Week - 5 - Modelling Spotwelds

Aim : Simulation of Crassbox and modeling of spotweld

Procedure :

open LS PrePost and open given file

File >> open >> Ls Dyna Keyword file

Select the file >> and open

as checked we have only geometry now we will deploy beam element for spotweld in middle of both plate juntion

for that we will hide half part as shown below

Element tool >> Blank >> pick element by area

now create beam element as shown below

mesh >> emenent generation >> select beam >> select beam by : TWO_NODE_SET>> select node on 1st part amd node 2 on 2nd part as shown below

click on create >> accept

repeat the same process to generate more 4 beam element as shown below are the region fro element

now unhide all element

element tool >> blank >> unblank all element

now create node set for all beam element node

model and part >> create entity >> set data>> node_set >> Create >>

Title : BEAM_NODESET

select node of each beam element

click on apply now create partset id for all parts except beam element

model and data >> create entity >> set data >> SET_PART >> create

title : ALL_PARTSET

select by part and select both part and click on apply

now we will create section for beam and part element

model and part >> keyword manager >> all >> section >> BEAM >> delete all auto generated beam element

Now create beam section using

Model and part >> keyword manager >> all >> section >> beam

title : SECTION_BEAM

SECID : 1

ELFORM : 9

CST : 1 tubular,

TS1 : 3

TS2 : 3

TT1 : 1

TT2 : 2

Accept >> done

now create shell section

Model and part >> keyword manager >> all >> section >> shell

title : SECTION_SHELL

SECID : 2

ELFORM : 2

T1/T2/T3/T4 : 1.5

accept >> done

now create material card for beam and part and we will use g-mm-ms unit system

Mass: Gram

Length : mm

Time : ms

Force : N

Stress : MPa

Energy : N-mm

Density Of steel : 7.83e-03 g/mm^3

Young's modulus of steel : 2.07e+05 MPa

Velocity at 50 KMPh : 13.889 mm/ms

model and part >> keyword manager >> all >> mat >> 071_CABLE_DISCREATE_BEAM>> delete all auto genertade Material card

Now create elastic material 001_elastic for all part element

model and part >> keyword manager >> all >> Mat >> 001_ELASTIC

Title : MAT_PARTS_STEEL

MID :1

Density Of steel : 7.83e-03 g/mm^3

Young's modulus of steel : 2.07e+05 MPa

Poission Ratio : 0.3

Accept >> done

Create material for spotweld

Model and part >> keyword manager >> all>> mat >> 100_spotweld

Title : MAT_SPOTWELD_STEEL

Mid : 2

Density Of steel : 7.83e-03 g/mm^3

Young's modulus of steel : 2.07e+05 MPa

Poission Ratio : 0.3

SIGY: 350 MPa

TFAIL: 1.5

EFAIL : 20

NRR : 10000

NRS : 10000`

NRT : 10000

NRR : 90000

MSS : 90000

MTT : 90000

Accept >> done

Create hourglass card

model and part >> keyword manager >> all >> Hourglass >> Hourglass

Title : Hourglass_card

HGID : 1

IHQ : 2 :Flanagan-Belytschko viscous form

Accept >> done

now assign Section , Material and hourglass to the part ID

model and part >> keyword manager >> model >> part >> Part

as we have 7 parts , 1st two parts are part body and rest 5 part are spotweld

for 1st part

title : Upper_palte_part

PID : 1

SECID : SHELL_SECTION : 2

MID : STEEL_MAT_ELASTIC :1

HGID : 1

for 2nd part

Title : LOWER_PLATE_PART

PID : 2

SECID : SHELL_SECTION : 2

MID : STEEL_MAT_ELASTIC :1

HGID : 1

for 3rd to 7th part

title : Beam_Part_1/2/3/4/5

PID : 3/4/5/6/7

SECID : 1 (SECTION_BEAM)

MID : 2 ( MAT_STEEL_BEAM)

now create cross-section to measure the cross-sectional force during the crass

to create cross-section on middle of both part

model and part >> create netity >> database >> cross_section >> create

select : plane

select node on middle of component in our case we have node id 503890 and node and 506933 for lower and upper plate respectively .

now craete rigid wall 10mm away from the start node

Model and part >> create entity >> rigid wall >> rigidwall >> Create >> Planner >> 1n+ NL

select node by pick option and provide translation of -10 mm magnitude in x axis

apply >> done

Now create velocity card for the movement of crassbox

Model and part >> keyword manager>> all >> intial >> velocity

for NSID >> create new Nod_entity

Title : ALL_NODE_SET_PART

SETID : 2

select node by part : select all 2 part ( except beam element )

ALL_NODE_SET_PART

click on apply

prvide Vx : -13.889

Accept >> done

now define control_enery card

model and part >> keyword manager >> all >> control >> energy

HGEN : 2

Rwen : 2

SLNTEN : 2

RYLEN : 2

IRGEN : 2

Now craete history node

Model and part >> keyword manager >> all >> database >> History_node

ID1 : 506933

ID2 : 503890

Insert >> accept >> done

Create contact between Beam element and part using beam node as slave and part element as master

Model and part >> Keyword manager >> all >> contact >> Tied_shell_edge_to_surface

SSYTP : 4 (node set ID for node to surface contact)

MSYTP : 2 ( part set ID,)

SSID:=Slave segment set ID : 1 ( Beam ELEMENT NODE SET)

MSID:=Master segment set ID : 1 ( PART_SET)

FS AND FD : 0.8 ( STEEL TO STEEL FRICTIONAL COEFFICIENT )

accept >> done

NOw define self contact for all part element

Model and part >> keyword manager >> all >> contact >> AUTOMATIC_SINGLE_SURFACE

SSYTP : 2 (PART_SET_

MSYTP : 2 (PART_SET)

SSID : 1 ( PART_SET)

MSID : 1 (PART_SET)

FS & FD : 0.8 ( steel to steel frictional coeffiecient )

accept >> done

now define termination card '

Model and part >> keywprd manager >> all >> control >> termination

ENDTIM: 3

accept >> done

now define output card

1. D3plot

Model and part >> keyword manager >> all >> database >> BINARY_D3Plot

Dt : 0.1 >>accept>> done

2. ASCII_OPTION

Model and part >> Keyword manager >> all >> Database >> ASCII_OPTION

Set Default DT : "0.1" and Default Binaty :" 3"

request for below output

ELOUT - Element Output Data

GLSTAT - Global Statistics

MATSUM - Material Energies

NODOUT - Nodal Displacement/Velocity/Acceleration data

RCFORC - Resultant Interface Forces

RWFORC - RigidWall Forces

SECFORC- Cross Section Forces data

SLEOUT - Sliding Interface Energies

SWFORC - Spotweld Nodal Constraint Reaction Forces

for all DT = 0.1

accept >> dnoe

now save the mode in seperate folder

now run the model using

File >> run LS-DYNA

Select new file which we saved .

and click on run

Our simulation in terminated normal .

Case 2 : we will import privious model and delete beam element and create solid hexa element

now to create hexa solid element in place of beam element

1st wwe will hide half element as previous

Element tool >> element edit >> blank >> select by area

now create hexa element on the place of beam element

Mesh >> element edit >> create >> Hexa

Select 4 node on lower part and respective 4 node on upper part in anticlock wise and click on accept

create same process to generated more 4 hexa element as shown below

Now unhide all element

element tool >> black >> unblank all

Now delete beam section and create solid section

model and part>> keyword manager >> all >> section >> solid

Title : SOld_spotweld_section

SECID : 1

ELFORM : 1

Accept done

Now create solid section for all hexa element

Model and part >> create entity >> set Data >> solid

Title :All_spotweld

SETID : 1

select all solid hexa element and apply >> done

goto part and create part id for hexa solid element

model and part >> keyword manager >> all >> Part >> part >>

Title : Part_Hexa_SPOTWELD

PID : 3

SECID : 1

MID : 2

Noe modeify contact

delete tied contact and craete spotweld

model and part >> keyword manager >> all >> contact >> spotweld

SSTYP : 3

MSTYP : 2

SSID : 3

MSID : 1

FS & FD : 0.8

Now save the file in different folder

file >> save as >> select location and rename file

now run the file

file >> run LS DYNA

select new file and run

Result

1. Von Mises stress in case 1

2. Von Mises Stress in case 2

Plots

3. Global energies in case 1

4. GLobal Energies in 2nd case

as we obserbed that hourglass energy developed more in case 1 compraed to case 2

5. Axial force developed at the beam element in case 1

6. axial force developed in case 2 on solid soptweld element

beam experiences more axial load compared to the solid element.

7. Shear Force on beam element in case 1

8. Shear force on solid element in case 2

Shear forcewe obserbed in 2nd case more than in case 1.

Conclusion :

1) we had succesfully run the simulation for all 2 case and compared the axial and shear forces in both case.

2) When a beam element is used for a spotweld, the axial load is higher than normal which may lead to earlier failure if force-based failure criteria are used.

3) so solid element is more suitable to model the spotweld it has 4 nodes in contact and has better axial and shear capabilities.