Week - 5 - Modelling Spotwelds

*Model name:-

Modelloing spotwelds

*Aim:-

-Simulate the modelling spotwelds using the LS-DYNA software & understand the concepts of how the conditions are produce after the heating car & it spotwelds to any particular steady object(Rigid wall).

Objective:-

-In this simulation we requests for the given delivers:-

*Procedure:-

1 Material creation

2 Section creation

3 Assigning material & section to their respective parts

4 Material & section creation for a beam elements & solide elements

5 Assigning material & section to beam elements & solid elements

6 Rigidwall creation

7 Definding boundary conditions & specifying initial velocity to the two parts.

8 Creating the contact definition.

9 Binary_D3plot & ASCII_opction define

10 Model check

11 Post processing

*Unit system:-

-in the question given that, unit system is:- gm,mm,ms.

-First of all start LSPP software & open the FEM which name is spotweld-assignment.k

-Here we seen that model consist of two parts, first one is upper part & second one is lower part.

1) Material:-

-Here we seen that shell elements are available in the box, so we create a material card for shell.

-We choose the material card is Piecewise_linear_plasticity(024)

-We use the material is steel for the made of this box.

-We provide the values are:-

*unit conversion:-

*Density:-

`ρ=7850 (Kg)/m^3`

`ρ=7850 *10^3/10^9 (gm)/(cm^3)`

`ρ=7.850×10^(-3) (gm)/(cm^3)`

*Young modulus:-

`E=210Gpa`

`E=210×10^9 pa`

`E=210×10^9 N/m^2`

`E=2.1×10^5 N/(mm^2)`

*Poisson ratio is:- 0.33

2) Section creation:-

-Session shell is taken for the two parts.

-For that we go to Model & part>keyword manager>all>section

-Here provide the element formulation is 16 & thickness is 1.5 mm.

3) Assigning material & section to their respective parts:-

-After the creation of material & session , next step is create the part.

-Here there is two parts available. provide the material id and section id for them.

4) Material & section creation for a beam elements & solid elements:-

-After the creation of material & section for part, now create the material & section for the beam element.

-Here, we use MAT_100 card for assign the material.

-Another thing, we use time base failure. It means fail the beam at 5 ms.

*For Beam elements & solid elements:-

-Here, we use section_beam card for the assign the section for beam.

-Provide the variuos values:-
ELFORM=9 (Element formulation)

CST=1

TS1=3 (Thickness)

*For Beam elements:-

*For solid elements:-

-Here, provide ELFORM=1

5) Assigning material & section to beam elements & solid elements:-

-After the creation of material & section card for the beam element, now assign that for every beam element.

-Here I create 8 beam elements.

*For Beam elements:-

*For solid elements:-

6) Rigidwall creation:-

-Now we create the rigid wall. '

-For that first of all create new node set.

-For that go to model & part>create> Set data> set node

-Here we select all nodes of the two parts.

-After that create planar rigid wall.

7) Definding boundary conditions & specifying initial velocity to the two parts:-

-Now we provide the velocity to the box.

-In the question velocity given is 50 kmph.

-`v=50 (Km)/(hr)`

`v=50 *10^6/(3600*10^3 ) (mm)/(ms)`

`v=0.01388*10^3 (mm)/(ms)`

`v=13.88 (mm)/(ms)`

8) Creating the contact definition:-

-We create the self contact for a two parts.

-For that go to the Model & part>keyword manager>all>contact

-Choose Automatic_single_surface type.

-Here we select the slave type is 4 & only select the slave id, don't select the master id.

-Now create contact between beam & two parts.

-We create CONTACT_TIED_SHELL_EDGE_TO_SURFACE card.

-choose SSTYP & MSTYP are 2.

-Here, provide beam as a slave id & parts as a master id.

8) Creating the contact definition:-

-Now we create control termination card.

-Control_termination keyword is crated for the end time provide. we provide end time is 10 ms.

9) Binary_D3plot & ASCII_opction define:-

*BINARY_D3PLOT:-

In this keyword the frequency with which the animation is to be crated will be given and is set to 0.1 ms.

*ASCII_OPCTION KEYWORD:-

-in this keyword

1)GLSTAT-Global data

2)MATSUM-Material energies

3)NODOUT

4)RCFORC

5)RWFORC

6)SECFORC

7)SLEOUT

-

10)Model check:-

-After assigning all the keyword check the model using the model checker and make sure that the file is error file.

-After that save the file as a".k" format.

-Run the file in the solver. if it's end as a normal termination then model is correct.

11) Post processing:-

-The D3 file open in LSPP using opction File>open>LS-DYNA binary plot

*von-mises stress:-

*Beam:- *Solid:-

-From this two cases we conclude that there are more stress concentration present near the spotweld region in case 2.

-This is becuse of the greater stiffness of spotweld modeled using solid elements.

*Effective plastic strain:-

*Beam:- *Solid:-

-The maximum strain produce 0.01559 in case 1 & 0.0517 in case 2.

*Von-mises stress:-

-Here, we plotting the von mises stress vs time diagram for elements number 101781 for both cases.

-we seen that higher amount of stress recorded in case 2 compare to case 1.

-The maximum stress is 199 Mpa in case 1 & in 269 Mpa case 2.

*x-velocity:-

*Beam:- *Solid:-

*x-acceleration:-

-The acceleration data were generated from historical data of node number 502061 in both cases.

*Beam:- *Solid:-

*Global data:-

*Beam:- *Solid:-

*spotweld axial force:-

*Beam:- *Solid:-

*spotweld shear force:-

*Beam:- *Solid:-

*spotweld resultant force:-

*Beam:- *Solid:-

*spotweld length:-

*Beam:- *Solid:-

*Conclusion:-

-Spotwelds were modelling using both Beam elements as well as Hexa elements.

-The spotweld modelled using the Hexa elements transfered more forces across the joining parts as a result of its higher stiffness.

-The simulation run succesfully. Post processing of the simulation had done using D3PLOT & ASCII results file.