introduction, literature review, material selection and dimensions, steps to perform simulation in ls-dyna ,implementation issues, results, conclusion and further implementation.

1. Finite Element Simulation Of Rotary Sheet
Bending
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
Submitted by:
KALOLA MEET M. (18BME050)
MECHANICAL ENGINEERING DEPARTMENT
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
2021

2. Declaration
This is certify to that
● The project work comprises my original work towards the Minor Project (ME 705)
subject of 7th
semester in Mechanical Engineering at Nirma University and has not
been submitted elsewhere.
● Due acknowledgement has been made in the text to all other material used.
Sign
Name: Kalola Meet M.
Roll No:18BME050
2

3. Undertaking For Originality Of The Work
I, Kalola meet (18bme050) gives undertaking that the Minor Project entitled finite element
simulation of “rotary sheet bending” submitted by me, towards the Minor Project (ME 705)
subject of 7th
semester of Bachelor of Technology in Mechanical Engineering of Nirma
University, Ahmedabad, is the original work carried out by us. We give assurance that no
attempt of plagiarism has been made. We understand that in the event of any similarity found
subsequently with any published work or any dissertation work elsewhere; it will result in
severe disciplinary action.
Signature of Student
Date:
Place: Ahmedabad
Endorsed by
(Signature of Guide)
3

4. Plagiarism Declaration
I hereby declare that the dissertation entitled “FE Simulation of Rotary Sheet Bending” is
my own work conducted under the supervision of Prof.Ashish.Gohil,Department Of
Mechanical engineering at institute of technology,nirma university,ahmedabad.
I further declare that to the best of my knowledge this report does not contain any part of
work that has been submitted for the award of any degree either in this university or in other
university without proper citation.
This is to certify that the above statement made by the candidate is correct to the best of my
knowledge.
Kalola Meet
(18bme050)
Signature of Guide
4

5. Certificate
TO WHOM IT MAY CONCERN
This is to certify that Mr. Kalola Meet M. student of Mechanical engineering, 7th
Semester of, Institute of Technology, Nirma University has satisfactorily completed
the project report titled “Finite Element Simulation Of Rotary Sheet Bending”.
Date:
Prof.Ashish Gohil
Guide, Assistant Professor,
Department of Mechanical Engineering,
Institute of Technology
Nirma University, Ahmedabad
Dr.K.M.Patel
Head and Professor,
Department of Mechanical Engineering,
Institute of Technology
Nirma University, Ahmedabad
5

6. Approval Sheet
The Project entitled Finite Element Of Rotary Sheet Bending by Kalola Meet
M.(18BME050) is approved towards the Minor Project (ME705) subject of the 7th semester
of Bachelor of Technology in Mechanical Engineering of Nirma University, Ahmedabad.
Examiners
___________________
___________________
___________________
Date: ___________
Place: Ahmedabad
6

7. Acknowledgments
I would like to express my special thanks to my project guide “Prof.Ashish Gohil” who
always gave me guidance and helped me to know about the subject and for support in
completing my project.
I would also like to extend my gratitude to the course coordinator “prof.Shruti Bhatt”and
department guide “Dr.K.M.Patel” for providing me with all the facilities that i required and
for giving me this golden opportunity.
Name : Kalola Meet M.
Signature :
Date:
Place: Ahmedabad
7

8. Abstract
This paper presents a Finite Element (FE) model developed for the 3-D numerical simulation
of rotary sheet bending by using EXPLICIT Finite Element Analysis (FEA) program with
anisotropic material properties and simplified boundary conditions.this fe simulation
performed ls-dyna software.Ls-dyna is is tool for finite element simulation The FE results are
compared with actual property of material for validation. The developed model can predict
the thickness distribution, thinning, and the maximum residual stresses of the sheet at given
physical parameters. First,the developed basic model is developed for trial purpose and after
finalizing dimensions the final model is prepared in ls-prepost.after that analysis done on that
model to predict failure of model Furthermore, it is used for predicting data for future
research,without expensive shop trials on physical setup.
Key words : Finite element analysis(FEA),Ls-Dyna,Rotary sheet bending
8

9. Chapter no: Table of contents Page no:
DECLARATION 2
UNDERTAKING FOR ORIGINALITY OF THE
WORK
PLAGIARISM DECLARATION
3
4
CERTIFICATE 5
APPROVAL SHEET 6
ACKNOWLEDGMENTS 7
ABSTRACT 8
1 INTRODUCTION 12-13
1.1 Objective 12
1.2 Problem Specification 13
1.3 Methodologies 13
2 LITERATURE REVIEW 14-15
3 SYSTEM DESIGN 16-29
3.1 Calculations 16-17
3.2 Systems dimensions 17
3.3 Material and properties 18
3.4 Steps for fe model 19-21
3.5 Define keywords 21-31
4 IMPLEMENTATION ISSUES 31
4.1 Error in simulation 31
4.2 Striking of tool and rotary die 31
4.3 Failure of sheet in bending operation 31
5 CONCLUSIONS & FUTURE ENHANCEMENTS 32-34
5.1 Result Analysis 32-34
5.2 Future works & concluding remarks 34
REFERENCES 36
9

10. List of Figures Page No.
Fig .1.1 Working of setup 12
Fig.2.1 Comparison for hole distortion 15
Fig.3.1 Bender location 16
Fig.3.2 Die clearance 16
Fig.3.3 Bending allowance 17
Fig.3.4 System dimensions 18
Fig.3.5 Drawing 2D-sketch in ls-dyna 19
Fig. 3.6 Generate surface model 20
Fig.3.7 Creating mesh 21
Fig.5.1 Generate Curve Of Effective Stress Vs Time 32
Fig.5.2 FLD Curve 33
Fig.5.3 Effective stress vs time 33
Fig.5.4 Engineering stress vs true stress 34
10

11. List of Tables Page No.
Table 3.1 Define keywords 22
Table 3.2 Define boundary 23
Table 3.3 Define contact 23-24
Table 3.4 Define control 25
Table 3.5 Define database keywords 26
Table 3.6 Define curve 27
Table 3.7 Define Hourglass 27
Table 3.8 Define material for rigid parts 28
Table 3.9 Define material for sheet 29
Table 3.10 Combine parts property 29
Table 3.11 Define section 30
11

12. CHAPTER 1
INTRODUCTION
● Although the concept of rotary sheet bending is not new, it is not extensively used in
industry due to a complete lack of knowledge and research. A rotary die is a type of
punch die combination which bends sheet metal with the help of a rotating cylinder
with a v opening cut into the side. The cylinder is mounted in a saddle which produces
the die's punch section. The sheet metal is pushed out over an anvil, and the rotary die
is pushed against its anvil/tool. The die starts to rotate as it engages the sheet, bending
the metal around the anvil's tip.
Fig .1.1- Simple Setup
● Different types of benders
​
Standard Bender
High production bender
​
Compact Bender
​
Standard bender
Compact bender
1.1 Objective
● Make a finite element model and perform finite element analysis to check that failure
occurs or not.
12

13. 1.2 Problem Specification
● Most of sheet bending processes affects sheet quality like on punched hole or sheet
thickness on stress due to thinning/decrease in thickness and because of that sheet fails
● Objective of this project is to develop a finite element model and its analysis of rotary
sheet bending process for 90 degree bend.after finite element analysis get the results of
the failure analysis of the sheet.
1.3 Methodologies
● Literature review
● Making basic model in ls-dyna
● Resolving error and perform simulation
● Find actual dimension and prepare surface model in ls-dyna
● Resolving errors and perform simulation
● Analysis of simulation(failure analysis)
13

14. CHAPTER 2
LITERATURE SURVEY
Finite element simulation of sheet bending is very effective because that saves cost of
experimental setup and gives accurate result.this bending process has many advantages over
other bending processes.[1]
About software
Ls-dyna is a general purpose software to perform finite element simulation of complete and
real world problems like in automobile,aerospace ,structural analysis it is available on
different platform like linux,windows,unix.explicit and implicit analysis for crack
propagation,crash test of vehicles,nonlinear dynamics and multi-physics etc.
Analysis in ls-dyna
In sheet metal forming, a forming limit diagram (FLD) is used to evaluate sheet metal
forming behavior. A mechanical test is done to evaluate whether a particular region has failed.
The formability limit diagram can be constructed as a line indicating failure starts by
repeating the mechanical test for sheet bending to generate a range of stress. FLD shows the
difference between safe and failure zones[2].
Experimental Comparison of Straight Flanging and Rotary Die Bending Based on
Springback
Increases in bending radius and die clearance for various materials increase the amount of
spring back in straight flanging/wipe bending. As the die clearance increases in the rotary die
bending process, the material does not completely wrapped around the punch radius, resulting
in a greater radius than desired. As a result of the experimental data, we can conclude that
rotary die bending has a more stable spring back behaviour than straight flanging. As a result,
the rotary die bending process is more suitable for large scale production of box-type parts
and decreasing geometric deviations[3].
14

15. Advantages of rotary sheet bending over other processes :
● Setup is very simple because of less parts and easy to operate.
● Saving time to set up for bending and increase production rate
● Setup is rigid in nature that increase accuracy of bending and part quality
● Rotary benders can bend as much as 120 degrees and are well-suited to bending
high-strength material[4].
● Less bending marks on sheet
Fig.2.1-Comparison For Hole Distortion
● Less hole distortion in rotary bending,when we bend sheet with punched hole due to
piercing action holes distort in convitional bending but in rotary sheet bending process
rocker benders fold the metal around the punch.so,hole distortion is eliminated[4].
Disadvantages of rotary sheet bending
● Setup is expensive
● Maintenance and cleaning is required
● It is used for straight line bending not for special shapes
● Less manufacturers
In short rotary sheet bending is a better choice for sheet bending in every condition.
15

16. CHAPTER 3
SYSTEM DESIGN
3.1 Calculations
3.1.1 Bender Location
For accurate bending of sheet where to put force of punch/tool is required and for that bender
location (k) is required.bender location depends on sheet thickness,radius of tool.
Fig.3.1-Bender Location
K = (part thickness +tool radius(R))/ )
(𝑡𝑎𝑛 43. 5°
K = (1+2)/tan(43.5°) = 3.15 mm
3.1.2 Die Clearance
Die clearance is important to prevent shearing of sheet during bending operation,this
clearance depends on sheet thickness.
Fig.3.2-Die Clearance
Die clearance = (Thickness of sheet +10% of Sheet thickness) = (1+0.1) = (1.1) mm
16

17. 3.1.3 Bending Allowance
Bending allowance is given to get accurate length of two ends of sheet after bending,without
calculating bending allowance some length used during bending in sheet corner radius to
prevent that bending allowance is provided.
L0 = 40 , A1 and A2 = 18 mm,BA = 4 mm
Fig.3.3-Bending Allowance
3.2 System Dimensions
Sheet thickness = PT = 1 mm
Die diameter(D) = 25.4 mm
Total length of all parts = 50 mm
Width of sheet = 44 mm
Bending radius(R) = 2 mm
Here,Rocker angle is 87° provided on all standard Metric benders. That allows for 3° of
overbend to get a final angle of 90°. Harder steel or larger part radius require more overbend.
17

18. Fig.3.4-System Dimensions[6].
NOTE : Above System dimensions are collected from industry catalogue of ready benders
company based on thickness of sheet,bending radius etc.
3.3 Material and property
● Tool : Steel(S7 Tool Steel)
● Die :Steel(S7 Tool Steel)
(Mass density = 7850 kg/m3,
Young's modulus = 200 Gpa, Poisson's ratio =
0.27–0.30)[7].
● Sheet : Aluminium 1050 H14
(Mass density = 2.7 g/cm³ , Young’s modulus = 71 GPa ,Poisson's ratio = 0.33,Strength
coefficient = 253.7 ,Hardening exponent = 0.23,UTS = 145 Mpa)[8].
18

19. 3.4 Steps For Finite Element Modeling In Ls-Dyna
3.4.1 Draw sketch (Geometry > Curve)
● In LS-dyna, the curve option allows the user to draw 2D sketches that include curves
like circles, arc, line, point, etc. The user can create a 2D sketch by defining points on
an existing sketch or model by starting from scratch.After obtaining the final
dimension from the industry catalogue of ready benders, manufacturing. Here we have
drawn a 2D sketch in LS-dyna.
Fig.3.5 Drawing 2d-Sketch In Ls-Dyna
3.4.2 Generate surface (Geometry > Surface > Extrude)
● After completion of 2d sketch we have extrude 2d sketch in surface to generate
surface model that is easy to analyse and required less computation time compare to
solid model.here we have taken length of extrusion is 50 mm but in real setup length
of setup is upto 80-90 cm to bend long sheets.
19

20. Fig. 3.6-Generate Surface Model
3.4.3 Creating mesh(FEM>Element and mesh>Auto mesher)
● The keyword auto MESHER tool is used to create a mesh from the generated surface
model that will be used in the analysis. So far only tetrahedral (or triangular in 2-d)
elements can be generated.auto mesher divides whole assembly into small shell
elements that are used for analysis.here we have used quad shape for meshing and
auto measure is used to mesh surface model.Here,we have taken maximum element
size is 1 and minimum element size is 0.195.total number of elements are 17700 and
nodes are 18087.
● If the number of shell elements are more(fine mesh) it takes more time for
computation and gives accurate results and if shell elements are less(coarse mesh) it
takes less computation time and gives less accurate results.
20

21. Fig.3.7-Creating Mesh
3.4.4 Measurement (FEM>Element tools >Measurement)
● For the measurement of distance from element to element ,part to part or node to node
we have used the measurement option so that we can change distance whenever it’s
required.
3.4.5 Transform(FEM>element tools >transform )
● After measuring the distance to move the part, the transform tool is used to
move,rotate the part in x,y,z directions.
3.5 Define keywords in generated model (FEM>model and part>keyword manager)
● Defining keywords is very important to give motion ,material ,collect data form
simulation,contact between parts,constraints for parts.elements keyword shows the
total number of elements after generating mesh and node keyword shows the total
number of nodes in the whole meshed assembly.
21

22. Keyword Count
Boundary 2
Contact 2
Control 3
Database 1
Define 2
Element 17700
Keyword 1
Mat 3
Node 18087
Part 3
Section 3
Title 1
Table 3.1 - Define Keywords
3.5.1 Boundary
● Boundary keyword provides a way of defining imposed motions on boundary nodes
and provides constraints/degree of freedom to moving parts.here two moving parts are
added in boundary_prescribed_motion_rigid keyword.
22

23. Keyword Boundary_prescribed_motion_rigid
Parameter Value
Id 1
Pid 1
Title Tool
Dof 3(Z-Translational)
Sf (Default=1.0)
Vid 2(Displacement)
Table 3.2-Define Boundary
3.5.2 Contact
● The CONTACT keyword provides a way of treating interaction between disjoint parts
and contact of parts.here we have used contact_forming one way surface to surface
keyword and defined contact between sheet to die and sheet to tool.
Keyword Forming One Way Surface To Surface
Parameter Value
Title Sheet To Die
CID 1
SSID 3
MSID 2
SSTYP 2
MSTYP 3
VDC 20
23

24. Parameter Value
Title Sheet To Tool
CID 2
SSID 3
MSID 1
SSTYP 3
MSTYP 3
VDC 20
Table 3.3-Define Contact
3.5.3 Control
● Control keywords are optional and can be used to change defaults activate
solution options such as mass scaling, adaptive remeshing, and an implicit
solution,but it is compulsory to define the CONTROL_TERMINATION for the
termination or run time for simulation .
● There are many keywords, but we only define termination, accuracy, bulk viscosity,
energy contact, shell, time-step.Control_accuracy improves accuracy of the
calculation,Bulk viscosity is used to treat shock waves.This keyword resets the
default values of the bulk viscosity coefficients globally.As a result, shock wave by
sudden impact of tool of sheet can be neglected.
● Contact keyboard Change defaults for computation with contact surfaces.energy
keyword provides controls for energy dissipation.hourglass redefines the default
values of hourglass control type and coefficient.The Shell keyword provides controls
for computing shell response.time step Set structural time step size control using
different options that directly impact on the steps to run the simulation.
24

25. Main keyword Control
Sub Keyword Parameter Values
Accuracy OSU 1
INN 4
IACC 1
Bulk Viscosity TYPE -2
Contact SHLTHK 1
THKCHG 1
IGNORE 2
FRCENG 1
OUTSEG 1
SPOTDEL 1
Energy HGEN 2
SLNTEN 2
RYLEN 2
Shell ISTUPD 4
BWC 1
PROJ 1
CNTCO 2
Termination ENDTIM 10
Time Step DT2MS 1.01E-04
Figure 3.4 – Define Control
25

26. 3.5.4 Database
● Database keywords are optional, but they are necessary to obtain output files
containing results information for analysis of different parameters.ascii_option
keyword contain keywords like MATSUM(Material energies),RCFORC(Resultant
interface forces),GLSTAT(Global data),D3PLOT(generates Database for entire
model).
● This keyword helps to get the data from the performed simulation.extent_binary is
used to control to some extent the content of binary output databases like d3plot.
Main keyword Database
Sub Keyword Parameter Values
Ascii_option GLSTAT Dt - 0.001
MATSUM
RCFORC
Binary_d3plot NPLTC 1000
Extent_binary STRFLG 1
INTOUT Stress
NODOUT Stress
Fig.3.5-Define Database Keywords
26

27. 3.5.5 Define Curve
● Define >curve is used to give motion to parts like rotation displacement with the help
of distance VS time value.Here, we have given a termination time of 10 sec, so our
tool has to travel a particular distance towards the sheet(-Z direction) and reading in
radian for rotation of the rotary bender.
Keyword DEFINE_CURVE
Parameter Value
Title Tool
LCID 1
A1 0-10
O1 0-12
Title Die
LCID 2
A1 0-10
O1 0-(-0.7857)[Rad]
Table 3.6-Define Curve
Keyword Hourglass
Parameter Value
Title Hourglass
IHQ 4
QM 0.05
Table 3.7-Define Hourglass
27

28. 3.5.6 Material
● It is compulsory to define the material for each part of the assembly .Here we have
defined steel for die, punch(tool) and aluminium for metal sheet and define values of
young modulus,mass density and degree of freedom of parts.
Keyword Mat_rigid
Parameter Value
Title Tool and die
MID 2 and 3
RO 7.85E-06
E 2.00E+05
PR 0.3
CMO 1
CON1 Tool : 4
Die : 7
CON2 Tool : 7
Die : 6
Fig.3.8-Define Material For Rigid Parts
28

29. Keyword Mat_power low plasticity
Parameter Value
Title Sheet
MID 1
RO 2.71E-06
E 7.00E+04
PR 0.33
K 278.5811
N 0.2653
SIGY 111.582
Fig.3.9-Define Material For Sheet
3.5.7 Parts
● After giving values for all parameters in keywords we hate to combine section
property, material information, hourglass type, thermal properties for each part in
assembly.
Keyword Part Parameter Value
PART
SHEET
PID 3
SECID 1
MID 1
HGID 1
TOOL
PID 1
SECID 2
MID 2
Die
PID 2
SECID 3
MID 3
Fig.3.10-Combine Parts Property
29

30. 3.5.8 Section
● The section_shell keyword specifies the section properties for shell elements, node
thickness, and part section properties in an assembly.
Keyword Section_shell
Title sheet
SECID 1
ELFORM 2
SHRF 0.8333333333
NIP 5
T1 1
Title Tool and tool
SECID(tool) 2
SECID(die) 3
ELFORM 2
SHRF 0.8333333333
NIP 3
T1 1
Table.3.11-Define Section
30

31. CHAPTER 4
IMPLEMENTATION ISSUES
4.1 Error In Simulation
During simulation of the basic model, some errors were generated because of giving wrong
keywords and missing information like material properties and section properties that
resulted in the failure of the model.
4.2 Striking Of Tool And Rotary Die
Due to inaccurate moving distance between tool-sheet, sheet-die or tool-die and clearance
between parts results in striking parts and tool penetration in rotary die gives wrong readings.
4.3 Failure of sheet in bending operation
During the analysis part, due to improper thickness,missing value of parameters,
distance/clearance or material property of the sheet, it is near to failure.
31

32. CHAPTER 5
CONCLUSIONS & FUTURE ENHANCEMENTS
5.1 Result Analysis
For finite element analysis(FEA) post-processing method is used to generate curves with
different relationship.for that run simulation,FEM>Post>history.
Fig.5.1-Generate Curve Of Effective Stress Vs Time
To generate the Fld curve follow a given path FEM>POST>FLD change the value of sheet
thickness and n and select sheet as a part and plot the curve.
32

33. Fig.5.2-Fld Curve
Above FLD curve shows that safe points are below safety margin so fracture is not occuring
in the sheet.
Fig.5.3-Effective Stress Vs Time
In post processing of the final model, we have selected two elements, one in a bending region
at 90 degrees and the second on the vertical side of the sheet after bending.The red graph
shows failure of element in bending region and green curve shows element sustained after
bending above curve shows effect of effective stress on selected element.
33

34. Fig.5.4- Engineering Stress Vs True Stress
From the above v-m Vs t curve, we can say that neaking of sheet is occurring and fracture is
not happening in sheet because true stress is more than engineering stress. Here we get
effective stress = 160 Mpa which is less than true stress.
5.2 Future works & concluding remarks
From the above analysis, we can conclude that rotary sheet bending is a very efficient process
that reduces energy for bending sheets and it can be used for mass production for fixed
designed components, but because of lack of a information and less availability of
components, machines and research work, this process is not widely used worldwide. Future
work is an improvement in model and reading comparison of experimental or other bending
processes with current readings.
34

35. References
[1] Hedrick, A. (2018, July 18). Die basics 101: Rotary and reverse U bending. The
Fabricators. Retrieved December 2, 2021, from
thefabricator.com/thefabricator/article/stamping/die-basics-101-rotary-and-reverse-u-b
ending.
[2] Global Journal of Researches in Engineering Automotive Engineering “Sheet Metal
Forming Simulations for Heavy Commercial Vehicle Parts by LS-DYNA” Volume 13
Issue 1 Version 1.0 Year 2013 Type: Double Blind Peer Reviewed International
Research Journal Publisher: Global Journals Inc. (USA)
[3] Livatyali, H., Turan, S. E., Birol, F., & Türköz, M. (2021). Experimental comparison
of straight flanging and rotary die bending based on
Springback.https://doi.org/10.21203/rs.3.rs-667515/v1
[4] (Rotary Die – SheetMetal.Me, 2021)
[5] Spa,E., 2021. EnginSoft - Ansys LS-DYNA. Enginsoft.com.Available at:
enginsoft.com/solutions/ls-dyna.
[6] Sponsored by Aalco - Ferrous and Non-Ferrous Metals StockistApr 18 2005. (2020,
October 16). Aluminium alloys - aluminium 1050 properties, fabrication and
applications. AZoM.com. Retrieved December 4, 2021, from
azom.com/article.aspx/ArticleID=2798.
[7] AISI S7 Tool Steel: 1.2355: 50CRMOV13-15. Otai Special Steel. (2020, March 6).
Retrieved December 4, 2021, from astmsteel.com/product/aisi-s7-tool-steel/.
[8] (Sponsored by Aalco - Ferrous and Non-Ferrous Metals StockistApr 18 2005,
Aluminium alloys - aluminium 1050 properties, fabrication and applications 2020)
35

36. Finite Element Simulation Of Rotary Sheet
Bending
By
Kalola Meet M.
(18BME050)
DEPARTMENT OF MECHANICAL ENGINEERING
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
AHMEDABAD-382481
DECEMBER 2021
36