradius (right horizontal curve, right vertical curve)

0.1

radius (left vertical curve, left horizontal curve)

0.1

CURVE TYPE

CIRCLES: CENTER/RADIUSRETURN

CURVES ADD

0 .2 0

.1

ELEMENTS ADD (pick points on grid)

Grid spacing 0.1" X 0.1"

u=1

v=0.4Grid Spacing 0.1 in

Y

Z


5/16


NODE (-.9,0,0), NODE(.9,0,0)NODE(.9,.1,0), NODE(-.9,.1.0)

SUBDIVIDEDIVISIONS

30, 3, 1

ELEMENTS

ALL:EXISTING

RETURN

SWEEPALL

RETURN

RENUMBERALL

RETURN

COORDINATE SYS: SET GRID OFF

RETURN (twice)

BOUNDARY CONDITIONSMECHANICAL

FIXED DISP

X=0

OK

NODES:ADD (pick nodes along x=0,)

MAIN

MATERIAL PROPERTIES

MATERIAL PROPERTIESNEW

STANDARD

STRUCTURAL

E = 3E7= .3

OKELEMENTS ADD

ALL: EXISTING

TABLES

NEW

1 IND. VARIABLE

TABLE TYPE


6/16


3.9-6

Figure 3.9-4 Flow Stress

eq_plastic_strainOK

FORMULAENTER

5E4*(1+V1^.6) The equation describing the flow

FIT stress isNEW

1 IND. VARIABLE

TABLE TYPE time

OK

ADD POINT

0, 0, .5, -.3, 1, 0FIT

SHOW MODEL

RETURN

6

5

4

3

2

1

1

0.510

F (x1e5)

V1

table1

7

8

9

1011

y 5x104

1. p.6

+ =


7/16


Figure 3.9-5 Punch Position

STRUCTURAL

PLASTICITY (twice)INITIAL YIELD STRESS

1

TABLE1

table1 (eq_plastic_strain)

OK (twice),MAIN

CONTACTCONTACT BODIES

DEFORMABLE

OK

ELEMENTS ADD

ALL:EXISTING

NEW

RIGIDPOSITION PARAMS

Y=1

TABLEtable2 (time),

OK (twice)

table2

V1

F (x.1)

-3

0 1

2

3


8/16


3.9-8

CURVE ADD (pick cylinder)

END LIST

ID CONTACT

NEWCONTACT BODY TYPE RIGID

OK

CURVES ADD (pick all remaining curves)

END LIST

MAIN

Figure 3.9-6 Identify Contact Bodies

LOADCASES

MECHANICAL

STATICLOADCASE TIME

.5

# OF STEPS

50

CONVERGENCE TESTINGDISPLACEMENTS

RELATIVE DISPLACEMETN TOLERANCE

0.001

OK (twice)COPY

STATICLOADCASE TIME

.5

# OF STEPS

20

OK

MAINJOBS

NEW

MECHANICAL

PROPERTIES

ANALYSIS OPTIONSLARGE STRAIN

OK

lcase1

cbody1

cbody2

cbody3

X

Y

Z


9/16


lcase2

ANALYSIS DIMENSION: PLANE STRAIN

JOB RESULTSEQUIVALENT VON MISES STRESS

TOTAL EQUIVALENT PLASTIC STRAIN

OK

CONTACT CONTROL

ADVANCED CONTACT CONTROL

SEPARATION FORCE

.1

OK

OK (thrice)SAVE

Run Job and View ResultsRUN

SUBMIT

MONITOR

Figure 3.9-7 Run Job Menu

OPEN POST FILE (RESUTLS MENU)

DEF ONLY

SCALARTOTAL EQUIVALENT PLASTIC STRAIN

CONTOUR BANDSSKIP TO INCREMENT 50


10/16

Marc Users GuideRun Job and View Results

3.9-10

Figure 3.9-8 Plastic Strain Plot at Increment 50

RESULTSSKIP TO INCREMENT 70

Figure 3.9-9 Plastic Strain Plot at Increment 70

-2.149e-004

4.581e-002

9.184e-002

1.379e-001

1.839e-001

2.299e-001

2.759e-001

3.220e-001

3.680e-001

4.140e-001

4.600e-001

lcase1


Inc: 50Time: 5.000e-001

X

Y

Z

1

-2.149e-004

4.581e-002

9.184e-002

1.379e-001

1.839e-001

2.299e-001

2.759e-001

3.220e-001

3.680e-001

4.140e-001

4.600e-001

lcase2


Inc: 70Time: 1.000e+000

X

Y

Z

1


11/16


RESULTSHISTORY PLOT

SET LOCATIONSn:63 # (pick bottom middle node n:63)

ALL INCS

ADD CURVES

GLOBAL

Pos Y cbody2

Force Y cbody2FIT

Figure 3.9-10 History Plot of Punch Force versus Stroke

job1

70696867666564636261

Pos Y cbody2 (x.1)


-3 0

60

1.289

0 5957

4039

383736

35343332

3130

4142

4344

5655545352 5851

49

48

4746

45

50

292826

9

8

7654321

0

10111213

25

2423222120181716151419

27

M U G id3 9 12


12/16

Marc Users GuideRun Job and View Results

3.9-12

RESULTS

HISTORY PLOT

CLEAR CURVES

ALL INCSADD CURVES

ALL LOCATIONS


Equivalent Von Mises Stress

FIT

Figure 3.9-11 Stress versus Plastic Strain Node 63

0.0 0.2 0.4 0.6 0.8 1.00

20000

40000

60000

80000

100000

Strength

Equivalent Von Mises Stress Node 63


Elastic Unload

3 9 13CHAPTER 3 9


13/16


Discussion

Since the sheet will completely wrap around the rigid cylinder an the end of the bending, we can estimatethe strain assuming that the sheet completely surrounds the cylinder, and by knowing the strain, the stress

can also be estimated as shown in Figure 3.9-12.

Figure 3.9-12 Estimating the bending strain and stress in the center of the sheet

With the stresses estimated we can assume that a fully plastic hinge forms in the center of the sheet and

estimate the punch load as shown in Figure 3.9-13.

Figure 3.9-13 Estimating the bending moment and maximum punch load

The estimate for the maximum punch load, 1250 lbf, is very close to that found by the analysis as shown

in Figure 3.9-10 of 1289 lbf. Finally, although the final angle after spring back appears close to 90o, its

actual value is 84o, and the punch stroke should be slightly reduced to form a right angle after springback.

A B

C D

A B

O

C D

( )= =

( )( ) = 75 Ksi

CD

C D C D

CD---------------------------=

C D A B=

A B AB=

CD

CD AB

AB-----------------------

rOC rOA

rOA ---------------------------------

rOC r OA

rOA

-------------------------=

CD

0.20 0.15

0.15---------------------------

0.05

0.15----------

1

3---= = =

CD 5x10

31 1 3

0.6+ /

r = 0.1

t = 0.1

0.3

M

M

P/2P/2

(y)

y

y

x

x

Marc Users Guide3 9-14


14/16

Marc User s GuideModeling Tips

3.9 14

Modeling Tips

The punch force in Figure 3.9-10 has an abrupt jump at increment 50 which is caused by a new node

entering contact between the sheet and the rigid table. This can be improved by using segment to

segment contact and entered in the modeling under contact control; the comparison between node to

segment and segment to segment contact is shown in Figure 3.9-14.

JOBS

NEW

MECHANICALPROPERTIES

CONTACT CONTROLMETHOD: SEGMENT TO SEGMENT

OK (twice)

RUN, SUBMIT....

Figure 3.9-14 Comparison of Node to Segment versus Segment to Segment Contact

5554535251

50

49

48

4746

454443

4241

56 57 58 59

1.289

00-3

Y (x1000)

Pos Y cbody2 (x.1)

70

40

6967666463626160 68

Force Y cbody2

3937 16151413121110

9

8

765432

17181920363534

33323130

38

29272625

24232221

28

1

06565 68

4948

4746

4544

50

43

4140

39383736

4235

51 53 676664636252 61595857565554 60 69

3432 13

12111098

14

7

5432

1

0

6

33

1517313029

282726 162523222120191824

Segment to Segment Contact

Segment to Segment Contact

Node to Segment Contact

Node to Segment Contact

0.000e+000

8.587e+001

1.717e+002

2.576e+002

3.435e+002

4.293e+002

5.152e+002

6.011e+002

6.869e+002

7.728e+002

8.587e+002

Contact Normal Force

Inc: 50

Time: 5.000e-001

X

Y

Z

3.9-15CHAPTER 3 9


15/16

3.9 15CHAPTER 3.9Break Forming

Input Files

The files below are on your deliverymedia or they can be downloaded by your web browser by clickingthe links (file names) below.

Also this problem can be automatically run from the HELP menu under DEMONSTRATIONS > RUN

A DEMO PROBLEM > CONTACT as shown below.

File Description

s4.proc Mentat procedure file to run the above example

Marc Users Guide3.9-16
http://../chapt_1/ug_ch1_01.pdfhttp://www.mscsoftware.com/doc/mentat/examples/marc_ug/s3/c3.9/s4.prochttp://www.mscsoftware.com/doc/mentat/examples/marc_ug/s3/c3.9/s4.prochttp://../chapt_1/ug_ch1_01.pdf


16/16

Animation

AnimationClick on the figure below to activate the video; it lasts about 10

minutes and explains how the steps above are done. Once the video isactivated, a right click of the mouse will open the menu shown at the

right; you can switch to various screen sizes or stop the video by

disabling the content.

Full Screen MultimediaClose Floating Window

Disable Content

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chapter 3.9: break forming

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